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Carbon and nitrogen transformations in some forest floors Lacelle, Larry E. H. 1971

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CARBON AND NITROGEN TRANSFORMATIONS IN SOME FOREST FLOORS by Larry E. H. L a c e l l e B.S.F., The U n i v e r s i t y of B r i t i s h Columbia, 1969  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department °f S o i l Science  We accept t h i s thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA J u l y , 1971  ii.  In presenting this thesis in p a r t i a l fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library shall make i t freely available for reference and  study.  I further agree that permission for extensive copying of this thesis for scholarly purposes may by his representatives.  be granted by the Head of my  Department or  It is understood that copying or publication  of this thesis for financial gain shall not be allowed without my written permission.  tS^Lyr  Department of  A^X&visVsZ.  The University of B r i t i s h Columbia Vancouver 8, Canada  Date  tf^  + T,?  fr/.  ABSTRACT An and  i n o r g a n i c n i t r o g e n a c c u m u l a t i o n i n samples o f D o u g l a s - f i r and a l d e r  forest and  i n c u b a t i o n technique was used t o examine carbon m i n e r a l i z a t i o n  f l o o r s developed over s o i l s d e r i v e d  limestone  parent  materials  from g r a n i t i c ,  i n western B r i t i s h Columbia and Washington.  Samples i n c l u d e d L, F, and H or H i h o r i z o n s m u l l - l i k e moder and m u l l  ultrabasic  o f D o u g l a s - f i r mor, raw moder,  f o r e s t f l o o r s and a l d e r t y p i c a l moder  forest  floors. Carbon d i o x i d e p r o d u c t i o n an estimate of gross  o f gross  nitrogen mineralization.  of the m i n e r a l i z e d  floor materials  provided  carbon m i n e r a l i z a t i o n and an approximate  accumulated and g r o s s  Comparison o f i n o r g a n i c  carbon m i n e r a l i z e d  to d e n i t r i f i c a t i o n .  containing considerable  indication  nitrogen  i n d i c a t e d that a large  i n o r g a n i c n i t r o g e n i s immobilized  p o p u l a t i o n and (or) l o s t horizons  by the f o r e s t  fraction  by the m i c r o b i a l  The H i h o r i z o n s  incorporated mineral  (organic  matter) accumulated  more i n o r g a n i c n i t r o g e n than d i d the L and F h o r i z o n s . Alder  forest  Douglas-fir forest  f l o o r s accumulated more i n o r g a n i c n i t r o g e n than d i d floor materials.  ammonium n i t r o g e n w h i l e D o u g l a s - f i r mor f o r e s t moder c o u n t e r p a r t s  Alder L horizons  the F and H i h o r i z o n s  tended t o accumulate  accumulated n i t r a t e  nitrogen.  f l o o r s were d i s t i n g u i s h e d from t h e i r mull and  by slower d e c o m p o s i t i o n and l e s s  inorganic  a c c u m u l a t i o n , and by l a r g e l y a c c u m u l a t i n g ammonium n i t r o g e n  nitrogen  i n a l l horizons.  I r r e g u l a r n i t r o g e n a c c u m u l a t i o n curves, f o r some samples o f Douglasf i r L and F h o r i z o n s were probably Incubation accumulated  due t o d e n i t r i f i c a t i o n  conditions favoring n i t r i f i c a t i o n , with i n o r g a n i c n i t r o g e n , may have f a v o r e d  losses.  no p l a n t s i n k s to remove denitrification  losses.  iv.  ACKNOWLEDGEMENTS T h i s study was made p o s s i b l e by g r a n t s from the U n i v e r s i t y o f B r i t i s h Columbia  and the N a t i o n a l Research C o u n c i l .  ledgement i s o f f e r e d to Dr. T. M. B a l l a r d  acknow-  f o r s u g g e s t i n g the nature  of the r e s e a r c h and f o r h i s a s s i s t a n c e and a d v i c e . wishes  Special  The author  also  t o thank Dr. C. A. Rowles and Dr. J . P. Kimmins f o r t h e i r a d v i c e  and c r i t i c a l review o f the m a n u s c r i p t .  V.  TABLE OF CONTENTS Page INTRODUCTION  I  LITERATURE REVIEW  2  STUDY OBJECTIVES  4,  LOCATION AND DESCRIPTION OF SITES  •5  MATERIALS AND METHODS  10  RESULTS AND DISCUSSION  13-  CONCLUSIONS  39  LITERATURE CITED  41  APPENDIX I : Cumulative carbon mineralized  43  APPENDIX I I : Rate of carbon m i n e r a l i z a t i o n  46  APPENDIX I I I : N i t r a t e nitrogen accumulated  49;  APPENDIX IV. Ammonium nitrogen accumulated  52  APPENDIX V:  55  Inorganic nitrogen accumulated  APPENDIX V I : Outline of the c l a s s i f i c a t i o n used i n c h a r a c t e r i z i n g horizons and f o r e s t f l o o r s  58  vi.  TABLES Table  Page  1  Location and d e s c r i p t i o n of s i t e s  7  2  Elemental composition of the forest f l o o r materials  14  3  Summary of r e s u l t s of a n a l y s i s of variance and Duncan's New M u l t i p l e Range Test applied to the three-week means of carbon mineralized and inorganic nitrogen accumulated for tree species, forest f l o o r types, horizons and parent materials  17  4  Mean values f o r carbon mineralized and inorganic nitrogen accumulated f o r horizons and tree species  22  5  Summary of carbon mineralized and n i t r a t e , ammonium and inorganic nitrogen accumulated f o r a l l samples  24  6  Summary of r e s u l t s of a n a l y s i s of variance and Duncan's New M u l t i p l e Range Test applied to the three-week means of n i t r a t e nitrogen, ammonium nitrogen and inorganic nitrogen accumulated for a l l Douglas-fir samples  30  7  Summary of r e s u l t s of a n a l y s i s of variance and Duncan's New M u l t i p l e Range Test applied to the three-week means of rate of carbon m i n e r a l i z a t i o n f o r a l l samples  32  8  Summary of c o r r e l a t i o n c o e f f i c i e n t s r e l a t i n g C/N r a t i o s and pH to carbon mineralized and inorganic nitrogen accumulated f o r a l l samples  35  vii.  FIGURES Figure  Page  1  S i t e locations  2  Carbon mineralized and inorganic nitrogen accumulated f o r Douglas-fir samples, s i t e number 8  18  Carbon mineralized and inorganic nitrogen accumulated f o r alder samples, s i t e number 13  19  Carbon mineralized and inorganic nitrogen accumulated f o r mor, moder and mull forest f l o o r s  20  Inorganic nitrogen, n i t r a t e nitrogen and ammonium nitrogen accumulated f o r alder samples, s i t e number 15  27  Inorganic nitrogen, n i t r a t e nitrogen and ammonium nitrogen accumulated f o r Douglas-fir samples, s i t e number 3  28  Rate of carbon m i n e r a l i z a t i o n f o r Douglas-fir samples, s i t e number 8, and alder samples, s i t e number 14  31  Inorganic nitrogen accumulated f o r Douglas-fir samples, s i t e number 5  33  Carbon mineralized, p l o t t e d against pH f o r a l l samples  36  Inorganic nitrogen accumulated, p l o t t e d against C/N r a t i o f o r a l l samples  37  10  6  1.  INTRODUCTION In many of the forested areas of the world nitrogen d e f i c i e n c i e s are a common tree n u t r i t i o n a l problem.  As a f i r s t step i n s o l v i n g such  problems, the pathways, rates and q u a n t i t i e s of organic and mineral nitrogen accumulation must be understood.  Because a large proportion  of the inroganic nitrogen content of forest f l o o r materials i s often immobilized, mineralized.  i t i s d i f f i c u l t to gain an estimate of gross nitrogen However, t h i s can be achieved i n d i r e c t l y by using the  quantity of carbon mineralized over a given period of time as an i n d i c a t o r of gross nitrogen m i n e r a l i z a t i o n .  Carbon m i n e r a l i z a t i o n i s r e l a t i v e l y  easy to measure and as organic carbon makes up a r e l a t i v e l y large portion of the forest f l o o r material (30-507,) i t s m i n e r a l i z a t i o n gives a s a t i s factory representation of gross organic matter decomposition. Two common methods of analyzing the rates and patterns of carbon and nitrogen m i n e r a l i z a t i o n are:  a n a l y s i s of changes under natural f i e l d  conditions using p e r i o d i c d e s t r u c t i v e sampling or lysimetry, and laboratory incubation of s o i l samples.  