Open Collections

UBC Undergraduate Research

Productivity of mixed-species vs. single-species forest stands : an analysis of a mixed lodgepole pine-interior… Carsky, Grace Apr 11, 2016

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
52966-Carsky_Grace_FRST_498_2015.pdf [ 1.03MB ]
Metadata
JSON: 52966-1.0314333.json
JSON-LD: 52966-1.0314333-ld.json
RDF/XML (Pretty): 52966-1.0314333-rdf.xml
RDF/JSON: 52966-1.0314333-rdf.json
Turtle: 52966-1.0314333-turtle.txt
N-Triples: 52966-1.0314333-rdf-ntriples.txt
Original Record: 52966-1.0314333-source.json
Full Text
52966-1.0314333-fulltext.txt
Citation
52966-1.0314333.ris

Full Text

Productivity of mixed-species vs. single-species forest stands: an analysis of a mixed lodgepole pine-interior hybrid spruce spacing trial in interior British Columbia  Grace Carsky   Submitted to the Department of Forest and Conservation Sciences of the University of British Columbia in partial fulfillment of the requirements for the degree of  Bachelor of Science, Forest Sciences  Thesis Advisor: Dr. Bianca Eskelson, Dept. of Forest Resources Management  Vancouver, British Columbia, Canada April 11, 2016  ii  Productivity of mixed-species vs. single-species forest stands: an analysis of a mixed lodgepole pine-interior hybrid spruce spacing trial in interior British Columbia  Abstract: Though most forest plantations are planted with a single species, there has been a push in forest management to switch to mixed species stands. To further understand the effects of density and species mixture on size, growth, and yield in pure- and mixed-species plots, this thesis analyzes a 20-year-old mixed lodgepole pine – interior hybrid spruce installation across three densities (1000, 1500, and 2000 stems per hectare [SPH]) and five species mixtures (1:0, 3:1, 1:1, 1:3, and 0:1 Pine:Spruce [Pl:Sx]). Results show that there is no interaction between density and mixture, but both factors have a significant effect on total volume per hectare, merchantable volume per hectare, and total basal area per hectare. Differences in density and mixture levels were significant between 1000 and 2000 SPH and between mixtures 3:1 and 1:3 Pl:Sx, mixtures 1:0 and 1:3 Pl:Sx, and mixtures 1:0 and 1:1 Pl:Sx. Pure pine plots (1:0 Pl:Sx) at a density of 2000 SPH resulted in the highest yield, but the 3:1 Pl:Sx treatment at a density of 2000 SPH showed potential for higher yield. Although monocultures tend to yield higher total volumes, planting mixed-species stands that produce similar volumes provides additional increases to pest and disease resistance and biodiversity.  Keywords: growth and yield; stand dynamics; mixed-species stands; interior British Columbia   iii  Table of Contents Table of Tables ............................................................................................................................................. iii Table of Figures ............................................................................................................................................ iii Introduction……………………………………………………………………………………………………………………………………………. 1 Methods…………………………………………………………………………………………………………………………………………………. 3 Study Area and Site Description ............................................................................................................ 3 Data Compilation .................................................................................................................................. 4 Statistical Analysis ................................................................................................................................. 5 Results……………………………………………………………………………………………………………………………………………………. 8 Size ........................................................................................................................................................ 8 Growth ................................................................................................................................................ 13 Yield ..................................................................................................................................................... 17 Discussion…………………………………………………………………………………………………………………………………………….. 22 Effects of Size, Growth, and Yield ........................................................................................................ 22 Managing for the future ..................................................................................................................... 24 Conclusions…………………………………………………………………………………………………………………………………………… 24 Acknowledgements ..................................................................................................................................... 25 References……………………………………………………………………………………………………………………………………………. 25 Appendix………………………………………………………………………………………………………………………………………………. 29  Table of Tables Table 1. Response variables and factors. ...................................................................................................... 6 Table 2. Test statistics for size variables. .................................................................................................... 10 Table 3. Analysis of size variables using the last measurement (2013). ..................................................... 11 Table 4. Test statistics for growth variables. .............................................................................................. 14 Table 5. Analyses of growth variables using the last measurement (2013). .............................................. 15 Table 6. Test statistics for yield variables. .................................................................................................. 17 Table 7. Analysis of growth variables using the last measurement (2013). ............................................... 18 Table of Figures Figure 1. Location map for installation EP964.22 near Vernon, British Columbia. ...................................... 4 Figure 2. Merchantable volume for lodgepole pine over time. .................................................................... 9 Figure 3. Total volume/ha (m3/ha) for lodgepole pine (black) and interior hybrid spruce (grey) by density (A) and mixture (B), analyzed across all measurements. ............................................................................ 12 iv  Figure 4. Total BA/ha (m2/ha) for lodgepole pine (black) and interior hybrid spruce (grey) by density (A) and mixture (B), analyzed across all measurements……………………………………………………………………………… 13 Figure 5. Total volume/ha mai (m3/ha/year) for lodgepole pine (black) and interior hybrid spruce (grey) by density (a) and mixture (b). .................................................................................................................... 