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The effect of coarse woody debris on site productivity of some forest sites in southwestern British Columbia Kayahara, Gordon John 2000

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THE EFFECT OF COARSE WOODY DEBRIS ON SITE PRODUCTIVITY OF SOME FOREST SITES IN SOUTHWESTERN BRITISH COLUMBIA by Gordon John Kayahara B.Sc.F., University of Toronto, 1978 M.Sc, University of British Columbia, 1992 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Forest Sciences) We actejpt this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA July 2000 © Gordon John Kayahara, 2000 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of P-ftfi-EVT ^ C l E K E C E . ^ The University of British Columbia Vancouver, Canada Date Z*7j DE-6 (2/88) ABSTRACT I explored the importance of decaying wood to survival and growth of trees in south coastal British Columbia, and the effect of decaying wood on the intensity of podzolization on mesic sites. A field pot study was carried out in both high light and low light conditions using woody and non-woody forest floor materials. After two growing seasons, Pseudotsuga menziesii, Tsuga heterophylla, and Abies amabilis seedlings growing in clearcuts had greater survival and growth in the non-woody substrate; however, in the understory, the effect was much less. The proliferation of western hemlock roots was used as an indicator of the value of decaying wood to trees. In both greenhouse trials (using seed sown on a series of planting pots with each half filled with either a woody substrate or a non-woody substrate), and in field sampling of woody and non-woody substrates in mature stands, the non-woody substrate had a larger density of fine and very fine roots compared to the woody substrates or mineral soil. Ten litres of concentrated solutions of non-woody humus substrate and woody substrates were leached through soil columns. Both the non-woody and woody solutions had similar mean pH but significantly different chemical properties. The non-woody solution leachate had greater net average output of dissolved organic C, Fe, and Mn. The mineral soil treated with the non-woody solution had significantly greater concentrations of total N and pyrophosphate-extractable Fe. In the field, forest floor and soil samples were compared between pedons having large accumulation of decaying wood and pedons with non-woody humus forms. Despite large and significant differences in chemical properties between the two substrates, there were generally no significant differences between the chemical properties of the soils directly under these substrates. In most cases, the results of (3-analyses showed that the means were not pedologically different. Additionally, 18 pairs of zero tension plate lysimeters were installed under the two substrates. The lysimeter solutions showed no significant differences. I concluded that coarse woody debris appears not to have either a positive effect of increased productivity of trees or a negative effect of increased intensity of podzolization. ii T A B L E O F C O N T E N T S ABSTRACT i i T A B L E OF CONTENTS i i i LIST OF T A B L E S v LIST OF FIGURES ix ACKNOWLEDGEMENTS xi Chapter 1. GENERAL INTRODUCTION 1 SECTION I: SHORT-TERM PRODUCTIVITY 3 Coarse woody debris as a source of nutrients 3 Coarse woody debris, seedlings, and fine roots 4 Research Focus 4 Chapter 2. SURVIVAL AND GROWTH OF PLANTED SEEDLINGS ON W O O D Y AND N O N -W O O D Y FOREST FLOOR SUBSTRATES IN HIGH A N D L O W LIGHT ENVIRONMENTS OF COASTAL BRITISH COLUMBIA Introduction 6 Materials and Methods 8 Study sites 8 Experiment 8 Measurement of survival and growth 11 Statistical analyses 13 Results 14 Discussion 15 Conclusions 22 Chapter 3. T H E ASSOCIATION BETWEEN WESTERN H E M L O C K FINE ROOTS WITH W O O D Y AND N O N - W O O D Y FOREST FLOOR SUBSTRATES IN COASTAL BRITISH COLUMBIA 23 Introduction 23 Roots as Indicators 23 Root Proliferation and Decaying Wood 24 Research Approach 25 Methods Greenhouse Study 26 Field Sampling 29 Results Greenhouse Study 34 Field Sampling 35 Discussion Greenhouse Study 41 Field Sampling 42 Conclusion 43 SECTION I DISCUSSION 44 U l SECTION II: L O N G - T E R M PRODUCTIVITY 45 Podzolization and Productivity 45 Coarse Woody Debris and Podzolization 46 Research Focus 48 Chapter 4. T H E RELATIVE POTENTIAL FOR INCREASED ACIDIFICATION AND INTENSITY OF PODZOLIZATION OF SOLUTIONS L E A C H E D F R O M W O O D Y K£&st/s N O N - W O O D Y FOREST FLOORS Introduction 49 Materials and Methods Soil Columns 50 Chemical analyses 52 Statistical analyses 53 Results 55 Solution and soil columns 55 Mineral soil and soil columns 56 Discussion 65 Conclusions 67 Chapter 5. COMPARISON OF SOIL ACIDIFICATION AND INTENSITY OF PODZOLIZATION BENEATH DECAYING W O O D VERSUS N O N - WOODY FOREST FLOORS Introduction 68 Methods Field Lysimeters 69 Mineral Soil Analyses 71 Mineral Soil Chemical Analyses 74 Statistical Analyses 76 Results Field Lysimeters 76 Mineral Soil Indicators of Podzolization Intensity 78 Non-woody vs. woody substrates 79 Discussion Sample Selection 92 Field Lysimeters 92 Mineral Soil and Indicators of Intensity of Podzolization 92 Conclusions 95 SECTION II: DISCUSSION 96 Chapter 6. GENERAL DISCUSSION A N D CONCLUSIONS 97 Short-Term Productivity 97 Long-Term Productivity 98 Conclusions 99 REFERENCES 100 APPENDIX 112 iv L I S T O F T A B L E S Table 2.1 Growth performance of seedlings growing in decayed wood, non-woody forest floors, and mineral soil for various species of northwestern North America reported in the literature 7 Table 2.2 Characteristics of the study sites in coastal British Columbia 9 Table2.3 Light environments for clearcuts and adjacent old-growth forest understories in coastal British Columbia. Measurements were recorded for three consecutive, predominately sunny days in from June 30 to July 2, 1996. Daily mean PPFD values are averages for PPFD measurements made between 06.00 and 21.00 local time 9 Table 2.4 Mean nutrient properties (standard error in brackets) of the woody substrate, non-woody substrate, and mineral soil (sample size is three for any given substrate and light condition) 16 Table 2.5 Effects of light (Lj), soil substrate (Sk), and species (P i ) on growth parameters 17 Table 3.1 Chemical measures (as described for the field study) for the three substrates used in the greenhouse pot experiment 27 Table 3.2 The distribution of sites by humus form across the sampled area 31 Table 3.3 Mean and standard error (in brackets) of height (cm) and caliper (mm) of the seedlings grown in five substrate combinations 34 Table 3.4 Mean, standard error (in brackets), alpha and beta error values for root density of half a pot. Each half of the pots were filled with the same substrate 35 Table 3.5 Mean, standard error (in brackets), and alpha error values for root density of half a pot. Each half of the pots were filled with various combinations of non-woody humus form, decay class IV wood, and the sawdust-wood chip mixture 35 Table 3.6 Mean and standard error (in brackets) of root density and chemical measures within the moder humus form grouping between the rooting substrates (n =3) 36 Table 3.7 Mean and standard error (in brackets) of root density and chemical measures within the mor humus form grouping between the rooting substrates (n =3) 37 Table 4.1 The mean concentration of the input solutions that were leached through the soil columns 57 Table 4.2 The mean concentration of the output leachates that leached through the V soil columns 58 Table 4.3 The mean ratio of the output to input solution concentrations that were leached through the soil columns 63 Table 4.4 The mean chemical properties between the mineral soil of the columns that were leached with non-woody solutions, woody solutions, and acidified (to pH 3.5) distilled water 64 Table 5.1 Location and description of the study sites 73 Table 5.2 Mean differences between the two forest floor substrates to be considered pedologically significant 77 Table 5.3 Mean chemical concentrations (standard error of the mean in brackets) of the solutions obtained from collectors in the open and collectors under the tree canopy (throughfall). The values for DOC and pH are based on averages of three rain periods for; and the remaining measures for one rainfall event 78 Table 5.4 Mean chemical concentrations (standard error of the mean in brackets) of the solutions obtained from zero tension lysimeters under non-woody and woody substrates 79 Table 5.5 Mean chemical properties (standard error of the mean in brackets; based on n = 3) and /7-value between the non-woody Bf horizon of the CWHxm compared to the MHmrn subzone, and the IDFxw compared to the ESSFmk subzone 81 Table 5.6 The mean chemical properties (standard error of the mean in brackets; based on n = 3) and/>value between the non-woody Ae horizon followed by the value for the underlying Bf horizon for the CWHvm, MHmm, and ESSFmk subzones 82 Table 5.7 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Very Wet Maritime Coastal Western Hemlock (CWHvm) subzone 83 Table 5.8 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the CWHvm subzone 84 Table 5.9 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Very Dry Maritime Coastal Western Hemlock (CWHxm) subzone 85 v i Table 5.10 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the CWHxm subzone 86 Table 5.11 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Maritime Mountain Hemlock (MHmm) subzone 87 Table 5.12 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the MHmm subzone 88 Table 5.13 Chemical properties and indices of degree of podzolization for the A horizon or upper 2 cm of the B horizon that showed significant differences of the mean values at a < 0.05 or no significant differences at P < 0.10 89 Table 5.14 Chemical properties and indices of degree of podzolization for the upper 10 cm of the B horizon that showed significant differences of the mean values at a < 0.05 or no significant differences at P < 0.10 90 Table 5.15 p-values for the indicators of podzolization if the alternative mean used in the equation was one-half of that specified in Table 5.3 91 Table A. 1 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Warm Interior Cedar Hemlock (ICHmw) subzone... 112 Table A.2 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the ICHmw subzone 113 Table A. 3 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Very Dry Warm Interior Douglas-Fir (IDFxw) subzone.... 114 Table A.4 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the IDFxw subzone 115 Table A. 5 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Cool Engelmann Spruce-Subalpine Fir (ESSFmk) subzone 116 Table A.6 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody vii humus form and the decaying wood (woody) in the ESSFmk subzone 117 Table A.7 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Wet Cool Interior Cedar Hemlock (ICHwk) subzone (north) 118 Table A. 8 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the ICHwk subzone 119 Table A.9 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Cool Sub-Boreal Spruce (SBSmk) subzone 120 Table A. 10 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the SBSmk subzone 121 Table A. 11 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Warm Boreal White and Black Spruce (BWBSmw) subzone 122 Table A. 12 Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the BWBSmw subzone 123 V l l l L I S T O F F I G U R E S Figure 2.1 A series of planting pots filled with the three indicated substrates were placed at the centre of a clearcut and beneath the overstory of an adjacent old growth forest. Seedlings of western hemlock, Pacific silver fir, and Douglas-fir were planted in the pots 10 Figure 2.2 Representative daily light environment pattern for the three study sites. Measurements were taken simultaneously on July 1, 1996 12 Figure 2.3 The effect of light condition (open and understory) and soil substrate (woody, non-woody, and mineral soil) on the survival surveyed at the end of second growing season 18 Figure 2.4 Base diameter and total height of planted seedlings in relation to light condition (open and understory) and soil substrate (woody, non-woody, and mineral soil) on the survival surveyed at the end of second growing season 19 Figure 2.5 Total biomass of planted seedlings in relation to light condition (open and understory) and soil substrate (woody, non-woody, and mineral soil) on the survival surveyed at the end of second growing season 20 Figure 3.1 Greenhouse pot set-up with each pot divided into two substrates. The pots are distributed randomly within a 20 cm tall styrofoam berm in the greenhouse with the middle separation line pointing south 27 Figure 3.2 An illustration of the blocked sampling design and the substrates sampled for root density 32 Figure 3.3 An illustration of the top view of the idealized sampling layout showing the position of the sampling points and the associated substrates that were sampled 32 Figure 3.4 Plot of the mean and standard error of the fine and very fine root density associated with each rooting substrate. (A) is for the moder humus form grouping, and (B) is for the mor humus form grouping 38 Figure 3.5 Plot of the mean and standard error of (A) pH, (B) C:N ratio, (C) total-N, and (D) mineralizable-N associated with each rooting substrate for the mor and moder humus form groupings 39 Figure 3.6 Illustration of the site x treatment interaction of (A) pH, and the natural logarithmic transformation of (B) C:N ratio, (C) total-N, and (D) mineralizable-N for the mor humus form grouping 40 Figure 3.7 Illustration of the site x treatment interaction of the natural logarithmic transformation of mineralizable-N for the moder humus form 41 ix Figure 4.1 Details of the soil column setup used for leaching of different solutions through a Bm horizon of basaltic parent material 51 Figure 4.2 The concentration of DOC at various times along the cumulative solution leaching volume for the three column sets (A vs B, C vs D, E vs F) of the non-woody substrate (A, C, E) and the woody substrate (B, D, F) 59 Figure 4.3 The concentration of Fe at various times along the cumulative solution leaching volume for the three column sets (A vs B, C vs D, E vs F) of the non-woody substrate (A, C, E) and the woody substrate (B, D, F) 60 Figure 4.4 The concentration of Mn at various times along the cumulative solution leaching volume for the three column sets (A vs B, C vs D, E vs F) of the non-woody substrate (A, C, E) and the woody substrate (B, D, F) 61 Figure 4.5 The concentration of Al at various times along the cumulative solution leaching volume for the three column sets (A vs B, C vs D, E vs F) of the non-woody substrate (A, C, E) and the woody substrate (B, D, F) 62 Figure 5.1 A profde pair with zero-tension lysimeters sampling the solution leaching from each of the two substrates 70 Figure 5.2 An example of a profile pair which will be sampled under each of the two substrates 74 Figure 5.3 Difference in total N between the non-woody and woody substrates (open boxes) and the upper 10 cm of the mineral soil and between the C in fulvic acid between the non-woody and woody substrates and pyrophosphate Fe in the upper 10 cm of the mineral soil 94 ACKNOWLEDGEMENTS To all my fellow graduate students who have suffered during these years: I hope we keep our perspective and continue to realize that education is a privilege... a lot of people in this world would love to have this kind of "suffering". If we use our knowledge to help ease the real suffering in the world, then I think we can say our degrees were worth it. And to my mother, who when I told her that I was enrolling in a Ph.D. program, answered with "Are you sure? Don't you have to be smart to do that?"... well I still have my doubts of whether I'm smart enough, but I did somehow make it through. Thank you for secretly praying that all turns out well in the end. Research in forestry requires a lot of funding, logistical support, and technical expertise. For direct or in-kind funding I thank the B C Science Council for the GREAT Scholarship, Fletcher Challenge Canada for collaboration funding, Forest Renewal BC for most of the research funding, and Glynn Road Laboratory for doing the chemical analyses for Chapter 5. I thank the Ministry of Environment, Lands, and Parks which gave permission to set up plots within Mount Cypress and Seymour Provincial Parks; and the Greater Vancouver and Victoria Regional Districts which gave permission to set up plots within the Vancouver and Victoria watersheds, respectively. I also am grateful to the many BC Ministry of Forests staff who took the time to show me prospective study areas. I especially thank the invaluable help given by all the field and laboratory staff which number too many to mention without forgetting someone (the consequence of staying in grad studies a long time - a lot of help from a lot of people, and a failing memory). Graduate school is made so much easier when you are surrounded by well-meaning and scholarly mentors. I wholeheartedly thank my committee, Bart van der Kamp for providing the idea of the first section in our discussion in a directed studies, at a time when I had reached a mental dead end and was ready to quit; and Les Lavkulich who taught me just about everything I know about soils, and really acted as a co-supervisor. I hope I do his teaching justice. And of course I am indebted to Karel Klinka whom I have spent the better part of the last 10 years as employee and graduate student. I thank you once again for putting up with me over all these years, and contributing so much to my growth and learning. Life's travels during the times at grad school when the question often arises "What the heck am I doing here?", are made so much easier when you are surrounded by friends. To Charlotte Chiba, who once again I am indebted to for getting me through these times, a "thank you" cannot do justice for your support. My fellow grad students, Audrey Pearson, Han Chen, Hong Qian, and David New... I thank you for sharing in the struggle making this time bearable in our shared experiences. M y gratitude goes to Michael Pitt who taught me how science is suppose to be done and rekindled my interest in the philosophy of science. His stories on canoeing kept reminding me that there is life beyond the computer. We still need to do that canoeing trip together. Especially I thank my friend and editor Christine McClarnon (Fietkau) who took a rather poorly written second draft and converted it as best as she could (given the quality of the material), to a defendable final product. Thank you to my friend Pal Varga, for sharing both Christmas' and kayaking courses together. Keep on rolling! Of course I will never forget my friend, co-worker, kayaking partner, and adopted sister (although she gets mistaken for my daughter), Christine Chourmouzis. We have been through a lot together, and I look forward to the future where we can continue our adventure. Thank you for your friendship and for being my sister. I hope you find your path to happiness. Finally, grad school is made much easier if the travels are not done alone. To that, I thank with all my love my partner, and soon-to-be wife, Leanne M c Kinnon. You were my shining light struggling through this uphill battle. Being with you made all of this worth it. Now we are on another journey, and together we shall meet the future, and forever together we shall be. xi Chapter 1. G E N E R A L I N T R O D U C T I O N In temperate coastal forests of northwestern North America with long fire return intervals, coarse woody debris (CWD) accumulations in the form of snags, downed boles, and large branches can be large in natural forest ecosystems. For example, in the Cascade Mountains of Oregon, estimates of the annual recruitment rate of CWD in a coastal 450 year-old Pseudotsuga-Tsuga forest ecosystems are from 4.5 to 7.0 Mgha^yr"1 (Sollins 1982; Grier and Logan 1977). Such accumulations in coastal forests represent a mass of 81 to 190 Mg-ha"1 of logs on the forest floor (Preston et al. 1998; Larsen 1992; Sollins 1982; Graham and Kromack 1982; Franklin and Waring 1980; Grier and Logan 1977), and wood in various stages of decomposition can account for as much as 79% of the forest floor mass (Grier and Logan 1977) with a projected area up to 20.2 % (Harmon et al. 1986). The importance of the structural role of these CWD accumulations [terminology of Seidl (1985) referring to habitat for flora and fauna] has been recognized. Coarse woody debris is important for: (1) plant, animal, invertebrate and fungal habitat; (2) stream ecology; and (3) slope stabilization (Rydin et al. 1997; Stevens 1997; McMinn and Crossley 1996; Machmer and Steeger 1995; Caza 1993; Franklin et al. 1987; Harmon et al. 1986; Maser and Trappe 1984). However, the functional role of CWD [terminology of Seidl (1985) referring to energy and nutrient cycling] to forest short- and long-term productivity is not as well established (Caza 1993) , with the possible exception of the inland forests of the Rocky Mountains (Graham et al. 1994) . Statements on the importance of the functional role of CWD to forest short- and long-term productivity varies from important, to indifferent, to detrimental. For example: 1. Hagan and Grove (1999) state "dead wood provides a stable, long-term source of nutrients"; 2. Spies and Cline (1988) state "drastically reduced accumulations of coarse woody debris... might reduce productivity"; 3. Heilman (1990) argues that "on most sites there is no indication that logs are critical for either growth beyond the seedling stage or sustained productivity of forests"; 4. Klinka et al. (1990; 1995) state that the accumulation of decaying wood may result in a more acidic forest floor which may be associated with an increased intensity of podzolization. Chapter 1, Page 1 Since recommendations are now being made on the modification of harvesting and slash treatment practices to preserve the ground structure of CWD (see for example Graham et al. 1994), forest managers need a resolution to the question of the effect of CWD on short- and long-term productivity. In British Columbia (BC), recommendations are based on the presumption that "they [larger size pieces of CWD] provide the greatest longevity and potential for nutrient cycling"1, and the importance of CWD is entrenched in the policy definition of CWD - "sound and rotting logs and stumps that provide habitat for plants, animal, and insects and a source of nutrients for soil development."1 [emphasis added]. Additionally, most of our knowledge about CWD comes from the forests in the northwestern United States, where the characteristics and dynamics of woody materials may be different than coastal BC (Caza 1993). Although nutrient cycling with regard to CWD has been researched extensively, research is lacking on the "bottom-line" concerns of forest managers - is CWD necessary for maintaining site productivity? Therefore, I investigated some aspects of the short- and long-term functional aspects of CWD in order to augment local knowledge to help in developing slash treatment guidelines for B.C. When the management objective is commodity production using intensive forestry practices, forest managers need to know the effect of CWD on short- and long-term productivity. This thesis addresses two concerns of forest managers. The first is: 1. Is there an immediate nutritional or moisture supply advantage to leaving a legacy of CWD for the survival and growth of trees especially in comparison to non-woody humus forms in the coastal climate of British Columbia? The second forest management concern is: 2. Does decaying wood cause acidification of the soil directly beneath and increase the intensity of podzolization compared to non-woody humus forms? The first short-term productivity concern is reported in Section I, and the second long-term productivity question is reported in Section II. ' British Columbia Ministry of Forests. 