The former method, while y i e l d i n g r e s u l t s  more comparable to those found i n nature, has the disadvantages of high cost and d i f f i c u l t y of standardizing experimental  conditions.  Incubation  r e s u l t s represent m i n e r a l i z a t i o n under a r t i f i c i a l c o n d i t i o n s , but i n s p i t e of t h i s are valuable as i n d i c a t o r s of a s o i l ' s m i n e r a l i z a t i o n potential.  Reviews of incubation technique and a p p l i c a t i o n of incubation  r e s u l t s to a g r i c u l t u r a l s i t u a t i o n s are contained  i n a r t i c l e s by Harmsen  and Van Schreven (1955) and Bremner (I960). Attempts to apply incubation techniques to f o r e s t f l o o r material have met with varying success as the forest f l o o r materials are v a r i a b l e i n state of decomposition, and being p a r t l y humified, are often r e s i s t a n t to decomposition.  Therefore, long incubations are required.  In addition,  i n f o r e s t r y work the r e l a t i v e importance of the various f o r e s t f l o o r horizons must be assessed as these organic horizons vary i n rate of decomposition.  I n view of these considerations, the incubation technique  used i n t h i s study involved three-month incubations of L, F and H or Hi horizon materials coupled with p e r i o d i c a n a l y s i s for carbon and n i t r o gen transformations.  ( D i s t i n c t i o n of horizons i s o u t l i n e d i n Appendix V I ) .  LITERATURE REVIEW Few studies dealing with rates and q u a n t i t i e s of carbon and nitrogen mineralized i n f o r e s t f l o o r s are a v a i l a b l e . In Germany, ZtJttl (1960) has studied rates of carbon dioxide production as an i n d i c a t o r of gross nitrogen m i n e r a l i z a t i o n f o r duff m u l l , mull and mor f o r e s t f l o o r s .  In  incubation studies he found no c o r r e l a t i o n between C/N r a t i o and accumulation  of mineral nitrogen f o r d i f f e r e n t f o r e s t f l o o r types.  a t t r i b u t e d t h i s to d i f f e r e n c e s i n decomposability.  He  However, f o r mor  and duff mull f o r e s t f l o o r s he found a p o s i t i v e correlation;; between i n i t i a l nitrogen content and accumulation of mineral nitrogen. For a Scots pine mor f o r e s t f l o o r , Zb'ttl observed that both C 0  2  production  and mineral nitrogen accumulation were greatest i n the L horizons, lower i n the F and least i n the H horizons.  Results f o r a Norway spruce stand  were s i m i l a r . In Norway, Mork (1939) studied the e f f e c t s of water content and incubation temperature on CO2 production and mineral nitrogen for three types of f o r e s t f l o o r m a t e r i a l .  accumulation  He showed that 40 to 55 volume  percent of water represented optimum moisture conditions for n i t r i f i c a t i o n and that ammonium nitrogen could accumulate at water contents as high as  3.  75 volume percent.  For mor f o r e s t f l o o r m a t e r i a l , 20°C represented the  optimum temperature for n i t r a t e nitrogen accumulation.  He found that  when temperature was increased over the range of 10 to 30°C, was more r a p i d i n i t i a l l y , but less rapid subsequently. contents, such as 75 volume percent,  production  At high water  production was i n h i b i t e d . In  general, Mork found t h a t , f o r the range of temperatures and water contents studied, nitrogen m i n e r a l i z a t i o n was l e s s a f f e c t e d by water content than by temperature.  He recommended use of a 20°C temperature and 55 volume  percent water content (about 2/3 of f u l l saturation) as standard  conditions  to be used i n incubation studies of forest f l o o r m a t e r i a l s . Cole (1963) and B a l c i (1963) used lysimetry to study q u a n t i t i e s of several elements leached from d i f f e r e n t Washington f o r e s t f l o o r s and soils.  B a l c i showed that f o r alder f o r e s t f l o o r s approximately 0.74%  of the t o t a l nitrogen was released over an eight month period.  Similarly,  for D o u g l a s - f i r , Cole observed release of 1.8 to 2.2% df the t o t a l forest f l o o r nitrogen over one year. In an incubation t e s t with F and A-Q horizon material from a Douglasf i r , hemlock and S i t k a spruce stand, B o l l e n et a l . (1963) determined the amounts of t o t a l nitrogen mineralized to n i t r i t e , n i t r a t e and ammonium nitrogen.  The c o n i f e r F horizons had greater accumulations of both  n i t r a t e and ammonium nitrogen (0.8% and 0.9% of the t o t a l nitrogen) but i n the A-Q horizon the c o n i f e r s accumulated less n i t r a t e nitrogen  (0.5%).  Alder F horizons accumulated s l i g h t l y less n i t r a t e and ammonium nitrogen (0.3 and 0.8%) than did c o n i f e r F horizons but alder A-Q horizons had much greater accumulations of n i t r a t e and ammonium nitrogen (1.4 and 2.2% of the t o t a l nitrogen).  STUDY OBJECTIVES The  main o b j e c t i v e o f t h i s study was t o examine carbon and n i t r o g e n  m i n e r a l i z a t i o n i n the many types and h o r i z o n s forest  floor materials.  I n a d d i t i o n , i t was d e s i r e d t o e v a l u a t e the  r e l a t i v e e f f e c t s o f limestone, mineralization. were s t u d i e d  o f D o u g l a s - f i r and a l d e r  u l t r a b a s i c and g r a n i t i c  parent  m a t e r i a l s on  D i f f e r e n t f o r e s t f l o o r types and t h e i r r e s p e c t i v e  i n order  to e v a l u a t e  horizons  differences i n quantities of minerali-  z a t i o n t h a t might be r e l a t e d t o m o r p h o l o g i c a l  features of f o r e s t f l o o r s .  M i n e r a l i z a t i o n i n D o u g l a s - f i r f o r e s t f l o o r m a t e r i a l was s t u d i e d because i n o r g a n i c n i t r o g e n d e f i c i e n c i e s a r e a common t r e e n u t r i t i o n a l problem f o r this  species;  Alder  f o r e s t f l o o r m a t e r i a l was s t u d i e d  i n order  the r e l a t i v e q u a n t i t i e s o f i n o r g a n i c n i t r o g e n accumulated under symbiotic  nitrogen f i x e r with  and  this  q u a n t i t i e s accumulated under D o u g l a s - f i r .  G r a n i t i c , u l t r a b a s i c and limestone to e v a l u a t e  to compare  parent  m a t e r i a l s were examined i n order  the e f f e c t s o f these m a t e r i a l s on f o r e s t f l o o r c h a r a c t e r i s t i c s  on r a t e s and q u a n t i t i e s o f m i n e r a l i z a t i o n . The  r a t e s and q u a n t i t i e s o f carbon m i n e r a l i z e d were measured i n order  to e s t i m a t e  the d e c o m p o s a b i l i t y  to e s t i m a t e  gross  organic i n order  nitrogen mineralization.  f o r e s t f l o o r h o r i z o n s and  P a t t e r n s and q u a n t i t i e s o f i n -  n i t r o g e n accumulated as n i t r a t e and ammonium n i t r o g e n were examined to evaluate  accumulated types.  o f the v a r i o u s  the r e l a t i v e q u a n t i t i e s o f each n i t r o g e n  i n the L, F and H or H i h o r i z o n s  o f the d i f f e r e n t  form forest floor  LOCATION AND DESCRIPTION OF SITES D o u g l a s - f i r and a l d e r stands were sampled Columbia and Washington parent m a t e r i a l s . s i t e s as p o s s i b l e  Samples were c o l l e c t e d from as great i n order  t o study carbon and n i t r o g e n Mor, moder  (Table 1 ) .  a v a r i e t y of mineralization  (duff m u l l ) and mull  (Appendix VI) were sampled by h o r i z o n  each parent, m a t e r i a l  British  (Figure 1) on g r a n i t i c , u l t r a b a s i c and limestone  under a range o f c o n d i t i o n s . floors  i n western  forest  f o r each t r e e s p e c i e s and  Table 1. S i t e and Horizon  Location and d e s c r i p t i o n of s i t e s Location  Elevation ft  Forest Floor Description  Horizon Thickness cm  Nature of S o i l Parent M a t e r i a l and Bedrock  Tree Species and Approx. Age  Mors 1 Lj F H  Hollyburn Mtn., B.C.  2,000  thick granular mor  .2 6.1 10.2  sandy g l a c i a l t i l l over g r a n i t i c rock  WH, WRC, PSF,* 200 y r s .  