16 Figure 6. Total baha mai (m2/ha/year) for lodgepole pine (black) and interior hybrid spruce (grey) by density (a) and mixture (b)……………………………………………………………………………………………………………………. 16 Figure 7. Total volume (m3/ha) for both species combined, by density (a) and mixture (b)………………….. 18 Figure 8. Total basal area/ha (m2/ha) for both species combined, by density (a) and mixture (b)………… 19 Figure 9.Total merchantable volume/ha (m3/ha) for both species combined, by density (a) and mixture (b)…………………………………………………………………………………………………………………………………………………………. 19 Figure 10. Standing volume over initial spacing for pure pine (solid line), 3:1 Pl:Sx (short dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line), and pure spruce (long dashed line). Each box represents a different measurement. .............................................................................................................................. 20 Figure 11. Relative yield by species (Pl, black; Sx, grey) and initial planting density for the last measurement. ............................................................................................................................................. 21    1  Introduction Most forest plantations consist of a single species, which are easier to manage and provide a high return of investment. However, recent studies have shown the benefits of planting mixed forest stands (Kelty 2006). First, planting species with complementary growth characteristics can reduce the effect of competition in the stand and in some cases promote individual tree growth (Kelty 1992). It is important to understand the characteristics of each species in order for these complementary effects to take place. If a stand is comprised of different species with similar growth characteristics, productivity will be lower or intermediate to single-species stands, whereas mixed-species stands with species of different growth characteristics may be more productive, depending on the site and stage of development (Chen et al. 2003). If too much of either species is planted, the total volume of the stand will likely decrease due to overcrowding and mortality (de Montigny and Nigh 2007). A diverse stand can also increase pest and disease resistance by limiting the amount of host trees available to the organism (Watt 1992). This in turn reduces the market risk. If an infestation or infection occurs in the forest stand, there is a better probability that some of the trees survive and the stand retains some value. Though mixed stands may not yield a higher volume than single species stands (Kelty 1992), the potential benefits, and risk aversion, can make up for the lack of growth and yield. Mixed stands in British Columbia are important because they can increase the resilience to biotic and abiotic disturbances commonly seen in the province (Watt 1992). In the last decade, interior British Columbia has experienced a severe mountain pine beetle epidemic, due to increasing summer temperatures, decreasing winter temperatures, and fire suppression (Taylor and Carroll 2003, Gayton 2008). Lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.), an important commercial species in the Interior, is the primary host of the mountain pine beetle, and much research has been done to combat the infestation. Reports by Carroll and Linton (2002) and Whitehead et al. (2004) suggest removing as much of the susceptible host as possible to decrease infestation of pine stands. One option is to replace susceptible hosts with species that can survive potential disturbances. Although it may not decrease the susceptibility of the stand to infestation (Amman and Baker 1972), the severity of an attack would be much less in a mixed stand than in a pure lodgepole pine stand, simply because there is a smaller 2  proportion of host species available. In turn, this can prevent a loss in valuable wood. Mixed forests have also been found to reduce the spread and severity of fires, another concern for forest managers in British Columbia, especially when mixtures included deciduous species (Hély et al. 2000, Moreira et al. 2009, Wang et al. 2000). While the Pacific Northwest has been an active area for mixed forest stand research (e.g. Binkley 1984, Garber and Maguire 2004, Reyes-Hernandez and Comeau 2014), no studies have been done on lodgepole pine (P. contorta) and interior hybrid spruce (Picea glauca x engelmannii) mixtures, to my knowledge.  Spacing trials can provide information on how initial planting densities affect size, growth and yield of trees in a stand (e.g. Harrington et al. 2009, Reyes-Hernandez and Comeau 2014, de Montigny et al. 2016). Long-term monitoring can provide data to assess 1) the effects of spacing across sites; 2) the optimal planting density to achieve the highest timber value; and 3) the optimal planting density to decrease the risk of disease and insect attacks (de Montigny et al. 2016). Through spacing trials, we know that high stand densities increase the amount of competition between trees due to limited resources (Harrington et al. 2009), increase the mortality rate of trees in a stand (Binkley 1984), decrease the diameter of individual trees, and increase the overall stand volume (Johnstone and Pollack 1990). This thesis provides insights to how mixed species stands comprised of lodgepole pine and interior hybrid spruce compare to single species stands. This species mixture is important to study because it is commonly harvested and regenerated throughout interior British Columbia (Johnstone 1999). Research for mixtures of these two species is lacking and this thesis fills some of the existing knowledge gaps. It can also provide assistance for managers in future silviculture practices, such as whether to plant mixtures of different species or mini-monocultures adjacent to each other, as well as which density to plant at. The objectives of this thesis are to assess size (e.g. diameter, height), growth (e.g. diameter mean annual increment), and yield (e.g. volume per hectare) by species mixture and density. Mixed plots will then be compared to pure plots to evaluate if any difference exists with regards to size, growth, and yield. Using data from a spacing trial established by the British Columbia Ministry of Forests, Land, and Natural Resource Operations (BCMFLNRO), four 3  measurements of experimental mixed-species plots over the last 19 years will be analyzed to meet these objectives. Overall, this thesis aims to find the optimal density and species composition to ensure the highest volume from a forest stand.  