1995. Forest Practices Code: Biodiversity Guidebook. Victoria, BC. Chapter 1, Page 2 S E C T I O N I: S H O R T - T E R M P R O D U C T I V I T Y The preservation of organic matter on a site is necessary to maintain maximum sustainable site productivity (Powers et al. 1990; Harvey et al. 1987), and fallen trees represent a "substantial reservoir of soil organic matter" (Maser et al. 1988). Although the importance of organic matter in maintaining forest productivity is not in dispute, the importance to soil productivity of organic matter from CWD is not known (Heilman 1990). The relationship between the presence of large fallen wood and site productivity has yet to be clearly demonstrated (Fisher and Binkley 2000). This section addresses the question of the immediate value of CWD as a source of organic matter for survival and growth of seedlings and mature (90 year old) trees. Forest managers operating under an objective of commodity production, need to know if a legacy of CWD maintains or increases short-term forest productivity by giving an advantage to survival and growth of trees on various sites and under various silvicultural systems. Coarse Woody Debris as a Source of Nutrients In past views, CWD was seen as important to nutrient cycling and the nutrient "savings account" metaphor (where nutrients accumulate during the decay process and are available at some undefined future where a critical C:N ratio allows for net nutrient mineralization) prevailed. This metaphor was supported by research showing that decaying wood provides a substrate for free-living nitrogen-fixing bacteria (Jurgensen et al. 1984, 1987) and showing an increase in concentration of nutrients, especially N (either based on a mass or volume basis) (Preston et al. 1998; Ostrofsky et al. 1997; Busse 1994; Keenan et al. 1993; Alban and Pastor 1993; Means et al. 1992; Arthur and Fahey 1990; Fahey 1983; Grier 1978; Lang and Forman 1978; Lambert et al. 1980; Foster and Lang 1982; Graham and Cromack 1982; Sollins et al. 1987). However, this metaphor is currently being questioned. With some exceptions (Fahey 1983), research generally shows that total nutrient levels (as opposed to nutrient concentrations) decrease as mass and volume decrease with later stages of decay; although in some cases nutrients appear to initially increase in the early stages of decay (Laiho and Prescott 1999; Krankina et al. 1999; Brown et al. 1996; Arthur et al. 1993; Lambert et al. 1980; Grier 1978). By the time decay class IV and V wood is reached (decay class IV and V logs are well-decayed wood which has a soft texture either in blocky pieces or powdery; Maser et al. 1988), there are much lower nutrient contents and high C:N ratio (Kayahara et al. 1996; Klinka et al. 1995; Sidle Section I, Page 3 and Shaw 1983; Foster and Lang 1982), and are composed primarily of recalcitrant lignin (Preston et al. 1990, 1998). Net mineralizable N does occur in decay class IV and V wood, despite C:N ratios that exceed 200 (Busse 1994; Edmonds 1987; Sollins et al. 1987), to the point where decay class IV and V is equal to that of the mineral soil (Hart 1999; Hope and Li 1997). However, this mineralization is much lower than that that occurs in non-woody humus forms (Hope and Li 1997). Thus the nutrient availability associated with CWD compared to other sources is considered minor (Laiho and Prescott 1999; Krankina et al. 1999; Busse 1994), especially compared to the net N dynamics of the non-woody forest floor (Hart 1999). Heilman (1990) suggests that CWD is unimportant to tree growth relative to other detrital pools. Coarse Woody Debris, Seedlings and Fine Roots Although nutrition research shows that CWD is relatively unimportant as a nutrient source, regeneration studies show that growth of seedlings on wood is as good or better than on mineral soil (Day 1964; Bernsten 1960), though moisture supply may have played a larger role over nutrients. Additionally, the importance of CWD as a nutrient and/or moisture source for trees is inferred from the association of fine roots and mycorrhizal root tips with CWD. Fine root mass and/or mycorrhizal root tips within CWD was greater than, or at least comparable to, non-woody forest floors in Northern Rocky Mountain forests (Harvey et al. 1978, 1979, 1986, 1987a,b). The latter indicates an important source of water and/or nutrients for trees according to the concept of "root foraging" (Cook 1983; Santantonio and Hermann 1985). Research Focus Jurgensen et al. (1990) suggest that CWD is important to tree survival and growth in the Northern Rocky Mountain Forests, but is unimportant or even detrimental in the wetter and colder climates of coastal Alaska. In this section, I investigated whether this reported importance of CWD, inferred for the interior climates of the Rocky Mountains, extends to the wetter climates of the coastal BC. The association between wood and seedlings and saplings is particularly strong in forests of coastal BC, leading one to expect that the relationship between trees and wood is obligatory. Thus CWD may have an immediate value for short-term productivity. Chapter 2 reports on the results of a trial using seedlings planted in various woody and non-woody substrates. Chapter 3 reports on the results extended to mature (90 year-old) Section I, Page 4 trees using the proliferation of fine roots as an indicator of substrates that are important to tree survival and growth. Section I , Page Chapter 2. S U R V I V A L A N D G R O W T H O F P L A N T E D S E E D L I N G S O N W O O D Y A N D N O N - W O O D Y F O R E S T F L O O R S U B S T R A T E S I N H I G H A N D L O W L I G H T E N V I R O N M E N T S O F C O A S T A L B R I T I S H C O L U M B I A Introduction In the wetter climates of coastal North America, coarse woody debris (CWD) forms a large portion of the organic matter pool on the forest floor (Harmon et al. 1986). Associated with these CWD accumulations is an abundance of regeneration growing upon stumps and downed logs in the understory of old-growth coastal forests (Harmon and Franklin 1989; Harmon et al. 1986; Christy and Mack 1984; Franklin et al. 1981; Triska and Cromack 1980; Franklin and Dyrness 1973; Minore 1972; Taylor 1935). The association between trees and woody microsites is so prevalent that the description embodied in the metaophor of a "nurse log" is commonly accepted (Maser et al 1979, 1988). The question remains though, whether CWD is a necessary component for seedling survival and growth in forests managed for commodity production. The reported importance of CWD to seedling growth compared to non-woody forest floors, and mineral soils is variable (Table 2.1). Since the results of these studies are not decisive, this study was undertaken using species of the coastal forest of BC, an area where the association between seedlings and saplings with CWD is particularly strong. The objective was to determine whether there is greater survival and growth for seedlings planted in decaying wood compared to non-woody humus forms and mineral soil under two different light environments (heavy shade and full light conditions) on coastal BC. Low light environments are of particular interest since reports of the high association between decaying wood and regeneration has primarily referred to understory seedlings and saplings in old-growth forests. The nutrientx light interaction has been shown using nitrogen fertilizer treatments under controlled shaded conditions in greenhouses. Fertilized seedlings are larger than unfertilized seedlings in full light conditions, but are the same size under shaded conditions (Reed et al. 1983; Canham et al. 1996; Walters and Reich 1996). However, studies of actual forest floor substrates under natural light conditions are few. Actual substrates are necessary since foresters are interested in whether seedling growth increases or decreases by using CWD as a regeneration medium. Chapter 2, Page 6 a o S3 o p . 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Seedlings of three tree species common to coastal BC, western hemlock (Tsuga heterophylla (Raf.) Sarg.), Pacific silver fir {Abies amabilis Dougl. ex Forbes), and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), were used. Seedlings were planted in plastic pots under both open light and shaded conditions. Materials and methods Study sites Three study sites were located in one watershed north of Vancouver, British Columbia (49°05'N, 122°30'W) located in the Submontane Very Wet Maritime Coastal Western Hemlock variant (CWHvml) (Green and Klinka 1994). The climate associated with this variant is mild, humid (mesothermal) with warm summers and no dry season (Cfb by Koppen; cited in Trewartha and Horn 1980). Heavy precipitation, upwards of 4000 mm annually, and the mild oceanic climate, with mean annual temperature approximately 8°C, are characteristic of this climate. The morphology and soil characteristics of the three sites were similar. Soils were identified as Humo-Ferric Podzols (Soil Classification Working Group 1998). Humus forms groups were identified either as Hemimor or Humimor (Green et al. 1993), 10-15 cm thick, including pockets of Leptomoder, 5 cm thick. The soil moisture regime was identified as fresh (no water deficit or excess), and the soil nutrient regime as medium using the methods outlined in Green and Klinka (1994). The sites were separated by clearcuts along the same south-facing slope (Table 2.2). Each site included a clearcut and an adjacent old-growth stand. Clearcutting occurred between 1990 and 1991. The clearcuts were 4-5 ha in area. Adjacent old growth forest stands, dominated by Douglas-fir, western hemlock, Pacific silver fir, and western redcedar (Thuja plicata), were characterized by canopy trees 60 m in height, 300-750 years of age, and 100-200 cm diameter at 1.3 m above the germination point. Experiment In April 1995, six plots of approximately 100 m in area were established, one in the center of each clearcut and one in each of the adjacent forest understories. At least 100 m from the edge Chapter 2, Page 8 of clearcuts, understory plots were established under old-growth forest stands which were relatively uniform in stand structure, understory vegetation, and light condition (Figure 2.1). The light conditions of the understory and clearcut plots were measured simultaneously. In each of the understory plots, a sunfleck ceptometer (model SF-80 Decagon Devices, Pullman, Wash., U.S.A.) was placed at 60 cm above the ground at plot centre. In each of the clearcut plots, three LI-COR 190 SA sensors, each connected to a LI-1000 datalogger (LI-COR Inc., Lincoln, Nebr., USA), were placed in the plot centre. The instruments were calibrated and their clocks were synchronized prior to taking measurements. All instruments were programmed to take one measurement every minute, and to average the measurements every 30 minutes. On sunny, summer days (June 30 to July 3, 1996), the mean daily photosynthetic photon flux density 2 1 2 1 (PPFD) was 42.3 mol m" day" in clearcuts and 1.25 mol m" day" in the forest understories (Table 2.3). The forest understory received only 3% of the PPFD in the clearcuts. Within each of the two light regimes, the differences in light availability among plots were small (Figure 2.2). T A B L E 2.2. Characteristics of the study sites in coastal British Columbia. Site 1 Site 2 Site 3 Clearcut Understory Clearcut Understory Clearcut Understory Elevation (m) 585 625 560 560 560 570 Aspect (°N) 160 180 148 152 160 142 Slope (%) 32 32 18 15 35 35 T A B L E 2.3. Light environments for clearcuts and adjacent old-growth forest understories in coastal British Columbia. Measurements were recorded for three consecutive, predominately sunny days in from June 30 to July 2, 1996. Daily mean photosynthetic photon flux density values are averages for measurements made between 06.00 and 21.00 local time. The standard error is given in brackets. Light descriptor Clearcut Understory Daily total PPFD (mol m"2 day"1) 42.3 (4.5) 1.25 (0.15) Daily mean PPFD (pmol m"2 s'1) 759 (75) 20.2 (4.2) Chapter 2, Page 9 < • < • > 100 m * 100 m F IGURE 2.1. A series of planting pots filled with the three indicated substrates were placed at the centre of a clearcut and beneath the overstory of an adjacent old growth forest. Seedlings of western hemlock, Pacific silver fir, and Douglas-fir were planted in the pots. This main effect set-up was replicated in three clearcut-old growth forest pairs. The understory vegetation within each plot was cleared. Three types of soil substrates, woody debris of decay class IV and V, non-woody forest floor (L, F , and H horizons), and mineral soil (Ahe and Bf or Bhf horizons) were collected nearby each plot and a sample of uniform substrate was put into a planting pot (20 cm top diameter, 17 cm base diameter, 25 cm height). One sample of each substrate was taken from each plot to determine its nutrient properties. Samples for nutrient determination were air dried to constant mass. Mineral soil samples were passed through a 2 mm sieve and stored for chemical analyses; forest floor and decaying wood samples were ground with a Wiley mill to pass through a 2 mm sieve, and stored for chemical analyses. The following chemical analysis was undertaken for both forest floor and mineral soil samples, and expressed as a concentration on a unit of soil mass basis. The pH was measured with a pH meter and glass plus reference electrode in water, using a 1:5 suspension for Chapter 2, Page 10 forest floor material and a 1:1 suspension for mineral soils. Total C was determined by dry oxidation (combustion) with an induction furnace. Evolved CO2 was then determined with thermal conductivity measurements of the effluent gas using a Leco Induction Furnace and Carbon Analyzer (Tabatabai and Bremner 1970; Bremner and Tabatabai 1971). Total N was determined by semimicro-Kjeldahl digestion with H2SO4, followed by colourimetric determination of ammonium in the digest (Bremner and Mulvaney 1982) using a Technicon Autoanalyzer (Anonymous 1976). Mineralizable N was determined by an anaerobic incubation procedure (Waring and Bremner 1964) as modified by Powers (1980), where the soils were incubated at 40°C for 7 days. Released ammonium was determined colourimetrically with the use of a Technicon Autoanalyzer. Extractable P was determined by the Mehlich III method where P was extracted by reaction with acetic acid and fluoride compounds, and the extracted P determined by the Mo blue colourimetric method (Mehlich 1984). Total SO4-S was determined by the reduction of sulphate to H2S with a reagent containing hydriodic acid; and the H2S liberated was determined by methylene blue colour development (Johnson and Nishita 1952). Extractable K, Ca, and Mg were extracted with neutral 1 N ammonium acetate (NH4OAC), and determined by atomic emission spectrometry (Wood and Deturk 1940). In each of the six plots, 180 pots were set up for a total of 1080 pots (3 substrates x 60 pots/substrate * 2 light conditions/replicate * 3 replicates). Pots were placed together, and a berm was constructed around the pots. The spaces between the pots were filled with a combination of mineral soil, wood, and humus material. In April 1995, 1-year-old, styrofoam container-grown seedlings of western hemlock, amabilis fir, and Douglas-fir were obtained from a nursery (Pacific Regeneration Technology, Ltd., Vancouver, BC). Before planting, each seedling was measured for height and base diameter. Within each plot, 60 seedlings of each species were then planted in 60 separate pots, with 20 of the pots containing one of the three substrates (3 species x 3 substrates x 20 pots). Twenty additional seedlings for each species were taken to the laboratory to determine height, caliper, total leaf area, and dry weight of leaves, branches, stem, and roots. Within each plot, a completely randomized layout was implemented for species and substrates, with one seedling planted per pot. Measurements of survival and growth In September 1996 (i.e., after two growing seasons), seedling survival surveys were conducted. Any visible damage such as dieback, foliage chlorosis, browsing, pathological symptoms, and Chapter 2, Page 11 other injuries was noted. Three healthy seedlings from each of the three replicated sites, two light conditions, three substrates, and three species were randomly sampled. Only a total of 155 seedlings were sampled as most of the Douglas-fir seedlings in the understory plots were either dead or damaged at the end of the second growing season. Seedling height and basal diameter were measured in the field, after which the seedlings were taken to the laboratory to determine dry weight of leaves, branches, stem, and roots. The total biomass for each sampled seedling was the sum of dry weight of leaves, branches, stem, and roots. 2000 1500 o E a. Q O, 1000 500 2000 1500 o E Q u-0-Cu IOOO A 500 H 2000 -r 1500 -CN e "o E 1000 -1 PPFD 500 -4 6 Solar time (hour) FIGURE 2.2. Representative daily light environment pattern for the three study sites. Solid lines represent clearcuts, and dashed lines, understories. Measurements were taken simultaneously on July 1,1996. Chapter 2, Page 12 Statistical analysis The nutrient measures were treated as a split-plot design with three replicates. The two light conditions were the main effects, and the three substrates were the split-plot effects. If differences in the split-plot effects were significant, Tukey's multiple range test was used to test for differences between the three substrates. Survival was calculated as the proportion of surviving seedlings to total planted seedlings. To eliminate factors other than light and soil substrate, seedlings with signs of browsing were not included in calculations of survival. Proportion of survival, weighted by the number of all seedlings within each group, was tested with likelihood ratio chi-square (% ) tests following Hicks (1993) and Neter et al. (1996). For growth measures, the experimental design was a split-plot design (Hicks 1993). Light (L) was the main effect (whole-plot) and replicated in three clearcuts and old-growth forest understories. Species (P) and soil substrate (S) were arranged in a completely randomized layout within each of six whole-plots. The analysis of variance (ANOVA) was used to detect effects of light, soil substrate, and species on growth parameters: Yijklm = M + Ri+Lj+RxLij+Sk + RxSik + Pt + Rx Pti + S x Pkl + Rx S x Pkl + LxSik +Rx LxSijk + Lx Pji + Rx Lx Pyi + LxSx Pjkl + Rx LxSx Pijk! + e3m^jk^ where Yijkim is an observation for a particular dependent variable; ju is the overall mean of the dependent variable; Rj (i = 1, 2, 3) is the site replicates; Lj (j = 1, 2) is the effect of light; RxLjj is the experimental error of whole-plot to test the effect of light; Sk (k = 1,2, 3) is the effect of soil substrate; RxSjk is the error to test the effect of soil substrate; Pi (1 = 1, 2, 3) is the effect of tree species; RxPn is the error to test the effect of species; SxPk) is the interaction of substrate and species; RxSxPiki is the error to test the interaction of substrate and species; LxSjk is the interaction of light and substrate; RxLxSjjk is the error to test the interaction of light and substrate; LxPji is the interaction of light and species; RxLxPyi is the error to test the interaction of light and species; LxSxPjki is the interaction of light, substrate, and species; Rx LxSxPjki is the error to test the interaction of light, substrate, and species; and sm(ijki) is the sampling error within treatments and replicates. If differences were significant, Tukey's multiple range test was used to detect for differences between substrates. Chapter 2, Page 13 Results Nutrient properties were significantly different among the three substrates (P < 0.05), but did not differ between the clearcut and the understory (Table 2.4). A significant difference in pH was not detected between the woody and non-woody substrates, although both were significantly more acid than the mineral soil. The non-woody substrate had significantly greater concentrations of all nutrient measures except extractable Mg compared to the woody substrate. The woody substrate had greater concentrations of total N, mineralizable N, extractable P, K, Ca, and Mg than the mineral soil. However, since mineral soil has a bulk density approximately six times larger than both woody and non-woody substrates (Sidle and Shaw 1983), on a volume basis, the differences change - the largest nutrient measures are associated with the non-woody substrate (although to a much lesser degree), but the smallest nutrient measures are associated with the woody substrate. The effects of light conditions and soil substrates on survival varied significantly among the three species (P < 0.05; Fig. 2.3). Douglas-fir survival was significantly higher in clearcuts than in the understories, but was not significantly affected by soil substrate. Survival of western hemlock was also not affected by soil substrates, but was significantly higher in the understories. Survival of Pacific silver fir was significantly lower on woody substrates in the clearcuts than in the understories, but not different among other growing conditions. After two growing seasons, surviving seedlings had significantly different growth rates influenced by growing conditions (Table 2.5). A significant interactive effect between light and soil substrate was apparent for all measures of seedling growth (Table 2.5, Figures 2.4 and 2.5). The diameter, height, and total biomass of Douglas-fir and western hemlock seedlings were significantly smaller in the understories than in the clearcuts. The effect of light on diameter and height growth in Pacific silver fir was less pronounced than that for Douglas-fir and western hemlock, but total biomass of seedlings was significantly smaller in the understories than in the clearcuts. In the understory, no significant differences were detected for all measures between the rooting substrates for the three species. However, the clearcut was completely different. Douglas-fir seedling diameter, height, and total biomass were significantly greater in the non-woody substrate compared to the woody substrate; but significant differences were not detected between the seedlings growing in the non-woody substrate versus the mineral soil. Additionally, significant differences in diameter were not detected between the seedlings growing in the woody substrate versus the mineral soil. Western hemlock seedling diameter, height, and total Chapter 2, Page 14 biomass were significantly greater in the non-woody substrate compared to both the woody substrate and mineral soil, but significant differences were not detected in these measures between the seedlings growing in the woody substrate versus the mineral soil. Pacific silver fir seedling diameter and height were significantly greater in the non-woody substrate compared to both the woody substrate and mineral soil, but significant differences were not detected between these measures for the seedlings growing in the woody substrate versus the mineral soil. However, there were significant differences in total biomass between the three substrates. Discussion The location in the summer wet climate of the CWHvml variant of BC, presumably eliminates moisture as a factor in substrate advantage to seedling survival and growth. There was no indication that the summer weather during the period this trial was set up was unusually dry or wet. However, the use of planting pots with small volumes of rooting substrate means that different moisture availability associated with the three different substrates may have played a role. A greenhouse trial (Chapter 3) in part addressed this point by allowing full control over moisture conditions. Except for Pacific silver fir, substrate did not appear to influence seedling survival after two growing seasons. Seedling growth though, was substrate dependent in the clearcut but not substrate dependent under shaded conditions. The nutrientxlight interaction is as apparent for natural substrates under natural lighting conditions as for nitrogen fertilizer treatments under controlled shaded conditions in greenhouses (Reed et al. 1983; Canham et al. 1996; Walters and Reich 1996). However, natural substrates do differ in response compared to fertilizer treatments. In the open, both western hemlock and Pacific silver fir grew best in the non-woody organic substrate compared to the woody substrate and mineral soil. This relationship has a general positive correlation with the nutrient measures of the substrates on a mass basis. However, when expressed on a volume basis, the mineral soil has larger nutrient availability compared to the woody substrate. Thus, the growth of all three species in this study does not strictly follow the nutrient availability of the three substrates. Significant differences in growth between open grown seedlings in the non-woody organic substrate compared to seedlings in the mineral soil were non-detectable or greater in the organic substrate. Comparing open grown seedlings in the woody and non-woody organic substrates, growth followed the nutrient availability associated with the substrates. Woody and non-woody nutrient measures on a mass basis are comparable Chapter 2, Page 15 since the bulk densities of decay class IV and V wood is similar to non-woody humus substrates (Sidle and Shaw 1983). T A B L E 2.4. Mean nutrient properties (standard error in brackets) of the woody substrate, non-woody substrate, and mineral soil (sample size is three for any given substrate and light condition). Values with the same letter in the same row are not significantly different (p < 0.05). Nutrient properties Woody substrate Non-woody substrate Mineral soil Clearcut understory Clearcut understory Clearcut Understory pH 3.5b 3.4b 3.9b 3.6b 4.6a 4.9a (0.1) (0.1) (0.1) (0.3) (0.1) (0.2) total C (%) 50.3a 50.1a 43.5a 46.4a 4.4b 8.1b (0.9) (0.9) (2.5) (1.7) (1.1) (5.6) total N (%) 0.22b 0.20b 1.09a 0.94a 0.15c 0.09c (0.04) (0.02) (0.05) (0.22) (0.01) (0.02) C:N 239a,b 251a,b 40b,c 57b,c 29b,c 124b (32) (22) (1) (17) (7) (100) min-N (mg/kg) 55b 48b 344a 309a 24c 11c (10) (8) (103) (119) (5) (2) extractable P (mg/kg) 24.2b 14.1b 48.7a 60.3a 5.7c 2.4c (8.3) (6.4) (10.5) (25.2) (4.7) (2.1) total S04-S (mg/g) 0.30b 0.42b 2.20a 1.62a 0.23b 0.75a,b (0.07) (0.03) (0.35) (0.28) (0.05) (0.3) extractable K (mg/kg) 21.3b 30.3b 74.3a 133.3a 11.7c 5.7c (0.3) (2.8) (12.1) (32) (2.2) (0.3) extractable Ca (mg/kg) 633b 368b 1867a 1023a 70c 37c (44) (71) (349) (328) (15) (2) extractable Mg (mg/kg) 133.3a 161.7a 203.3a 211.7a 8.7b 5.3b (7.3) (29) (16) (21) (0.7) (1.5) The results of this study have greater power (1-P) than Bernsten (1960) for Douglas-fir growing in full light conditions. Bernsten (1960) was unable to detect significant differences between 4-year total height of seedlings growing in decayed wood compared to mineral soil. This study showed that there were significant differences in 2-year growth of seedlings between the two substrates. Kropp (1982) and Christy et al. (1982) researched the growth of five year-old western hemlock (Tsuga heterophylla) seedlings growing in the shade on different substrates. Similar to this study, they did not detect differences in height growth of seedlings growing in Chapter 2, Page 16 decay class logs III to V (decay class III logs are semi-decayed wood which has a hard texture in large blocky pieces; Maser et al. 1988) compared to seedlings growing in mineral soil, and the difference in mean values was very small. T A B L E 2.5. Effects of light (Lj), soil substrate (Sk), and species (P i ) on growth parameters. Differences are significant at ***p < 0.001, **p < 0.01, *p < 0.05, and/? > 0.05 (ns). Source 1 DF Diameter (mm) Height (cm) Total mass (g) MS F MS F MS F R. 2 10.1 704.4 102.5 1 846.0 2437*** 6405 91.1* 27512 603** RxLij 2 0.3 70.3 45.6 S k 2 63.7 31.5** 1249.9 10.0* 3261.3 28.2** RxS i k 4 2.0 124.5 115.6 P, 2 226.0 167.7*** 9780.2 72.0*** 7337.4 369.0*** RxPi, 4 1.3 135.9 19.9 SxP k l 4 6.9 8.4** 296.6 7.8** 402.6 4.4* RxSxP i k , 8 0.8 38.0 90.8 LxSj, 2 60.7 19.6** 1051.0 14.8* 3463.1 26.2** RxLxSjji 4 3.1 71.0 132.4 LxPji 2 71.5 35.0** 1273.5 2.2ns 5131.6 43.6** RxLxPjj, 4 2.0 592.3 117.8 LxSxPjk] 4 3.1 12.2** 168.2 5.3* 285.8 3.1ns RxLxSxPjj ki 8 0.3 31.6 92.1 Em(ijkl) 102 2.5 83.1 184.1 Sources are the same as in the model [1]. Chapter 2, Page 120 80 Douglas-fir cd & 40 a a a b b b rh if! o u Light condition Western hemlock 120 80 3 C / J 40 m i • b b b *$ i t i o u Light condition Pacific silver fir o u Light condition FIGURE 2.3. The effect of light condition (U - understory and O - open clearcut) and soil substrate (within each light condition, the bars are in the order woody substrate, non-woody substrate, and mineral soil) on survival at the end of the second growing season. Error bars represent 1 standard error of the mean. Values with the same letter are not significantly different (p < 0.05). Chapter 2, Page 1 o