2 L F •H  Twin S i s t e r s Mtn., Wash.  3,400  thick granular mor  .4 6.9 6.4  ultrabasic rock outcrop  DF, WH, WRC 294 y r s .  Raw Moders 3 L F Hi  Coquitlam Watershed, B.C.  650  raw moder  i.l 3.1 1.3  sandy loam, glacio-fluvial deposits over g r a n i t i c rock  DF, WH, wr.c, 70 y r s .  4 L F Hi  Fulford Harbor, B.C.  100  raw moder  .4 1.9 1.3  granitic outcrop  Df, a, go, 86 y r s .  5 L F Hi  Boston Bar B.C.  2,500  raw moder  .2 3.5 3.2  ultrabasic talus slope  DF, 420 y r s .  6 L F Hi  Texada I s l a n d , B.C.  calcareous raw moder  .2 5.7 6.4  limestone rock outcrop  DF, WRC, 96 y r s .  600  rock  Table 1 continued.  Location and d e s c r i p t i o n of s i t e s  S i t e and Horizon  Location  Elevation ft  Forest Floor Description  Horizon Thickness cm  Nature of S o i l Parent M a t e r i a l and Bedrock  Tree Species and Approx. Age  7 L.-: F Hi  19 Mile Creek, B.C.  3,000  calcareous raw moder  .2 4.9 1.9  limestone rock outcrop  DF, wrc, * 465 y r s .  8 L F Hi  Limestone Junction, Wash.  1,800  calcareous raw moder  .3 3.2 3.2  sandy loam over limestone rock  DF, GF, bm, be, 60 y r s .  M u l l - l i k e Moders and M u l l s Seymour River, 1,000 B.C.  mul1-1ike moder  .1 2.5  10 L F  Twin S i s t e r s Mtn., Wash.  2,300  mul1-1 ike moder  .1 .6  11 L F  Quadra Island,  200  mul1-1ike moder  7.6  12 L • V F  Cathedral Grove, B.C.  900  coarse mull  9 L F  B.C.  sandy a l l u v i u m DF, r a , wh, over g r a n i t i c r k . psf, s s , 348 y r s . sandy loam over u l t r a b a s i c rock  DF, WRC, 56 y r s .  limestone rock outcrop  DF, WRC, wh, 56 y r s .  .2 4.1  s i l t y c l a y loam over b a s a l t i c rock  DF, WRC, wh, 600 y r s .  .1 1.9 1.3  sandy loam, glacio-fluvial deposits over g r a n i t i c rock  RA, 30 yrs,  Typical Moders 13 L F Hi  Capilano Lake, B.C.  650  typical moder  oo  Table 1 continued. S i t e and Horizon  Location and d e s c r i p t i o n of s i t e s  Location  Elevation ft  Forest Floor Description  Horizon Thickness cm  Nature of S o i l Parent M a t e r i a l and Bedrock  Tree Species and Approx. Age  14 L F Hi  Twin S i s t e r s Mtn., Wash.  2,000  t y p i c a l moder  .1 1.9 1.3  sandy loam over u l t r a b a s i c rock  RA,* 25 y r s .  15 L F Hi  Popkum, B.C.  500  t y p i c a l moder  .1 .9 5.4  loam over limestone rock  RA, bm, be, 25 y r s .  *  DF - Douglas-fir, WRC - western red cedar, WH - western hemlock, GF - grand f i r , PSF - P a c i f i c s i l v e r f i r , SS - S i t k a spruce, A - arbutus, BC - b i t t e r cherry, GO - Garry oak, BM - b i g l e a f maple, RA - red a l d e r . Small l e t t e r s designate minor stand components.  MATERIALS AND METHODS On each s i t e F and H horizons were sampled at the four corners of a 12 m square.  Because of i t s r e l a t i v e s c a r c i t y (Table 1) f r e s h L  horizon m a t e r i a l was c o l l e c t e d at as many points as required i n order to obtain s u f f i c i e n t sample for incubation and a n a l y s i s . In order to d i s r u p t the normal m i n e r a l i z a t i o n processes as  little  as p o s s i b l e , samples were c o l l e c t e d , composited, transported and stored i n the minimum amount of time p o s s i b l e . Replicate horizon samples were composited and stored i n a i r - t i g h t p l a s t i c bags i n a portable cooler u n t i l transported to the laboratory f o r r e f r i g e r a t i o n at 3°C.  Samples were  roughly sorted through a 0.6 cm screen i n order to remove wood, roots and other large d e b r i s . Alder L and F m a t e r i a l was chopped i n a Waring commerical blender i n order to reduce i t to a s i z e able to pass through the screen. In the l a b o r a t o r y , f o r e s t f l o o r samples were placed i n c y l i n d e r s w i t h wire screen bases and wetted u n t i l a free water f i l m was evident at the sample surface.  The water content of t h i s sample, a f t e r overnight drainage  w i t h r e s t r i c t e d evaporation, was assumed to represent the maximum water holding capacity.  Samples to be incubated were adjusted to 60% of t h i s  water content. For each h o r i z o n , two 10-g C O 2 a n a l y s i s and two 15-g  (oven dry weight equivalent) samples for  (oven dry weight equivalent) samples for nitrogen  a n a l y s i s were placed i n a P e r c i v a l growth chamber (Model PGC-78) and incubated at 18°C and 98 to 99% r e l a t i v e humidity for 12 weeks.  The high  humidity was maintained by using 2 or 3 Sovereign h u m i d i f i e r s (model adjusted to operate continuously.  707)  Water contents were checked p e r i o d i c a l l y  and samples were rewetted with d i s t i l l e d water i f they showed evidence of drying.  The 18°C temperature used i n t h i s study approximates mean  summer temperature near the surface of the mineral s o i l for coastal B r i t i s h Columbia better than do the commonly used incubation temperatures of 20 to 35°C (Brook, 1965; McMinn, 1957). For CO2 a n a l y s i s , measurements were made using a Beckman Infrared Analyzer  (model 215A).  A i r of known CQ2 content was passed over the  samples a t a constant flow rate and when a steady state had been a t t a i n e d the output CO2 concentration was measured. 18°C  Samples were maintained at  during C 0 a n a l y s i s by immersion i n a water bath. 2  The rate of C 0  2  production was measured d a i l y at f i r s t , then l e s s frequently as the rate of carbon m i n e r a l i z a t i o n approached a steady s t a t e . Mass of carbon mineralized was c a l c u l a t e d from volumetric CO2 concentration using the conversion 0.5 g carbon equals 1 l i t r e CO2 a t c a l i b r a t i o n and a n a l y s i s conditions of 22°C and 1 atmosphere. Five g (wet weight) of each sample being incubated for nitrogen a n a l y s i s was removed every three weeks and analyzed for n i t r a t e and ammonium nitrogen by e x t r a c t i n g the inorganic nitrogen with a 1% KAl(SO^) solution.  This e x t r a c t was used i n the ammonium nitrogen determination  using a m i c r o - d i f u s i o n technique, N e s s l e r i z a t i o n and colorimetry at 431 ration, a Bausch and Lomb Spectronic 20 spectrophotometer.  Quantities  of n i t r a t e nitrogen were evaluated using a x y l e n o l - c o l o r i m e t r i c  technique  These two methods of inorganic nitrogen a n a l y s i s are. described by Zb"ttl (1960) and were selected as they proved to be r e l i a b l e i n detection of the small amounts of inorganic nitrogen generally present i n f o r e s t f l o o r material.  A n a l y s i s was not made for n i t r i t e nitrogen, as for P a c i f i c  Northwest conditions q u a n t i t i e s of t h i s nitrogen from are generally much smaller than amounts of ammonium and n i t r a t e nitrogen (Bollen et a l . , 1963). Considering the scope of t h i s project and the amount of time a v a i l a b l e f o r a n a l y s i s , i t was not considered p r a c t i c a l to evaluate losses due to d e n i t r i f i c a t i o n during incubation. Total nitrogen was estimated by using a standard technique  (Black, 1965).  micro-Kjeldahl  A Caro's a c i d digest was prepared f o r the  determination of K, P, Mg and Ca (Lindner and Harley, 1942) the q u a n t i t i e s of these elements being determined using a Perkin-Elmer  Atomic Adsorption  Spectrophotometer (Model 303). Total phosphorus was determined using a wet ashing technique and a n a l y s i s by the vanadomolybdophosphoric yellow c o l o r t e s t (Jackson, 1958).  Total carbon was determined by volumetric  CO2 a n a l y s i s a f t e r o x i d a t i o n of a 0.1-g sample with i r o n and t i n a c c e l e r ators i n a Leco Induction furnace  (Model 507-100).  A l l pH measurements  were made on an Instrument Laboratories Portomatic pH Meter using a glass electrode and a 7/1 r a t i o of water to f o r e s t f l o o r m a t e r i a l . In the f o l l o w i n g s e c t i o n s , q u a n t i t i e s of carbon mineralized are expressed as percentages of i n i t i a l t o t a l carbon.  