Methods Study Area and Site Description The BCMFLNRO established a series of long term installations (EP964) with the objective of finding the effects of initial planting density on growth and development of several coniferous species throughout BC. Only one installation (EP964.22) includes more than one species in its plots: lodgepole pine (Pl) and interior hybrid spruce (Sx). The installation is a complete random block design with two fixed effects: density and species composition mixture (referred to as mixture in the following). It combines three density levels (1000, 1500, and 2000 stems per hectare [SPH]) with five mixture levels (1:0, 3:1, 1:1, 1:3, and 0:1 Pl:Sx). Each of these fifteen treatment combinations was replicated twice resulting in thirty total experimental plots. Each plot is square and differs in size depending on its density and mixture levels. The single species plots have 12 x 12 rows (144 trees in total) and the mixed species plots have 15 x 15 rows (225 trees in total). The outer two rows were considered buffer trees, leaving 64 (8x8) and 121 (11x11) “sample” trees in pure- and mixed-species plots, respectively (Johnstone 1999, 2004). This installation is located northwest of Vernon, British Columbia (50° 20’ 30”N, 119° 38’ 00”W) in the Okanagan Shuswap Forest district (Figure 1). It is classified as a Subalpine fir- Rhododendron- Grouseberry (01) site series in the Thompson Dry Cold variant of the Engelmann Spruce- Subalpine Fir (ESSFdc2) biogeoclimatic subzone. The trial is at an elevation of 1560 m and is located on a gentle slope (10%), mid-slope site with an east-northeast aspect (Lloyd et al. 1990 site identification guide). The soil is classified as a Brunisol, is loamy in texture, well-drained, and has a rooting depth of 30cm. The soil moisture regime is mesic to submesic and the soil nutrient regime is medium. The site was previously occupied by subalpine fir (Abies lasiocarpa (Hook.) Nutt.) and Engelmann spruce (Picea engelmannii Perry) until 1991-1992, when it was clearcut (Johnstone 1999). In 1994, the trial was planted with lodgepole pine and 4  interior hybrid spruce seedlings (Johnstone 1999, 2004). The trial was remeasured every five years (1998, 2003, 2008, 2013) after initial planting (Johnstone 2004).    Figure 1. Location map for installation EP964.22 near Vernon, British Columbia.  Data Compilation Using SAS 9.4, data were checked and formatted. Buffer trees, damaged trees, and dead trees were removed from the dataset. Shrinking trees (i.e. trees that decreased in diameter [dbh] or height over time) were removed as well, since they were most likely dead the following year. Trees less than 1.3 meters in height were removed. Any missing heights were estimated from 5  measured dbh values using a Chapman-Richard’s equation (Richards 1959). Individual tree volumes were calculated using the taper function defined by Kozak (1988). Individual heights, DBHs, basal areas, and volumes were then used to calculate species means and overall means for each plot by measurement. Merchantable volume was calculated using the stem of the tree from a 30 cm meter stump to the top of the stem at 10 cm inside bark diameter.  Statistical Analysis Data were summarized by treatment, density, and mixture. An analysis of variance (ANOVA) with two fixed factors and a random plot effect was performed using the model: y𝑖𝑗𝑘 =  µ +  A𝑖  + B𝑗  +  AB𝑖𝑗 +  𝛿𝑘(𝑖)  +  ε𝑖𝑗𝑘  where: yijk = response variables measured at time k at the ith level of factor A and the jth level of factor  B (see Table 1 for list of response variables) µ = the overall mean regardless of treatment Ai = the treatment effect for the ith level of factor A, i = 1, 2, 3 representing three density levels Bj = the treatment effect for the jth level of factor B, j = 1,…, J, where J = 4 mixture levels for size  and growth analysis and J = 5 mixture levels for yield analysis ABij = the interaction effects between factors A and B δk(i) = random plot effect ),0(~2Niid  εijk = random error term ),0(~2Niid  A random plot effect δk(i) was included in the model to account for the serial correlation due to the repeated measurements on each plot. The model was fit using PROC MIXED in SAS 9.4. 6  Table 1. Response variables and factors. Response variables Acronym Response variables Acronym Response variables Acronym Size  Growth Yield Mean diameter at breast height ( = 1.3 m) dbh Mean Diameter at breast height mean annual increment (m/yr) dbh mai Total volume per hectare (m3/ha) vol/ha Mean Height (m) ht Mean Height mean annual increment ht mai Total basal area per hectare (m2/ha) baha Mean Volume per tree (m3/tree) vol/tree Mean Volume per tree mean annual increment (m3/tree/yr) vol/tree mai Total merchantable volume per hectare (m3/ha) mvol/ha Total Volume per hectare (m3/ha) vol/ha Total Volume per hectare mean annual increment (m3/ha/yr) vol/ha mai   Mean Basal area per tree (m2/tree) ba/tree Mean Basal area per tree mean annual increment (m2/tree/yr) ba/tree mai   Total Basal area per hectare (m2/ha) baha Total Basal area per hectare mean annual increment (m2/ha/yr) baha mai   Total Merchantable volume per hectare (m3/ha) mvol/ha      7  F-tests were used to test statistical significance at an α = 0.05 level, unless otherwise noted. The initial analysis included all four measurements (1998, 2003, 2008, and 2013). An additional analysis was then conducted on the last measurement (2013) only if the variable was found to be significant over all measurements. First, density-mixture interactions were tested for significance. If no significant interaction occurred, then density and mixture were separately tested for significance. If density or mixture or an interaction of the two was significant, factor or treatment levels were tested, respectively, for differences using least square means with a Bonferroni adjustment. Residuals were examined for equal variances and normality using residual plots and the Shaprio-Wilk’s normality test. If equal variance was not met, the variable was log transformed (unless otherwise stated) using the natural logarithm:  ln_variable = ln (𝑣𝑎𝑟𝑖𝑎𝑏𝑙𝑒 + 0.001) Because most variables had some ‘0’ values, a constant of 0.001 was added prior to the log transformation.  Graphs were produced in R 3.2.2 to illustrate differences in treatment, density, or mixture levels that showed significant differences for analyses of all measurements.  