u Light condition 1 0 0 8 0 J , 6 0 •a 4 0 2 0 0 Douglas-fir a a a o u Light condition O U Light condition O U Light condition 2 0 ^ 15 E E, B s 5 Pacific silver fir a,c c c +1 ll o u Light condition 1 0 0 8 0 §, 6 0 I 40 2 0 0 Pacific silver fir b a a a,b a a 1 -t-1 •A f 1 0 U Light condition FIGURE 2.4. Base diameter and total height of planted seedlings in relation to light condition (U -understory and O - open clearcut) and soil substrate (within each light condition, the bars are in the order woody substrate, non-woody substrate, and mineral soil) at the end of the second growing season. Error bars represent 1 standard error of the mean. Values with the same letter are not significantly different (p < 0.05). Chapter 2, Page 19 1 0 0 F S o "ca o 10 Douglas-fir C C C O U Light condition B o H o u Light condition O U Light condition FIGURE 2.5. Total biomass of planted seedlings in relation to light condition (U - understory and O - open clearcut) and soil substrate (within each light condition, the bars are in the order woody substrate, non-woody substrate, and mineral soil) at the end of the second growing season. Error bars represent 1 standard error of the mean. Values with the same letter are not significantly different (p < 0.05). Chapter 2, Page 20 Despite the problem with the shade tents used by Minore (1972), and his use of the "largest surviving seedling" as opposed to the mean, his results are very similar to this study. Shade tents confound reduced light level treatments with changes in temperature of air and root medium, air turbulence and relative humidity that are different from natural conditions (Waggoner et al. 1959). Minore (1972) also observed a nutrient-by-light interaction for all three species using woody and non-woody organic substrates. The height and total biomass of seedlings growing in the non-woody forest floor substrates was greater than those in the woody substrates in full light but the difference in height and weight were much less pronounced under heavy (2% of full sunlight) shade treatment. Although CWD is a nutrient poor substrate, there may be one possible advantage to the slower seedling growth associated with woody substrates or mineral soils under high light conditions. If a small gap is created, then seedlings and saplings growing in the non-woody forest floor would grow in response to the increased light conditions. The seedlings growing on CWD or on exposed mineral soil (such as found on a windthrow root mound) would likely maintain a slower growth rate. Under subsequent rapid canopy closure however, seedlings growing on the non-woody forest floor may have exceeded their "waiting height" (Kubota et al. 1994), a maximum sustainable height for the new shaded light conditions (Givinsh 1988). Consequently, seedlings growing on the non-woody forest floor may not survive when the gap subsequently closes. The seedlings growing on CWD or exposed mineral soil however, may be able to survive in the post-gap low light conditions since their constant slow growth, even in response to increased light, may mean that the maximum sustainable height for the shaded conditions is not exceeded. Some caution is needed when extending the results to formulate management recommendations. One concern is that only one seedlot was used for each of the species for all three replicates. These results are dependent upon each respective seedlot not being a genetically anomalous group having nutrient and moisture uptake properties different from the rest of the population of each respective species. A bigger concern is that pots were used rather than out-planting under non-restricting root conditions. The choice of pots was made for two reasons: 1) to reduce variability, and 2) to allow the measurement of root biomass. Under completely natural conditions, the variability in response in growth in each substrate may be confounded with not being able to isolate the substrate the roots actually grow in. A seedling may be planted in decaying woody but the roots may proliferate in the adjacent non-woody humus form or mineral soil. The large variability under field conditions may be the reason for the lack of power Chapter 2, Page 21 in detecting significant differences in past studies (Loopstra et al. 1988; Bernsten 1960). In addition, the shaded understory variation can be reduced when using pots by grouping the pots within homogenous light conditions as possible. The second reason, to include root biomass, was based on the possibility that total biomass may be a more sensitive measure to capture any growth differences. Seedlings may not respond to a great degree in increased above ground biomass but may respond in increased below ground biomass. Measurement of the above ground biomass only may lead to tests that do not detect differences. Indeed, in the case of Pacific silver fir, total biomass showed differences more clearly than either height or diameter. By creating a berm and filling in between the pots, I attempted to minimize any pot effect. Nevertheless, small pot effects must be recognized since root restriction is known to be a limiting factor when using small pots (Will and Teskey 1997; Thomas and Strain 1991). However, in this study any reduction in growth due to root restriction would tend to dampen differences so the pot effect actually favours the null hypothesis. Any significant differences that were detected then, would presumably be even greater if pots were not used. Thus the effect on qualitative differences (i.e, comparative growth rates between substrates) would not be a concern, but the results should not be used as a measure of quantitative (i.e, actual growth rates) differences. Conclusions Similar to southeastern Alaska, CWD does not provide any advantage for seedling growth in the wetter climates of south coastal BC, on sites not having a water deficit or excess. Greater availability of nutrients and increased growth are associated with the non-woody humus substrate. Thus the non-woody humus layer is by far the most important organic material to maintain after any logging practice. On the other hand, CWD is not as poor a substrate for seedling growth as implied by its high C:N ratio, lower nutrient content, and recalcitrant lignin composition. Decay class IV and V wood is as good as mineral soil for the growth of western hemlock and Pacific silver fir seedlings. Douglas-fir, however, does not grow as well in woody substrates compared to non-woody organic substrates and mineral soil. When seedlings are established under shaded conditions, rooting substrate appears not to make a difference for growth. Chapter 2, Page 22 Chapter 3. T H E A S S O C I A T I O N B E T W E E N W E S T E R N H E M L O C K F I N E R O O T S W I T H W O O D Y A N D N O N - W O O D Y F O R E S T F L O O R S U B S T R A T E S IN C O A S T A L B R I T I S H C O L U M B I A Introduction In chapter 2,1 concluded that a legacy of coarse woody debris (CWD) is not necessary for seedling survival and growth on sites without a water deficit or excess in the summer wet climate of coastal British Columbia (BC). In this chapter, I examine the importance of CWD to the immediate nutrition or moisture requirements of mature (90 year old) trees. The investigation of mature trees is necessary since results of the nutrition requirements of seedlings can not necessarily be extended to mature trees. Because of the difficulty in experimenting with 100 year-old trees growing in different substrates, I utilized fine root distribution, or proliferation, as an indicator of important substrates. This chapter extends, with some modification, the research of Harvey et. al. (1987b) from the Northern Rocky Mountains of the United States to the coastal forests of BC. However, Harvey et al. (1987b) used mycorrhizal root location as a "bioindicator" of the importance of woody forest floor substrates, where I used the proliferation of very fine and fine roots. A greenhouse study using seedlings was initially carried out to test the applicability of the use of root proliferation as a biodindicator with western hemlock and using woody and non-woody substrates. This controlled trial was then followed by sampling in a mature (90 year old) western hemlock second-growth forest. Roots as Indicators Roots in higher plants have the tendency to proliferate in locally rich patches of water or nutrients (Cook 1983; Santantonio and Hermann 1985). Such local root growth stimulation has been reported for agriculture species (Drew et al. 1973; Drew 1975; Drew and Saker 1975, 1978; Larigauderie and Richards, 1994; Robinson 1994), and for some forest tree species (Coutts and Philipson 1976; Philipson and Coutts 1977; Kimmins and Hawkes 1978; St. John 1983; Friend et al. 1990; George et al. 1997). Local root growth stimulation has also been associated with local concentrations of soil humic acids (Van de Venter et al. 1991). Therefore, if one accepts the "root foraging" concept, whether for nutrients or moisture, then we have a method which Chapter 3, Page 23 integrates nutrition and moisture importance into one measure. Root proliferation can be used to test the relative importance of CWD to tree survival and/or growth for mature trees (approximately 90 years old) compared to non-woody forest floor substrates and to mineral soil. This method is simpler than (i) measuring nutrients of each substrate directly, and then determining the critical amounts available for plant uptake; (ii) directly measuring the solution from each substrate that is being taken up by trees through the use of suction lysimeters, and then determining whether these amounts meet the trees' needs; or (iii) resolving whether Maser et al. (1988) are correct in the claim that the nitrogen from decaying wood becomes available for plant growth at higher C:N ratios, and then determining a critical C:N ratio. Additionally, using root proliferation circumvents determining exactly why certain substrates are favourable or detrimental to tree survival and growth. Identifying the many interacting factors important to trees (which include soil nutrients, moisture, aeration, microbial populations) are reduced to one factor - if there is a proliferation of roots in a certain substrate, then that substrate must be of some benefit to the tree. Root Proliferation and Decaying Wood Reports of a strong association between roots and decaying wood have been both anecdotal and experimental. Ausmus (1977) postulated that "root distribution and root uptake has been dominated by the development of soil organic matter beneath and within log substrates." Maser and Trappe (1984) stated that "in general, as decay proceeds, plant rooting increases in all substrates (bark, sapwood, heartwood) because they become excellent rooting medium." This claim has been supported by unpublished data of Sollins and Cline (cited in Maser and Trappe 1984) which shows that "when a tree reaches decay class IV... nearly all our samples (87 percent) contained roots. Finally, trees in decay class V are not only completely colonized by roots but are actually held together by them." Similarly, Triska and Cromack (1980) stated "root systems may bind the decayed material [wood] into a coherent structure." Eis (1974,1987) found, in excavations of western hemlock roots, that although the concentration of fine roots was in the organic horizon and top 10 cm of mineral soils, the roots also tended to follow buried wood. Day (1964) reported that the lateral root development of four to six year-old hybrid spruce (Picea engelmannii x P. glauca) seedlings growing on logged-over land is best on decayed wood compared to mineral soil and non-woody humus; and that spruce seedlings Chapter 3, Page 24 produce extensive lateral roots running parallel to the tracheids along planes of weakness in rotten logs. The most compelling evidence of the association between roots and CWD is from the northern Rocky Mountains forests of the United States where class IV logs gradually become well permeated with roots as it decays into class V. Although the intent of the research by Harvey et al. (1976, 1978, 1979, 1986, 1987a,b) was to investigate mycorrhizal relationships, not to examine substrate importance using the root foraging concept, their research easily extrapolates into the latter. It is thought that well-rotted wood provides a moist substrate in which mycorrhizal fungi and roots can continue to interact into the summer, well beyond the time that fungi and fine roots have become dormant or dead from drought in the upper layers of mineral soil. Thus, well-rotted wood is considered to be important on dry sites within dry climates of the Rocky Mountain Forests (Harvey et al. 1978; 1979; 1986). However, even the mesic sites dominated by western hemlock (in what would be equivalent to zonal sites within the Interior Cedar Hemlock zone of BC; Lloyd et al. 1990) has more, or at least comparable, amounts of mycorrhizal root tips associated with wood than either the non-woody humus forms or mineral soil (Harvey et al. 1979, 1986, 1987a,b). Such sites are thought only to have a small growing season water deficit from 0-30 days (Lloyd et al. 1990). The conclusion reached by Harvey et al. (1976, 1978; 1979; 1986) for dry sites within dry climates appears to also apply to mesic sites within wetter climates of the "interior wetbelt". By the "root foraging" concept, the implication of the presence of greater amounts of mycorrhizal root tips in decaying wood compared to either non-woody forest floor substrates or mineral soil is that wood is important to tree growth and/or survival in the Rocky Mountain forests of the United States in both dry (Interior Douglas-Fir zone equivalent in BC) and wet (ICH equivalent in BC) climates (zone descriptions are given in Lloyd et al. 1990). Research Approach In this chapter I used the presence of root proliferation to test whether the results of Harvey et al. (1976, 1979), reported for xeric and mesic sites within the forests of the Rocky Mountains can be extended to the wetter summer climates of coastal BC. The objective was to investigate whether the very fine and fine roots (<1 mm and 1-2 mm in diameter, respectively) of mature western hemlock (approximately 90 years old) proliferate to a different degree in different forest floor rooting substrates. Western hemlock was chosen since it is most strongly associated with CWD Chapter 3, Page 25 (Krajina 1969; Minore 1972; Franklin and Dyrness 1973; Christy and Mack 1984; Harmon and Franklin 1989). If root proliferation is more strongly associated with CWD compared to non-woody forest floor substrates and mineral soil, then the implication is that CWD provides an immediate benefit as a moisture and/or nutrient source. Initially, a greenhouse pot trial was undertaken, given that there is evidence that some conifer tree species may not respond with increased root growth in nutrient-rich soil (George et al. 1997). Thus, I first examined the applicability of using root proliferation as a bioindicator of important substrates to trees. In the greenhouse trial, seeds were germinated in pots where one-half of the pot contained one type of forest floor substrate and the other half a different substrate. This trial served three purposes: 1) to demonstrate that western hemlock does exhibit the "root foraging" ability; 2) to examine whether root proliferation in a certain substrate is correlated to growth; and 3) to provide a further test of the importance of decaying wood to seedlings. The first two purposes, then, serves as a test of the applicability of the root proliferation technique as a method of determining the importance of decayed wood to western hemlock productivity. In the field study, western hemlock stands approximately 90 years old were sampled. Fine and very fine root mass were measured in decay class II and IV logs, mor and moder humus forms, and the top 10 cm of the underlying mineral soil. Sampling took place during the summer, since it is during the drier months that mycorrhizal root tips are most common in CWD in the Rocky Mountain forests (Harvey et al. 1978). Methods Greenhouse Study Three substrates (non-woody humus form, decay class IV wood, and a fresh mixture of western hemlock sawdust and wood chips) were used. The forest floor and decaying wood substrates were collected from the Capilano watershed north of Vancouver (site description is given in Chapter 2), and the hemlock sawdust and wood chips were purchased from a local sawmill. Chemical analyses of the three substrates showed very different nutrient concentrations (Table 3.1). After air-drying the substrates to constant mass, a series of plant pots (20 cm top diameter, 17 cm base diameter, 25 cm height) were filled half with one substrate and half with another substrate. This half-half combination per pot was used since the root "foraging" concept is based Chapter 3, Page 26 on the proliferation or roots in adjacent substrates. Two combinations were used (i) a non-woody humus form versus decay class IV wood; and (ii) a non-woody humus form versus wood chips-sawdust mixture. Additionally, a series of plant pots were fdled half with one substrate and then the other half with the same substrate (Figure 3.1). T A B L E 3.1: Chemical measures (as described for the field study) for the three substrates used in the greenhouse pot experiment. substrate pH total C (%) total N (%) C:N non-woody forest floor 3.7 48.0 1.6 30 decay class TV wood 3.4 58.8 0.6 98 hemlock wood chips 4.5 46.8 0.1 468 FIGURE 3.1: Greenhouse pot set-up with each pot divided into two substrates. Western hemlock seed was sown along the centre line of each pot. The pots are distributed randomly within a 20 cm tall styrofoam berm in the greenhouse with the middle separation line pointing south (i.e., south is to the right of the figure). Ten pots each of the top two combinations, and 5 pots each of the bottom three combinations were used. Ten pots each of the two mixed substrates combinations, and five pots each for the Top View Chapter 3, Page 27 homogeneous substrates were set up. The planting pots were randomly located within a square styrofoam 20 cm tall berm in a greenhouse, with the orientation of the line created by the two substrates pointing south. A coin flip determined which substrate was placed east of the southerly orientation. In May 1997, western hemlock seeds from a Vancouver Island seed source were then placed along the seam or centre line separating the two halves of the pot combinations, and shaded to approximately 50% of full sunlight. Each substrate was monitored for moisture level using a moisture probe, and watered accordingly on a daily (twice a day during sunny, hot days mostly during July and August) basis until November. Thereafter, seedlings were watered once a week as deemed necessary from the moisture probe. The water was tested for dissolved organic carbon using persulfate-ultraviolet oxidation (2.6 mg/L), ammonium using semi-micro-Kjeldahl (0.03 mg/L), nitrate (0.11 mg/L), phosphate (<0.01 mg/L), and sulphate (2.06 mg/L) using ion chromatography (methods outlined in Eaton et al. 1995). Thus the nutrient addition due to the water supply was minimal. In January 1998 the seedlings were thinned (by cutting) to eight seedlings in each pot for the combinations of (i) wood chips-wood chips, and (ii) decay wood IV-decay wood IV. Four seedlings were left in each pot for the combinations of (i) wood chips-non-woody humus; and (ii) decay wood IV-non woody humus. Three seedlings were left in the non-woody humus-non-woody humus combination. The seedlings were then grown in full sunlight, moisture conditions monitored, and watered daily as needed, from May 1998 until January 1999. Seedlings were harvested in January. The roots from each of the two halves were carefully separated and washed to remove any substrate. The shoot height and caliper were measured. The roots and the shoots were oven-dried at 70° C for 24 hours. The mass was determined, and root density calculated (expressed as mg cm"3). For height and caliper, a completely randomized design was used to test for significant differences; and Tukey's multiple comparison test was used to detect differences between the five susbstrates. Transformations were not considered for the analyses since analysis of variance is robust, operating well even with considerable heterogeneity of variances, as long as all nt are equal or nearly equal (Glass et al. 1972); and is also robust with respect to the assumption of the underlying populations' normality (Zar 1984). For root density, a paired Mest was used to test for significant differences between the mean root density of the pairs of substrates. If differences were not significant at a < 0.05, then there was insufficient evidence to reject the null hypothesis. Thus to test whether the mean is not significantly different from a specified alternative mean, the Type II error was calculated (expressed as the power of the test, 1 - P) Chapter 3, Page 28 using a modification of the formula given in Ott (1993), where a two-tailed r-value with 9 degrees of freedom was substituted for the z-value. The value used to calculate P was the difference between the root mass of each half of the substrate pairs. For example, given the non-woody humus-class IV wood pot combination, p was calculated using the difference: root mass of non-woody humus minus root mass of the class IV wood. The alternative mean value used to detect a meaningful difference was based on 10% of the total root biomass for each combination. There was significant power if 1-p was greater than 0.80, as recommended as a "reasonable choice" by Hinkelmann and Kempthorne (1994). Field sampling The study sites were located in the Submontane Very Wet Maritime Coastal Western Hemlock (CWHvml) variant (Meidinger and Pojar 1991). The associated climate is mild and humid (mesothermal), with warm summers and no dry season (Cfb by Koppen; cited in Trewartha and Horn 1980). However, summer hot dry spells can be frequent (Meidinger and Pojar 1991). Large amounts of precipitation, upwards of 4000 mm annually, and the mild oceanic climate with mean annual temperature of approximately 8°C are characteristic of this climate. I looked at how two humus form groups and the adjacent CWD substrates affected root proliferation. The first humus form group (Green et al. 1993) was either a Hemimor or Humimor (referred to as "mor"), 10 - 15 cm thick; and the second group was either a Leptomoder or Mullmoder (referred to as "moder"), 2 - 5 cm thick. To isolate only the roots of western hemlock, thereby avoiding the task of identification and separation of roots of other understory plant and tree species, the chosen sites were second-growth stands approximately 90 years old, with a dominant cover (greater than 70%) of western hemlock. The closed canopy prevented adequate light for the survival of most herbaceous plants and all shrubs. The understory plant species associated with mor humus forms was a complete moss mat cover consisting primarily of Hylocomium splendens, and Rhytidiadelphus loreus; the understory associated with moder humus forms included the fern Polystichum munitum. To eliminate the influence of water tables and associated anaerobic soil conditions, only sites without a water table or evidence of a fluctuating water table (gleying or mottling) within 60 cm of the surface were chosen. The soil moisture regime (Pojar et al. 1987) of sites with mor humus forms were identified as fresh; and sites with moder humus forms were identified as fresh to moist. Moisture deficits or excess are presumed not to occur on theses sites. Chapter 3, Page 29 Three areas were sampled: the Capilano watershed north of Vancouver, the Malcolm Knapp Research Forest east of Vancouver, and southeastern Vancouver Island (Table 3.2). These areas have a history of clearcutting during the early 1900's, followed by a period of natural regeneration, and are now mature stands of predominantly western hemlock. Other species within these stands were western redcedar (Thuja plicata) and Douglas-fir (Pseudotsuga menziesii), which comprised up to 20% of the tree species at the Capilano watershed, 30% at the Malcolm Knapp Research Forest, and 10% on Vancouver Island. These areas were chosen since they did not have a history of fertilization and/or spacing - the former adding extraneous nutrient additions and the latter having all trees growing on logs removed. Six sites were sampled within each area: three sites with mor humus forms, and three sites with moder humus forms, for a total of eighteen sample sites (Table 3.2). To minimize observer influence over the choice of sampling site, candidate stands were identified on a map, a grid placed on the map, and then three stands for each area were selected as close as possible to an equal distant grid pattern. The chosen stand was then visited, and the first sampling site meeting the following criteria was chosen. Within each stand a sampling site of approximately 100 m2 was selected containing only western hemlock, and having a western hemlock growing upon a class II downed log (the log is elevated on support points with intact to partly soft wood; Maser et al. 1988) in the centre. Six sampling points were then selected (two sampling points per substrate) (Figure 3.2, 3.3): (i) a western hemlock tree or sapling growing on a class II downed was the centre of the plot. Two points approximately 2-4 m from each side of the tree along the log were sampled. (ii) from the centre tree, as close to a 90° angle from the direction of the log legnth, another two points (one on each side of the log) containing a decay class IV or V log (these classes of decayed wood form a mound on the ground with small soft blocky pieces or a soft powdery texture; Maser et al. 1988). This sampling points were 2-4 m away from a western hemlock tree. (iii) as close as possible to sample (ii), the prevalent non-woody humus form. An exact distance and exact angle was not possible but the closest point criterion prevented observer influence. The substrates sampled were (i) non-woody humus form over mineral soil; (ii) the mineral soil under the non-woody humus form; (iii) non-woody Chapter 3, Page 30 humus form over the decay class II log; (iv) the decay class II log; (v) non-woody humus form over the decay class IV or V wood; and (vi) the decay class IV or V wood. TABLE 3.2: The distribution of sites by humus form across the sampled area. Site Latitude/longitude Humus form Mor Moder Total