Rates of carbon minera-  l i z a t i o n are expressed as a percentage of the i n i t i a l t o t a l carbon mineralized i n one day. Quantities  of n i t r a t e nitrogen, ammonium nitrogen and inorganic  nitrogen (the sum of ammonium and n i t r a t e nitrogen) accumulated are expressed i n terms of percentages of i n i t i a l t o t a l nitrogen.  RESULTS AND Concentrations given i n Table limestone  2.  areas.  f l o o r samples Mg  Ca and  C i n a l l samples t e s t e d are  High c o n c e n t r a t i o n s o f Ca a r e e v i d e n t  i n samples from  c o n c e n t r a t i o n s a r e not e v i d e n t i n  i n areas o f u l t r a b a s i c parent m a t e r i a l s .  In most  forest  c o n c e n t r a t i o n i n c r e a s e s w i t h depth w h i l e K c o n c e n t r a t i o n  w i t h depth.  order L, F and  P, K, Mg,  However, h i g h Mg  samples c o l l e c t e d  decreases  of N,  DISCUSSION  Carbon c o n c e n t r a t i o n g e n e r a l l y decreases  i n the  H or H i h o r i z o n s , w h i l e t o t a l n i t r o g e n c o n c e n t r a t i o n i s  generally highest  i n the F, f o l l o w e d by the H or H i and  the L h o r i z o n s .  A l d e r L h o r i z o n s are an e x c e p t i o n , o f t e n having a h i g h e r  concentration  o f t o t a l n i t r o g e n than the F or H i . When a l d e r t y p i c a l moders a r e compared w i t h D o u g l a s - f i r mors, moders and m u l l s  i t appears t h a t a l d e r H i h o r i z o n s a r e r e l a t i v e l y  i n Ca u n l e s s the parent m a t e r i a l i s limestone.-  A l d e r L and  g e n e r a l l y appear to have g r e a t e r c o n c e n t r a t i o n s of K and ponding D o u g l a s - f i r h o r i z o n s . litter,  the c/N  decrease  ratio  w i t h depth as  Due  F o r e s t f l o o r s from limestone less acid  than f o r e s t  and  to the  fact  of a l d e r  significantly  H or H i h o r i z o n s .  u l t r a b a s i c areas g e n e r a l l y are  f l o o r samples from g r a n i t i c a r e a s .  a r e many e x c e p t i o n s , due  N than do c o r r e s -  f l o o r m a t e r i a l does not  i t does i n D o u g l a s - f i r L, F and  deficient  F horizons  to the h i g h n i t r o g e n content  i n alder forest  raw  t h a t pH was  However, t h e r e  measured i n h i g h l y  organic forest  f l o o r m a t e r i a l s t h a t do not n e c e s s a r i l y r e f l e c t  o f the m i n e r a l  soil  the  acidity  or parent m a t e r i a l .  T o t a l percentages  o f carbon m i n e r a l i z e d and  inorganic nitrogen  accumulated f o r each sample were grouped a c c o r d i n g to t r e e s p e c i e s , horizon, forest tages  f l o o r type or parent m a t e r i a l t y p e .  o f carbon m i n e r a l i z e d and  The  means o f  percen-  i n o r g a n i c n i t r o g e n accumulated were used  Table 2. Elemental composition of the forest f l o o r materials Site and Horizon  % N  P  K  Mg  Ca  C  C/N Ratio  PH  .551 .141 .210  49.91 48.64 49.64  47.49 30.96 30.87  4.12 3.79 3.89  .531 .176 .140  50.07 50.17 48.73  54.48 33.94 33.33  4.25 4.38 3.80  Mors 1 L F H  1.051 1.571 1.608  .104 .124 .104  Trace .006  .033 .043 .040  2 L F H  .919 1.479 1.462  .064 .124 .111  .059 .043 .029  .042 .056 .060  II  Raw Moders 3 L F Hi  1.125 1.656 1.660  .064 .124 .124  .019 .017 Trace  .049 .081 .154  .571 .150 .042  49.09 45.45 35.09  43.63 27.45 21.14  6.52 4.42 4.29  4 L F Hi  1.104 1.579 1.303  .215 .155 .226  .586 .106 .086  .155 .157 .316  .811 .546 .055  49.58 45.80 20.73  44.91 29.01 15.91  3.98 5.12 5.63  5 L F Hi  .901 1.539 1.242  .173 .165 .192  .307 .084 .084  .116 .278 .559  .812 .892 .606  48.11' 42.06 29.88  53.40 27133 24.06  4.28 5.42 5.97  6 L F Hi  1.348 1.393 1.368  .215 .143 .135  .258 .025 .021  .103 .121 .138  1.463. 3:257| 3;:537#  48.39 39.29 37.25  35.90 28.20 27.23  4.27 7.92 7.72  7 L F Hi  .885 1.340] 1.315  .184 .111 .135  .289 .062 .098  .070 .135 .456  1.263 . 1.523 1.463  50.09 44.77 33.54  56.60 33.41 25.51  4.29 5.52 3.93  continued.  Table 2 continued. S i t e and Horizon 8 L F . Hi  Elemental composition of the forest f l o o r materials  N  P  K  1.291 1.689 1.376  .226 .135 .143  .360 .064 .039  %  Ca  Mg .133 .166 .211  C  1.082 ' 49.25 43.12 1.693 1.453 31.27  C/N i Ratio  PH  38.15 25.53 22.72  4.22 6.38 6.53  M u l l - l i k e Moders and Mulls 1.392 1.717  .093 .124  .186 .089  .100 .240  .852 .416  50.15 42.49  36.03 24.75  5.07 5.12  10 L F  1.189 1.254-  .123 .124  .078 ,037  .166 .330  .832 ,235  45.50 37.22  38,27 29.68  4.99 5.22  11 L F  .719 1.413  .104 .143  .041 .066  .057 .178  1.052 1.223  49.54 47.09  68.90 33.33  4.68 6.16  12 L F  1.185 1.153  .124 .165  .215 .053  .129 .428  .761 .156  49.30 41.31  41.60 35.83  4.72 4.74  9 L F  Typ i c a l Moders 13 L F Hi  3.329 2.615 1.831  .124 .124 .155  14 L F Hi  3.179 2.899 2.645  .135 .124 .111  15 L F Hi  2.136 2.485 1.559  .104 .135 . .192  1.134 .064 .031 .606 .051 Trace 1.349 .203 .072  .165 .141 .313  .851 .591 .090  47.99 48.51 27.59  14.42 18.55 15.07  5.79 4.32 4.22  .371 .177 .377  .702 .451 .065  48.97 47.61 40.60  15.40 16.42 15.35  4.80 4.23 6.42  .148 .155 .421  1.423 .431 .702  47.80 43.94 18.52  22.38 17.68 11.88  5.73 5.58 5.29  i n the a n a l y s i s of variance and Duncan's New M u l t i p l e Range Test i n order to detect s i g n i f i c a n t d i f f e r e n c e s .  Results are shown i n Table 3 and  i n d i c a t e that percentages of i n i t i a l t o t a l carbon mineralized and percentage of inorganic nitrogen accumulated were s i g n i f i c a n t l y greater f o r alder than f o r Douglas-fir f o r e s t f l o o r s (Table 5; Figures 2 & 3 ) . This i s probably a r e f l e c t i o n of the greater decomposability  of f r e s h alder  debris and the high n u t r i e n t status of alder forest f l o o r materials (Table 2). With abundant t o t a l nitrogen, as i n alder f o r e s t f l o o r materials immobilization i s l e s s than i n Douglas-fir f o r e s t f l o o r s and more inorganic nitrogen can accumulate as a by-product of m i c r o b i a l a c t i v i t y . In the a n a l y s i s of variance t e s t comparing horizons, the L horizons had s i g n i f i c a n t l y greater m i n e r a l i z a t i o n of carbon than d i d the F and H or H i horizons  (Table 3; Figure 4 ) . The L horizons have a greater concen-  t r a t i o n of r e a d i l y decomposable organic matter compared to the F and H or H i horizons, where such materials have been l a r g e l y l o s t through mineralization.  Percentages of carbon mineralized i n the F horizons were  generally greater than i n H or H i horizons but the d i f f e r e n c e , on the average, was not s t a t i s t i c a l l y s i g n i f i c a n t (Table 3 ) . In a few cases, m i n e r a l i z a t i o n rates were more r a p i d i n the H i horizons An example i s s i t e number 4 from the Gulf Islands. extensive understory  (see Appendix I ) .  This s i t e had an  vegetative cover with large q u a n t i t i e s of l i v e root  material i n the H i , t h i s f r e s h material being r e a d i l y mineralized. Although percentages of carbon mineralized i n alder L horizons were much greater than i n Douglas-fir L horizons  (Table 4) the proportion of  carbon mineralized i n the F and H i horizons was not appreciably for alder than f o r Douglas-fir.  greater  Thus, i t appears that the alder L horizons  Table 3. Summary of r e s u l t s of a n a l y s i s of variance and Duncan's New M u l t i p l e Range Test applied to the three-week means of carbon mineralized.(percentage of i n i t i a l t o t a l C) and inorganic nitrogen accumulated (percentage of i n i t i a l t o t a l N) for tree species, forest f l o o r types, horizons and parent materials Carbon  Nitrogen alder 8.04  Douglas-fir 1.65  Typical Moder 8.04  Raw Moder • 1.82  H & Hi 6.11  F 2.31  granitic 4.46  *  Mull .147  ultrabasic 2.48  Mor 1.38*  L 1.16 limestone 2.48  alder 29.23 Typical Moder 29.23  Douglas-fir 18.59 Mull 21.42  L 28.74 limestone 24.25  Raw Moder 18.97  F 16.01  granitic 19.96  Mor 9.22 H & Hi 14.01  ultrabasic 17.27  Means underlined by the same l i n e d i d not d i f f e r s i g n i f i c a n t l y according to Duncan's New M u l t i p l e Range'Test at the 5% l e v e l .  