Relative yield was also calculated using the last measurement only (Harper 1977): 𝑅𝑌𝑇 =  𝑌𝐴|𝐵𝑌𝐴 +  𝑌𝐵|𝐴𝑌𝐵 where  RYT = relative yield total  YA|B = yield of lodgepole pine in a mixed plot  YA = yield of lodgepole in a pure pine plot  YB|A = yield of interior hybrid spruce in a mixed plot   YB = yield of interior hybrid spruce in a pure spruce plot Relative yield helps asses the effect of combining species in a plot by comparing the yield of a species in its pure plot against the yield of a species in a mixed plot. If the relative yield total is less than 1, then the two species are in competition with each other. If the relative yield total is greater than 1, then the two species are using up different resources and avoiding competition 8  (Harper 1977). If the relative yield total equals 1, then there is no effect of one species on the other. After the analysis, results were plotted over density. Results Size Seven variables (Table 1) were analyzed for size for each species separately, looking at all four measurements. Of all size variables, a density-mixture interaction was only significant for lodgepole pine merchantable volume (p = 0.0203). Pure pine stands (1:0 Pl:Sx) differed at density levels 1000 and 2000 (p = 0.0454). The difference between pure pine stands at density level 1000 SPH and stands with mixture 1:3 Pl:Sx at the same density was suggestive but inconclusive (p = 0.0766). No other treatments were significantly different from each other (Figure 2). An additional analysis of pine merchantable volume was done using only the last measurement (2013). The results suggested the interaction was still significant, but evidence was inconclusive to any differences between treatments (p = 0.0593). 9   Figure 2. Merchantable volume for lodgepole pine over time. Line type indicates species mixture: pure pine (solid line), 3:1 Pl:Sx (dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line). Shade indicated density: 1000 sph (black), 1500 sph (dark grey), and 2000 sph (light grey).   Density and mixture were statistically significant for total volume per hectare, merchantable volume per hectare, and total basal area per hectare (Table 2). An additional analysis was done on these variables using only the last measurement from 2013. Density and mixture were significant for total volume per hectare and total basal area per hectare for the 2013 measurements (Table 3). There is suggestive but inconclusive evidence that merchantable volume for spruce is significantly different among mixture levels (p = 0.0593). 10  Table 2. Test statistics for size variables.  Variable Lodgepole pine  F-value (p-value) Interior Hybrid spruce  F-value (p-value)  density mixture density mixture Mean DBH  0.28 (0.7631) 1.84  (0.1929) 0.08 (0.9241) 1.57 (0.2480) Mean height  0.21 (0.8134) 0.51 (0.6810) 0.27 (0.7702) 2.48 (0.1114) Mean vol/tree 0.22* (0.8018) 1.16* (0.3665) 0.06* (0.9433) 2.46*  (0.1125) Total vol/ha 4.80* (0.0294) 10.09* (0.0013) 5.17* (0.0241) 1.77*  (0.2068) Mean ba/tree 0.32* (0.7322) 1.66* (0.2288) 0.05* (0.9539) 1.93*  (0.1783) Total baha 4.83* (0.0289) 10.17* (0.0013) 7.13* (0.0091) 2.85*  (0.0820) Total mvol/ha 2.34** (0.1390) 3.52**  (0.0489) 1.39** (0.2857) 3.26**  (0.0593) *Variable was log transformed **Variable was transformed to reciprocal  Bold indicates the variable was significant at the α = 0.05 level; italics indicate that significance is suggestive  at a α = 0.10 level  Densities 1000 and 2000 SPH differed for total volume per hectare for both pine and spruce (p = 0.0304 and p = 0.0240, respectively) (Figure 3A). Mixtures 3:1 and 1:3 Pl:Sx, mixtures 1:0 and 1:3 Pl:Sx, and mixtures 1:0 and 1:1 Pl:Sx differed for total volume per hectare for pine (p = 0.0134, p = 0.0020, and p = 0.0292, respectively). There were no differences in total volume among mixture levels for spruce (Figure 3B). Densities 1000 and 2000 SPH differed for basal area per hectare for both pine and spruce (p = 0.0304 and p = 0.0086, respectively) (Figure 4A). Mixtures 3:1 and 1:3 Pl:Sx, mixtures 1:0 and 1:3 Pl:Sx, and mixtures 1:0 and 1:1 Pl:Sx differed 11  for basal area per hectare for pine (p = 0.0110, p = 0.0017, and p = 0.0401, respectively). No differences were found between mixture levels for basal area per hectare for spruce (Figure 4B). Merchantable volume for spruce was ignored since differences were detected between pure spruce plots, that contained no merchantable volume, and the other plots.  Table 3. Analysis of size variables using the last measurement (2013). Variable Lodgepole pine  F-value (p-value) Interior Hybrid spruce  F-value (p-value)  density mixture density mixture Total vol/ha 13.98 (0.0007) 35.46 (< 0.0001) 8.75* (0.0045)* 6.13*  (0.0090)* Total baha 23.10  (<0.0001) 55.92 (<0.0001) 14.85* (0.0006)* 15.73*  (0.0002)* Total mvol/ha 0.72 (0.5063) 1.31  (0.3173) 1.39** (0.2857)** 3.26** (0.0593)** *Variable was log transformed **Variable was transformed to reciprocal Bold indicates the variable was significant at the α = 0.05 level; italics indicate that significance is suggestive  at a α = 0.10 level  For the 2013 measurements, densities 1000 and 2000 SPH differed for total volume for pine and spruce (p = 0.0006 and p = 0.0038, respectively) and between densities 1000 and 1500 SPH for total volume for pine (p = 0.0389). All mixtures except mixtures 1:1 and 1:3 Pl:Sx differed from each other for total volume per hectare for pine (Appendix 1). Mixtures 3:1 and 0:1 Pl:Sx, mixtures 1:1 and 0:1 Pl:Sx, and mixtures 3:1 and 1:3 Pl:Sx differed from each other for total volume for spruce (Appendix 1). Densities 2000 and 1000 SPH (p = <0.0001), densities 2000 and 1500 SPH (p = 0.0321), and densities 1500 and 1000 SPH (p = 0.0081) differed for total basal area per hectare for pine. Densities 2000 and 1000 SPH and densities 2000 and 1500 SPH differed (p = 0.0014 and p = 0.0438, respectively) for total basal area per hectare for spruce. All mixtures differed from each other for total basal area per hectare for pine (Appendix 2), while 12  mixtures 1:1 and 0:1 Pl:Sx (p = 0.0121), mixtures 3:1 and 0:1 Pl:Sx (p = 0.0003), and mixtures 3:1 and 1:3 Pl:Sx (p = 0.0015) differed for total basal area per hectare for spruce.  Figure 3. Total volume/ha (m3/ha) for lodgepole pine (black) and interior hybrid spruce (grey) by density (A) and mixture (B), analyzed across all measurements. In A, line type indicates density: 1000 SPH (soild line), 1500 SPH (short dashed line), 2000 SPH (dotted line). In B, line type indicates species mixture: pure pine (solid line), 3:1 Pl:Sx (short dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line), 0:1 Pl:Sx (long dashed line).   13   Figure 4. Total BA/ha (m2/ha) for lodgepole pine (black) and interior hybrid spruce (grey) by density (A) and mixture (B), analyzed across all measurements. In A, line type indicates density: 1000 SPH (soild line), 1500 SPH (short dashed line), 2000 SPH (dotted line). In B, line type indicates species mixture: pure pine (solid line), 3:1 Pl:Sx (short dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line), 0:1 Pl:Sx (long dashed line).  