Capilano 49°157123°10' 3 3 6 Haney 49°147123°5' 3 3 6 Vancouver Island 50°207123°55' 3 3 6 Total 9 9 18 Root density was determined by excavating from 750 cm3 to 1500 cm3 of each respective substrate, and collecting the substrate and associated fine and very fine roots (< 1mm and 1-2 mm in diameter, respectively; Green et al. 1993) from the hole. The volume of the hole was determined by lining the hole with a plastic bag and filling the hole with 2 mm diameter glass beads; the volume of glass beads was then measured. Moder humus forms were collected by excavating a square of approximately 750 cm3. Decay class IV and V wood were collected by excavating a cylinder 15-20 cm deep with a volume of approximately 1500 cm3. Mor humus forms were collected by either excavating a square or cylinder, depending on the depth of the LFH layer, until approximately 750 cm3 was collected. Decay class II logs were collected by excavating the top 2 to 4 cm of the log, which was decayed enough to chip an adequate volume sample of 750 cm3. Mineral soil was collected by excavating a cylinder 10 cm deep with a volume of approximately 1500 cm3. The 10 cm mineral soil depth was chosen since this depth was noted by Eis (1974, 1987) to contain the highest root concentration in the mineral soil profile. For each substrate, two such excavation holes were collected at each sample point (i.e., two holes for each of the six sampling points). Root samples were then placed in a cooler at 4°C until ready for processing not more than 31 days after collection. Roots were separated from the root samples according to size class by careful washing, and then oven dried at 65°C for 8-48 hours to constant weight. The root density of the very fine and fine roots was expressed as mg-cm"3 calculated from the volume of sample cores. The mean root density of the four sample cores for each substrate was used in the statistical analyses. Chapter 3, Page 31 decay class decay class upper 10 cm of non-woody IV or V log II log the mineral soil humus form FIGURE 3.2: An illustration of the blocked sampling design and the substrates sampled for root density. western hemlock (shaded circle) growing on a decay class II log FIGURE 3.3: An illustration of the top view of the idealized sampling layout showing the position of the sampling points (2 sub-samples were collected per box) and the associated substrates that were sampled. H = non-woody humus form; DW2 = the decay class II log; DW4 = the decay class IV or V wood. The arrowed lines represent a distance of 2-4 m. An attempt was made to capture this idealized pattern in the actual layout Chapter 3, Page 32 Immediately after sampling for root density, separate samples for chemical analysis of each substrate were also collected. Approximately 700 cm3 of each substrate surrounding each hole was kept for chemical analyses; the four samples for each substrate were collected in one container forming a composite sample for chemical analyses. Samples were then air dried to constant mass. Mineral soil samples were passed through a 2 mm sieve, and organic forest floor samples were ground with a Wiley mill to pass through a 2 mm sieve. For both organic forest floor and mineral soil samples the following chemical analysis was undertaken and expressed as a concentration on a unit of soil mass basis. The pH, total C, and total N was determined by the methods described in chapter 2. Statistical analyses for the density of fine and very fine roots, and chemical properties were done separately for the mor and moder humus form groupings. Since the number of experimental units were equal, the analysis of variance is robust (Zar 1984). Consequently, transformations were not considered for the root density. The following statistical model was applied to test for differences in the chemical properties of the substrates, and mass of fine and very fine roots combined: .Vijk = u + tk + S{ + b(s)ij + Si*tk + £ i j k where _Vijk = response of an observation on the i site, j block, and k treatment. [x = overall mean tk = effect of k treatment (k = 1 - 6) s, = effect of i site (i = 1, 2, 3) b(s)jj = effect of j block (in this case Figure 3.3 represents a blocks) (j = 1, 2, 3) within .th . I site s\*tk = effect of interaction between the k treatment in the i site Syk = residual variation. The treatment effect (the six substrates) was tested against the sitextreatment interaction mean square error. The sitextreatment interaction was tested against the residual variation. Since averages of samples were used, there was no sample error term. Tukey's multiple comparison test was then used to detect differences in the chemcial properties of the substrates and mean mass of fine roots between the six substrates. Differences were considered statistically significant at a = 0.05, and considered biologically significant with a mean difference of at least 1 mg-cm"3. Chapter 3, Page 33 Results Greenhouse Study For height and caliper, ANOVA followed by Tukey's multiple range test indicated that the largest seedlings (p < 0.05) grew on the substrate combination with non-woody humus form on both halves; followed by the two combinations which included non-woody humus form on one of the halves; and the smallest seedlings were on the combinations with woody substrates on both halves (Table 3.3). In the pots filled with the same substrate in both halves, paired ^ -comparisons indicated no significant differences (p < 0.001) between each half in very fine and fine root density (Table 3.4). The power of the test was only strong enough (l-(3 = 0.80) for the pot with the non-woody humus substrate on both halves. Thus only the pots with both halves of non-woody humus substrate had a sample size large enough to be able to accept that very fine and fine root density did not differ between the two halves of the pot by 10% of the total root biomass at P = 0.20. For the combinations with half non-woody humus substrate and half either the decay class IV wood or the sawdust-wood chips mixture, the -^paired comparisons indicated a significant difference in either combination (Table 3.5). The non-woody humus substrate had slightly less than twice the root mass for the same volume than the decay class IV wood; and had more than three times the root mass for same volume than the sawdust-wood chips mixture. T A B L E 3.3: Mean and standard error (in brackets) of height (cm) and caliper (mm) of the seedlings grown in five substrate combinations. LFH is the non-woody humus form, CWDIV is the decay class IV wood, and wood is the mixture of sawdust and wood chips. Values with the same letter in the same row are not significantly different (a = 0.05). seedling Substrate combinations in planting pots characteristic LFH-LFH LFH- LFH-CWDII CWDIV- wood-wood CWDIV CWDIV n 5 20 20 5 5 height (cm) 32.6a 21.0b 19.1b 2.5c 1.7c (1.7) (1.8) (1.8) (0.2) (0.2) caliper (mm) 4.6a 2.5b 2.3b 0.6c 0.4c (0.2) (1.7) (1.2) (0.0) (0.0) Chapter 3, Page 34 TABLE 3.4: Mean, standard error (in brackets), alpha and beta error values for root density of half a pot. Each half of the pots were filled with the same substrate. LFH is the non-woody humus form, CWDIV is the decay class IV wood, and wood is the mixture of sawdust and wood chips. Paired comparisons are for the combinations LFH vs. LFH, CWDIV vs. CWDIV, and wood vs. wood. Seedling Substrate combinations in planting pots characteristic LFH LFH CWDIV CWDIV wood wood root density 3.0(0.2) 3.0(0.1) 0.5(0.1) 0.5(0.1) 0.3 (0.0) 0.3 (0.1) (mg cm"3) P a = 0.973; P p = 0.094 P a = 0.740; P p = 0.819 P a = 0.883; Pp = 0.741 TABLE 3.5: Mean, standard error (in brackets), and alpha error values for root density of half a pot. Each half of the pots were filled with various combinations of non-woody humus form (LFH), decay class IV wood (CWDIV), and the sawdust-wood chip mixture (wood). Paired comparisons are for the combinations LFH vs. DWIV and LFH vs. wood. Seedling Substrate combinations in planting pots characteristic LFH DWIV LFH wood root density 2.5(0.2) 1.4(0.2) 2.8(0.3) 0.8(0.1) (mg cm"3) P< 0.001 P< 0.001 Field sampling Significant differences (p < 0.001) in mean values for root density were detected between the different substrates within both moder and mor humus form groupings. For both moder and mor humus form groupings, the root density was separated into two groups: one composed of the LFH layers, and the other composed of the two decay classes of wood and the mineral soil (Tables 3.6 and 3.7; Figure 3.4). Approximately two to three times greater root density occurred in the woody LFH substrates compared to the woody substrates and mineral soil. Significant differences (p < 0.001) in mean values for all chemical measures were detected between the different substrates within both moder and mor humus form groupings (Tables 3.6 and 3.7). Total-N, C:N ratio, and mineralizable-N showed patterns of separation into two groups Chapter 3, Page 35 similar to those of root density (Figure 3.5). With some exceptions, two groups were distinguished, a very strong group of the non-woody LFH layers with much larger values than a weaker group of the other two classes of CWD and the mineral soil. The site-by-treatment interaction was significant (p < 0.05) for mineralizable-N of the moder humus form grouping; and for pH, C:N ratio, total-N, and mineralizable-N of the mor humus form grouping. However, the interaction primarily occurred within the two groupings separated by Tukey's multiple range comparison (Figures 3.6, 3.7), so the treatment differences detected by the ANOVA still holds. TABLE 3.6: Mean and standard error (in brackets) of root density and chemical measures within the moder humus form grouping between the rooting substrates (n =3). LFH = non-woody humus form; log II = decay class II log; log IV = decay class IV/V wood. Values with the same letter in the same row are not significantly different (a = 0.05). root or substrate Rooting substrate characteristic L F H on L F H on log L F H on log log II log IV mineral soil mineral soil II IV root density 2.86a 3.71a 3.87a 1.41b 1.27b 1.40b (mg/cm3) (0.56) (0.82) (0.44) (0.31) (0.36) (0.37) pH 3.87b 3.39c 3.41c 3.40c 3.34c 4.43a (0.13) (0.07) (0.09) (0.10) (0.06) (0.06) total-C 44.18b 58.68a 57.15a,b 61.14a 59.44a 7.78c (%) (6.15) (2.27) (2.45) (1.23) (1.19) (1.13) total-N 1.61a 1.66a 1.60a 0.27c 0.44b 0.34b,c (%) (0.13) (0.05) (0.11) (0.01) (0.02) (0.07) C:N 27.6c,d 35.5c 37.3c 247.8a 139.2b 23.3d (2.3)* (2.6) (5.0) (12.9) (2.2) (1.9) mineralizable-N 467.64a 447.09a 459.92a 40.37c 65.19b,c 95.96b (ppm) (51.53) (39.40) (66.77) (6.54) (8.59) (33.39) Considering the three nitrogen measures, total-N, C:N ratio, and mineralizable-N, there was a similar pattern overall for both humus forms. Mean values for the non-woody LFH layers were consistently significantly different from the two woody decay classes, but with no significant differences detected within this grouping. For both the moder and mor humus forms, the two decay classes of wood and the mineral soil showed different groupings for the three nitrogen measures. However, there was significant interaction in the moder humus form for Chapter 3, Page 36 mineralizable-N (p < 0.001), and in the mor humus forms for total-N (p < 0.001), C:N ratio (p = 0.002), and mineralizable-N (p = 0.001). In general, the interaction occurred within the groupings that were not significantly different (Figures 3.5 B,C,D; Figure 3.6); thus, the results of the Tukey's multiple range test still hold. TABLE 3.7: Mean and standard error (in brackets) of root density and chemical measures within the mor humus form grouping between the rooting substrates (n =3). LFH = non-woody humus form; log II = decay class II log; log IV = decay class IV/V wood. Values with the same letter in the same row are not significantly different (a = 0.05). root or substrate Rooting substrate characteristic LFH on LFH on log LFH on log log II log IV soil mineral soil II rv root density 5.66a 4.44a 5.40a 1.90b 2.09b 2.47b (mg/cm 3) (1.05) (0.30) (0.82) (0.31) (0.56) (0.64) pH 3.56b 3.44b,c 3.35b,c 3.23c,d 3.06d 4.13a (0.09) (0.11) (0.08) (0.04) (0.08) (0.18) total-C 55.73a 52.47a 56.44a 59.59a 60.24a 3.85b (%) (0.83) (5.07) (0.96) (2.22) (1.91) (0.89) total-N 1.373a 1.341a 1.391a 0.302b 0.357b 0.110c (%) (0.067) (0.107) (0.011) (0.057) (0.080) (0.040) C:N 41.0b 41.2b 40.9b 220.6a 189.0a 38.9b (2.1) (7.9) (0.9) (52.2) (34.9) (3.1) mineralizable-N 445.91a 322.49a 380.42a 35.01b,c 38.72b 19.21c (ppm) (22.24) (47.07) (21.82) (18.43) (10.19) (9.98) Chapter 3, Page 37 hms ~i r hdw2 hdw4 dw2 dw4 Rooting substrate ms o bo a CU T3 -*-» O O l l <u a 5 H 4 H 3 H 2H T 1 r hms hdw2 hdw4 dw2 dw4 Rooting substrate r ms FIGURE 3.4. Plot of the mean and standard error of the fine and very fine root density associated with each rooting substrate. (A) is for the moder humus form grouping, and (B) is for the mor humus form grouping. For the rooting substrate hms = LFH over the mineral soil, hdw2 = LFH over the decay class II log, hdw4 = LFH over the decay class IV log, dw2 = decay class II log, dw4 = decay class IV log, and ms = upper 10 cm of the mineral soil under the LFH substrate. Chapter 3, Page 38 - 1 (%) N - P J O I < Wh-o—l HM H KH S '5 Q I - » H a ICH 1—•—Hoi 1—»OH s 5 * '5 JSl 3[qBZI|BJ3UllU Hd OIJBJ NO CO * S u 43 to f - 1 X l 3 co" co CD 60 "y C C »- O 43 =3 2 ° co _ ^ CD CO 23 JS o £ S o o CD — u CD CD a. T! ~ P r •5 it c fe fe 3 — 73 CD CD CO O J> £ a. Z .22 U 00 3 .3 3 §• "3 2 00 73 c cd 60 O 3 • « > fe. I _ ' T3 co o 23 o -S fe, CO o CD •o CD S3 fa O , , C n Q co w 3 73 3 C 3 CO 43 i s CO „ . 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( t v I - 3 [qBZ I lBJ3UIU l ) u i 00 .s r 1 (NiBjoj)ui <H o .2 i—i U> o ^ cd d o d CN O O H H o d o cd O Jj c/3 , d CQ i n CD (D T3 2 S 3 .a O CD £ -El -o 2 > , 0 c/3 H H Cd g O r d CD T3 CD o -S o c/3 d '5 £ cd cd d CD -d cd C/3 CD d > d d " I C/3 M - l d - d -a o o i d o d CD . d T3 -5 X a, o d _o *-d o CS I n cd d O I-I d CD 3 22 I-I CD -a d d CO >~> CD T3 • § d w O d ll CD - d •tf- +-' r J5 "3 I 1 d CD cd CD l-i "O CD - d H-1 I—I C/3 M S en C/3 cd d o <4H o 2 CD O CD OH X CD CD - d CD I-i ,o o cd cd CD CD - d P >7 £ H H o d o C/3 3 C/3 DC O W T3 a CD g I-I c H H £ H H H H cd d C/3 5 +H S d - d <u C3 , iV CD ^ ta ° OH O S £ cd o CD -a 1 T3 o on a 1 1 1 1 1 1 hms hdw2 hdw4 dw2 dw4 ms Rooting substrate FIGURE 3.7. Illustration of the site x treatment interaction of the natural logarithmic transformation of mineralizable-N for the moder humus form. Each line represents a different site. The acronyms for the rooting substrates are: hms = non-woody humus form over the mineral soil, hdw2 = non-woody humus form over the decay class II log, hdw4 = non-woody humus form over the decay class IV log, dw2 = decay class II log, dw4 = decay class IV log, and ms = upper 10 cm of the mineral soil under the non-woody humus form. Discussion Greenhouse Study The greenhouse study served several purposes: 1. By maintaining an adequate moisture supply in both woody and non-woody substrates, the study attempted to isolate CWD's potential as a nutrient source for tree growth. Root proliferation occurred within the non-woody humus form when adjacent to CWD, and seedlings growing in the non-woody humus form were significantly larger than those grown in CWD. Thus, wood does not appear to be as an important nutrient source for trees. If there is value of CWD to trees, then the presumption of Harvey et al. (1976; 1981) that CWD acts as a moisture source during drought periods is very likely. Chapter 3, Page 41 2. The high positive correlation between nutrient availability of the three substrates, height and caliper growth, and increased root proliferation suggests that western hemlock does respond to nutrient and/or moisture sources with root proliferation. Western hemlock roots strongly responded to the non-woody substrate when moisture stress was eliminated. Thus, this technique appears to be a useful method for indication of substrate contribution to short-term productivity, and supports its use in the following field sampling on mature trees. 3. The greenhouse experiment with random assignment of substrates also addresses the one restriction to the field study - the inability to randomly assign treatments, and the consequent inability to eliminate location effects. In the field study, the non-woody humus forms are primarily on top of the wood or mineral soil (the one exception was when the non-woody humus form and decay class IV wood were at similar forest floor levels). There were a few constraints to this study. Only one seed source was used but it was assumed that this source does not represent a genetic anomaly. The results were very clear and did not contradict what was found in the field, so the seed source likely is representative of the western hemlock population. Additionally, any mycorrhizal source may not have survived through the air drying process. The association between mycorrizhae and decaying wood has been demonstrated for coastal forests of Washington and Oregon (Christy et al. 1982), and the interior forests of the Northern Rocky Mountains (Harvey et al. 1976; 1981). Thus the seedlings in the decayed wood may have been grown under less than optimum conditions. Field sampling The density of fine and very fine roots were used as an indicator of the relative importance to tree growth of various forest floor substrates instead of mycorrhizal root tips as used by Harvey et al (1976). Root proliferation was chosen because: (i) the "root foraging" concept is based on root proliferation not mycorrhizal formation; and (ii) relationships between organic matter volume classes using root weight are similar to the sum of ectomycorrhizal root tips (Graham et al. 1994). Despite statements that root proliferation occurs in decaying wood (Triska and Cromack 1980; Sollins and Cline, cited in Maser and Trappe 1984; Eis 1974, 1987), this relationship does not appear to hold on sites presumed not to have a water deficit in the wetter coastal climates of Chapter 3, Page 42 southern BC. This result differs from the association of mycorrhizal roots with CWD in the Rocky Mountains forests of the Unites States (Harvey etai. 1976, 1978, 1979, 1981, 1987). In this study, the non-woody forest floor, whether mor or moder humus forms, had much greater fine and very fine root densities than the decay class IV wood or the top 5 cm of the decay class II log. This result occurred despite a sampling design that purposely favours wood by locating the plot centre at a tree growing on a decay class II log. Therefore, non-woody humus forms appeared to be the most important rooting medium for western hemlock. Using the root proliferation technique, CWD appears to provide little immediate benefit to tree growth in the presence of non-woody humus forms on sites presumed not to have a water deficit within a cool mesothermal climate. Since the climate of the areas used in this study does not typically have a long dry growing season, and the sites in this study presumably did not have a soil water deficit, the moisture value of CWD can be disregarded. Root proliferation follows the nutrient content to some extent. However, since mineral soil has a bulk density approximately six times greater than both woody and non-woody substrates (Sidle and Shaw 1983), on a volume basis the nutrient relationships change. On a volume basis then, the largest nutrient measures are associated with both non-woody substrates (forest floor and mineral soil), but the smallest nutrient measures are associated with the woody substrate. Yet root proliferation between the woody substrate and mineral soil are almost identical. In addition, some correlated property such as soil humic acids may cause the proliferation of roots (Van de Venter 1991; Chukov et al. 1996; Vallini et al. 1997). This study did not address the reason for root proliferation, whether caused by moisture, nutrients, or humic acid, or even whether there is root avoidance of woody substrates due perhaps to a lack of aeration. Conclusions If root proliferation is accepted as a good indicator of substrates that benefit tree survival and growth, then CWD has relatively less immediate value to trees compared to non-woody humus substrates on sites without a water deficit in the summer wet climates of coastal B.C. Coarse woody debris does not appear to have the same value to trees as in the drier ICH-equivalent or IDF-equivalent climates of the interior Pacific Northwest of the United States. The importance of CWD established for the Rocky Mountain forests of the United States does not extend to the coastal BC. Despite the strong association of seedlings and saplings with CWD in coastal BC, the relationship between CWD and tree productivity is not obligatory. Chapter 3, Page 43 S E C T I O N I: D I S C U S S I O N Jurgensen et al. (1990) maintain that during the dry summer conditions in the forests of the Northern Rocky Mountains of the United States, well decayed wood becomes the most active site for mycorrhizal roots. However, citing Loopstra et al. (1988), they suggest that on sites where the soil already is cool and moist (e.g., Alaska), well decayed wood may actually be detrimental to root growth. This study suggests that, similar to southeastern Alaska, CWD on sites not having a water deficit on the coast of BC is not important to seedling and tree growth. In the wetter climates of coastal BC, CWD does not appear to be a necessary component if there is an adequate non-woody humus substrate. The results here support the statement by Heilman (1990) that "on most sites there is no indication that logs are critical for either growth beyond the seedling stage or sustained productivity of forests." Coarse woody debris may not have as an important immediate value to tree growth compared to non-woody humus substrates on sites without a water deficit in wet coastal BC climates. However, this does not rule out other indirect values. Coarse woody debris may be important for tree survival and growth in one or more or the following indirect roles: 1. CWD may sequester nutrients through fungi and wood-inhabiting invertebrates, and return the nutrients to the forest floor through the sporocarps for the former (Harmon et al. 1994; Edmonds and Lebo 1998), and through waste and decay of invertebrates for the latter (Edmonds and Eglitis 1989; Zhong and Schowalter 1989). 2. Decayed wood may provide habitat and refugia during periods of drought for mycorrhizae (Harvey et al. 1976, 1979), and invertebrates such as Collembella, which may be necessary in nutrient cycling (Setala et al. 1995; Marshall et al. 1998). 3. CWD may provide a seedbed more conducive to germination and growth of seedlings compared to non-woody organic forest floor substrates due to the lack of herb and moss competition on CWD (Harmon and Franklin 1989), or lack of seed pathogens on CWD (Zhong and van der Kamp 1999). 4. If small mammals are necessary for the dissemination of spores of mycorrhizae with hypogeous fruiting bodies (Maser et al. 1978a,b), then maintaining the structural habitat component for small mammals becomes critical. Section I Discussion, Page 44 S E C T I O N II: L O N G - T E R M P R O D U C T I V I T Y This section addresses the question of whether CWD accumulations increase the intensity of podzolization, thus reducing the long-term productivity of a site. Forest managers concerned with maintaining a soil's productive potential must consider the impact various forestry practices will have upon the "malleable" features of a site (Powers et al, 1990). One such feature is the amount and type of organic matter on a site, which affect soil properties through eluviation and illiuviation, and may result in difference in the intensity of podzolization. Podzolization and Productivity Podzolization is defined as the chemical downward translocation of aluminum, iron and organic matter, resulting in the concentration of silica in the eluviated mineral soil layer, and deposition and accumulation of the three products in the illuviated mineral soil layer below (Buol et al. 1989). From a soil productivity perspective, podzolization is often thought to result in forest productivity decline. This decline has been referred to by several descriptors: 1) "degeneration" in the context of a succession sequence of vegetation from deciduous forests to conifer forests or heathland in southern Sweden (Tamm 1932 cited in Jenny 1994, pp 229); 2) the "acceleration of podzoliation" in the context of the how some heath plant species appear to accelerate the process (Powers et al. 1990); 3) greater "intensity of podzol development" in the context of the importance of windthrow disturbance as a "natural form of cultivation" (Armson and Fessenden 1973); or 4) "ecosystem deterioration" in the context of succession following glacier retreat in Alaska (Bormann and Sidle 1990). In this section, I use the term "greater or lesser intensity of podzolization" when discussing the effect of CWD accumulations upon the soil directly beneath, in comparison to non-woody humus forms. The negative impact of podzolization on site productivity is attributed to nutrition properties associated with Podzol soil development. These properties include: 1. upper horizons leached of cations and consisting of nearly pure Si (Pedro et al. 1978); 2. increased acidity (Jenny 1994); 3. decreased nutrient availability as N and P are immobilized in recalcitrant organic soil horizons (Borman and Sidle 1990; McClellan et al. 1990), and due to the high capacity of Podzolic soils to fix phosphate (Soil Classification Working Group 1998) Section II, Page 45 4. build-up of a thick, slow-decomposing, acid mor humus form (Bormann and Sidle 1990; Bormann et al. 1995; Jenny 1994); 5. precipitated organic matter that is relatively resistant to decomposition except by some fungi (Mathur 1969); 6. the extreme leaching characteristics of Podzolic soil formation may result in the development of impermeable placic or orstein layers (Spurr and Barnes 1980), and the resulting paludification may leading to a bog climax community (Klinger 1996; KXmgQxetal. 