OP  CARBON MINERALIZED (PERCENTAGE OF INITIAL TOTAL C)  c ro  O O S3 M H cr a o 0 p era g P p Hi  CO (D  1 H H- Il-f p. Hi S3  1  N  CO  tD  13  a  fu S3 3 P t—  1  ro co CD Hrr  p O H  09  ro fu P  s ; Ho o p OO Hrf i-i O  INORGANIC NITROGEN ACCUMULATED (PERCENTAGE OF INITIAL TOTAL N)  09  ro p S3  o o p  I  o  ro o  m m  ro a.  o -n  -i  o o c CD >  —I —  •8T  CD  <o  m v  — ro  s  OP  CARBON MINERALIZED (PERCENTAGE OF INITIAL TOTAL C)  c  ri  ro  rf,  O O ft) H i-i cr o ft) ' P 1  CL  ro g  i-i H-  0  3 m m  IK.  CO  CD ft) pi I-i  g £u  x> '  1  I—'  H-  rt> N cn fD  »  cn  Ch  ft)  H- P  rt CL ro  3 0 o  •  1—'  U>  z o c CD  o  l-t  OQ  ft)  0  o  0  H-  INORGANIC NITROGEN ACCUMULATED (PERCENTAGE OF INITIAL TOTAL N)  nH o  OQ  ro 0  a> o o  1  3  ro a.  CA  m m  ro o T  O  ~r  o  20  o c CD  >  '61  o o m  CARBON OF  MINERALIZED (PERCENTAGE  INITIAL TOTAL  C)  MORS RAW MODERS MULL-LIKE MODERS AND MULLS TYPICAL MODERS  MORS RAW MODERS MULL-LIKE MODERS AND! MULLS TYPICAL MODERS  MORS RAW MODERS TYPICAL MODERS  INORGANIC  NITROGEN  ACCUMULATED  (PERCENTAGE OF INITIAL TOTAL  N)  21.  contain more r e a d i l y decomposable material than does the Douglas-fir l i t t e r , but once t h i s i s mineralized, the alder F and H i horizons are almost as r e s i s t a n t to m i n e r a l i z a t i o n as are the corresponding  Douglas-  f i r horizons. Patterns observed f o r carbon m i n e r a l i z a t i o n do not apply to net nitrogen accumulation,  as the concentrations of inorganic nitrogen are  s i g n i f i c a n t l y greater i n the H and H i horizons than i n the F and L horizons  (Tables 3 & 4; Figures 2 & 3).  The mean percentage of nitrogen  accumulated i n inorganic forms i n the H and H i horizons i s 81 and greater than the corresponding  62%  values for the L and F horizons, r e s p e c t i v e l y ,  the mean value for accumulated inorganic nitrogen i n F horizons i s greater than the comparable value for L horizons but the d i f f e r e n c e i s not s i g n i ficant.  The greater inorganic nitrogen accumulations i n the H or H i  horizons probably r e s u l t from the tendency for l e s s nitrogen immobilizat i o n to occur i n the more decomposed organic matter and from leaching of the products of m i n e r a l i z a t i o n into the lower horizons. The H i horizons appear to represent an optimum combination of n u t r i t i o n and environment for m i c r o b i a l a c t i v i t y and subsequent release of inorganic nitrogen.  I t i s i n t e r e s t i n g to note that for alder s i t e s  13 and 14, the percentage of inorganic nitrogen accumulated i n the Hi i s s i m i l a r to the percentage of t o t a l carbon mineralized (Figure 3). Generally, q u a n t i t i e s of carbon mineralized are much greater than q u a n t i t i e s of inorganic nitrogen accumulated (Figure 4 ) .  In samples 13 and 14, where  gross carbon m i n e r a l i z a t i o n and net nitrogen accumulation are s i m i l a r , inorganic nitrogen immobilization must be r e l a t i v e l y small, and conditions optimum for inorganic nitrogen  accumulation.  Table 4. Mean values f o r carbon mineralized (percentage of i n i t i a l t o t a l C) and inorganic nitrogen accumulated (percentage of i n i t i a l t o t a l N) f o r horizons and tree species Horizon Element  L N  F C  . :N  H or H i C  N  C  % Douglas-fir  .36  23.21  1.52  15.62  3.80  13.72  alder  4.36  50.80  5.46  17.53  14.29  19.39  both  1.16  28.74  2.31  16.01  6.11  14.01  In a l d e r t y p i c a l moders, ammonium nitrogen accumulation  i s common  i n the L horizons while the F and H i horizons tend to accumulate a greater proportion of n i t r a t e nitrogen (Table 5; Figure 5; Appendices I I I and I V ) . Douglas-fir mors accumulate mostly ammonium nitrogen (Table 5) while raw moders accumulate both n i t r a t e and ammonium nitrogen i n the F and L horizons w i t h a greater proportion of ammonium nitrogen i n the H i horizons (Table 5; Figure 6 ) . In a comparison of f o r e s t f l o o r types i t was found that alder t y p i c a l moders and Douglas-fir mulls had s i g n i f i c a n t l y greater carbon m i n e r a l i z a t i o n than d i d Douglas-fir raw moders and mors (Table 3; Figures 2, 3 & 4). Alder t y p i c a l moders and Douglas-fir mulls and raw moders had s i g n i f i c a n t l y greater carbon m i n e r a l i z a t i o n than d i d mor f o r e s t floors. With regards to r e l a t i v e inorganic nitrogen accumulation, moders had s i g n i f i c a n t l y greater accumulations  typical  than d i d raw moders,  mulls or mors (table 3). Lower inorganic nitrogen accumulation  i n mors  i s a t t r i b u t e d to the advanced stage of h u m i f i c a t i o n and to less m i c r o b i a l activity.  As mentioned p r e v i o u s l y , mors had l e s s n i t r i f i c a t i o n than the  other types of f o r e s t f l o o r and as a r e s u l t , accumulated ammonium nitrogen, e s p e c i a l l y i n the H horizon (Table 5; Appendices I I I and I V ) . In the a n a l y s i s of variance and Duncan's New M u l t i p l e Range Test applied to the tree types of parent m a t e r i a l s , the three week means of q u a n t i t i e s of carbon mineralized and inorganic nitrogen accumulated d i d not d i f f e r V s i g n i f i c a n t l y w i t h parent m a t e r i a l type  (Table 3). However,  e f f e c t s of parent materials were apparent i n the higher n i t r i f i c a t i o n evident i n horizon  samples c o l l e c t e d from s i t e s 6, 7, 8, 11 and 15, areas  of limestone parent materials (Table 5; Figure 5 ) .  Table 5. Summary of carbon mineralized (percentage.of i n i t i a l t o t a l C) and n i t r a t e , ammonium and inorganic nitrogen accumulated (percentage of i n i t i a l t o t a l N) for a l l samples a f t e r 12 weeks of incubation S i t e and Horizon  Carbon Mineralized  Nitrate Nitrogen. Accumulated  Ammonium Nitrogen Accumulated  Inorganic Nitrogen Accumulated  kg/ha Inorganic Nitrogen Accumulated  1 Mors 1 L F H  18.7 8.6 4.3  .5 .2 .1  .2 3.5 2.1  .7 3.7 2.2  .19 45.83 48.40  2 L F H  17.8 7.1 6.8  0 0 .2  .1 .1 1.3  .1 .1 1.5  .04 1.97 18.96  Raw Moders 3 L F Hi  12.2 10.4 8.6  .1 .1 2.8  .1 1.6 3.4  .2 1.7 6.2  .02 11.65 17.41  4 L F Hi  25.8 17.4 26.5  .2 .2 3.7  0 .4 6.6  .2 .6 10.3  .10 2.05 22.63  5 L F Hi  25.5 14.6 16.4  .4 .2 1.9  .2 .1 1.0  .6 .3 2.9  .12 1.91 15.06  6 L F Hi  26.2 17.3 15.2  .2 1.3 .1  .1 .2 .3  .3 1.5 .4  .09 16.01 4.75 continued.  Table 5 continued. Summary of carbon mineralized (percentage of i n i t i a l t o t a l C) and n i t r a t e , ammonium and inorganic nitrogen accumulated (percentage of i n i t i a l t o t a l N) for a l l samples a f t e r 12 weeks of incubation Site and Horizon  Carbon Mineralized  Nitrate Nitrogen Accumulated  Ammonium Nitrogen Accumulated  7 L F Hi  20.3 15.2 16.2  .1 0 1.3  . .1 .2  8 L F Hi  35.9 21.9 15.9  .1 .2 5.3  .1 0 .1  1  Inorganic Nitrogen Accumulated  .  2  Kg/ha Inorganic Nitrogen Accumulated  .1 1.5  .06 .51 4.89  .2 .2 5.4  .09 1.45 30.95  M u l l - l i k e Moders and Mulls 9 L F  16.5 19.8  0 3.7  0 .2  0 3.9  0 21.81  10 L F  16.3 18.4  .1 0  0 0  .1 0  .02 0  11 L F  23.5 17.8  .9 .3  .2 .3  1.1 .6  .29 8.79  12 L F  40.1 19.0  .4 .3  .2 .3  .6 .6  .17 3.47  5.3 .2 2%  5.5 5.7 16.3  2.38 3,7.25 50.36  Raw Moders 13 L F Hi  49.2 17.2 15.6  .2 5.5 13.9  continued.  