Growth Six variables (Table 1) were analyzed for growth for each species. No interactions were found between density and mixture, but both factors were significant for total volume per hectare mai and basal area per hectare mai (Table 4). An additional analysis was performed on these variables using only the measurements from 2013. Density and mixture were significant for total volume per hectare mai and basal area per hectare mai for the last measurement (Table 5).     14  Table 4. Test statistics for growth variables. Variable Lodgepole pine  F-value (p-value) Interior Hybrid spruce  F-value (p-value)  density mixture density mixture Mean dbh mai 0.13 (0.8792) 1.37  (0.3000) 0.10 (0.9085) 1.72 (0.2154) Mean height mai 0.20 (0.8234) 0.63 (0.6076) 0.42 (0.6641) 2.43 (0.1158) Mean vol/tree mai 0.53* (0.6021) 1.54* (0.2551) 0.18* (0.8411) 2.04* (0.1625) Total vol/ha mai 7.48* (0.0078) 14.59* (0.0003) 5.42* (0.0210) 1.96*  (0.1738) Mean ba/tree mai 0.82 (0.4635) 2.51 (0.1083) 0.10 (0.9046) 1.66  (0.2291) Total baha mai 9.01* (0.0041) 17.44* (0.0001) 7.64* (0.0073) 3.37*  (0.0546) *Variable log transformed Bold indicates the variable was significant at the α = 0.05 level; italics indicate that significance is suggestive  at a α = 0.10 level  Total volume per hectare mai and basal area per hectare mai were tested for differences at density and mixture levels. Densities 1000 and 2000 SPH for total volume per hectare mai for pine and spruce (p = 0.0072 and p = 0.0201, respectively) (Figure 5A). Mixtures 3:1 and 1:3 Pl:Sx, mixtures 1:0 and 1:3 Pl:Sx, and mixtures 1:0 and 1:1 Pl:Sx differed for total volume per hectare mai for pine (p = 0.0040, p = 0.0004, and p = 0.0064, respectively) (Figure 5B). Densities 1000 and 2000 SPH differed for basal area per hectare mai for pine and spruce (p = 0.0037 and p = 0.0065, respectively) (Figure 6A). Mixtures 3:1 and 1:1 Pl:Sx, mixtures 1:0 and 1:3 Pl:Sx, and mixtures 1:0 and 1:1 Pl:Sx differed for basal area per hectare mai for pine (p = 0.0016, p = 0.0002, and p = 0.0044, respectively) (Figure 6B).  15  Table 5. Analyses of growth variables using the last measurement (2013). Variable Lodgepole pine  F-value (p-value) Interior Hybrid spruce  F-value (p-value)  density mixture density mixture Total volume per hectare MAI* 24.23  (< 0.0001) 53.69 (< 0.0001) 8.74 (0.0046) 6.13  (0.0091) Basal area per hectare MAI 23.10  (< 0.0001) 55.92 (< 0.0001) 14.81* (0.0006)* 15.68*  (0.0002)* *Variables were log transformed Bold indicates the variable was significant at the α = 0.05 level  For the 2013 measurements, densities 1000 and 2000 SPH and densities 1500 and 1000 SPH differed for total volume per hectare mai for pine (p = <0.0001 and p = 0.0029, respectively). Densities 2000 and 1000 SPH differed for total volume per hectare mai for spruce (p = 0.0038). All mixtures differed from each other for total volume per hectare mai for pine (Appendix 3). Mixtures 3:1 and 0:1 Pl:Sx and mixtures 3:1 and 1:3 Pl:Sx differed for total volume per hectare mai for spruce (p = 0.0225 and p = 0.0284, respectively). Densities 2000 and 1000 SPH (p = <0.0001), densities 2000 and 1500 SPH (p = 0.0321), and densities 1500 and 1000 SPH (p = 0.0081) differed for total basal area per hectare mai for pine. Densities 2000 and 1000 SPH and densities 2000 and 1500 SPH differed for total basal area per hectare mai for spruce (p = 0.0005 and p = 0.0423, respectively). All mixtures differed from each other for total basal area per hectare mai for pine (Appendix 4), while mixtures 1:1 and 0:1 Pl:Sx (p = 0.0121), mixtures 3:1 and 0:1 Pl:Sx (p = 0.0003), and mixtures 3:1 and 1:3 Pl:Sx (p = 0.0015) differed for total basal areas per hectare mai for spruce.  16   Figure 5. Total volume/ha mai (m3/ha/year) for lodgepole pine (black) and interior hybrid spruce (grey) by density (a) and mixture (b). In A, line type indicates density: 1000 SPH (soild line), 1500 SPH (short dashed line), 2000 SPH (dotted line). In B, line type indicates species mixture: pure pine (solid line), 3:1 Pl:Sx (short dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line), 0:1 Pl:Sx (long dashed line).   Figure 6. Total baha mai (m2/ha/year) for lodgepole pine (black) and interior hybrid spruce (grey) by density (a) and mixture (b). In A, line type indicates density: 1000 SPH (soild line), 1500 SPH (short dashed line), 2000 SPH (dotted line). In B, line type indicates species mixture: pure pine (solid line), 3:1 Pl:Sx (short dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line), 0:1 Pl:Sx (long dashed line). 17  Yield Three variables (Table 1) were analyzed for yield at the plot level. No interaction was found between density and mixture, but both factors were significant for all variables (Table 6). An additional analysis was done using the last measurements from 2013 (Table 7). Only merchantable volume showed suggested but inconclusive evidence that mixture was significant for the last measurement.  Table 6. Test statistics for yield variables. Variable Lodgepole pine and interior hybrid spruce F-value (p-value)  density mixture Total vol/ha 6.15*  (0.0112) 37.78* (< 0.0001) Total baha 6.61 (0.0088) 32.66 (< 0.0001) Total mvol/ha 6.15 (0.0112)* 37.78 (< 0.0001)* *Variables were log transformed Bold indicates the variable was significant at the α = 0.05 level  Densities 1000 and 2000 SPH (p = 0.0105) and mixtures 1:0 and 1:3 Pl:Sx (p = 0.0365) and 0:1 Pl:Sx and all other mixtures (p = <0.0001) differed for total volume per hectare (Figure 7). Densities 1000 and 2000 SPH (p = 0.0077) and mixtures 1:0 and 1:3 Pl:Sx (p = 0.0359) and 0:1 Pl:Sx and all other mixtures (p = <0.0001) differed for total basal area per hectare (Figure 8). For merchantable volume per hectare, densities 1000 and 2000 SPH (p = 0.0105) and mixtures 1:0 and 1:3 Pl:Sx (p = 0.0356) and 0:1 Pl:Sx and all other mixtures (p = <0.0001) differed (Figure 9).  18  Table 7. Analysis of growth variables using the last measurement (2013). Variable Lodgepole pine and interior hybrid spruce F-value (p-value)  density mixture Total volume per hectare* 0.16  (0.8537) 0.98 (0.4194) Total Basal area per hectare 0.20 (0.8172) 1.01 (0.4052) Merchantable volume per hectare* 0.06 (0.9416) 2.20 (0.0736) *Variables were log transformed Italics indicate that significance is suggestive  at a α = 0.10 level   Figure 7. Total volume (m3/ha) for both species combined, by density (a) and mixture (b). In A, line type indicates density: 1000 SPH (soild line), 1500 SPH (short dashed line), 2000 SPH (dotted line). In B, line type indicates species mixture: pure pine (solid line), 3:1 Pl:Sx (short dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line), 0:1 Pl:Sx (long dashed line). 