1990). The pedogenetic process of podzolization (in terms of iron and aluminum mobilization, migration, and accumulation) does not cause declining productivity; rather, the associated soil properties after Podzolic soil development are thought to be the cause. The intensity of these processes is seen as a measure of the rate of soil development towards the six aforementioned characteristics. Since a negative correlation between intensity of podzolization and site productivity exists, intensity of podzolization measures can be used as indicators or indices of the potential for reduced forest site productivity. Coarse Woody Debris and Podzolization Plants, through detrital accumulations, affect soil properties (Zinke 1962; Alban 1982), with some species accelerating Podzolic soil formation (Buol et al. 1973). Therefore, if we are to maintain the long-term productive potential of forest soils, we need to understand the impact large CWD accumulations, which differ in chemical properties from non-woody humus forms, have on these pedogenetic process. Where moist cool climate conditions exist, podzolization is an inevitable process (Spurr and Barnes 1980) with or without forest management activity. However, forest managers need to know if their management practices will alter the natural rate of change by accelerating the process, or moderating the process. Coarse woody debris accumulations may have a concomitant positive-negative relationship on tree nutrition and soil development. Windthrow, one contributor to CWD accumulations, and the associated pedoturbation caused by tree uprooting, has been considered to be important for maintaining forest productivity by disrupting and mixing soil (Mcintosh 1961; Schaetzl et al. 1989), with an effect similar to ploughing (Armson 1977). Tree uprooting then rejuvenates leached surface soil by exposing more fertile subsoil (Beke and McKeague 1984), thus slowing the process of podzolization by keeping soils in a juvenile, or semi-mature stage of development (Keenane/tf/. 1994). Section II, Page 46 Conversely, since the chemical nature of decaying wood is so different from non-woody humus forms (Klinka et al. 1990), and different sources of organic matter have different effects on the soil below, the effect of decaying wood on eluviaton and illuviation could be altogether different from non-woody humus forms. Additionally, the residence time for logs to fully decay can be substantial, with persistence as recognizable wood for over one or two hundred years (Brown et al. 1998; Means et al. 1992; Harvey et al. 1981; McFee and Stone 1966); and persistence into decay class IV wood (wood that has lost all structure) for upwards of 700 years (Feller 1997) and up to 1200 years in coastal rainforests of BC (Daniels et al. 1997). This long persistence of decaying wood, and the relatively short period of less than 250 years for the formation of Podzolic soils (Bormann and Sidle 1990; Crocker and Major 1955), suggests that large accumulations of decaying wood persist long enough to affect the soil directly beneath. The effect of CWD on potential soil productivity can be either positive (arrests or reverses the podzolization) or negative (intensifies podzolization). This effect may be important in the wetter climates of British Columbia where large accumulations of CWD with long persistence are common. The accumulation of decaying wood may result in a more acidic forest floor (Klinka et al. 1990), which may be associated with an increased intensity of podzolization (Klinka et al. 1995). Gardening experience suggests that sawdust or wood chips are effective in lowering the pH of alkaline soils (Ellis 1990). Additionally, dark acidic (pH 4.0) leachate with high phenol and organic carbon content is observed in water near trembling aspen (Populus tremuloides) log piles during logging operations (Taylor et al. 1996). McKeague et al. (1983) first mentioned the possible effect of CWD when they noted that "deep tonguing of E horizons in some otherwise normal Spodosols appears to be due to... conditions [that] may occur beneath a decaying log." More recently, Harmon and Sexton (1995) proposed that, given the results of Yavitt and Fahey (1985) showing acidity and high organic content of the water flowing through logs in early stages of decay, "the potential exists to alter the properties of the underlying soil." Humus form studies in coastal forests indicate that CWD-dominated forest floors are more acidic than forest floors derived from other materials (Klinka et al. 1990). Preliminary studies (Klinka et al. 1995; Kayahara et al. 1996) showed some differences between the mineral soil directly beneath CWD compared to the prevailing non-woody forest floor, though the results were inconclusive. Finally, anecdotal statements that CWD may "to a greater or lesser degree... contribute to soil acidification and podzolization" (Stevens 1997) have been made without reference to scientific studies. In contrast, some evidence suggests the opposite effect. Since decayed wood appears to Section II, Page 47 have less fulvic acid than non-woody forest floors (Kayahara et al. 1996; Klinka et al. 1995), and the fulvic acid component is responsible for chelation and metal movement through the soil, the potential for increased intensity of podzolization may be associated more with non-woody organic substrates. Research Focus Given recent recommendations and decisions to modify harvesting and slash treatment practices to leave CWD on harvested sites, I investigated the long-term productivity implications of CWD accumulations by addressing the hypothesis: Compared to non-woody forest floor substrates, woody forest floor substrates have greater potential to acidify the mineral soil directly beneath, and have greater potential to increase the intensity of podzolization. The first step was to test for the relative potential for acidification and increased intensity of podzolization of woody forest floors compared to non-woody forest floors under controlled laboratory conditions (Chapter 4). Soil columns leached with concentrated solutions of each of the woody and non-woody substrates was used for this purpose. Once the relative potential for acidification and increased podzolization has been established, then a field study was implemented as follow-up to determine if this relative potential derived under laboratory conditions can be extrapolated to field conditions (Chapter 5). Sampling of the solution that leaches out of each of the two substrates under field conditions was carried out, and then soil samples collected from directly under the woody and non-woody substrates were analysed for acidity and measures of podzolization. Section II, Page 48 Chapter 4. T H E R E L A T I V E P O T E N T I A L F O R I N C R E A S E D A C I D I F I C A T I O N A N D I N T E N S I T Y O F P O D Z O L I Z A T I O N O F S O L U T I O N S L E A C H E D F R O M W O O D Y VERSUS N O N - W O O D Y F O R E S T F L O O R S Introduction Since the chemical nature of decaying wood is so different from non-woody humus forms (Klinka et al. 1990), there is an expectation that its effect on the mineral soil directly beneath should also differ. Particularly, the differences in concentration of fulvic acid (Klinka et al. 1995) leads to the expectation that the intensity of podzolization associated with each of the two substrates would be different. Based on current information, the effect of CWD on potential soil productivity could be either positive (arrests or reverses the podzolization) or negative (intensifies podzolization). This effect may be important in the wetter climates of British Columbia where large accumulations of CWD with long persistence are common. Where such moist cool climate conditions exist, podzolization is an inevitable process (Spurr and Barnes 1980) with or without forest management activity. However, forest managers need to know if their management practices will alter the natural rate of change by accelerating or moderating this process. This chapter presents the results of leaching non-woody and woody solutions through soil columns. To assess whether CWD has a greater relative potential to acidify the soil directly beneath and increase the intensity of podzolization, I addressed the questions: 1. Does the non-woody forest floor substrate or the woody substrate have greater concentration of dissolved organic carbon (DOC) in solution per unit mass? 2. Does the non-woody or woody solution have a greater potential to acidify the mineral soil directly beneath, and increase the intensity of podzolization? Chapter 4, Page 49 Materials and Methods Soil Columns Eighteen soil columns were constructed with 5-cm diameter acrylic tubes, 30 cm long. The tubes were placed vertically on one-holed rubber stoppers that were sealed to the bottom of the tube with silicon cement. The bottom of the tubing was fitted with a fibre glass mesh and 5 cm depth of Teflon boiling chips. A plastic tube through a hole in the stopper was connected to another stopper sealing off a glass Erlenmeyer flask which was placed in a container of ice. The flasks were connected to a vacuum source to be able to draw solutions through the soil column with 20 kPa of soil suction. A dripping apparatus that was placed over each tube was constructed from plastic funnels capable of holding 125 mL of water, and the outflow was controlled by acetal screw clamps placed on the neck of the funnels(Figure 4.1). The columns were wrapped in black paper to eliminate light which causes growth of algae along the tubing. Soil from a Bm horizon of basaltic parent material was collected from three different locations on southeastern Vancouver Island, BC. Soils were air dried, passed through a 2-mm sieve and used to fill the soil columns above the Teflon chips. Approximately 780 g of soil was placed into each tube, and the soil from each location filled 6 tubes. There were three sets of columns with six tubes per set, representing the three soil collection locations. Each set had equal mass of soil in each of the six tubes, and each set was used as a block for statistical analysis. Two sets were designated as primary blocks (chemical analyses of leachate to be performed at regular intervals), and the third as a secondary block (chemical analyses performed at key points during leaching derived from the primary blocks). Soil particle size was determined for each of the three soils by removing organic matter by oxidation with hydrogen peroxide (H2O2), and determining the percentage of sand, silt, and clay by the hydrometer method (Gee and Bauder 1986). The mineral soil in the two primary blocks was identified as clay loam, and the soil in the secondary block identified as a loam. Clay loam and loam was chosen for the tubes as a compromise between having particles fine enough to ensure chemical reactions with the solutions, yet not too fine so that the solution could freely leach through the cores without constant application of a vacuum. Initially, 360 mL of distilled water was leached through all columns. It was determined that the columns' soil water storage capacity was on average 115 mL of water. Once the columns were saturated, an input of 125 mL of water had an output of an average of 121 mL. Chapter 4, Page 50 FIGURE 4.1: Details of the soil column setup used for leaching of different solutions through a Bm horizon of basaltic parent material. Non-woody Mor or Mormoder humus forms and decay class IV or V wood were collected from three locations in the Capilano watershed north of Vancouver, BC (the site description was given in Chapter 2). The substrates were air-dried, roots removed, and ground in a Wiley mill to pass through a 2 mm sieve. Eighty grams of each substrate was placed in 1 L acid-rinsed glass jars, and 800 mL of distilled water was added to each jar. These mixtures were then hand-shaken and refrigerated at <4°C for 72 hours; hand shaking was repeated every four hours from 8:00 a.m. to 8:00 p.m. Distilled water, acidified with HC1 to pH 3.5, was also refrigerated and shaken in the same manner as the organic matter mixtures. After three days, the two organic matter-water mixtures and the acidified distilled water were vacuum filtered through a 2 urn glass fibre filter. The resulting solutions, the non-woody solution, the woody solution, and the acidified distilled water were used as treatments for the soil columns. Three sets of these Chapter 4, Page 51 solutions were prepared, with the non-woody and woody substrates collected from three different locations for each set. Each of the three treatments was assigned randomly to two soil columns within a block . For 80 days, 125 mL of each solution was poured into the funnels above the soil columns. Acetal clamps were adjusted to render a constant drip which emptied 125 mL of solution in 4 hours. Approximately one hour after the funnels were emptied, there was no longer flow out of the soil columns into the Erlenmeyer flask. At this time, a vacuum of 20 centibars of suction was applied until water no longer was detected dripping out of the columns. The solution sampling schedule for chemical analyses was different between the two primary blocks and the third secondary block. Chemical analyses of the solutions from the two primary blocks was done after an initial leaching of distilled water through the columns. Thereafter, samples were collected after 500 mL, 2000 mL, 4500 mL, 5000 mL, 6000 mL, 8000 mL and 10000 mL of each of the respective solutions were leached through the columns. For the third secondary block, solution sampling for chemical analyses was taken at the initial distilled water leacching, and then at point where 5000 mL and 10000 mL of the solution was leached through the column. Chemical Analyses Both input solutions poured into the soil columns and output leachate from the soil columns were chemically analyzed. The solutions were filtered through a 0.45 um polycarbonate membrane filter into vacuum flasks that were placed on ice. The solutions were refrigerated and analyzed within 48 hours for analyses for concentration of dissolved organic carbon (DOC); and the solutions were acidified to pH<2 with HNO3, refrigerated and analyzed within five days for analyses for concentrations of cations and metals. All analyses followed the procedures of Eaton et al. (1995). Dissolved organic C concentration was determined by persulfate-ultraviolet oxidation, followed by infrared detection of the liberated C O 2 ; concentrations of K, Ca, Mg, and Na were determined by atomic adsorption spectroscopy (AAS); and the concentrations of Si, Al, Fe, Mn, Cu, and Zn were determined by direct-coupled plasma spectroscopy (ICP). The ratios of DOC:AI, DOC:Fe, and DOC:Mn were calculated. For statistical analyses, an average value of input solution and output leachate was calculated for each tube. Additionally, the ratios of the output to input solution for each of the respective elements was calculated. These ratios were used to test whether the output concentration was greater than the input concentration. Chapter 4, Page 52 After 10 L of solution were leached through, the soil was removed from the columns for chemical analyses. From each column, the mineral soil was removed from three sections: (1) from the top of the column to 8 cm deep, (2) from 8 cm to 16 cm deep, and (3) from 16 cm to the bottom of the mineral soil layer. The mineral soil samples were analyzed for extractable Fe and Al using the following selective dissolution methods. Organically complexed Fe, Al, and Mn (pyrophosphate-Fe, -Al and -Mn) was extracted using a 0.1 M sodium pyrophosphate solution (Na4P 207 • IOH2O) shaken overnight at 25°C, and the resulting extracted Fe, Al and Mn determined by atomic adsorption spectrophotometry (McKeague 1967; Bascombe 1968). Organically complexed Fe and Al plus the poorly crystalline inorganic forms of Fe and Al (oxalate-Fe and -Al) were extracted using a 0.2 M oxalate-oxalic acid solution, a mixture of ammonium oxalate solution [(NH^CzO* • H2O] and oxalic acid solution [H2C2O4 • 2H2O], shaken in the dark for 4 hours, and the resulting extracted Fe and Al determined by atomic adsorption spectrophotometry (Schwertmann 1964; McKeague and Day 1966). The Fe not included in silicate minerals (organically complexed plus poorly crystalline and crystalline Fe; citrate-bicarbonate-dithionite Fe), was extracted using a 0.3 M sodium citrate (NasCeHsO?) as a chelating agent, sodium bicarbonate (NaHC.03) as a buffer, and sodium dithionite (Na2S204) as a reducing agent, heated in a water bath, and the resulting dissolved Fe determined by atomic adsorption spectrophotometry (Mehra and Jackson 1960). This extraction was also done to give CBD Al, which is less effective in the dissolution of non-silicate crystalline Al (Wada 1989). The final extraction was done with NaOH to give the concentration of Al that is not included in silicate minerals. Five chemical measures based on Canadian and American soil classification definitions of an "f' horizon were used as indicators of the intensity of podzolization: the organically complexed Fe and Al (pyrophosphate extractable); the organic C to organically complexed Fe (total C pyrophosphate Fe); the ratio of the organically complexed Fe and Al to the total free Fe and Al (pyrophosphate Fe+A1:CBD Fe+Al; pyrophosphate Fe+A1:CBD Fe + NaOH Al); and, the iron activity ratio (Blume and Schwertmann 1969), the ratio of organically complexed plus non-crystalline Fe to total free Fe (oxalate Fe:CBD Fe). Statistical Analyses Since the number of experimental units are equal, transformations were not considered for most variables. Only the C:A1, C:Fe, and C:Mn ratios were transformed using a natural logarithm, since the minimum and maximum variance differed over 100 times. The average concentration Chapter 4, Page 53 of both input and output solutions over the 10 L leaching period were used for statistical analyses. Comparisons between the input solution concentration to the respective output solution concentration was tested by a paired-comparison Mest. The following statistical model was tested for differences between the woody and non-woody input solutions: yij = p + tj + Si + flxfy where yij = response of an observation on the i column, and j treatment u- = overall mean tj = effect of j treatment (j = 1, 2, 3) Si = effect of i column set(i =1,2) th . .th Si><tj = effect of interaction between the j treatment in the I column set Treatment effects were tested against the s^tj interaction term. The following statistical model was tested for differences between the three different output solutions (woody, non-woody, acidified distilled water) and the outputinput ratio for each element in solution (woody, non-woody): yij = p + tj + Si + Si><tj + Ey where th .th yij = response of an observation on the l column, and j treatment (j. = overall mean tj = effect of j treatment (j = 1,2,3) Si = effect of i column set(i =1,2) SjX/j = effect of interaction between the j treatment in the i column set syi< = residual variation. Treatment effects were tested against the s^tj interaction term, and the ^x/j interaction was tested against the residual variation. Orthogonal contrasts (using the s^tj interaction as the error term) were used to test for significant differences between the woody and non-woody treatments, and the average of the woody and non-woody treatments compared to the acidified distilled water treatment. Chapter 4, Page 54 Results All doubles, blanks, and standards were correctly identified by the analyses to acceptable levels. During all filtering events, a few samples of distilled water were also filtered to test for contamination. The concentration of the filtered distilled water was consistently less than 1 % of the non-woody and woody leachate concentrations. The concentrations of elements in the input acidified distilled water also gives an indication of contamination. Solution and the soil columns The pH of the non-woody and woody input solutions were identical (pH = 3.5). For the input solutions, the average concentrations of DOC, Fe, Al, Mg, and K of the non-woody solution were significantly greater (a = 0.05) than those of the woody solution (Table 4.1). Comparing the input solutions to output leachates, only Fe and Mn had greater concentrations in the output leachate compared to the input solutions for all three treatments (Tables 4.1 and 4.2). Greater concentrations of the remaining elements were measured in the input solutions compared to the output leachates for both the non-woody and woody solutions. The acidified distilled water solution had greater concentrations of most elements in the output solution than in the input solution, except for the lack of differences for Cu and Zn. The C:Fe ratio was much larger in the input non-woody solution than in the output leachate, and the C:Mn ratio was much larger in the input solutions of both non-woody and woody solutions than the output leachate. Examining the output leachates, the C:Fe ratio was much less in the non-woody solution than in the woody solution but significant differences could not be detected between the two solutions for C:Mn and C:A1 ratios. There was significant interaction (p = 0001) for the Si:Al ratio. Only the average concentrations of DOC, Mn, Mg, and Na in the woody and non-woody solutions were significantly greater than in the acidified distilled water. Considering only those elements having significant differences in average concentrations between treatments, the DOC concentration was consistently greater in the input solution than in the output leachate; and was greater in the output leachate of the non-woody solution than in the woody leachate (Figure 4.2). For Fe, the input solution had very low concentrations, but the non-woody output leachate exhibited peaks of high concentration above an input of 4,000 mL of solution (Figure 4.3). The woody output leachate remained essentially the same as the input solution, and the woody output leachate was the same as the acidified distilled water output Chapter 4, Page 55 leachate. The pattern for Mn was similar to that for Fe, except that the output woody leachates had peaks of greater concentration of Mn than the input solution (Figure 4.4). The average concentration of Fe in the non-woody output leachate was significantly greater (a = 0.05) than the woody output leachate, but the average of both of these leachates was not significant compared to the acidified distilled water. The average concentration of Mn in the non-woody solution was significantly greater than the woody solution, and the average concentration of Mn of the two organic solutions was greater than the acidified distilled water. The pattern of solution concentration of Al was similar to that of the other elements, where the input solution had much greater concentrations than the output leachates (Figure 4.5). Only for Fe, Mn and Si was the ratio of output to input solution concentration greater than 1 (Table 4.3). Of these three elements, only Fe was significantly greater in the non-woody solution compared to the woody solution. The mean difference for Mn was large but significant differences could not be detected at a = 0.05. Mineral soil and the soil columns Preliminary analyses of the mineral soils in the columns indicated that significant differences could not be detected in any measure when comparisons between treatments were done by soil column depth. Consequently, an average of the three depths per column was used for further analysis. The results of the mineral soil chemical analyses followed, to some extent, the results of the soil columns (Table 4.4). Significant differences between the non-woody and woody soils, and between the average of the non-woody and woody soils versus the acidified distilled water soil, were detected for total N and organically complexed Fe (pyrophosphate extractable-Fe). Total C was marginally non-significant (at a = 0.05) between the non-woody and woody soils, but the average concentration of the two substrates was significantly different from the acidified distilled water. The organically-complexed Fe plus Al (pyrophosphate extractable-Fe+Al) was significantly different between the non-woody and woody soils, but not between the average of the non-woody and woody solutions versus the acidified distilled water. The organically-complexed Mn was not significantly different between the non-woody and woody soils, but was significantly different between the average of the non-woody and woody solutions versus the acidified distilled water soil. The pH of the mineral soils leached with woody and non-woody solutions were similar. Significant differences could not be detected for all other chemical measures. Chapter 4, Page 56 TABLE 4.1: The mean concentrations of the input solutions that were leached through the soil columns (standard error in brackets). The p-values are for the contrasts between the non-woody solution versus the woody solution. chemical measure of solutions leached through the soil columns the input solution non-woody woody water (pH = 3.5) DOC (mg L"1) 569.5 (61.1) 198.3 (28.5) JC = 0.013 0.2 Fe (mgL- 1) 0.47(0.07) 0.04(0.01) p = 0.024 0.01 Mn (mg L"1) 0.19(0.04) 0.23 (0.07) p = 0.703 <0.01 A l (mg L"1) 2.96(0.65) 0.97(0.33) p = 0.027 0.01 Ca(mgL-*) 11.57(3.38) 4.03 (0.56) p = 0.128 0.16 MgtmgL- 1 ) 3.25 (0.31) 1.84 (0.25) /? = 0.016 0.02 K(mgL- ' ) 28.57(1.62) 5.49(1.37) p = 0.015 0.23 Na (mg L"1) 4.88 (0.34) 3.57 (0.65) p = 0.300 0.77 Si ( m g L 4 ) 0.56 (0.05) 0.33 (0.05) /? = 0.156 0.02 Cu (mgL" 1) 0.04 (0.02) 0.03 (0.02) ^ = 0.555 0.03 Zn (mgL" 1) 0.235 (0.04) 0.18(0.05) ^ = 0.113 0.05 C:Fe 1275.9(219.2) 5545.0(2055.7) = 0.153 16.7 C:Mn 3658.1 (1430.0) 991.2(235.1) p = 0.227 56.0 C:A1 208.0(40.9) 264.0(109.5) p = 0.502 31.2 Si :Al 0.2(0.1) 0.4(0.1) ^ = 0.015 4.3 Chapter 4, Page 57 TABLE 4.2: The mean concentrations of the output leachates that leached through the soil columns (standard error in brackets). The /7-values are for the orthogonal contrasts between the non-woody solution versus the woody solution, and the average of the non-woody and woody solutions versus the acidified distilled water. chemical measure of solutions leached through the soil columns the input solution non-woody woody water (pH3.5) DOC (mg L"1) 132.0 (27.1) 41.7 (8.5) 1.9 (0.3) P = 0.021 /? = 0.016 Fe (mg L"1) 5.818 (2.700) 0.069 (0.026) 0.043 (0.029) P = 0.016 ^ = 0.080 Mn (mg L"1) 5.326(1.460) 1.457(0.543) 0.106 (0.051) P = 0.025 p = 0.026 A l (mgL" 1) 0.579 (0.116) 0.150(0.161) 0.244 (0.110) P = 0.058 p = 0.442 CaOngL- 1 ) 9.834(3.535) 3.954 (1.506) 2.190 (0.427) P = 0.077 p = 0.093 M g (mg L"') 2.686 (0.715) 1.594 (0.292) 0.415 (0.205) P = 0.051 p = 0.007 K (mg L"1) 17.794 (2.114) 1.127 (0.214) 0.398(0.160) P = 0.001 p = 0.004 Na (mg L"1) 4.278 (0.332) 3.572 (0.638) 0.691 (0.136) P = 0.337 p = 0.005 Si (mgL" 1) 4.834(1.484) 2.654 (0.074) 2.360 (0.145) P = 0.158 /? = 0.272 Cu (mgL" 1) 0.014(0.004) 0.010(0.001) 0.018 (0.007) P = 0.607 p = 0.423 Zn (mgU 1 ) 0.74 (0.018) 0.079 (0.028) 0.058 (0.029) P = 0.820 p = 0.409 C:Fe 27.1 (2.0) 1158.2 (721.3) 113.7 (54.7) P = 0.027 ^ = 0.439 C:Mn 28.6 (9.2) 39.4(10.6) 160.7(145.9) P = 0.830 ;? = 0.852 C:A1 235.7 (31.7) 342.8 (138.2) 30.8 (25.5) P = 0.827 /? = 0.017 Si:Al 8.5(1.0) 21.3 (5.4) 29.2 (21.6) p = 0.552 (plus si gnificant interaction) p = 0.449 Chapter 4, Page 58 I — I 1 1 1 1 1 I— 1 1 I 1 1 0 2000 4 0 0 0 6000 8000 10000 0 2000 4000 6000 8000 10000 Solution volume (mL) Solution volume (mL) FIGURE 4.2: The concentration of D O C at various points along the cumulative solution leaching volume for the three column sets (A vs B, C vs D, E vs F) of the non-woody substrate (A, C, E) and the woody substrate (B, D, F). The solid line represents the input solution concentration, the dotted line the average output concentration of the acidified distilled water, and the two dashed lines, the concentration of the output solution of each column set. Chapter 4, Page 59 2(100 2000 4000 6000 8000 10000 10000 S o l u t i o n v o l u m e ( m L ) 2000 4 0 0 0 6000 8000 10000 S o l u t i o n v o l u m e ( m L ) FIGURE 4.3: The concentration of Fe at various points along the cumulative solution leaching volume for the three column sets (A vs B, C vs D, E vs F) of the non-woody substrate (A, C, E) and the woody substrate (B, D, F). The solid line represents the input solution concentration, the dotted line the average output concentration of the acidified distilled water, and the two dashed lines, the concentration of the output solution of each column set. Chapter 4, Page 60 18 -r 16 -14 -£ 12 -tion' 10 -i— 8 -C <D 6 -o 4 -e s 2 -V /I i/ i *-o—8^- — - 8 ^ -(A) 2000 4000 6 0 0 0 8000 10000 18 -r 16 -14 -s, 12 -c o 10 -trat 8 -)ncen 6 -o 4 -Mn 2 -(C) 2000 4 0 0 0 6000 8000 10000 2000 4 0 0 0 6000 8000 10000 0 2000 4000 6000 8000 10000 0 2000 4000 6000 8000 10000 Solution volume (mL) Solution volume (mL) FIGURE 4.4: The concentration of Mn at various times along the cumulative solution leaching volume for the three column sets ( A vs B, C vs D, E vs F ) of the non-woody substrate (A , C , E ) and the woody substrate (B, D, F) . The solid line represents the input solution concentration, the dotted line the average output concentration of the acidified distilled water, and the two dashed lines, the concentration of the output solution of each column set. Chapter 4, Page 61 0 2000 4000 6000 8000 10000 0 2000 4000 6000 8000 10000 FIGURE 4.5: The concentration of Al at various points along the cumulative solution leaching volume for the three column sets (A vs B, C vs D, E vs F ) of the non-woody substrate (A, C, E) and the woody substrate (B, D, F) . The solid line represents the input solution concentration, the dotted line the average output concentration of the acidified distilled water, and the two dashed lines, the concentration of the output solution of each column set. Chapter 4, Page 62 4.3: The mean ratio of the output:input solution concentrations that were leached through the soil columns (standard error in brackets). The p-values are for the contrasts between the non-woody solution versus the woody solution. ratio of the output: input solutions leached through the soil columns chemical measures non-woody woody DOC 0.23 (0.05) 0.23 (0.07) /> = 0.981 Fe 11.91 (1.83) 1.56 (0.37) /> = 0.021 Mn 28.78 (4.32) 10.26(6.91) p = 0.097 A l 0.21 (0.04) 0.18 (0.05) /7 = 0.140 Ca 0.99(0.51) 1.93 (0.74) /? = 0.364 M g 0.83 (0.22) 0.92 (0.27) p = 0.382 K 0.62 (0.05) 0.25 (0.08) p = 0.016 Na 0.87 (0.02) 1.01 (0.08) /? = 0.239 Si 8.81(2.81) 8.37(1.01) /? = 0.898 Cu 0.56(0.16) 0.45 (0.16) /? = 0.148 Zn 0.30 (0.03) 0.47 (0.08) /? = 0.217 Chapter 4, Page 63 T A B L E 4.4. The mean chemical measures for the mineral soil in the columns that were leached with non-woody solutions, woody solutions, and acidified (to pH 3.5) distilled water. The/?