Table 5 continued. Summary of carbon mineralized (percentage of i n i t i a l t o t a l C) and n i t r a t e , ammonium and inorganic nitrogen accumulated (percentage of i n i t i a l t o t a l N) f o r a l l samples a f t e r 12 weeks of incubation S i t e and Horizon  Carbon Mineralized  Nitrate Nitrogen Accumulated  Ammonium Nitrogen Accumulated  Inorganic Nitrogen Accumulated  kg/ha Inorganic Nitrogen Accumulated  14 L F Hi  49.7 10.5 6.8  .3 5.4 6.5  7.1 .6 1.8  7.4 6.0 8.3  '3;05 29.29 37.40  15 L F Hi  53.4 24.9 35.8  .1 4.6 18.1  .1 .1 .2  .2 4.7 18.3  .06 13.77 200.84  INORGANIC  NITROGEN  (PERCENTAGE OQ  c  H fD  m m  H P  CU O O  OJ  F7  ro  T  OQ  Co fD i- P Cu fD P  z o c CD > H  H  O  ro  2  NITRATE NITROGEN ACCUMULATED (PERCENTAGE OF INITIAL T O T A L N)  3 1—'  fD  fD fD P  JN2_  T  co i-i 1  •  —  GO  CD  r - o rt OP  o  O CD CD > rn z o  \ \ r \n " \  CO  CO  O  T  0> R  OP  TOTAL N)  ro o  H 1  t- P CO Hrt O fD Cu p H' hh r t O i-J i-i O  3  OF INITIAL  O  C  g  3  oo  ACCUMULATED  —  0>  ro T  Z Z —i H  m OJ  Co P . Cu  Ln Co  O > CD H  a>  m  m  O  P  P Hrt H  o c CD >  O OP  fD P  AMMONIUM  NITROGEN  (PERCENTAGE 3E m m CO  T  OF INITIAL  TOTAL  OJ H-  M m  h  5 _ ro  >  o o CD Z  0>  to  N)  oo r z  o o c CD >  ACCUMULATED  X  c  INORGANIC  NITROGEN  (PERCENTAGE OP  fD  OQ  C  IB  TOTAL  -Pi  CO  ft) Hrt fD O. 3 i-h r t O i-i i-i O  o  N)  T  m m  ft) H .O p D O  g  OF INITIAL  ro  H  ACCUMULATED  CM  H  O  o o m  o > z  o c CD  OQ  fD  O 0 C OQ  1  3  O  3  ft) i-  co r+ 1 i-i Hi ft) H- r t >-i fD  - Ll  ro  NITRATE  H-  (PERCENTAGE o  co 3 ft) H >  g rt 1  1— O fD OQ CD fD  <•  CO H-  rt fD  3  ft)  NITROGEN  CO  OF INITIAL  ro  T  m m  ACCUMULATED ^  T  z z H —1  OJ  TO  O > CD —1 m m z  3  a. ft)  cn  og • o CO  3  H-  § 3 H-  rt i-i O OQ  fD  TOTAL N)  o c CD  > H O Z  ro  3  AMMONIUM NITROGEN ACCUMULATED (PERCENTAGE OF INITIAL TOTAL N) O m m CO  CM  o  *  i i i  i  \ \ \  cn  o c 00  ID  > 82  H O z  ro  \  ro T  * z  >  Hi  si 51  Quantities of carbon mineralized are generally much greater than q u a n t i t i e s of inorganic nitrogen accumulated, e s p e c i a l l y i n the L horizons  (Table 5; Figures 2, 3 & 4; Appendices I & V).  This suggests  that during decomposition large q u a n t i t i e s of inorganic nitrogen are immobilized by the m i c r o b i a l population.  Many samples i n d i c a t e  immobilization i n that inorganic nitrogen content declines i n the f i r s t s three weeks of incubation (Appendix V; Figures 5 & 6).  However, comparison  of the three-week means of inorganic nitrogen accumulated f o r a l l samples by a n a l y s i s of variance and Duncan's New M u l t i p l e Range Test shows that on the whole, the differences between weeks 0 and 3 are not s i g n i f i c a n t (Table 6 ) . Figure'. 7 i l l u s t r a t e s rates of carbon m i n e r a l i z a t i o n and depicts a high i n i t i a l rate followed by a long period of reasonably  constant  m i n e r a l i z a t i o n when m i c r o b i a l populations have presumably s t a b i l i z e d somewhat a f t e r adjusting to incubation conditions.  A p p l i c a t i o n of  a n a l y s i s of variance and Duncan's New M u l t i p l e Range Test to the threeweek means of rates of carbon m i n e r a l i z a t i o n showed that the rate of carbon m i n e r a l i z a t i o n i n weeks 0 and 3 was s i g n i f i c a n t l y greater than the rate i n weeks 6 to 12 (Table 7). S t a b i l i t y of the m i c r o b i a l populations  i s implied by the fact that the rate of carbon m i n e r a l i z a t i o n  did not vary s i g n i f i c a n t l y during the l a s t 6 weeks of the t e s t . In some f o r e s t f l o o r samples ( e s p e c i a l l y Douglas-fir L and F horizons) inorganic nitrogen accumulation decreased during the l a t t e r part of the incubation t e s t (Figure 8; Appendix 5).  However, on the average,  the three-week means f o r each of n i t r a t e , ammonium and inorganic nitrogen accumulated d i d not vary s i g n i f i c a n t l y during the l a s t 6 weeks of the t e s t (Table 6 ) . Douglas-fir H and H i horizons and generally a l l alder  Table 6. Summary of r e s u l t s of New M u l t i p l e Range Test applied nitrogen, ammonium nitrogen and (percentage of i n i t i a l t o t a l N)  a n a l y s i s of variance and Duncan's to the three-week means of n i t r a t e inorganic nitrogen accumulated f o r a l l Douglas-fir samples  N i t r a t e Nitrogen weeks  12  9  6  0  3  means  .778  .706  .250  .222  .181*  Ammonium Nitrogen weeks  12  9  6  0  3  means  .772  .378  .300  .225  .119  Inorganic Nitrogen weeks  12  means  1.500  *  9 1.084  6  0  3  .550  .447  .300  Means underlined by the same l i n e d i d not d i f f e r s i g n i f i c a n t l y according to Duncan's New M u l t i p l e Range Test at the 5% l e v e l .  H-  *1  RATE OF CARBON MINERALIZED (PERCENTAGE OF INITIAL TOTAL MINERALIZED PER DAY)  OP  C  ii  fD  H-port co  CO  IT  o  m m  o  to  CO O p p  O -n  fD fD  a  O Hi  - H OO fo  Cu  z  „ g Co  CuH ii Hrr . i- H HiI-  1  C  p  fD  fD  o c  CD  CO  I—  1  CO  CO N g co 1  fD O co O p  ii  fD  O  s c  O OP • r—' Co  •H-Hi  I— CO L  •p- I  I-i  CD  RATE OF CARBON MINERALIZATION (PERCENTAGE OF INITIAL TOTAL C MINERALIZED PER DAY)  Co  g  T3  I—  1  fD CD  3  m m  CO  z  o cz CD >  Table 7. Summary of r e s u l t s of a n a l y s i s of variance and Duncan's New M u l t i p l e Range Test applied to the three-week means of rate of carbon m i n e r a l i z a t i o n (percentage of i n i t i a l t o t a l C mineralized per day) f o r a l l samples Rate of Carbon M i n e r a l i z a t i o n weeks  0  3  6  12  9  means  .585  .311  .161  .158  .152*  *  Means underlined by the same l i n e d i d not d i f f e r s i g n i f i c a n t l y according to Duncan's New M u l t i p l e Range Test a t the 5% l e v e l .  33.  2  _ 2  2  i  3 O O <  i  P _l <  /  2  •/Hi  -  z  UJ CD  O  rr i—  o z < o rr: o 2  CD <  Y-  2 Ul O CC UJ CL  12 WEEKS  Figure 8.  OF  INCUBATION  Inorganic nitrogen accumulation for Douglas-fir samples, s i t e No. 5  3 4 .  horizons test  ( F i g u r e s 5 , 6 & 8 ; Appendices I I I , IV & V ) .  mineral due  accumulated n i t r o g e n a t a f a i r l y r e g u l a r r a t e throughout the  n i t r o g e n a c c u m u l a t i o n observed i n some samples c o u l d have been  t o d e n i t r . i f i c a t i o n l o s s e s brought about by changes i n a c i d i t y ,  s t a t u s o r m o i s t u r e content attributed in  The slowdown i n  o f the incut>ated  s i m i l a r decreases to increased  samples.  nutrient  In Germany, Zb'ttl*  immobilization  by f u n g i  later  the i n c u b a t i o n . Q u a n t i t i e s o f carbon m i n e r a l i z e d and i n o r g a n i c n i t r o g e n accumulated  for  each h o r i z o n were compared t o pH and C/N r a t i o s t o see i f s t r o n g  l i n e a r r e l a t i o n s h i p s were e v i d e n t . pH and carbon m i n e r a l i z e d i n d i c a t e d by the data organic  A strong  l i n e a r c o r r e l a t i o n between  or i n o r g a n i c n i t r o g e n accumulated i s n o t 8 and F i g u r e  i n Table  9 .  T h i s l i k e l y due t o the  n a t u r e o f the samples and the v a r i e t y o f s i t e s  Comparison o f C/N r a t i o s w i t h  sampled.  carbon and n i t r o g e n v a l u e s  i n d i c a t e s that  h i g h carbon and n i t r o g e n m i n e r a l i z a t i o n i s a s s o c i a t e d w i t h This r e l a t i o n s h i p i s strongest accumulated and C/N r a t i o  low C/N r a t i o s .  i n the comparison o f i n o r g a n i c  f o r the F and H o r H i h o r i z o n s  nitrogen  (Table 8 ;  Figure 1 0 ) . I f gross  carbon m i n e r a l i z a t i o n can be used as an i n d i c a t o r o f the  r a t e o f o r g a n i c matter d e c o m p o s i t i o n and thus, l i z a t i o n of organic nitrogen and  (Zb'ttl,-.  H or H i h o r i z o n s r e s p e c t i v e l y ,  t o t a l n i t r o g e n was m i n e r a l i z e d Of  t h i s , only  was r e c o v e r e d immobilization  0 . 4 ,  1 . 5  and  3.87o  1 9 6 0 ) ,  2 3 . 2 ,  during  the r a t e o f gross  then f o r D o u g l a s - f i r  1 5 . 6  and  the twelve-week t e s t  This represents  f o r the L , F and H or H i h o r i z o n s  L ,  (table 4 ) .  9 8 . 3 ,  total 9 0 . 4  respecitvely.  For a l d e r , the gross  nitrogen  nitrogen  and  7 2 . 2 7 ,  The bulk  n i t r o g e n must be assumed t o have been immobilized  some l o s s e s t o d e n i t r i f i c a t i o n .  F  o f the i n i t i a l  r e s p e c t i v e l y , o f the i n i t i a l  as i n o r g a n i c n i t r o g e n .  