19   Figure 8. Total basal area/ha (m2/ha) for both species combined, by density (a) and mixture (b). In A, line type indicates density: 1000 SPH (soild line), 1500 SPH (short dashed line), 2000 SPH (dotted line). In B, line type indicates species mixture: pure pine (solid line), 3:1 Pl:Sx (short dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line), 0:1 Pl:Sx (long dashed line).   Figure 9.Total merchantable volume/ha (m3/ha) for both species combined, by density (a) and mixture (b). In A, line type indicates density: 1000 SPH (soild line), 1500 SPH (short dashed line), 2000 SPH (dotted line). In B, line type indicates species mixture: pure pine (solid line), 3:1 Pl:Sx (short dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line), 0:1 Pl:Sx (long dashed line). 20  Figure 10 shows the total stand volume by initial spacing, separated by measurement. Our first analysis using all measurement showed that there is a significant difference between densities and mixtures over time. When we analyze the variables using only the last measurement, we do not see significance in density levels, but we can see the suggested differences in mixture levels.   Figure 10. Standing volume over initial spacing for pure pine (solid line), 3:1 Pl:Sx (short dashed line), 1:1 Pl:Sx (dotted line), 1:3 Pl:Sx (dotdash line), and pure spruce (long dashed line). Each box represents a different measurement. 21  Analysis of relative yield suggested that density has an effect on relative yield (p = 0.0222). The difference between densities 1000 and 2000 SPH was suggestive but inconclusive (p = 0.0594). Plots with densities of 1500 SPH had the greatest relative yield total (RYT = 1.382) and plots initially planted at 2000 SPH had a total relative yield greater than 1 (RYT = 1.199). The relative yield totals in the 1000 SPH plot was just under 1.00 (RYT= 0.959) (Figure 11).    Figure 11. Relative yield by species (Pl, black; Sx, grey) and initial planting density for the last measurement.   22  Discussion Effects of Size, Growth, and Yield An interaction between density and mixture was significant for lodgepole pine merchantable volume where differences were found in the pure pine plot (1:0 Pl:Sx) between densities 1000 and 2000 SPH as well as between pure pine stands and the 1:3 Pl:Sx mixture at a density of 1000 SPH. Similar studies have had mixed results on whether density-mixture interactions exist. While some have found no interaction between density and mixture (e.g. de Montigny and Nigh 2007), many others have found some level of interaction (e.g. Garber and Maguire 2004, Garber and Maguire 2005, Grant et al. 2006, Forrester et al. 2013). It is important to note that all of these studies focused on different species mixtures with older trees. Most studies that did find interactions were analysing trees about 26-27 years old. Only de Montigny and Nigh (2007), which analysed Douglas-fir-western hemlock plots at age 14 years, and Grant et al. (2006), which analysed tropical species at age 5, have younger trees than this intallation. Though Grant et al. (2006) had a younger stand, tropical trees tend to have rapid growth and achieve higher biomass earlier (Evans 1982), so interactions may have been detected at an earlier plot age. This suggests that interactions between density and species mixtures may not be seen until the stand reaches a certain size. If interactions were found significant, they were at varying levels of significance. Garber and Maguire (2004) found strong interactions in one plot (age 26), but the significance decreased as age of the plots increased (e.g. plots at age 34 were only marginally significant). This is seen in the interaction between density and mixture for pine merchantable volume. When analyzing all measurements, a significant interaction was found, but the interaction was weak when only analyzing the last measurement. Forrester et al. (2013) only found strong interactions at higher densities, while lower densities had only marginally significant interactions (i.e. weak interactions). This analysis found significant interactions across all densities, but the plot densities were much larger (1000-2000 SPH vs Forrester et al. [2013] 100-400 SPH). Though the installation is young, the same patterns in other studies are beginning to show in this installation. Mixture had a significant effect on total volume, total basal area, and total merchantable volume. Studies have shown that mixture effects on size, growth, and yield are dependent on 23  the species and the sites that they grow on (Chen et al. 2003, Amoroso et al. 2004). This is seen in the relative yield analysis, where densities 1500 and 2000 SPH had relative yield totals greater than 1. A total relative yield value greater than 1 indicates that the two species are using resources differently or are avoiding competition (Harper 1977). Similar studies (DeBell et al. 1997, Amoroso et al. 2004, Garber and Maguire 2004) have found relative yield totals greater than 1 for a variety of species mixtures, concluding that mixing species benefits the yield of the stand. Several other studies have shown that species with different characteristics can utilize site resources differently and more efficiently than if they were to compete for the same resources, resulting in higher productivity than in single-species stands (Assmann 1970, Simard and Hannam 2000). Chen et al. (2003) found that mixed stands with one shade intolerant species and one shade tolerant species tended to be more productive than single species stands. When analyzing stands with similar characteristics (i.e. both shade tolerant or intolerant), productivity was equal or less than pure stands. Studies done in Scandinavia (Bergqvist 1999, Fahlvik et al. 2005) looked at mixture composition and found that reducing the proportion of taller species helped achieve a high stand production. These results can be applied to this mixed pine and spruce installation as well. In a mixed stand, lodgepole pine, a shade intolerant species, has the advantage of full light and can get a head start of growth, whereas the hybrid spruce, a shade tolerant species, can be protected from direct light underneath the pine canopy. By reducing the number of pine trees in a stand, stratification could provide a greater stand production. Results on density analysis showed that total volume and total basal area had higher values at 2000 SPH, while pine merchantable volume was greatest at 1000 SPH and total merchantable volume was greatest at 1500 SPH. These results are comparable to other findings on individual and total yield. Individual tree biomass is greatest at lower densities, where there is enough space to grow and fewer trees to take up site resources (Johnstone and Pollack 1990). Total