-values are for the orthogonal contrasts between the non-woody solution versus the woody solution, and the average of the non-woody and woody solutions versus the acidified distilled water. chemical measure of the mineral soil soil column treatment solutions from the columns non-woody woody water (pH3.5) total N (%) 0.034 (0.005) P = 0.019 (0.004) 0.001 0.014(0.006) p = 0.002 pyrophosphate Fe (%) 0.079 (0.022) P = 0.050(0.014) 0.009 0.044 (0.017) /> = 0.017 total C (%) 0.442 (0.150) P = 0.362 (0.183) 0.054 0.305 (0.132) p = 0.019 pyrophosphate (Fe+Al) (%) 0.250 (0.069) P = 0.209 (0.053) 0.040 0.201 (0.059) /? = 0.073 pyrophosphate Mn (%) 0.006 (0.001) P = 0.005 (0.001) 0.453 0.003 (0.000) ^ = 0.012 pH 4.39 (0.03) P = 4.43 (0.07) 0.893 4.59 (0.32) p = 0.460 C:N 13.9(1.8) P = 24.5 (3.9) 0.301 41.8(11.1) p =0.043 oxalate Fe (%) 0.401 (0.065) P = 0.370 (0.080) 0.533 0.343 (0.101) = 0.335 CBD Fe (%) 1.227 (0.217) P = 1.254(0.142) 0.719 1.245 (0.214) p = 0.943 pyrophosphate Al (%) 0.171 (0.050) P = 0.159(0.041) 0.202 0.158 (0.043) p = 0.334 oxalate Al (%) 0.479 (0.087) P = 0.476 (0.106) 0.943 0.459 (0.111) p = 0.664 CBD Al (%) 0.244 (0.065) P = 0.260 (0.052) 0.431 0.248 (0.070) ^ = 0.815 NaOH Al (%) 0.764 (0.197) P = 0.813 (0.165) 0.407 0.783 (0.214) p = 0.905 Chapter 4, Page 64 Discussion Although significantly larger concentrations of DOC, Al, Mg, and K were measured in the output leachate from the soil columns treated with the non-woody solution, the concentrations in the input solution were also greater. Consequently, the non-woody solution does not leach greater amounts of these elements relative to the input. In podzolization, both Fe and Al movement through the soil is important. The output solution had significantly greater Fe concentrations in the non-woody solution compared to the woody solutions. Although the input of Fe was greater in the non-woody solution than the woody solution, the output difference far surpassed this small input difference; consequently, the ratio of output to input solution concentration was significantly greater for the non-woody solution compared to the woody solution. Since nearly equal volumes of water leached out of each column, greater concentrations effectively translates to greater amounts. Further, significantly greater concentration of pyrophosphate extractable Fe were associated with the mineral soil treated with the non-woody solution.Aluiminum concentrations were not significantly different between the non-woody and the woody output solutions (p = 0.058). Even if the output non-woody solution had greater Al concentration, it would likely have only reflected the greater Al in the input non-woody solution. The C:A1 ratio was similar for both input and output solutions for both non-woody and woody solutions, thus Al moving through as an organo-Al complex is likely negligible. The relatively small amount of Al in the output leachate compared to the input solutions (in which the soil columns have a net gain of Al) was unusual given that podzolization involves Al as one of the major elements. One explanation may be that the unnaturally high DOC levels used in the solution and the laboratory conditions, interfered with the formation of amorphous Al since organic acids are reported to inhibit the formation of imoglite/allophane (Huang 1991; Inoue and Huang 1986, 1990). The significant interaction (and non-significant difference) in the Si:Al ratio between the non-woody and woody output solutions suggests the column leaching failed to capture differences in imogolite movement. Eluviation of Mn is not included in the definition of a Podzolic soil, but the Mn results indicated the greater chelating intensity of the non-woody substrate. Although the concentration of Mn in the input woody solution was actually greater than the non-woody solution, Mn in the woody leachate was significantly less than the non-woody leachate. Chapter 4, Page 65 Both the greatly reduced C:Fe and C:Mn ratios associated with the output leachates of the woody and non-woody solutions suggest that the organic matter leachate contained more Fe and Mn than the input solution. The C:Fe ratio was particular low for the non-woody substrate compared to the woody substrate, suggesting the organic matter leaching out of the non-woody leachate contains much more Fe. The movement of Fe and Mn in solution are of particular interest to long-term productivity since they are not only indicators of Podzolic soil formation, but are also implicated in the formation of Orstein and Placic hardpans, respectively (McKeague etal. 1983). The greater capacity for non-woody substrates to leach Fe would presumably be due to the demonstrated greater solubility of humus compared to woody substrates. Also, the C:Fe and C:Mn ratios suggest that the initial organic substances in solution are different. Possibly the non-woody solution contains primarily humic solutes, similar to lake water (Peuravuori et al. 1997), and the woody solution also includes a dissolved lignin component (Opsahl and Benner 1998). If the differences in leachates between the two substrates merely reflects the greater solubility of the non-woody forest floor, then the interpretation is not as concise. The leaching was stopped essentially when the levels of Fe spiked in concentration for the non-woody solution for column 2 (Figure 4.2C). This spike in concentration is typical of column leaching. If the woody solutions were leached further, then perhaps a spike in concentration would occur later with more input solutions. Although, two of the column sets with the non-woody solution peaked at approximately 5000 mL (Figs. 4.2A,C), the woody solution showed no increased concentration even at 10,000 mL (Figs 4.2B,F). Thus on an equal mass basis, non-woody substrates appear to have a greater capacity for increasing the intensity of podzolization. The role of low molecular weight organic acids (LMWOA) was not considered in this study, though LMWOA have been reported to affect mineral weathering processes (Pohlman and McColl 1988; Tarn and McColl 1991). However, one source of LMWOA is from root exudates (Mench 1988), and the greater root density in the non-woody forest floor (Chapter 3) would mean that the non-woody substrate has even greater potential than the woody substrate to increase the intensity of podzolization. Caution is needed in extrapolation of the results to field conditions. In open systems such as soil columns, the nature and concentration of solutes, flow rate and volume, and temperature are markedly different from those occurring in soils (McKeague et al. 1986). This study was conducted at room temperature, and the input solution concentrations were far greater than actual field conditions. Further, only three replicates of substrates and mineral soils were tested. Chapter 4, Page 66 However, the use of soil columns eliminates the time factor in attempting to assess the relative potential for increasing the intensity of podzolization. The study showed clearly the lack of difference in the potential for acidification between non-woody and woody substrates, and the greater potential for podzolization of the non-woody substrate. This greater potential obtained from laboratory results should be corroborated by field studies. Conclusions There appears to be no difference in potential for acidification between the non-woody and woody forest floor substrates. However, the greater solubility of C associated with the non-woody substrate suggests that the non-woody forest floor substrate has greater potential for increasing the intensity of podzolization compared to the woody material on a mass basis. Presumably, the greater concentration of fulvic acid-type constituents associated with the non-woody forest floor solution means greater potential for chelation of Fe and Mn and subsequent movement downwards through the soil. Chapter 4, Page 67 Chapter 5. C O M P A R I S O N O F S O I L A C I D I F I C A T I O N A N D I N T E N S I T Y O F P O D Z O L I Z A T I O N B E N E A T H D E C A Y I N G W O O D VERSUS N O N - W O O D Y F O R E S T F L O O R S Introduction The soil column experiment of Chapter 4 suggests that the potential for greater intensity of podzolization is associated with the non-woody forest floor substrates compared to woody substrates. If this relationship is true, then CWD may actually have the reverse effect than originally hypothesized by Kinka et al. (1995). Accumulations of CWD may be associated with less intensity of podzolization, thus the maintenance of accumulations of CWD during harvesting may have little impact, or even an ameliorating impact, upon the soil beneath. However, since in open systems such as soil columns, the nature and concentration of solutes, flow rate and volume, and temperature are markedly different from those occurring in soils (McKeague et al. 1986), corroboration from field studies is necessary. This chapter presents the results of a field study comparing the solution chemical concentration leached from non-woody humus forms and large CWD accumulations, and comparing chemical measures of the mineral soils themselves. I investigated the long-term productivity implications of accumulations of CWD by addressing the questions: 1. Is there less concentration of dissolved organic carbon and lower pH associated with the leachate from forest floor substrates with a large accumulation of decaying wood compared to forest floor substrates without decaying wood? 2. Is there: (i) a thicker Ae layer, (ii) greater acidification, and (iii) greater degree of podzolization in the soil associated with forest floor substrates with a large accumulation of decaying wood compared to forest floor substrates without decaying wood? Chapter 5, Page 68 Methods Field Lysimeters Three study sites were located along the same south-facing slope but separated by clear-cuts. Being near to the sites described in Chapter 2, the sites were similar in most site characteristics, except the elevation ranged from 450 - 600 m, and the percent slope from 45 - 65%. Site conditions were intermediate in both nutrient supply and soil water storage capacity fitting the zonal concept as defined by Pojar et al. (1987). Coarse woody debris accumulations were dispersed throughout. Although not random, the choice to use stands which were left unlogged according to a logging plan was practical and feasible, and minimized observer influence in the selection criteria. Within each site, a plot of approximately 0.5 ha was established. In each plot, six 1 m*l m pedons were systematically located (as systematically as possible on a 30 m grid). Each pedon consisted of one side with a forest floor layer comprising a decay class IV or V log (woody substrate), and the opposite side a prevailing humus form subgroup without a large accumulation of decaying wood (non-woody substrate). The average thickness of the woody substrate was 70 cm, with a range of 55-120 cm. The average thickness of the non-woody substrate was 15 cm, with a range of 8-25 cm. Zero-tension soil water collectors were placed directly under each substrate. The soil water collectors consisted of 15 cm Buchner funnels filled with acid-washed sand, with an outflow tube running to a poypropylene 500 mL bottle (Figure 5.1). Throughfall and rainfall collectors, consisting of a 15 cm funnel inserted in a polypropylene 1 L bottle and supported 1 m above the ground level, were placed at each soil pedons and in the adjacent clearcut, respectively. Samples for DOC were collected after three major autumn rainfall events and averaged; samples for nitrogen, sulphur, and phosphorus were collected only once. Within six hours of the completion of a rainfall event, the solutions were collected and placed in a cooler packed with ice, and taken to the laboratory within two hours; pH was measured in the field. Solution samples were filtered through a 0.45 um polycarbonate membrane filter into vacuum flasks that were placed on ice. The solutions were refrigerated and analyzed within 48 hours. All analyses followed the procedures of Eaton etai. (1995). The concentration of DOC was determined by the same method described for the soil columns. Organic nitrogen concentration was determined by semi-micro-Kjeldahl; total dissolved P concentration was Chapter 5, Page 69 determined by persulfate plus stannous chloride treatment and determined colourimetrically; and the sulphate concentration was determined by ion chromatography. FIGURE 5.1. An illustration of the profile pair with zero-tension lysimeters sampling the solution leaching from each of the two substrates. Since equal numbers of experimental units per treatment were used, variables were not transformed. The following statistical model was used: ^ i j k = u + tk + Si + b(s)ij + s\xtk + Sjjk where .th . th th ^ i j k = response of an observation on the 1 site, j block, and k treatment. |j. = overall mean tk = effect of k treatment (k = 1,2) S-, - effect of i site (i = 1, 2, 3) th th b(s)y = effect of j block (pedons will be used as blocks) (j = 1, 2 , 6 ) within i site th . .th . SjX^k = effect of interaction between the k treatment in the l site Sjjk = residual variation. The SjXtk interaction was used for the error term to test treatments; and the residual variation, siJk, was used to test the s, xt* interaction. Chapter 5, Page 70 Mineral Soil Analyses The study occurred along an elevation and latitudinal gradation in nine areas of varying climates in BC, represented by biogeoclimatic zones (Meidinger and Pojar 1991) (Table 5.1). The study areas were located in: (1) southwestern BC in each of the Very Dry Maritime Coastal Western Hemlock (CWHxm) subzone, the Very Wet Maritime Coastal Western Hemlock (CWHvm) subzone, and the Moist Maritime Mountain Hemlock (MHmm) subzone; (2) southern central BC in each of the Very Dry Warm Interior Douglas-fir (IDFxw) subzone, the Moist Warm Interior Cedar Hemlock (ICHmw) subzone, and the Moist Cool Engelmann Spruce - Subalpine Fir (ESSF mk) subzone; and (3) central B.C. in each of the Wet Cool Interior Cedar Hemlock (ICHwk) subzone, the Moist Cool Sub-Boreal Spruce (SBSmk) subzone, and the Moist Warm Boreal White and Black Spruce (BWBSmw) subzone. These locations covered a precipitation, temperature, and continentality gradient in three directions: west-east longitude, north-south latitude, and low-high altitude. The areas sampled covered approximately 2500 square km within each subzone. Within each area, candidate stands were chosen according to forest-cover maps, local knowledge, and road access. Candidate stands were intermediate in both nutrient supply and soil water storage capacity, fitting the concept of zonal as described by Pojar et al. (1987). Only old-growth stands dominated by the tree species of their respective zone names, with CWD distributed throughout, were chosen. All candidate stands were identified on a map, and three study stands were chosen according to a systematic distribution throughout each respective zone. Subsequent field inspections ensured that the sites were identified as zonal by a combination of plant indicators, soil morphological characteristics, and landform using the descriptions provided in Meidinger and Pojar (1991) and local field guides. Although not random, this method was practical and feasible, and eliminated observer influence in the selection criteria. Within each stand, a 1-ha site was established, and 12 pedons lmxlm were systematically located (as systematic as possible on a 30 m grid). One side of each pedon consisted of a forest floor layer with a decay class IV or V log (woody substrate); and the opposite side consisting of a prevailing humus form subgroup without a large accumulation of decaying wood, the non-woody substrate (Figure 4.1). Blocking in this manner minimized the effects of two opposing influences. The distance had to be far enough to prevent, or at least minimize, each of the two substrates affecting the soil beneath the opposite substrate. Yet the distance had to be close enough to minimize differences in soil properties simply due to the inherent spatial variability of Chapter 5, Page 71 soil chemcial measures (Carter and Lowe 1986), or due to other extraneous factors such as variability in microsite conditions due to canopy and gap effects. Both species and canopy location may cause differences in decomposition of the forest floor directly below (Zhang and Liang 1995; Zhang and Zak 1995; Bauhus 1996). A one metre distance was chosen since podzolic soil profiles of coastal BC typically have a Bf horizon less than one metre thick (Agriculture Expert Committee on Soil Survey 1987); therefore, if pedogenesis does not exhibit an effect one metre in a vertical direction in 10,000 years, then presumably two different substrates separated by one metre in a horizontal direction will not affect each other, at least for the duration time that the log was on the ground. A decay class IV or V log longer than two metres, with a diameter larger than 30 cm, and incorporated by at least 30% (by volume) into the forest floor was chosen. If the location of the log was on a slope greater than 10%, then only logs near perpendicular to the slope (i.e., in an uphill-downhill direction within 20°) were chosen. A coin flip determined which side of the log was sampled for the non-woody forest floor. A one metre long trench was dug through the centre (lengthwise direction) of the log, and extended perpendicularly for one metre to the non-woody forest floor, forming a lmxlm square soil pit (Figure 5.2). Forest floors and mineral soils were described and identified according to Green et al. (1993) and Soil Classification Working Group (1998), respectively. From each side of the pedon (i.e., the two different substrates), the depth of the Ae horizon was recorded, and an approximate volume of 2000 cm3 was collected from (i) the decaying log; (ii) the LFH layer; (iii) the Ae horizon if present or, if not, the top 2 cm of the B horizon, separately from beneath the woody and non-woody substrate; and (iv) the upper B horizon from a depth of below the Ae horizon or top to cm to a depth of 10 cm. All samples were then air-dried to constant mass. Forest floor samples were ground in a Wiley mill to pass through a 2-mm sieve, and mineral soil samples were passed through a 2-mm sieve to separate coarse fragments. Chapter 5, Page 72 CD O W) N ° >H CD T3 O O c/l CD 0 0 -4-» — * H S.2 § 3 -S cn ~ 2 «. C O CJ § g a 2 O ^ ccj a. 3 o 1-0 0 X 3 on o C/3 cu e "O £ , 3 • P CD +3 0 0 < c i . „ CD CD "O T 3 3 3 . "K .tS (50 fl CD OH OH CD ta CD S O N X> 3 0 0 i n i n i n co o 0\ o o i n s . 