o f the m i n e r a l i z e d  13.77>  minera-  with  mineralized  Table 8. Summary of c o r r e l a t i o n c o e f f i c i e n t s r e l a t i n g C.N r a t i o s and pH to carbon mineralized (percentage of i n i t i a l t o t a l C) and inorganic nitrogen accumulated (percentage of i n i t i a l t o t a l nitrogen) f o r a l l samples Horizon Element  L N "  F C  N r va 1 UP.  H or Hi C  N  C  C/N  - .622  .709  - .809  - .243  - .883  - .627  pH  + .212  + .196  - .374  + .544  - .064  +  .234  36.  60  50  o -j Q  iii N  o h-  F H and  40  _J <  -J h-  <  i  Ixl Z  Ix.  Z °  LU CD ^  <  ixl  30  o A  cc ±  i  Hi  A o  °  mcc zho oitcc  20  A o  10 -  Ixl  A  o  oA A  o o  0_  0  1  3  ' 4  1— 5  1  1  L  6  7  8  pH  Figure 9.  Carbon mineralized p l o t t e d against pH f o r a l l samples  INORGANIC NITROGEN ACCUMULATED (PERCENTAGE OF INITIAL TOTAL N) poo  T  I-i  fD  O  ro po oo  3  i-i  1  fo  3  o  3  P*  o  3  T  o  Q  Q.  I  fo 0 0  CD  =n  OJ  O  i—  T  T  II  l-h — I I i-l  ro o  Ol  c  O  x  13 P* I-i  o  CM  00  fD 3  00 00  Co  n n  I  I  ro ro OJ X  fD  Cu  X  33 rt fD  Cu Co  00  >  Q Q.  O  X  Co  P3  co  3  33  i-i  P-  o  3)  r  113  Co  O  oo o £ o > m m m  CO  CO  ?P o  cn  ->j o  ro  *  _L cn  INORGANIC NITROGEN ACCUMULATED (PERCENTAGE OF INITIAL TOTAL N)  oo  would approximate 50.8,  17.5  and  19.4%, o f the t o t a l n i t r o g e n , w h i l e  net n i t r o g e n accumulated would average 4.4, and  Hi horizons  immobilization In order  respectively. f o r the L, F and  5.5  This represents  and  14.3%  91.3,  68.6  the  f o r the L, and  F  26.3%  Hi horizons r e s p e c t i v e l y .  to suggest the r e l a t i v e s i g n i f i c a n c e of each h o r i z o n s  in  terms of q u a n t i t y o f n i t r o g e n accumulated, r a t h e r than percentage o f initial and  t o t a l n i t r o g e n accumulated, the h o r i z o n t h i c k n e s s e s  an assumed bulk d e n s i t y o f 0.13  for forest  r e s u l t s cannot be e x t r a p o l a t e d  plants.  the d e r i v e d v a l u e s are u s e f u l f o r comparison. Table  5 and  i t i s evident  most important h o r i z o n s  i n inorganic  It is realized  d i r e c t l y to the  Results  to supply  for tree n u t r i t i o n .  Values f o r D o u g l a s - f i r L, F and  average 0.1,  13.6  26.8  and  96.3  9.6  and  kg/ha.  kg/ha w h i l e  that  f i e l d but  t h a t the H and H i h o r i z o n s  i n terms o f a b i l i t y  1)  f l o o r m a t e r i a l were  used to c a l c u l a t e the kg/ha o f n i t r o g e n r e l e a s e d p o t e n t i a l l y a v a i l a b l e to h i g h e r  (Table  forms, incubation  nevertheless  are  shown i n  are by  f a r the  inorganic H or H i  comparable a l d e r v a l u e s  nitrogen  horizons are  1.8,  39.  CONCLUSIONS 1.  Limestone parent materials had a pronounced e f f e c t on calcium content of f o r e s t f l o o r s .  Other e f f e c t s of parent materials on f o r e s t f l o o r  composition were obscure. 2.  Carbon concentration of f o r e s t f l o o r s generally decreases with depth, except i n mor humus-.  In most f l o r e s t f l o o r s , magnesium concentration  increases with depth, while potassium concentration decreases w i t h depth. 3.  Alder H i horizons have r e l a t i v e l y low calcium contents except on limestone parent m a t e r i a l s .  In c o n i f e r forest f l o o r s , the  carbon/nitrogen  r a t i o decreases with depth, but i n alder f o r e s t f l o o r s , the C/N  ratio  tends to be low, and more constant with depth. 4.  Carbon m i n e r a l i z a t i o n rates i n alder L horizons are greater than i n Douglas-fir L horizons, but m i n e r a l i z a t i o n rates i n F and i n H i horizons are comparable for both species.  5.  Mineral nitrogen accumulation, as a percentage of t o t a l nitrogen content, i s generally higher for H or H i than L or F horizons.  6.  In alder t y p i c a l moders, most of the mineral nitrogen i n the L horizons i s i n the ammonium form; i n F and H i horizons, more tends to accumulate as n i t r a t e .  7.  Even under the uniform favorable incubation conditions of the c o n t r o l l e d environment chamber, mor  f o r e s t f l o o r materia3s decomposed  s i g n i f i c a n t l y more slowly than t h e i r raw moder or mull counterparts, as evidenced by C0£ production measurements. 8.  In mors, l i t t l e mineral nitrogen accumulated, and most ( i f not a l l ) of the mineral nitrogen occurred i n the ammonium form.  9.  The p r o b a b i l i t y of d e n i t r i f i c a t i o n losses occuring i n these incubation studies seems high for several reasons:  (1)  common occurrence  40.  of n i t r i f i c a t i o n , ( 2 ) absence of higher plant sinks for mineralized nitrogen, and  (3) a tendency for anaerobic microsites to exist under  the imposed conditions of temperature and moisture regime.  Presumptive  evidence for d e n i t r i f i c a t i o n losses includes declining mineral nitrogen accumulation rates accompanying r e l a t i v e l y constant mineralization rates after several weeks of incubation.  carbon  41.  LITERATURE CITED 1.  B a l c i , A.N.  1963.  P h y s i c a l , chemical and h y d r o l o g i c a l  of c e r t a i n Washington f o r e s t f l o o r types. of Washington, S e a t t l e , 2.  Bernier, B.  1968.  classification.  Black, C.A. Agron. No.  4.  B o l l e n , W.B.,  p.  Proc. of the 7th meeting of the National  ed. 9.  t h e s i s , Univ.  Descriptive o u t l i n e of f o r e s t humus-form  S c i . Comm. of Canada. 3.  192  Ph.D.  properties  U n i v e r s i t y of A l b e r t a , Edmonton.  1965.  Methods of s o i l a n a l y s i s .  Part  Chi-Sen Chen, K.C  chemical e f f e c t s .  Lu and R.F.  Tarrant.  Oregon State Univ., School of  Research B u l l . 12. Bremner, J.M.  61  Brooke, R.C.  1965.  1963.  1965.  Part 2.  1963.  Agron. No.  In C.A.  9.  Black  p. 1324-1345.  225  Ph.D.  t h e s i s , the Univ.  p.  Release of elements from the forest f l o o r  migration through associated Ph.D.  and  Vegetation-environmental r e l a t i o n s h i p s i h the  of B r i t i s h Columbia, Vancouver. Cole, D.W.  microbial  Forestry.  Nitrogen a v a i l a b i l i t y i n d i c e s .  subalpine moutain hemlock zone ecosystems.  7.  2.  p.  ed. Methods of s o i l a n a l y s i s . 6.  p. 1391154.  p. 1171-1175.  Influence of red alder on f e r t i l i t y of a forest s o i l :  5.  Soil  s o i l p r o f i l e s (a lysimeter  t h e s i s , Univ. of Washington, S e a t t l e .  109  and  study).  p. r  8.  Harmsen, G.W.  and D.A.  Van Schreven.  organic nitrogen i n s o i l . 9.  Hoover, M.D.  and H.A.  f o r e s t humus types. 10.  Jackson, M.L.  Lunt.  1955.  Adva. Agron. 1952.  M i n e r a l i z a t i o n of  8:299-398.  A key for the c l a s s i f i c a t i o n  S o i l S c i . Soc. Amer. Proc.  1958.  Englewood C l i f f s , N.J.  S o i l chemical a n a l y s i s . 498  p.  of  16:368-370. Prentice-Hall  Inc.,  42.  11.  Lindner, R.C. and C P . Harley. of nitrogen i n plant t i s s u e .  12.  McMinn, R.G.  1957.  Vancouver I s l a n d . Vancouver. 13.  Mork, E.  Z o t t l , H.  Science.  96:565-566,  Water r e l a t i o n s i n the Douglas-fir region on Ph.D. t h e s i s , the Univ. of B r i t i s h Columbia,  App. IV, p. 20. 1938.  og f u k t i g h e t . 14.  1942. A r a p i d method for determination  Omsetningen i humusdekket ved f o r s k j e l l i g temperatur  Medd.  1960.  Waldbodenmaterial.  Norske Skogsforsjiksv.  6:179-224.  Dynamik der S t i c k s t o f f m i n e r a l i s a t i o n im organischen Plant & S o i l .  13:166-182.  APPENDIX I  Cumulative carbon m i n e r a l i z e d (percentage o f i n i t i a l  total  C)  Appendix I Cumulative carbon mineralized  (percentage of i n i t i a l t o t a l C) Weeks  S i t e and Horizon  3  6_  9  12  Mors L F H  6.8 2.7 1.9  12.2 4.6 2.8  16.7 6.4 3.7  18.7 8.6 4.3  L F Hi  7.5 2.4 2.4  11.2 4.2 3.9  14.0 6.1 5.7  1.7.8 7.1 6.8  Raw Moders 3 L F Hi  5.7 4.1 3.1  8.5 6.1 4.9  11.1 8.1 7.1  12.2 10.4 8.6  4 L F Hi  13.1 6.9 10.1  18.6 11.4 16.9  23.4 15.1 21.4  25.8 17.4 26.5  5 L F Hi  10.9 5.9 .5.7  16.7 9.5 10.3  21. 