stand yield is greatest in stands with close spacing (Assmann 1970, Johnstone and Pollack 1990), but the onset of competition is earlier and more intense (Harper 1977, Harrington et al. 2009). Even in mixed stands with complementary species, complementary effects will disappear and competition will commence if densities are too high (Forrester et al. 2013). The trade-off 24  between individual tree size and total stand volume can most likely explain why we see the greatest total merchantable volume at intermediate densities. Planting at intermediate densities balances the number of trees with the amount of space and resources, decreasing the amount of stand growth while maintaining individual growth (Long 1985). Managing for the future Previous studies have found different results on whether mixed species stands can produce greater volume than single-species stands (Kelty 2006). Results from the analysis indicate that monocultures at high densities produce a higher volume than mixed stands, but monocultures planted at intermediate densities are the best option for operational activities. The overall yield of a stand may depend on the stage of stand development (DeBell et al. 1997). Since this installation only has four measurements, differences between density and mixture levels may not be statistically significant. Total volume for the 3:1 Pl:Sx mixture at a 2000 SPH planting density showed potential for a higher yield than the pure pine stand at the same planting density. This should be looked at closer once the newest remeasurement takes place (scheduled for 2018). Pure spruce stands showed very little total volume and almost no merchantable volume. This is expected, as spruce is a relatively slow growing species and is usually not commercially viable until about age 80 (Rausher 1987).  Whether or not yield is better in pure or mixed plots, forest managers should look to produce healthy forest rather than merchantable ones. As climate change continues to alter the land, forest structure and function will change (Gayton 2008). Managers need to focus less on how to prevent changes from happening and focus more on silvicultural practices that can overcome any negative effects. In cases where mixed stands do not produce greater yield than pure stands, mixed stands can still be beneficial for reducing competition (Kelty 2006) or increasing the resistance to insects and pathogens (Watt 1992). Conclusions Though single-species stands may be easier to plant and manage, mixed-species stands have been found to be much more beneficial in terms of biodiversity, forest health, and sometimes productivity. This thesis analyzed four measurements over the span of 19 years to see if mixed-25  species plots are more productive than single-species plots. Results showed that there was no interaction between density and mixture, except for pine merchantable volume, but both factors were significant for some variables at the plot level. In all treatments, the size, growth, and yield of P. contorta was greater than that of P. glauca × engelmannii, but the 3:1 Pl:Sx mixture at 2000 SPH shows potential to be a high producing stand. Only four measurements have been taken and it may still be too early to tell if there are any significant differences between other variables, or if these differences will increase or begin to decrease over time. Another remeasurement is scheduled for 2018, when the stand is 25 years old, so mixtures should be looked at more closely to see if they are more productive than pure stands.  Acknowledgements SAS code for data compilation and analysis of single species plots was provided by Suborna Ahmed and Jim Goudie. Thanks to Dr. Louise de Montigny for her guidance on this thesis. A special thanks to Dr. Bianca Eskelson for all her help and patience with this thesis. References Amman, G.D. and Baker, B.H. 1972. Mountain pine beetle influence on lodgepole pine stand structure. Journal of Forestry, 70(4), pp.204-209. Amoroso, M. M., Turnblom, E. C., and Briggs, D. G. 2004. Growth and Yield of a Douglas-fir and western hemlock in pure and mixed planted stands: results at age 12 from the SMC Type III Trials. Stand Management Cooperative. 3:1-45. Assmann, E. 1970. The Principles of Forest Yield Study. Pergamon Press, Oxford, 506 pp. Bergqvist, G. 1999. Wood volume yield and stand structure in Norway spruce understory depending on birch shelterwood density. For. Ecol. Manage. 122, 221–229. Binkley, D. 1984. Importance of size-density relationships in mixed stands of douglas-fir and red alder. Forest Ecology and Management 9(2):81-85. doi:10.1016/0378-1127(84)90075-6. Carroll, A.L. and Linton, D.A. 2002. Managing mountain pine beetle populations in British Columbia. Forest Health and Biodiversity News 6(1):2-5. Chen, H.Y.H., Klinka, K., Mathey, A.-H., Wang, X., Varga, P., and Chourmouzis, C. 2003. Are mixed-species stands more productive than single-species stands: an empirical test of three 26  forest types in British Columbia and Alberta. Canadian Journal of Forest Research 33:1227-1237. doi: 10.1139/X03-048. de Montigny, L. and Nigh, G.D. 2007. Growth and survival of Douglas-fir and western redce- dar planted at different densities and species mixtures. B.C. Min. For. Range, Res. Br., Victoria, BC Tech. Rep. 044. http://www.for.gov.bc.ca/hfd/pubs/Docs/Tr/Tr044.htm de Montigny, L., Ahmed, S., and LeMay, V. 2016. The effects of planting density on the growth and yield of lodgepole pine, interior spruce, interior Douglas-fir, and western larch: 16- to 26-year results from EP964. Prov. B.C., Victoria, B.C. Tech. Rep. In press. DeBell, D.S., Cole, T.G., and Whiteshell, C.D. 1997. Growth, development, and yield in pure and mixed stand of Eucalyptus and Albizia. For. Sci. 43(2):286-298. Evans, J. 1992. Plantation forestry in the tropics: tree planting for industrial, social, environmental, and agroforestry purposes. Oxford University Press. Fahlvik, N., Agestam, E., Nilsson, U., and Nystrom, K. 2005. Simulating the influence of initial stand structure on the development of young mixtures of Norway spruce and birch. For. Ecol. Manage. 213, pp. 297–311. Forrester, D. I., Kohnle, U., Albrecht, A. T., and Bauhus, J. 2013. Complementarity in mixed-species stands of Abies alba and Picea abies varies with climate, site quality and stand density. For. Ecol. Manage. 304(2013):233-242. Garber, S. and Maguire, D. 2004. Stand productivity and development in two mixed-species spacing trials in the Central Oregon Cascades. Forest Science 50(1):92-105. Garber, S. and Maguire, D. 2005. The response of vertical foliage distribution to spacing and species composition in mixed conifer stands in central Oregon. For. Ecol. Manage. 