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' s—s -^^  i n o o O r-~ VO CN "3" *—H CN tN CD ^ T3 i n O 2 O S 3 O N -a CD i o cn m m O PH i n CN i n o i n o CN E Q CD w _fl +-» H3 CD 2 * o CD s s 3 X ! TH o H ^ o class IV or V log i 1 m 1 W non-woody humus form >30cm 10 cm class IV or V ) j o g _ _ _ ^ y A or upper 2 cm 1 m 10 cm FIGURE 5.2. An example of a profile pair which will be sampled under each of the two substrates. The top illustration represents the top view, and the bottom illustration represents the side view. Mineral Soil Chemical Analyses Forest floor and upper B horizon mineral soil samples were analyzed, and their concentration expressed on a unit of soil mass basis. The pH, total C, total N, and mineralizable N was determined by the procedures described in Chapter 2. The upper B mineral soil samples were analyzed for extractable Fe and Al using the selective dissolution methods described in Chapter 4 Chapter 5, Page 74 with one exception. The concentration of Fe that is not included in silicate minerals, i.e., organically-complexed plus poorly crystalline and crystalline (dithionite Fe), was extracted using a 0.68 M sodium citrate solution (NasCeHsO? • 2H2O) with dithionite (Na2S204), shaken for 12 hours, and the resulting dissolved Fe determined by atomic adsorption spectrophotometry (McKeague et al. 1971; Sheldrick and McKeague 1975). This extraction gave dithionite Al, which is less effective in the dissolution of non-silicate crystalline Al (Wada 1989). The following chemical measures, based on Canadian and American soil classification definitions of an "f' horizon, were used as indicators of the intensity of podzolization: organically complexed Fe and Al (pyrophosphate extractable); ratio of organic C to organically complexed Fe (total C pyrophosphate Fe); ratio of the organically-complexed Fe and Al to the total free Fe and Al (pyrophosphate Fe + Ahdithionite Fe + Al); and the iron activity ratio (Blume and Schwertmann 1969), the ratio of organically complexed plus non-crystalline Fe to total free Fe (oxalate Fe:dithionite Fe). Forest floor samples were subjected to sequential fractionation (Lowe 1974) with 1:1 ethanol:benzene, yielding fraction A (lipids); and cold 0.1 M NaOH extraction yielding a soluble extract which was then treated with HC1 yielding a precipitated humic acid fraction (HA) and a dissolved fulvic acid fraction (FA). Each fraction was analyzed for carbon content (C in humic acid and carbon in fulvic acid) by ignition for 3 hours at 550 °C and the evolved CO2 was determined gravimetrically. The C in FA is indicative of the amount of fulvic acid-type constituents thought to be responsible for the chelation of Al and transition metals, especially Fe, and their subsequent downward movement through the soil. The HA:FA ratio is an indicator of the degree of humification, with higher ratios reflecting more intense humification from greater biological activity (Anderson and Coleman 1985). Lipids accumulate in acidic or anaerobic soil conditions where biological activity is low (McKeague et al. 1986). In addition to submitting the soil samples to the laboratory with hidden standards, blanks, spikes, and/or doubles, the following comparisons were done after the laboratory analyses as a further check to give confidence to the chemical measures and to test which chemical measures would be most useful. Using only those analyses from zones having distinct Ae horizons, each measure was compared between the Ae horizon and the upper Bf horizon of the non-woody pedons. A paired-comparison /-test was used to test for significant differences in chemical measures between the two horizons. The Fe and Al concentrations should be less in the Ae horizon compared to the Bf horizons. The upper B horizons of the non-woody pedons in very distinct climates and soil subgroups were compared using an independent sample, unequal Chapter 5, Page 75 variance /-test. Thus the Brunisols of the CWHxm and IDFvw subzone were compared to the Podzols of the MHmm and the ESSFmk subzone, respectively. Statistical Analyses Each subzone was analyzed separately with the statistical model used for the lysimeters. For the mineral soil samples, if differences were not significant at a = 0.05, then there is insufficient evidence to reject the null hypothesis. Thus to test whether to accept the null hypothesis, the Type II error was calculated (expressed as the power of the test, 1 - P) using a modification of the formula given in Ott (1993), where a two-tailed /-value with 9 degrees of freedom was substituted for the z-value. The value used to calculate p was the mean difference between the chemical measure of interest between the mineral soils from beneath the woody and non-woody substrates for each pair (block). For example, if a value for total C is required then p was calculated using the difference: %C for the mineral soil beneath the non-woody humus minus %C for the mineral soil beneath the class IV or V log. The alternative mean value used to detect a meaningful difference was chosen to specify a pedologically significant difference that we are attempting to detect, and was based on soil classification and soil nutrient regime identification systems (Table 5.2). There was significant power if 1-P was greater than 0.80, as recommended as a "reasonable choice" by Hinkelmann and Kempthorne (1994). Results Field Lysimeters The mean concentrations of DOC, ammonium, nitrate, phosphate, and sulphate was low whether collected in the open and under the canopy (Table 5.3). There were no significant differences between the solution chemical measures from lysimeter leachates collected beneath the non-woody and the woody substrates; although the mean concentration of DOC was only slightly non-significant (p = 0.051) between the two substrates (Table 5.3). Chapter 5, Page 76 TABLE 5.2. Mean differences between the two forest floor substrates to be considered pedologically significant. This mean difference was used to calculate ap-va\ue for P error. Rationales that are blank are based on personal judgement. Factor pedologically significant Rationale Ae horizon thickness pH total N mineralizeable-N total C C:N ratio C in humic acid (%) C in fulvic acid (%) C in HA:C in FA lipids (%) pyrophosphate Fe pyrophosphate Fe+Al pyrophosphate Fe + A l dithionite Fe + A l oxalatle Fe/dithionite Fe organic C/pyrophosphate Fe 2 cm 0.5 0.1 % 20 ppm 5% 10 5 5 2 1 0.3% 0.6% 0.5 0.2 20 Based on the soil nutrient regime field identification of the biogeoclimatic classification. A two cm thick Ae horizon is one of the identifiers separating nutrient poor from rich sites (Green and Klinka 1994). based on the difference between a nutrient poor and medium and rich soil nutrient regime (Klinka et al. 1994) based on the difference between a nutrient poor and rich soil nutrient regime (Klinka et al. 1994) Based on the difference between a Bh horizon and Bf horizon (Agriculture Expert Committee on Soil Survey) Based on a C:N ratio of 20-30 having neither net mineralization nor immobilzation of nitrogen Based on the definition of a podzolic B horizon (Soil Classification Working Group 1998) Based on the definition of a podzolic B horizon (Soil Classification Working Group 1998) Based on the definition of a spodic horizon (Soil Survey Staff 1975) Based on Blume and Schwertmann (1969) Based on the definition of a podzolic B horizon (Soil Classification Working Group 1998) Chapter 5, Page 77 TABLE 5.3: Mean chemical solution concentrations (standard error of the mean in brackets) obtained from collectors located in a clearcut and collectors under the tree canopy (throughfall). The DOC and pH values are based on averages of three rain periods. The values of the remaining measures are based on one rainfall event. s o l u t i o n c h e m i c a l m e a s u r e s o l u t i o n c o l l e c t o r l o c a t i o n o p e n t h r o u g h f a l l DOC (mg L"1) 0.0 (0.0) 6.9(1.2) pH 5.2 (0.3) 4.7 (0.3) ammonium (mg L"1) 0.05 (O.01) 0.04 (<0.01) nitrate (mg L"1) 0.05 (0.01) 0.14(0.01) phosphate (mg L"1) 0.03 (<0.01) 0.03 (<0.01) sulphate (mg L"1) 1.12(0.08) 3.63 (0.43) Mineral Soil Indicators of Podzolization Intensity Confidence would be placed in chemical measures that show differences between the Ae horizon and the underlying Bf horizon, and that show differences from contrasting climates. If a measure fails to detect these differences, than the measure would be of limited use in detecting differences between two different organic substrates. Differences in contrasting climates for total N, C:N ratio, mineralizable N and the organic C/pyrophosphate Fe ratio were inconsistent - generally significant differences could not be detected between the non-woody Bf horizon in the CWHxm vs. the MHmm subzone, and the IDFxw vs. the ESSFmk subzone (Table 5.5). The other measures appeared to be effective at detecting significant differences at this scale of resolution. Comparing chemical measures of the non-woody forest floors of the Ae horizon to their respective underlying Bf horizon, significant differences (a = 0.05) were not detected for total N and mineralizable N using this sample size (Table 5.6). Total C or organic Cpyrophosphate Fe ratio was not consistent with a sample size of three sites within subzones. The oxalate Fe:citrate dithionite Fe ratio had trouble in the MHmm subzone, where the mean between the Ae horizon and underlying Bf horizon were similar (Table 5.6). The other measures were able to detect significant differences at this scale. Chapter 5, Page 78 TABLE 5.4: Mean chemical leachate concentrations (standard error of the mean in brackets) obtained from zero tension lysimeters placed under non-woody and woody substrates. The DOC and pH values are based on averages of three rain periods. The values of the remaining measures are based on one rainfall event. None of the interactions were significant. leachate chemical measure forest floor substrate non-woody woody DOC (mg L"1) 13.7 (0.6) P = 19.6 (2.8) 0.051 pH 4.3 (0.1) P = 4.1 (0.1) 0.774 ammonium (mg L -1) 0.047 (0.009) P = 0.067 (0.020) 0.206 nitrate (mg L_1) 0.002 (0.001) P = 0.000 (0.000) 0.340 phosphate (mg L_1) 0.051 (0.027) P = 0.076 (0.025) 0.454 sulphate (mg L_1) 9.834(1.433) P = 13.190 (2.780) 0.464 Non-woody vs. woody substrates The results from all subzones were similar - either mean differences between the non-woody and woody substrates were not significantly different or mean differences were not pedolgocially different. Therefore, only the results of the three coastal subzones are presented in detail, with the remaining subzones being included in summary tables. The specific results for the remaining subzones are presented in the appendix. Comparing the mean pH of the non-woody versus woody substrates, significant differences (a = 0.05) were only detected in the CWHvm and CWHxm subzones. The interaction term was either non-significant, or, if significant, had similar patterns of constantly increasing or decreasing pH (Tables 5.7, 5.9, 5.11). Woody substrate acidity was greater in these two subzones, although in the CWHvm subzone the difference in mean pH was less than the meaningful criteria of a pH difference of 0.5 (Table 5.2). In the MHmm subzone, the difference Chapter 5, Page 7 9 in pH of the two substrates was not greater than the pedologically significant criteria of 0.5 (P = 0.006). Total C and N, the C:N ratio, C in the humic acid fraction, C in the fulvic acid fraction, and the ratio of the two fractions between the two forest floor substrates were significantly different at a = 0.05 in all three subzones (Tables 5.7, 5.9, 5.11). The HA concentration was greater in the woody substrates, the FA concentration greater in the non-woody substrates, and the HA:FA ratio greater in the woody substrates. For the both the A horizon (or upper 2 cm of the soil profile) and the upper 10 cm of the B horizon directly under each forest floor substrate, significant differences were few and scattered (Tables 5.7 to 5.12). The C:N ratio in the CWHxm and CWHvm was significantly different in either one or both of the upper 2 and 10 cm of the soil profile. However, the mean differences were less than the meaningful criteria of 10 (Table 5.3). In the upper 2 cm directly beneath the substrates, the soil beneath the woody substrate was associated with lower pH in the CWHxm subzone (Table 5.9); and total N was less in soil beneath the woody substrate in the MHmm subzone (Table 5.11). Significant differences in any chemical measure were not detected for the upper 10 cm of the B horizon. The Beta-analyses indicated that the power of the test was adequate (1-p > 0.80) for most of the measures used to infer that the difference between the woody and non-woody substrates were not pedologically significant, according to the criteria in Table 5.2 (Tables 5.13 and 5.14). However, if meaningful differences in the measures of podzolization are halved, then a larger number of sites would be needed to increase the power of the test to detect differences between measures under the non-woody versus woody substrates (Table 5.15). Chapter 5, Page 80 TABLE 5.5: Mean chemical properties (standard error of the mean in brackets; based on n = 3) and /rvalue between the non-woody Bf horizon of the CWHxm compared to the MHmm subzone, and of the IDFxw compared to the ESSFmk subzone. Chemical property CWHxm vs MHmm IDFmm vs. ESSFvk pH 5.05 (0.09); 4.43 (0.05) p = 0.009 5.85(0.14); 4.57(0.07) p = 0.003 total C (%) 2.27(0.29); 6.32(0.18) p< 0.001 2.40(0.34); 3.97 (0.05) p = 0.041 total N (%) 0.07(0.01); 0.25 (0.03) p = 0.008 0.14(0.02); 0.17(0.01) p = 0.208 C:N 31.1(2.8); 26.4(1.9) p = 0.245 17.4(0.5); 24.1(1.1) /? = 0.011 min-N (ppm) 22.9(8.2); 33.4(12.2) p = 0.522 62.7(6.7); 23.3(2.4) = 0.018 pyrophosphate Fe (%) 0.26(0.01); 0.84(0.13) p = 0.044 0.17(0.02); 0.71(0.05) p = 0.003 pyrophosphate (Fe+ Al) (%) 0.56(0.03); 1.73 (0.05) p< 0.001 0.29(0.02); 1.38 (0.06) p< 0.001 organic C pyrophosphate Fe 8.9(0.9); 11.3(1.3) p = 0.225 14.9(1.0); 6.1(0.3) /7 = 0.008 pyrophosphate (Fe + Al) dithionite (Fe + Al) 0.32(0.03); 0.75(0.01) < 0.001 0.19(0.03); 0.60(0.01) ^ = 0.003 oxalate - Fe dithionite - Fe 0.34(0.04); 0.60(0.02) /? = 0.014 0.21(0.03); 0.84(0.01) p< 0.001 Chapter 5, Page 81 O O CL) < T3 O O i c o c <u 4 3 +H c ft ^ £ s +-» O ft N 4 3 £3" co 'cd > s § W m c II «3 CJ c o -o CD co ccj 4 3 CD 44 CD cd ui X ) G a a > o CD 43 CD a CD X ! -*-» <+H o U i O fc CD 7 3 U l cd 7 3 a C o "C o 43 DO c CD 7 3 C 3 co CD u i OH 3 u i cd a > cd CD CD CD CU s * S c ° W O J _C CQ ^ < 44 E PH oo W E £ ffi CD C L o u a, 13 CD CD 4= CD /—s s s ,—s /•—\ i n i n p p © . — 1 © p © © ' © C N © © N — ' N ' r - -i n C D o Os m 00 C N m r n m i n © o o r n C N © p r n o © C N © C N o © © © © © © ' o © © II I  II , , II /—~v II II i n ll C N I II i n II »-H II C N p a , ci, O Cl, ci, ^ J a . © a , © © © © — ' © O m i n 00 o o o o Os , — H C N © C N o © © ffi a. r n © © od s o © © © © o Os S O o o o o c~- © © © © © o © ' © © II M II II 00 11 C N 11 Cl, © Cl, © a . © © i n OO r n © © ^—s - — -C N © >n p 00 m © Os CN~ m i n © r n © © o © C N © © © © 4.43 C N so © 6.32 Os C N 0.25 S O r n 26.4 OO i n i n 33.4i i n m 0.84 oo © 1.73 Os C N O 11.3 m © 0.75 C N © 0.60 m O © © © © © © © © © /j—^ || . r. 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C L ca 43 u TABLE 5.7: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Very Wet Maritime Coastal Western Hemlock (CWHvm) subzone. Below the mean and standard error are the treatment ^ -values followed by the /?-value for |3, where applicable. For site x treatment interaction /^ -values, an asterix indicates that although there is a significant interaction effect, the effect is in one direction. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.20) values. Short-form acronyms are: min-N = mineralizable N; HA = humic acid; FA = fulvic acid. chemical Forest Floor Mineral soil horizon property Ae Upper B non-woody woody non-woody woody non-woody woody depth 3.5 (0.7) 3.8 (0.8) (cm) 0.506; 0.216 pH 3.72 (0.04) 3.41 (0.02) 4.00 (0.08) 3.95 (0.11) 4.42 (0.05) 4.36 (0.07) 0.022 0.447; 0.026 0.168; 0.003 total C 48.87 (0.45) 58.84 (0.42) 2.95 (0.75) 3.55 (0.35) 5.43 (0.55) 5.17 (0.19) (%) 0.001 0.369; 0.029 0.713; 0.0.036 totalN 1.58 (0.06) 0.62 (0.05) 0.16 (0.05) 0.15 (0.04) 0.23 (0.01) 0.19(0.02) (%) <0.001 0.396; 0.157 0.247; 0.860 C:N 31.1 (1.4) 104.4 (9.8) 22.5 (3.4) 27.4 (4.3) 25.3 (2.8) 27.9 (2.9) 0.013 0.139; 0.891 0.001 min-N 17.0 (5.0) 13.5 (1.7) 24.6(1.9) 21.2 (2.6) (ppm) 0.403; 0.267 0.386; 0.212 C i n H A 12.73 (0.28) 15.11 (1.71) (%) <0.001 C in F A 10.23 (0.43) 6.57 (0.53) (%) 0.007 H A : F A 1.28 (0.06) 2.52 (0.14) 0.013 lipids 3.59 (0.15) 1.68 (0.20) (%) 0.031* Chapter 5, Page 83 TABLE 5.8: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the CWHvm subzone. Below the mean and standard error are the treatment p-values followed by site x treatment interaction />-values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, the /rvalue for p. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.10) values. Short-form acronyms are: pyrophosphate = sodium pyrophosphate extractable; dithionite = dithionite-citrate extractable. chemical property Ae non-woody Mineral so woody il horizons upper non-woody B woody Pyrophosphate Fe 0.30 (0.09) 0.24 (0.04) 0.75 (0.14) 0.67 (0.05) (%) 0.555; 0.817 0.468; 0.900 pyrophosphate (Fe + Al) 0.56(0.11) 0.45 (0.07) 1.57 (0.18) 1.43 (0.13) (%) 0.353; 0.228 0.150; 0.040 organic C 61.7 (31.4) 43.3 (10.8) 9.2 (2.0) 9.1 (0.9) pyrophosphate Fe 0.521; 0.974 0.909; 0.003 pyrophosphate (Fe + Al) 0.43 (0.05) 0.43 (0.06) 0.63 (0.07) 0.60 (0.07) dithionite (Fe + Al) 0.980; <0.001 0.212; <0.001 oxalate - Fe 0.47 (0.05) 0.49 (0.03) 0.62 (0.06) 0.64 (0.07) dithionite - Fe 0.652; 0.057 0.245; 0.003 Chapter 5, Page 84 TABLE 5.9: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Very Dry Maritime Coastal Western Hemlock (CWHxm) subzone. Below the mean and standard error are the treatment ^ -values followed by site x treatment interaction p-values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, the p-va\ue for p. For site x treatment interactionp-values, an asterix indicates that although there is a significant interaction effect, the effect is in one direction. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.20) values. Short-form acronyms are: min-N = mineralizable N; HA = humic acid; FA = fulvic acid. chemical Forest floor Mineral so il horizon property upper 2 cm upper B non-woody woody non-woody woody non-woody woody depth (cm) pH 4.97 (0.16) 3.67 (0.02) 4.85 (0.18) 4.40 (0.11) 5.05 (0.09) 4.86 (0.15) 0.011; 0.035* 0.022; 0.649 0.089; 0.403; 0.206 total C 37.71 (5.48) 58.39 (0.14) 4.33 (1.61) 2.43 (0.14) 2.27 (0.29) 2.15 (0.19) (%) 0.065; O.001* 0.327; <0. 001; 0.922 0.571; 0.221; 0.001 totalN 0.92 (0.13) 0.45 (0.02) 0.13 (0.06) 0.05 (0.01) 0.07 (0.01) 0.05 (0.01) (%) 0.052; <0.001* 0.282; <0 001; 0.969 0.117; 0.002*; 0.018 C:N 41.5 (0.7) 142.8 (10.2) 36.0 (2.3) 45.7 (2.4) 31.1(2.8) 40.5(1.8) 0.009; 0.202 0.001; 0.106 0.083; 0.025*; 0.972 min-N 24.6 (7.7) 9.9(1.4) 22.9(8.2) 13.4(3.7) (ppm) 0.141; 0.008; 0.963 0.171; 0.020*; 0.908 C in H A 9.59 (1.29) 14.17 (0.98) (%) 0.026; 0.095* C in FA 9.12 (0.41) 5.05 (0.51) (%) 0.014; 0.295 H A : F A 1.10 (0.17) 3.09 (0.12) 0.014; 0.232 lipids 2.75 (0.71) 2.07 (0.30) (%) 0.561; 0.973 Chapter 5, Page 85 TABLE 5.10: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the CWHxm subzone. Below the mean and standard error are the treatment p-values followed by site x treatment interaction /^ -values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, thep-va\ue for p. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.10) values. Short-form acronyms are: pyrophosphate = sodium pyrophosphate extractable; dithionite = dithionite-citrate extractable. chemical property Mineral so il horizons upper 2 cm upper B non-woody woody non-woody woody pyrophosphate Fe 0.26 (0.01) 0.26 (0.01) 0.26 (0.01) 0.27 (0.02) (%) 0.961; 0.001 0.561; 0.011 pyrophosphate (Fe + Al) 0.47 (0.01) 0.49 (0.03) 0.56 (0.03) 0.60 (0.02) (%) 0.581; 0.001 0.192; 0.001 organic C 18.0 (7.4) 9.8 (0.4) 8.9 (0.9) 8.2 (1.3) pyrophosphate Fe 0.371; 0.940 0.284; <0.001 pyrophosphate (Fe + Al) 0.82 (0.03) 0.78 (0.01) 0.32 (0.03) 0.33 (0.02) dithionite (Fe + Al) 0.849; 0.001 0.276; 0.753; <0.001 oxalate - Fe 0.44 (0.05) 0.48 (0.04) 0.34 (0.04) 0.37 (0.06) dithionite - Fe 0.230; 0.034 0.347; 0.224 Chapter 5, Page 86 TABLE 5.11: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Maritime Mountain Hemlock (MHmm) subzone. Below the mean and standard error are the treatment />-values followed by site x treatment interaction /rvalues (an asterix indicates significance differences at p < 0.05 without any significant interaction effect), and where applicable, the;?-value for p. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.20) values. Short-form acronyms are: min-N = mineralizable N; HA = humic acid; FA = fulvic acid. chemical Forest floor Mineral so il horizon property Ae upper B non-woody woody non-woody Woody non-woody woody depth 4.7 (0.8) 2.8 (1.1) (cm) 0 .775 ; 0 .044 pH 3.68 (0.04) 3.57 (0.05) 4 .10 (0.12) 4.08 (0.08) 4.43 (0.05) 4.48 (0.03) 0 .063 ; 0 .006 0 .734; 0 .010 0 .309 ; 0.008 total C 52.90 (0.45) 60 .52 (0.11) 5.98 (0.97) 4.93 (0.69) 6.32 (0.18) 6.23 (0.47) (%) 0 .004 0 .067; 0 .005 0 .832; 0.005 totalN 1 .52(0 .13) 0 . 3 4 ( 0 . 0 6 ) 0.23 (0.03) 0.18 (0.03) 0.25 (0.03) 0.23 (0.04) (%) 0 .005* 0.043 0.615; 0.616 C:N 35.6 (3.1) 201 .5 (25.6) 28.1 (0.6) 30.0(1.3) 26.4 (1.9) 27.6 (2.3) 0 .019* 0.401; 0.457 0.338; 0.020 min-N 26.5 (8.1) 18.6 (4.3) 33.4 (12.2) 32.7 (13.7) (ppm) 0.190; 0.838 0 .783 ; 0.017 C in H A 10.22 (1.01) 12.30 (1.14) (%) 0.006 C in FA 7.58 (0.68) 4.40 (0.16) (%) 0.027 H A : F A 1.42 (0.02) 2.91 (0.18) 0.013 lipids 3.70(0.47) 1.29(0.16) (%) 0.059* 0.973 Chapter 5, Page 87 TABLE 5.12: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the MHmm subzone. Below the mean and standard error are the treatment /^ -values followed by site x treatment interaction p-values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, the/>-value for p. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.10) values. Short-form acronyms are: pyrophosphate = sodium pyrophosphate extractable; dithionite = dithionite-citrate extractable. c h e m i c a l property M i n e r a l so 1 ho r i zons A e upper B n o n - w o o d y w o o d y n o n - w o o d y w o o d y pyrophosphate F e 0.38 (0.10) 0 .35 (0.11) 0 .84 (0.13) 0.98 (0.15) (%) 0 .335 ; 0 .013 0 .115 ; 0 .180 pyrophosphate (Fe + A l ) 0 .675 (0.151) 0.653 (0.165) 1.732 (0.051) 1.906 (0.091) (%) 0 .784 ; 0 .036 0.191; 0.342 organ ic C 26.6 (3.8) 22 .9 (5.3) 11.3 (1.3) 8.9 (1.3) pyrophosphate F e 0 .280 ; 0.081 0 .059 ; 0.001 pyrophosphate ( F e + A l ) 0.58 (0.04) 0.59 (0.03) 0 .75 (0.01) 0.727 (0.06) d i th ioni te (Fe + A l ) 0 . 8 5 1 ; 0.003 0 . 7 0 5 ; * * 0.023 oxalate - F e 0.59 (0.03) 0 .542 (0.01) 0 .597 (0.02) 0.61 (0.04) d i th ion i te - F e 0 .176 ; 0 .077 0 .678 ; 0.073 Chapter 5, Page 88 CD Cd -t-> ~ S ,2 -CD CO H >-» ci> o ~o fi CO o ^ £ -fi 3 fi "t~* o 'SH O CQ CD 43 -a ° > II cD-cD CO c+_< co cd « U CD CD fi CD a CD CN U i CD P H 5^  U i O c O • . ~ N T) M •c fi o 43 <D , c u Cd M-H u '43 ui 73 SO +n * u CD CD .a -a CO O fi CO cu td < 3' CD 73 43 £ •£3 cd cd 43 " 43 S "o ^ N w 73 W O - f i P H H <+H o ^ tu o 2 o 8> II o CD tU .a > o 43 a ^ s (U o 43 fi H g .-H -*-> o cu P H -ft co 73 O co a OH < ~ °°, U l CO a g CD <D tu 3^ 43 43 U .2 3 * cd oJ) £ 3 co O 43 fi 3 CU « CD >•> GO P O fi fi o fi CU 43 m CD — : « ^ fi Ui OD H O co £ -ft & § r v cd fi OT C CD ° 43 O 13 00 CQ o o 4«H > ffi O > PH 00 o o W S ffi O tu CL, O cd o e CD 43 O Z < z c o _N 'C O 43 C+H O CL, CD Q OS oo CD 00 CD a. 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Sweeping generalizations cannot be made; conclusions must be made with caution, and more controlled randomization laboratory experiments are needed to augment field studies. In this study, the sampling of sites was not random, although an effort was made to eliminate any user influence. Additionally, the treatments were not assigned randomly, but rather chosen from what already existed on the ground. There is, however, no conceivable reason why the place on which a falling log finally rests should not be considered a random location. Field Lysimeters The field lysimeters suggest that there little differences between the DOC leaching from non-woody and woody substrates. Since the chemical solubility differences between the two substrates is large (Chapter 4), and the concentration of FA is greater in the non-woody forest floor, it seems inconceivable that there would be so little difference in the lysimeter solutions. However, the volume of solution flowing through the two substrates was not measured and may be as important as concentration. Given the relatively similar humic material concentrations, the substrate that is associated with greater water flow would presumably have a greater potential for increased intensity of podzolization. The much thicker CWD forest floor may mean that less precipitation would leach through simply due to water flowing off of the raised log. Mineral Soil and Indicators of Intensity of Podzolization Only for the CWHxm subzone was the pH of the woody substrates both significantly and pedologically different from the non-woody substrates. The much smaller difference in pH of the upper 2 cm was 0.45. However, in the upper B horizon, the power to detect a difference of at least 0.5 was lost. The two subzones having Podzol soils either had mean differences that were Chapter 5, Page 92 too small to be pedologically significant (CWHvm), or had (3 values indicating that the means were pedologically the same (MHmm). Significant and large differences in nutrition measures (total C, total N, C:N ratio) between the non-woody and woody substrates for all subzones was detected. Since the bulk density of decay class IV and V wood is similar to non-woody humus forms (Sidle and Shaw 1983), the large differences between the two substrates would still be maintained on a volume basis. Consequently, if CWD accumulations were large enough to cover a large proportion of an area, then the resulting woody forest floor would have lower nutrient availability compared to a non-woody forest floor. Despite differences in nutrient properties and humus fractions between the non-woody and woody substrates, there were little differences in the corresponding nutrition and Podzol measures (depth of the Ae horizon; Fe and Al extractions) of the soil directly beneath (Figure 5.3). In particular, the greater concentration of fulvic acids associated with the non-woody substrate in the CWHvm, CWHxm, and MHmm did not translate into equivalent differences in the measures of the degree of podzolization. Fulvic acid is the main constituent of organic material responsible for chelation of Fe and Al, and the subsequent downward movement of this organo-metallic complex (Schnitzer 1969). Although not all of the measures in all subzones had a large enough sample to conclude that there was no meaningful difference, the overall pattern of significant P's (Tables 5.12 and 5.13) appeared to be consistent in that within every zone, always one of the measures of the degree of podzolization was present at p < 0.20. If smaller differences are determined to be meaningful, then a larger sample size would be required to detect the smaller differences. Contrary to two previous exploratory studies (Klinka et al. 1995; Kayahara et al. 1996), significant differences were not detected between the depth of the Ae horizon of the non-woody pedon versus the woody pedon. Despite the greater sample size in this study, the mean differences in Ae horizon depth were simply too small for all zones. However, the differences in the previous studies were not large nor consistent. Thus, the anecdotal observations of McKeague et al. (1983) that a deeper Ae horizon is associated with accumulations of CWD appears to be wrong for soils on zonal sites in BC. There is a discrepancy in results from soil columns and the concentration of fulvic acid-type constituents. Considering the large chemical differences in the substrates themselves, it was surprising that the only difference in the mineral soil horizon was the C:N ratio, and even these differences were too sporadic and small to be considered meaningful. This small impact of such contrasting forest floor substrates is puzzling since the non-woody substrate has a significantly Chapter 5, Page 93 greater concentration of fulvic acid-type constituents, and the non-woody forest floor clearly has greater potential to increase the intensity of podzolization compared to the woody forest floor (Chapter 4). The lysimeter results of Chapter 4 suggested that a greater volume of water was flowing through the non-woody forest floor, thus lowering the solution concentration of DOC. Yet if this flow difference did occur, it would be expected that the podzolization indicators of extractive Fe and Al would be larger in the mineral soil under the non-woody substrate. Lateral soil water flow may be mixing with the vertical flow from the substrates. Although the one metre distance between substrates omitted the effect of the decaying wood upon the soil under the non-woody forest floor, I did not find the converse situation (i.e., large enough accumulations of decaying wood that would eliminate the influence of the adjacent non-woody forest floor upon the soil beneath the decaying wood). However, even if this latter situation was true, differences should occur within the 2 cm depth. Neither Brunisolic or Podzolic soils had differences in soil chemical properties, so the initial degree of podzolization of Podzol soils does not account for the lack of effect of the CWD substrate. non-woody woody 12 10 H 5? 