11. 12.  25. 14. 16.  6 L F Hi  11.6 5.8 5.0  17.4 11.1 99; 5  22.0 14.6 12.0  26. 17. 15.  7 L F Hi  10.8 6.0 4.6  14.6 9.2 7.2  17.9 12.8 10.6  20.3 15.2 16.2  8 L F Hi  16.8 7.1 5.9  24.3 12.1 9.7  30.3 15.9 12.0  35.9 21.9 15.9  M u l l - l i k e Moders and Mulls 9 L F  ,2 8 ,7  11.6 12.6  14.3 17.3  16.5 19.8  10 L F  6.3 7.1  10. 11.  13.9 15.5  16, 18,  11 L F  8.8 6.0  13.0 10.6  18.3 13.7  23.5 1.7.8 continued.  Appendix I continued Cumulative carbon mineralized  (percentage of i n i t i a l t o t a l C) Weeks  S i t e and Horizon 12 L F  3 15.3 6.8  6 26.4 11.4  9 34.5 16.5  12 40.1 19.0  Typical Moders 13 L F Hi  26.6 6.3 5.9  37.0 10.8 9.3  42.4 13.3 11.2  49.2 17.2 15.6  14 L F Hi  27.9 5.5 2.9  39.2 8.5 4.6  44.0 9.8 5.5  49.7 10.5 6.8  15 L F Hi  29.8 12.3 11.2  41.7 18.0 20.6  48.0 22.1 29.2  53.4 24.9 35.8  46.  APPENDIX I I  Rate o f carbon m i n e r a l i z a t i o n (percentage o f i n i t i a l  total  C mineralized  per  day)  Appendix I I Rate o f carbon m i n e r a l i z a t i o n (percentage o f i n i t i a l per day)  total C mineralized  Weeks S i t e and Horizon  0  3  6  9  12  Mors 1 L F H  .31 .11 .04  .27 .11 .10  .19 .05 .03  .19 .07 .04  .10  2 L F H  .29 .04 .04  .19 .10 .10  .11 .10 .05  .14 .08 .08  .18 .05 .05  Raw  .10 .03  Moders  3 L F Hi  .41 .17 .09  .18 .21 .14  .10 .05 .07  -.13 .09 .07  .05 .10 .07  4 L F Hi  .79 .34 .41  .38. .27 .43  .10 .21 .12  .18 .16 .20  .12 .11 .24  5 L F Hi  .49 .29 .31  .42 .29 .19  .20 .06 .17  .20 .09 .08  .20 .14 .16  6 L F Hi  .79 .23 .17  .32 .31 .26  .25 .13 .13  .19 .18 .10  .20 .13 .16  7 L F Hi  .38 .27 .19  .31 .27 .17  .10 .03 .04  .14 .16 .17  .11 .11 .27  8 L F Hi  1.71 .34 .36  .48 .31 .29  .20 .21 .08  .26 .17 .08  .27 .28 .18  Mul1-1 ike Moders and M u l l s 9 L F  .73 .35  .36  .24  .10 .11  .14 .22  .10 .12  10 L F  .24 .40  .27 .33  .20 .16  .17 .20  .10 .13  L F  .41 .26  .31 .26  .27 .19  .21 .12  .25 .19  1 1  48.  Appendix I I continued Rate of carbon m i n e r a l i z a t i o n (percentage of i n i t i a l t o t a l C mineralized per day) Weeks S i t e and Horizon 12 L F  0  3  6  .52 .30  .61 .30  .48 .13  9  12  . .37 .22  .27 .12  Typical Moders 13 L F Hi  3.60 .44 .27  .72 .25 .21  .34 .18 .09  .22 .12 .09  .32 .18 .21  14 L F Hi  3.20 .33 .14  .76 .26 .12  .48 .12 .06  .18 .04 .03  .27 .03 .06  15 L F Hi  3.00 .72 .50  .75' .43 .49  .35 .30 .27  .24 .20 .20  .26 .13 .31  APPENDIX I I I  N i t r a t e n i t r o g e n accumulated (percentage o f i n i t i a l  total  N)  Appendix I I I N i t r a t e nitrogen accumulated  (percentage of i n i t i a l t o t a l N) Weeks  S i t e and Horizon  0  3  6_  9  12  Mors L F H  .1 .1 0  .2 0 .1  0 0 0  .0 .9  L F H  .2 .1 .0  0 0 0  0 0 0  .3 .1 .3  .4  .7.5'  ,2 .1  Raw Moders 3 L F Hi  .3 .1 0  0 0 0  0 .1 .2  .2 .1 .2  .1 .1 2.8  4 L  .4  .2 .2  F Hi  .2 .5  .2 .2 .3  .4 .7  .9 .9 1.6  5 L F Hi  0 .1 .2  0 0 .1  .2 .1 .6  1.1 .6 1.1  .2 1.9  6 L F Hi  .1 0 .3  0 0 0  .1 0 0  .2 .1 .1  .2 1.3 .1  L F Hi  .3 .1 .2  .1 0 .5  .2 .1 .7  .6 .2 .9  .1 0 1.3  8 L F Hi  .4  .1 0 .3  .2 .1 .2  .3 .2 2.1  .1 .2 5.3  7  .1 .2  .3  3.7  .4  M u l l - l i k e Moders and Mulls 9 L  0 .1  0 0  .2 .5  .1 .8  10 L F  .4  0  . 0 0  0 0  .1 .2  .1 0  11 L F  .1 0  1.9 .9  2.1 0  .9 .5  .9 .3  F  0 3.7  Appendix I I I continued N i t r a t e nitrogen accumulated  (percentage of i n i t i a l t o t a l  N}  Weeks S i t e and Horizon 12 L F  0  3_  1.4 .1  .5 .4  6  9  12  0 0  1.4 1.2  .4 .3  .1 2.9 7.7  .2 5.5 13.9  Typical Moders 13 L F Hi  . 1 .3 1.6  14 L F Hi 15 L F Hi  115  1.3 6.1  0 2.8 . 7.4  .1 1.1 2.2  0 2.1 3.0  3.0 4.2  .3 3.6 3.9  .3 5.4 6.5  .6  . .1 1.8  .4 5.6  .5 2.0 10.0  .1 4.6 18.1  3.9  0  :2  1  0  52.  •' :»  APPENDIX IV  i Ammonium n i t r o g e n accumulated (percentage o f i n i t i a l t o t a l  N)  Appendix IV Ammonium nitrogen accumulated  (percentage of i n i t i a l t o t a l N) Weeks  S i t e and Horizon  0  3  __6  9  12  Mors. 1 L F H  .1 .4 .1  0 .4 .3  .2 1.7 1.2  0 2.6 1.6  .2 3.5 2.1  2 L F H  0 .1 .  0 0  .2 .2 1.1  :0 0 .8  .1 .1 1.3  1  0  Raw Moders 3 L F Hi  0 .2 .6  .1 .1 .5  .1 .3 .7  0 .6 2.1  .1 1.6 3.4  4 L F Hi  .2 .2 1.0  0 0 1.3  0 0 2.3  0 .1 2.8  0 .4 6.6  5 L F Hi  0 .1 .2  0 .1 .5  0 0 .2  0 .1 .3  .2 .1 1.0  6 L F Hi  .2 .2 .2  .1 .1 0  .1 .1 .2  .2 .1 .3  .1 .2 .3  7 L F Hi  .1 .2 .2'  0 0 .  0 0  0 0 0  .1 .1 .2  8 L F Hi  .2 .1 .3  0 0 0  0 0 0  0 0 0  .1 0 .1  1  0  M u l l - l i k e Moders and Mulls 9 L F  .1 .4  0 .1  .1 .6  0 .4  0 .2  10 L F  .2 .2  0 .1  .1 .2  0 0  0 0  Appendix IV continued Ammonium nitrogen accumulated (percentages.? of i n i t i a l t o t a l N) Weeks S i t e and Horizon  0  3  6  9  12  11 L F  .3 .4  0 0  0 0  0 0  12 L F  .3 .3  0 0  0 0  .1  .2 .3 0  .  2 .3  Typical Moders 13 L F Hi  .2 .4 .2  1.9 .1 0  . 4.5 .2 .2  4.6 .1 .5  5.3 .2. 2.4  14 L F Hi  .1 .8 .3  6.0 .1 .2  7.9 .4 .6  8.0 .5 1.1  7.1 .6 U-8  15 L F Hi  .3 .2 . 2  .1 0  0 0 0  .1 0 0  ,1 .1 .2  0  APPENDIX V  I n o r g a n i c n i t r o g e n accumulated (percentage o f i n i t i a l  total  N)  Appendix V Inorganic nitrogen accumulated' (percentage of i n i t i a l t o t a l N) Weeks S i t e and Horizon  0  3  6  9  12  .2 1.7 1.2  liO 3.5 2.0  .7 3.7 2.2  .2 1.1  .3 .1 1.1  .1 .1  1.5  Mors 1 L F H  .2 .5 .1  .2 .4 .4  2 L F H  .2 .2 1.1  0 0 0  .  2  Raw Moders 3 L F Hi  .3 .3 .6  .1 .1 .5  .1 .4 .9  .2 .7 2.3  .2 1.7 6.2  4 L F Hi  .6 .4 1.5  .2 .2 1.6  .4 .3 3.0  .9 1.0 4.4  .2 .6 10.3  5 L F Hi  .2 .4  .1 .6  .2 .1 .8  1.1 .7 1.4  .6 .3 2.9  6 L F Hi  .3 .2 .5  .1 .1 0  .2 . .1 .2  .4 .2 .4  .3 1.5 .4  7 L F Hi  .4 .3 .4  .1 0 -  .2 .1 -  .6 .2 -  .2' .1 1-5  8 L F Hi  .6 .2 .5  .1 0 .3  .2 .1 1.2  .3 .2 2.',1  .2 .2 5.4  .'1  0  ,  0  6  "  7  9  M u l l - l i k e Moders and Mulls 9 L F  .1 .5  0 .1  .3 1.1  1.2  0 3.9  10 L F  .6 .2  0 .1  .1 .2  .1 .2  .1 0  Appendix V continued Inorganic nitrogen accumulated (percentage of i n i t i a l t o t a l N) S i t e and Horizon  Weeks 0  3  6  9  12  ll- L F  ,4 '.4  .9 1.9  •2.1 0  2.9 1.5  1.1 .6  12 L F  1.7 .4  .5 .4  0 0  1.4 1.3  .6 .6  Typical Moders 13 L F Hi  .3 .7 1.8  1.9 1.4 6.1  4.5 3.0 7.6  4.7 3.0 8.2  5,5.: 5.7 16.3  14 L F Hi  .2 1.9 2.5  6.0 2.2 3.2  8.1 3.4 4.8  8.3 4.1 5.0  7.4 6.0 8.3  15 L F Hi  .9 1.7 4.1  .2 .1 1.8  0 .4 5.6  .6 2.0 10.0  .2 4.7 18.3  Appendix IV Outline of the c l a s s i f i c a t i o n used i n c h a r a c t e r i z i n g horizons and forest f l o o r s *  Horizons L - L i t t e r , f r e s h l y f a l l e n leaves and other plant d e b r i s , the s t r u c t u r e of which i s not a l t e r e d by decomposition. F - An organic horizon c o n s i s t i n g mostly of s l i g h t l y decomposed plant remains s t i l l recongnizable as to t h e i r o r i g i n . H - An organic horizon characterized by advanced decomposition, the structure or o r i g i n of the plant materials for the most part being unrecognizable. Hi - An organic h o r i z o n w i t h considerable mineral matter intermixed. T r a n s i t i o n to the mineral s o i l i s gradual.  Forest Floor Types Mors  L, F and H horizons present, p r a c t i c a l l y no mixing of organic matter w i t h mineral s o i l .  Moders  L, F and Hi horizons present (no H i i n m u l l - l i k e moders), the H i intermixed with mineral s o i l but organic and mineral p a r t i c l e s e x i s t as d i s t i n c t elements. Subtypes of Moders T y p i c a l Moder - (fine mull) Generally formed under mixed or hardwood f o r e s t s , with a t h i n F and a predominant H i . Raw Moder - (duff mull) Has a comparatively t h i c k F horizon and i s t r a n s i t i o n a l to a mor. M u l l - l i k e Moder - (sand mull) Resemble mulls but lack the intimate mixture of organic matter and mineral s o i l of mulls, has a t h i n F and a t h i c k H i or Ah.  Mulls  No H or H i , the Ah an intimate mixture of organic matter mineral s o i l .  * A f t e r Bernier, 1968 and Hoover and Lunt,  1952.  and  

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