211(3):341-355. Gayton, D.V. 2008. Impacts of climate change on British Columbia's biodiversity: A literature review. Journal of Ecosystems and Management, 9(2). Grant, J. C., Nichols, J. D., Pelletier, M-C., Glencross, K., and Bell, R. 2006. Five year results from a mixed-species spacing trial with six subtropical rainforest tree species. For. Ecol. Manage. 233(2-3):309-314. Harper, J.L. 1977. Population Biology of Plants. Academic Press, New York, NY. Harrington T.B., Harrington C.A., and DeBell, D.S. 2009. Effects of planting spacing and site quality on 25-year growth and mortality relationships of Douglas-fir (Pseudotsuga menziesii var. 27  menziesii). Forest Ecology and Management 258(2009): 18-25. doi: 10.1016/j.foreco.2009.03.039. Hély, C., Bergeron, Y. and Flannigan, M.D. (2000). Effects of stand composition on fire hazard in mixed- wood Canadian boreal forest. Journal of Vegetation Science, 11(6): 813–824. doi: 10.2307/3236551. Kelty, M. J. 1992. Comparative productivity of monocultures and mixed-species stands. The ecology and silviculture of mixed-species forests. Kluwer, Dordrecht, pp.125-141. Kelty, M. J. 2006. The role of species mixtures in plantation forestry. Forest Ecology and Management 233(2-3):195-204. doi:10.1016/j.foreco.2006.05.011. Kozak, A. 1988. A variable-exponent taper equation. Can. J. For. Res. 18: 1363-1368. Johnstone, W.D. 1999. E.P. 964-22: A mixed lodgepole pine-interior hybrid spruce espacement trial, establishment and progress report. Internal report. B.C. Ministry of Forests, Research Branch, 12 pp. Johnstone, W.D. 2004. E.P. 964-22: A mixed lodgepole pine-interior hybrid spruce espacement trial, 10-year progress report. Internal report. B.C. Ministry of Forests, Research Branch, 15 pp. Johnstone, W.D. and Pollack, J.C. 1990. The influence of espacement on the growth and development of a lodegpole pine plantation. Canadian Journal of Forest Research 20:1631-1639. doi: 10.1007/s13398-014-0173-7.2. Lloyd, D., Angove, K., Hope, G., and Thompson, C. 1990. A guide for site identification and interpretation for the Kamloops Forest Region. B.C. Ministry of Forests, Res. Br., Victoria, B.C. Land Management Handbook No. 23. Long, J.N., 1985. A practical approach to density management. The Forestry Chroni- cle 61, 23–27. Moreira, F., Vaz, P., Catry, F. and Silva, J.S. 2009. Regional variations in wildfire susceptibility of land-cover types in Portugal: implications for landscape management to minimize fire hazard. International Journal of Wildland Fire. 18(5), pp.563-574. Rauscher, H. M. 1987. White spruce plantations in the Upper Great Leakes region: Status and problem-solving needs. North. J. Appl. For. 4:146-149. 28  Reyes-Hernandez, V. and Comeau, P. 2014. Survival probability of white spruce and trembling aspen in boreal pure and mixed stands experiencing self-thinning. Forest Ecology and Management 323(2014):105-113. doi:10.1016/j.foreco.2014.03.010. Richards, F.J. 1959. A flexible growth function for empirical use. J. Exp. Bot. 10: 290–300. doi:10.1093/jxb/10.2.290. Simard, S.W. and Hannam, K.D. 2000. Effects of thinning overstory paper birch on survival and growth of interior spruce in British Columbia: implications for reforestation policy and biodiversity. For. Ecol. Manage. 129, 237–251. Taylor, S.W. and Carroll, A.L., 2003. October. Disturbance, forest age, and mountain pine beetle outbreak dynamics in BC: A historical perspective. In Mountain pine beetle symposium: Challenges and solutions (pp. 41-51). Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Information Report BC-X-399, Victoria, BC. Wang, J.R., Letchford, T., Comeau, P. and Kimmins, J.P. 2000. Above-and below-ground biomass and nutrient distribution of a paper birch and subalpine fir mixed-species stand in the Sub-Boreal Spruce zone of British Columbia. Forest Ecology and Management, 130(1), pp.17-26. Watt, A.D. 1992. Insect pest population dynamics: effects of tree species diversity. In: Cannell, M.G.R., Malcolm, D.C., Robertson, P.A. (Eds.), The Ecology of Mixed-Species Stands of Trees. Blackwell Scientific Publications, Oxford, pp. 267–275. Whitehead, R.J., Safranyik, L., Russo, G.L., Shore, T.L., and Carroll, A.L. 2004. Silviculture to Reduce Landscape and Stand Susceptibility to the Mountain Pine Beetle. In: T.L. Shore, J.E. Brooks, and J.E. Stone (eds.), Mountain Pine Beetle Symposium: Challenges and Solutions. Natural Resources Canada, Canadian Forest Service, Victoria, BC, pp. 233-244.   29  Appendix  Appendix 1. Test statistics for total volume (m3/ha), using last the measurement (2013). Mixture comparison Lodgepole pine  p-value Mixture comparison Interior Hybrid spruce  p-value  mixture  mixture 1:0 – 3:1 0.0310 0:1 – 3:1 0.0223* 1:0 – 1:1 <.0001 0:1 – 1:1 0.2238* 1:0 – 1:3 <.0001 0:1 – 1:3 1.0000* 3:1 – 1:1 0.0205 3:1 – 1:1 1.0000* 3:1 – 1:3 0.0003 3:1 – 1:3 0.0283* 1:1 – 1:3 0.1425 1:1 – 1:3 0.2822* * Indicates log transformation Bold indicates the variable was significant at the α = 0.05 level Appendix 2. Test statistics for total baha (m2/ha), using the last measurement (2013). Mixture comparison Lodgepole pine  p-value Mixture comparison Interior Hybrid spruce  p-value  mixture  mixture 1:0 – 3:1 0.0066 0:1 – 3:1 0.0003* 1:0 – 1:1 <0.0001 0:1 – 1:1 0.0121* 1:0 – 1:3 <.0001 0:1 – 1:3 1.0000* 3:1 – 1:1 0.0040 3:1 – 1:1 0.2611* 3:1 – 1:3 <0.0001 3:1 – 1:3 0.0015* 1:1 – 1:3 0.0385 1:1 – 1:3 0.0845* * Indicates log transformation Bold indicates the variable was significant at the α = 0.05 level; italics indicate that significance is   suggestive at a α = 0.10 level 30  Appendix 3. Test statistics for total volume mai (m3/ha/yr), using last measurements. Mixture comparison Lodgepole pine  p-value Mixture comparison Interior Hybrid spruce  p-value  mixture  mixture 1:0 – 3:1 0.0496* 0:1 – 3:1 0.0225* 1:0 – 1:1 <0.0001* 0:1 – 1:1 0.2238* 1:0 – 1:3 <0.0001* 0:1 – 1:3 1.0000* 3:1 – 1:1 0.0067* 3:1 – 1:1 1.0000* 3:1 – 1:3 <0.0001* 3:1 – 1:3 0.0284* 1:1 – 1:3 0.0043* 1:1 – 1:3 0.2831*  * Indicates log transformation Bold indicates the variable was significant at the α = 0.05 level Appendix 4. Test statistics for total baha mai (m2/ha/yr), using last measurements. Mixture comparison Lodgepole pine  p-value Mixture comparison Interior Hybrid spruce  p-value  mixture  mixture 1:0 – 3:1 0.0066 0:1 – 3:1 0.0003* 1:0 – 1:1 <.0001 0:1 – 1:1 0.0120* 1:0 – 1:3 <.0001 0:1 – 1:3 1.0000* 3:1 – 1:1 0.0040 3:1 – 1:1 0.2683* 3:1 – 1:3 <.0001 3:1 – 1:3 0.0015* 1:1 – 1:3 0.0385 1:1 – 1:3 0.0838*  * Indicates log transformation Bold indicates the variable was significant at the α = 0.05 level; italics indicate that significance is   suggestive at a α = 0.10 level 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.52966.1-0314333/manifest

Comment

Related Items