6 (B) fulvic acid pyro-Fe non-woody woody FIGURE 5.3: Difference in (A) total N between the non-woody and woody substrates (open boxes) and the upper 10 cm of the mineral soil (shaded boxes) and (B) between the C in fulvic acid between the non-woody and woody substrates and pyrophosphate Fe in the upper 10 cm of the mineral soil. Standard error is indicated with the bars. Chapter 5, Page 94 Although there is an apparent discrepancy between what appears to be a greater potential for the non-woody forest floor material to increase the intensity of podzolization compared to the woody forest floor, and the lack of differences in the field measured effects, the original concern of this Section has been addressed. At minimum, CWD has an equal potential compared to non-woody forest floor with regards to intensity of podzolization; at maximum, CWD has less potential. Either way, long term site productivity appears to be unaffected by leaving a legacy of CWD. Conclusions Based on the similarity of the depth of Ae horizon, pH, and the chemical measures used to define a Bf horizon, current evidence suggests that decaying wood does not increase acidification and eluviation of mineral soils on zonal sites in the climates studied here. The theory that accumulations of decaying wood cause increased acidification and eluviation compared to non-woody forest floors appears not to be true in this case. Based on the evidence to date, forest managers deciding to leave a legacy of CWD for habitat and biodiversity need not be concerned that the long-term productivity of the zonal sites is being negatively impacted. Chapter 5, Page 95 S E C T I O N II: D I S C U S S I O N The pH of both non-woody and woody forest floor materials is essentially the same so neither of the two substrates has a greater potential for acidification over the other. Although the soil columns suggest that the non-woody forest floor material has greater potential for increasing the intensity of podzolization, the field lysimeter sampling and soil sampling suggest that neither the non-woody forest floors nor large accumulations of CWD increase the intensity of podzolization. Certainly, the intensity of podzolization is not similar in extent to the creation of heathlands reported in England (Spurr and Barnes 1980). Missing from the explanation is the amount of water leaching from each substrate. Possibly, the amount of water leaching through each substrate far over-rides the concentration of the solution. The "bottom line" is that the differences in the chemical properties of the two substrates makes little difference to the soil directly beneath. The theory that accumulations of decaying wood cause greater acidification and eluviation than non-woody forest floors, or the contrary theory that the greater fulvic acid type constituents in the non-woody forest floor causes greater eluviation than woody forest floors, appear not to hold on the zonal sites sampled. Section II: Discussion, Page 96 Chapter 6. GENERAL DISCUSSION AND CONCLUSIONS The importance of the functional role of CWD is recognized, and if biodiversity concerns are a management objective, then the maintenance of a legacy of CWD is necessary upon harvesting. However, if commodity management is the objective, then the importance of CWD for tree survival and growth needs to be addressed. The intent of this thesis was to address two concerns of forest managers who are faced with decisions on the maintenance of CWD while operating under objectives of commodity management. Short-Term Productivity The first concern was: Is there an immediate nutritional or moisture supply advantage to leaving a legacy of CWD for the survival and growth of trees especially in comparison to non-woody humus forms in the coastal climate of BC? If the work of Harvey et al. (1979) is extended to the ICH and IDF zones of BC, then the evidence suggests that CWD may be important to tree survival and growth. On the other hand, if the work of Loopstra et al. (1988) is extended to the North Coast of BC, then the evidence suggests that CWD is relatively unimportant. There then exists the climates that are wetter than the ICH and IDF zones, but warmer and drier than the North Coast of BC, to contend with. The results of Section I of this thesis suggests that CWD is relatively unimportant to seedling survival and tree growth within the wetter south coastal climates of BC, on sites not having a moisture deficit or excess. The non-woody humus forms are the important substrate for short-term productivity. I would even propose that the nutrient properties of decay class IV and V wood is primarily due to humic substances leaching from the over-lying non-woody LFH layer into the relatively inert lignin matrix. By definition, decay classes IV and V wood are buried under the prevalent non-woody humus forms. Decay classes I to III are relatively unimportant to short-term productivity since it is during these stages that the wood has net nutrient immobilization. Some caution is needed, since the aforementioned statements assume some sort of planting (CWD may be important for seed germination and survival as discussed in Section I Discussion), and does not take into account whether mycorrhizal dispersal is dependent on small mammals (see Section I Discussion). Chapter 7, Page 97 Long-Term Productivity The second concern was: Does decaying wood cause acidification of the soil directly beneath and increase the intensity of podzolization compared to non-woody humus forms? This concern is especially necessary in scenarios where plantation management is carried out to meet commodity objectives, but a legacy of CWD is left to ameliorate biodiveristy issues. Since plantation management minimizes blowdown and the associated "ploughing effect" (Armson and Fessenden 1973), leaving a legacy of CWD may increase the intensity of podzolization without the natural blowdown disturbance to "reverse" the process. However, the results of Section II suggest that CWD does not increase the intensity of podzolization, and, in fact, has a lower potential for podzolization than non-woody humus forms. The higher fulvic acid-type constituents associated with the non-woody humus forms would appear to confer greater potential for increased podzolization, although this could not be demonstrated in the field. Again, I propose that the humus fractions present in decay class IV and V wood is primarily due to humic substances leaching from the over-lying non-woody LFH layer into the relatively inert lignin matrix. The one concern not addressed in this thesis is the importance of asymbiotic nitrogen fixation within CWD, and the long-term nutrient sequestering role of CWD. For the former concern, the rates of nitrogen fixation are considered relatively small (Harmon et al. 1986), and primarily occurs during the initial period of fungal decay from class I to III where there are labile sources of carbon within the fungal mycosphere. This initial period is relatively short (approximately 50 years; see Preston et al. 1990), continuing only while a supply of cellulose or hemi-cellulose is available. (In fact, most biological activity takes place within this short initial period; see Edmonds and Lebo 1998; Harmon et al. 1994; Edmonds and Eglitis 1989; Zhong and Schowater 1988). The much longer period of the presence of recalcitrant lignin (on the scale of greater than 1000 years; Daniels et al. 1997) is associated with much reduced levels of nitrogen fixation, and biological activity in general. Further, any asymbiotic nitrogen fixation associated with CWD should be compared to nitrogen fixation associated with non-woody humus forms. For the latter concern of nutrient sequestering, this functional role can be viewed either as negative or positive. The negative view suggests that CWD sequesters nutrients which become unavailable for plant uptake thus leading to forest decline (Murty et al. 1996). The positive view suggest that CWD acts as a "nutrient savings account" that preserves nutrients and organic matter within an ecosystem which otherwise would be leached from the system, and makes them Chapter 7, Page 98 available in the future (Lang and Forman 1978; Maser and Trappe 1984; Maser et al. 1988). However, total nutrients decrease as mass decreases despite increasing concentrations (Laiho and Prescott 1999; Hart 1999; Lambert et al. 1980). So some doubt exists as to the negative impact of CWD in sequestering nutrients or to the importance of CWD suggested by the metaphor of a "nutrient savings account." The non-woody humus substrates continues to be the important functional organic matter in terms of productivity. Therefore, if CWD serves an important nutrient function, then it is likely in the humus formation (if lignin is a precursor to humus). Additionally, with recent concerns over global warming, CWD may be important in carbon sequestering (Krankina and Harmon 1999; Harmon et al. 1990, 1996). C O N C L U S I O N S The importance of decaying wood as a moisture source for tree growth determined for the drought prone Northern Rocky Mountains of the United States, cannot be extended to the summer wet coastal forests of BC, at least on sites without water deficits. Similar to Alaska, once moisture is not a factor for tree survival and growth, non-woody humus substrates with higher nutrient availability becomes relatively more important. However, there may be other indirect nutrient roles that make CWD important for tree survival and growth. The hypothesis that decaying wood creates a more acidic forest floor which in turn increases the rate of podzolization appears to be false. Even though the wood itself actually has less fulvic acids than non-woody humus material, the soils beneath the two substrates appeared to be the same. On sites not having a water deficit or excess located in the coastal forests of BC, it appears that CWD has neither a negative effect of increased acidification and intensity of podzolization, nor a positive effect of providing nutrients or water. However, the literature shows that the habitat CWD supplies is a necessary component for wildlife and stream ecology. For the rainforests of coastal BC, decisions on the modification of harvesting and slash treatment practices for preserving the ground structure of CWD need to be based primarily on biological diversity and habitat requirements, and not so much for maintaining long-term site productivity. 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Res. 29: 187-193. Zinke, P.J. 1962. The pattern of individual forest trees on soil properties. Ecology 43: 130-133. References, Page 111 Appendix Table A. 1: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Warm Interior Cedar Hemlock (ICHmw) subzone. Below the mean and standard error are the treatment /?-values followed by the p-value for p, where applicable. For site x treatment interaction p-values, an asterix indicates that although there is a significant interaction effect, the effect is in one direction. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.20) values. Short-form acronyms are: min-N = mineralizable N; HA = humic acid; FA = fulvic acid. Forest floor non-woody woody Mineral so upper 2 cm non-woody woody il horizons upper B non-woody woody Depth (cm) p H 4.32 (0.21) 3.61 (0.05) 4.82(0.34) 4.66(0.31) 5.33 (0.14) 5.46 (0.22) 0.056; 0.012*; 0.956 0.268; 0.249; 0.805 0.532; 0.043; 0.917 total C 42.82 (0.75) 59.29 (0.96) 2.86 (0.77) 2.51 (0.56) 2.09 (0.51) 1.82 (0.31) (%) 0.004; 0.352 0.233; 0.471; 0.001 0.371; 0.105; 0.002 totalN 1.18 (0.03) 0.53 (0.05) 0.11 (0.03) 0.07 (0.02) 0.07 (0.02) 0.05 (0.01) (%) 0.002; 0.616 0.029; 0.370; 0.024 0.253; 0.019; 0.049 C : N 36.4 (0.6) 121.7 (8.0) 28.1 (1.4) 40.3 (1.3) 31.1(1.6) 35.4(1.6) 0.008; 0.215 0.036; 0.303 0.029; 0.664 min-N 28.5 (9.7) 16.5 (5.2) 20.7(10.3) 11.0(4.7) (ppm) 0.124; 0.233; 0.939 0.223; 0.011*; 0.934 C in H A 11.44 (0.57) 13.46 (0.51) (%) 0.040; 0.579 C in F A 8.45 (0.39) 5.83 (0.97) (%) 0.046; 0.099* H A : F A 1.36(0.02) 2.66 (0.40) 0.085; 0.003*; 0.938 Lipids 4.50 (0.05) 2.37 (0.14) (%) 0.007; 0.666 Appendix, Page 112 TABLE A.2: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the ICHmw subzone. Below the mean and standard error are the treatment /^ -values followed by site x treatment interaction /^ -values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, the/7-value for p. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.10) values. Short-form acronyms are: pyrophosphate = sodium pyrophosphate extractable; dithionite = dithionite-citrate extractable. M i n e r a l so upper 2 c m N o n - w o o d y w o o d y i l hor izons upper B n o n - w o o d y w o o d y pyrophosphate F e (%) pyrophosphate (Fe + A l ) (%) organic C pyrophosphate F e pyrophosphate ( F e + A l ) d i th ioni te ( F e + A l ) oxalate - F e di th ioni te - F e 0.19 (0.08) 0.18 (0.06) 0 .737; 0 .136; 0.011 0.42 (0.22) 0.41 (0.17) 0 .926; 0 .158; 0 .015 22.7 (5.3) 23.8 (2.9) 0 .258; 0 .965 ; 0.001 0.45 (0.06) 0.41 (0.06) 0 .037; 0.902 0.79 (0.04) 0.81 (0.04) 0 .404; 0 .514; 0.036 0.19 (0.04) 0.16 (0.03) 0 .239 ; 0 .205; 0.003 0.55 (0.07) 0.48 (0.05) 0 .142 ; 0 .447; 0.002 12.9 (2.8) 13.6 (3.0) 0 .149; 0 .931 ; <0.001 0.30 (0.06) 0.28 (0.08) 0 .486 ; 0 .574; 0.001 0 . 4 7 ( 0 . 0 5 ) 0 .49 (0 .03 ) 0 .899 ; 0 .557; 0.011 Appendix, Page 113 TABLE A.3: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Very Dry Warm Interior Douglas-Fir (IDFxw) subzone. Below the mean and standard error are the treatment ^ -values followed by the /?-value for p, where applicable. For site x treatment interaction p-values, an asterix indicates that although there is a significant interaction effect, the effect is in one direction. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.20) values. Short-form acronyms are: min-N = mineralizable N; HA = humic acid; FA = fulvic acid. Forest floor Mineral so il horizons non-woody woody Ah non-woody woody upper B non-woody woody depth 2.0 (0.0) 2.0 (0.0) (cm) 0.183; 0.611; <0.001 pH 5.46 (0.09) 4.03 (0.07) 5.90 (0.16) 5.61 (0.25) 5.85 (0.14) 6.17 (0.23) 0.002; 0.591 0.217; 0.068; 0.953 0.103; 0.104; 0.940 total C 32.43 (1.40) 57.81 (0.59) 4.95 (0.48) 4.82 (0.17) 2.40 (0.34) 2.04 (0.16) (%) 0.003; 0.438 0.719; 0.547; 0.004 0.178; 0.455; 0.001 totalN 1.35 (0.07) 0.57 (0.02) 0.27(0.03) 0.23 (0.01) 0.14(0.02) 0.11(0.01) (%) 0.006; 0.301 0.181 0.415 0.819 0.115; 0.473; 0.019 C:N 24.3 (0.5) 109.2 (1.0) 18.1 (0.8) 20.7 (1.0) 17.4 (0.5) 17.6 (0.5) 0.000; 0.973 0.017; 0.657 0.533; 0.489; 0.001 min-N 81.4(3.0) 68.4(5.2) 62.7 (6.7) 62.3 (4.9) (ppm) 0.055; 0.916 0.916; 0.562; 0.071 C in HA 9.20 (0.58) 13.56(0.55) (%) 0.061; 0.013*; 0.968 C in FA 9.65 (0.88) 7.76 (0.63) (%) 0.262; 0.011; 0.888 HA:FA 1.01 (0.17) 1.87 (0.18) 0.111; 0.001; 0.709 lipids 3.18(0.28) 2.94 (0.26) (%) 0.557; 0.229; 0.913 Appendix, Page 114 TABLE A.4: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the IDFxw subzone. Below the mean and standard error are the treatment p-values followed by site x treatment interaction p-values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, thep-value for p. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.10) values. Short-form acronyms are: pyrophosphate = sodium pyrophosphate extractable; dithionite = dithionite-citrate extractable. Mineral so Ah non-woody Woody il horizons upper B non-woody woody pyrophosphate Fe (%) pyrophosphate (Fe + Al) (%) organic C pyrophosphate Fe pyrophosphate (Fe + Al) dithionite (Fe + Al) oxalate - Fe dithionite - Fe 0.17 (0.02) 0.18 (0.01) 0.227; 0.503; 0.001 0.27 (0.04) 0.29 (0.03) 0.227; 0.666; <0.001 32.0 (2.6) 27.1 (1.7) 0.143; 0.487; 0.048 0.20 (0.03) 0.21 (0.04) 0.385; 0.630; <0.001 0.31 (0.05) 0.33 (0.05) 0.264; 0.692; 0.006 0.17 (0.02) 0.16 (0.01) 0.724; 0.287; 0.001 0.29 (0.04) 0.28 (0.02) 0.519; 0.334; <0.001 14.9 (1.0) 12.9 (0.3) 0.102; 0.705; 0.001 0.19 (0.03) 0.18 (0.04) 0.359; 0.827; O.001 0.21 (0.03) 0.22 (0.04) 0.774; 0.263; 0.002 Appendix, Page 115 TABLE A.5: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Cool Engelmann Spruce-Subalpine Fir (ESSFmk) subzone. Below the mean and standard error are the treatment p-values followed by the /?-value for (3, where applicable. For site x treatment interaction p-values, an asterix indicates that although there is a significant interaction effect, the effect is in one direction. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.20) values. Short-form acronyms are: min-N = mineralizable N; HA = humic acid; FA = fulvic acid. Forest floor Mineral soil horizons Ae upper B non-woody woody non-woody woody non-woody woody depth 4.3 (0.8) 3.8 (0.3) (cm) 0.503; 0.316; 0.885 pH 4.11 (0.10) 3.78 (0.04) 4.08 (0.04) 4.08 (0.03) 4.57 (0.07) 4.59 (0.04) 0.054; 0.033* 0.917; 0.329; 0.007 0.840; 0.216; 0.115 total C 42.93 (3.35) 57.25 (0.15) 2.90 (0.23) 2.72 (0.30) 3.97 (0.05) 4.59 (0.30) (%) 0.047; 0.007* 0.114; 0.927; <0.001 0.1447; 0.727; 0.004 totalN 1.42 (0.07) 0.62 (0.02) 0.14(0.02) 0.10(0.01) 0.17 (0.01) 0.17 (0.02) (%) 0.008; 0.118 0.068; 0.108; 0.183 0.983; 0.674; 0.027 C:N 30.2 (0.8) 97.7 (3.7) 21.5(1.4) 27.4(1.1) 24.1 (1.1) 27.8 (0.9) 0.002; 0.540 0.019; 0.832 0.030; 0.689 min-N 16.5 (1.5) 13.5 (0.9) 23.3 (2.4) 20.9 (2.9) (ppm) 0.098; 0.738; 0.003 0.549; 0.348; 0.223 C in H A 10.83 (0.46) 14.16 (0.17) (%) 0.017; 0.324 C in F A 11.13 (0.04) 8.63 (0.63) (%) 0.065; 0.093*; 0.684 H A : F A 0.99 (0.04) 1.69 (0.14) 0.039; 0.012* lipids 4.06 (0.33) 2.17(0.25) (%) 0.079; 0.003*; 0.944 Appendix, Page 116 TABLE A.6: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the ESSFmk subzone. Below the mean and standard error are the treatment /^ -values followed by site x treatment interaction /^ -values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, thep-value for p\ Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.10) values. Short-form acronyms are: pyrophosphate = sodium pyrophosphate extractable; dithionite = dithionite-citrate extractable. n o n - w o o d y M i n e r a l so i l ho r i zons A e I upper B w o o d y | n o n - w o o d y w o o d y pyrophosphate F e (%) pyrophosphate (Fe + A l ) o rgan ic C pyrophosphate F e pyrophosphate (Fe + A l ) d i th ioni te ( F e + A l ) oxalate - F e d i th ion i te - F e 0.08 (0.01) 0.07 (0.01) 0 .170; 0 .821 ; <0.001 0.14 (0.02) 0.14 (0.03) 0 .992; 0 .392; <0.001 64.6(8.0) 74.2(10.3) 0.505; 0.553; 0.962 0.35 (0.08) 0.40 (0.04) 0 .363 ; 0 .313; 0.011 0.48 (0.02) 0.47 (0.01) 0 .502; 0 .962; 0.003 0.71 (0.05) 0.67 (0.05) 0 .204; 0 .790; 0.009 1.38 (0.06) 1.41 (0.15) 0.838; 0.376; 0.196 6.1 (0.3) 7.3 (0.2) 0 .058 ; 0 .822; <0.001 0.60 (0.01) 0.58 (0.01) 0 . 4 5 1 ; 0 .537; 0.001 0.84(0.01) 0.80(0.04) 0.521; 0.064; 0.748 Appendix, Page 117 TABLE A.7: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Wet Cool Interior Cedar Hemlock (ICHwk) subzone (north). Below the mean and standard error are the treatment /^ -values followed by the p-value for (3, where applicable. For site x treatment interaction ^ -values, an asterix indicates that although there is a significant interaction effect, the effect is in one direction. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.20) values. Short-form acronyms are: min-N = mineralizable N; HA = humic acid; FA = fulvic acid. Forest floor Mineral so il horizons non-woody woody Ahe non-woody woody upper B non-woody woody depth 1.6 (0.1) 1.7 (0.2) (cm) 0.317; 0 .265; 0.007 pH 3.76 (0.22) 3.54 (0.15) 4.05 (0.23) 4.02 (0.27) 4 .62 (0.14) 4 .77 (0.17) 0.099; 0.277; 0.722 0.676; 0 .388; 0.041 0 .029; 0 .830 total C 51.79 (1.43) 60 .05 (0.37) 5.29 (0.29) 5.49 (0.43) 3.88 (0.21) 3.52 (0.10) (%) 0 .020 ; 0.251 0 .643 ; 0 .256; 0.007 0 .179 ; 0 .493 ; 0.001 totalN 1.24 (0.05) 0.59 (0.03) 0.21(0.03) 0.18(0.01) 0.15 (0.00) 0.14 (0.01) (%) 0 .003 ; 0.483 0.243; 0.059; 0.860 0 .312 ; 0 .167; 0.024 C:N 42.6 (2.1) 112.5 (5.1) 26.2 (1.9) 30 .9 (1.1) 25 .7 (1.5) 26.4 (1.8) 0 .003 ; 0.757 0 .036 ; 0.342 0 .184; 0 .659; 0.001 min-N 34.0(5.8) 28.5 (8.2) 19.4(8.0) 22.1(9.1) (ppm) 0.172; 0.615; 0.164 0.515; 0.028; 0.266 C in H A 13.13 (1.25) 15.94 (0.52) (%) 0.126; 0.010; 0.927 C i n FA 8.60 (0.41) 6.95 (1.04) (%) 0.120; 0.081; 0.208 H A : F A 1.56(0.09) 2.55 (0.33) 0.132; 0.001; 0.892 Lipids 4.45 (0.26) 1.96 (0.21) (%) 0 .029; 0 .020* Appendix, Page 118 TABLE A.8: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the ICHwk subzone (north). Below the mean and standard error are the treatment ^ -values followed by site x treatment interaction p-values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, the/?-value for p. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.10) values. Short-form acronyms are: pyrophosphate = sodium pyrophosphate extractable; dithionite = dithionite-citrate extractable. M i n e r a l so A h e n o n - w o o d y W o o d y i l ho r i zons upper B n o n - w o o d y w o o d y pyrophosphate F e (%) pyrophosphate (Fe + A l ) (%) organic C pyrophosphate F e pyrophosphate ( F e + A l ) d i th ioni te ( F e + A l ) oxalate - F e di thioni te - F e 0.75 (0.10) 0.82(0.07) 0.377; 0.542; 0.728 1.05 (0.11) 1.14 (0.05) 0.447; 0.355; 0.243 10.8 (1.5) 7.8 (2.9) 0 .080 ; 0 .663 ; 0.002 0.43 (0.02) 0.47 (0.03) 0 .142; 0 .404; 0.001 0.61 (0.03) 0.69 (0.02) 0.033; 0.469 1.03 (0.06) 0.95 (0.05) 0 .028; 0.963 1.65 (0.14) 1.55 (0.09) 0 . 2 4 1 ; 0 .590; 0.038 4.5 (0.5) 4.3 (0.6) 0 .199 ; 0 .759; <0.001 0.40 (0.04) 0.37 (0.05) 0 .157 ; 0 .448; O .001 0.57 (0.02) 0.60 (0.03) 0 .230 ; 0 .342; 0.005 Appendix, Page 119 TABLE A.9: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Cool Sub-Boreal Spruce (SBSmk) subzone. Below the mean and standard error are the treatment />values followed by the jo-value for P, where applicable. For site x treatment interaction ^ -values, an asterix indicates that although there is a significant interaction effect, the effect is in one direction. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.20) values. Short-form acronyms are: min-N = mineralizable N; HA = humic acid; FA = fulvic acid. Forest floor Mineral so il horizons non-woody woody Ahe non-woody woody Upper B non-woody woody depth 2.3 (0.3) 2.2 (0.2) (cm) 0.423; 0.566; <0.001 pH 4.44 (0.22) 3.79 (0.04) 4.08(0.10) 4.01(0.14) 4.46 (0.09) 4.59 (0.11) 0.068; 0.000*; 0.962 0.519; 0.013; 0.276 0.049; 0.705 total C 44.31 (1.55) 57.40 (0.71) 3.94 (0.37) 3.74 (0.50) 2.55 (0.55) 2.53 (0.63) (%) 0.004; 0.535 0.588; 0.335; 0.004 0.845; 0.844; <0.001 totalN 1.63 (0.04) 0.77 (0.06) 0.16(0.04) 0.17(0.01) 0.13 (0.03) 0.12 (0.02) (%) 0.011; 0.211 0.817; 0.001; 0.897 0.058; 0.710; 0.001 C:N 27.5 (1.0) 83.9 (7.4) 32.6 (9.0) 25.9 (2.7) 19.3 (0.6) 21.3 (1.3) 0.013; 0.131 0.399; 0.043; 0.968 0.119; 0.175; 0.013 min-N 25.18 (3.5) 20.0 (2.5) 15.6 (1.1) 14.6 (2.5) (ppm) 0.069; 0.793; 0.013 0.681; 0.035; 0.016 C in H A 10.98 (0.35) 14.54 (0.37) (%) 0.001; 0.960 C in FA 11.14 (0.49) 7.26 (0.27) (%) 0.018; 0.029* H A : F A 1.00 (0.03) 0.008; 2.04 (0.09) 0.321 lipids 3.87 (0.43) 3.74 (0.49) (%) 0.895; 0.005; 0.960 Appendix, Page 120 T A B L E A . 10: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the SBSmk subzone. Below the mean and standard error are the treatment p-values followed by site x treatment interaction p-values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, the p-value for p\ Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.10) values. Short-form acronyms are: pyrophosphate = sodium pyrophosphate extractable; dithionite = dithionite-citrate extractable. n o n - w o o d y M i n e r a l s o i l ho r i zons A h e I upper B w o o d y I n o n - w o o d y w o o d y pyrophosphate F e (%) pyrophosphate (Fe + A l ) (%) o rgan ic C pyrophosphate F e pyrophosphate ( F e + A l ) d i th ion i te ( F e + A l ) oxalate - F e d i t h i o n i t e - F e 0.17 (0.05) 0.23 (0.06) 0.290; 0.036; 0.073 0.30 (0.09) 0.38 (0.10) 0.324; 0.008; 0.030 55.1 (30.1) 26.2 (12.5) 0.473; 0.001; 0.972 0.17 (0.05) 0.20 (0.04) 0.540; 0.004; 0.005 0.28 (0.05) 0.33 (0.06) 0.089; 0.832; 0.008 0.42 (0.09) 0.45 (0.12) 0.449; 0.232; 0.021 0.73 (0.19) 0.77 (0.24) 0.403; 0.217; 0.008 6.5 (0.6) 6.0 (0.3) 0.248; 0.448; O.001 0.32 (0.04) 0.33 (0.05) 0.325; 0.502; O.001 0.34 (0.05) 0.34 (0.05) 0.342; 0.901; <0.001 Appendix, Page 121 T A B L E A. 11: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the non-woody humus form and the decaying wood (woody), and between the mineral soil beneath the substrates in the Moist Warm Boreal White and Black Spruce (BWBSmw) subzone. Below the mean and standard error are the treatment ^ -values followed by the /?-value for p, where applicable. For site x treatment interaction /^ -values, an asterix indicates that although there is a significant interaction effect, the effect is in one direction. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.20) values. Short-form acronyms are: min-N = mineralizable N; HA = humic acid; FA = fulvic acid. Forest floor Mineral sc il horizons non-woody woody Ah non-woody woody upper B non-woody woody Depth 2.2 (0.1) 2.3 (0.1) (cm) 0.667; 0.277 0.001 pH 4.76 (0.23) 4.41 (0.46) 4.50 (0.23) 4.51 (0.27) 4.70 (0.17) 4.71 (0.17) 0.275; 0.003 0.966 0.812; 0 .339; 0.011 0 .588; 0 .348; 0.003 totalC 38.21 (2.19) 53 .32 (1.68) 5.34 (1.47) 4.92 (1.39) 2 .29 (0.84) 2.08 (0.83) (%) 0.029; 0 .002* 0 .510; 0 .199; 0.023 0 .105 ; 0 .863; <0.001 totalN 1.44 (0.11) 0.85 (0.14) 0.37 (0.12) 0.35 (0.13) 0.19 (0.08) 0.18 (0.08) (%) 0.014; 0 .090* 0.606; 0.135; 0.921 0.200; 0 .892; 0.002 C:N 26.8 (0.7) 73.2(13.6) 15.2 (1.3) 15.5 (1.8) 12.2 (0.8) 12.1 (0.9) 0.068; 0.001* 0.644; 0 .101 ; 0.002 0 .770; 0 .542; 0.001 min-N 45.7(15.1) 46.2(18.5) 29.9(11.9) 28.2(13.6) (ppm) 0.935; 0.259; 0.716 0.663; 0.165; 0.181 C in HA 10.24 (0.55) 15.91 (0.41) (%) 0.019; 0 .088* C in FA 11.99 (0.16) 9.89(1.52) (%) 0.335; 0.000; 0.937 HA:FA 0.87 (0.04) 1.74 (0.31) 0.085; 0.000*; 0.550 lipids 2.88 (0.50) 3.24 (0.31) (%) 0.414; 0.225; 0.935 Appendix, Page 122 TABLE A . 12: Differences in mean chemical properties (standard error of the mean in brackets; based on n = 3) between the mineral soil beneath the non-woody humus form and the decaying wood (woody) in the BWBSmw subzone. Below the mean and standard error are the treatment /7-values followed by site x treatment interaction /^ -values (an asterix indicates significance differences atp < 0.05 without any significant interaction effect), and where applicable, thep-value for p. Cells in bold have either significant alpha (p < 0.05) or beta (p < 0.10) values. Short-form acronyms are: pyrophosphate = sodium pyrophosphate extractable; dithionite = dithionite-citrate extractable. non-woody Mineral soil horizons A h I upper B woody I Non-woody woody pyrophosphate Fe pyrophosphate (Fe + A l ) organic C pyrophosphate Fe pyrophosphate (Fe + A l ) dithionite (Fe + Al ) oxalate - Fe dithionite - Fe 0.35 (0.08) 0.35 (0.07) 0.822; 0.639; 0.002 0.57 (0.14) 0.57 (0.13) 0.863; 0.865; <0.001 15.5 (0.7) 13.9 (1.2) 0.119; 0.734; 0.001 0.29 (0.04) 0.30 (0.04) 0.105; 0.932; O.001 0.43 (0.05) 0.43 (0.04) 0.828; 0.607; 0.006 0.29 (0.07) 0.29 (0.06) 0.983; 0.523; 0.001 0.44 (0.11) 0.44 (0.11) 0.942; 0.571; 0.001 7.6 (0.9) 6.8 (1.0) 0.483; 0.175; 0.002 0.26 (0.03) 0.27 (0.03) 0.153; 0.853; <0.001 0 . 4 2 ( 0 . 0 4 ) 0 . 5 5 ( 0 . 1 4 ) 0 . 3 8 1 ; 0 . 4 3 0 ; 0 . 9 6 8 Appendix, Page 123 

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