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Some aspects of the nitrogen cycle in soil of the Douglas-fir forest Garm, Richard 1958

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SOME' ASPECTS OP THE NITROGEN CYCLE IN SOIL OP THE DOUGLAS-FIR FOREST by RICHARD GARM B.A., U n i v e r s i t y of B r i t i s h Columbia, 19^5 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Bio l o g y and Botany and the Department of S o i l Science We accept t h i s t h e s i s as conforming to the standard required from candidates f o r the degree of Master of .Science THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 19^8 i i ABSTRACT Studies were c a r r i e d out on n i t r i f y i n g c a p a c i t i e s of duff m u l l and raw liumus s o i l s of the D o u g l a s - f i r f o r e s t . For t h i s purpose, p e r f u s i o n apparatuses were set up accord-in g to the technique described by I . J . Audus (8) w i t h c e r t a i n m o d i f i c a t i o n s which seemed to: improve considerably the a p p l i c a t i o n of t h i s apparatus f o r s o i l s t u d i e s . C e r t a i n changes were introduced i n t o the method as given by H. Lees and J.H. Q u a s t e l l . The q u a n t i t a t i v e estimations of ammonia and n i t r a t e s were made by c o l o r i m e t r i c method using phenoldisulphonic and NaOH-EDTA s o l u t i o n f o r n i t r a t e s and Nessler's reagent f o r ammonium determinations. S o i l s used f o r t h i s experiment were tested f o r t o t a l organic matter and t o t a l n i t r o g e n . From the r e s u l t s obtained, the most s t r i k i n g d i f f -erence between the raw humus (mor) and duff m u l l was observed i n the t o t a l absence of n i t r i f i c a t i o n i n a l l samples of mor and the comparatively vigorous n i t r i f i c a t i o n i n a l l samples of m u l l . There was f u r t h e r c o n f i r m a t i o n that the a c i d i c c o n d i t i o n of mor': humus alone i s not the l i m i t i n g f a c t o r i n n i t r i f i c a t i o n i n such f o r e s t s o i l s . In duff m u l l , n i t r i -f i c a t i o n occurred over a wide range of pH. In raw humus, a f t e r a d j u s t i n g pH to 6 . ^ and 7 -0 and i n o c u l a t i n g with a c t i v e l y n i t r i f y i n g garden s o i l , no n i t r i f i c a t i o n was observed. I t was of i n t e r e s t to note that n i t r i f i c a t i o n i i i occurred only when mor s o i l was subjected to complete drying or steam s t e r i l i z a t i o n before being i n o c u l a t e d . This phenomenon might i n d i c a t e the presence of some i n h i b i t o r y a c t i o n against n i t r i f y i n g organisms. This i n h i b i t o r y e f f e c t i s t y p i c a l of raw humus (mor) but l a c k i n g when i t i s s t e r i -l i z e d by steam. In a l l leachates of raw humus some ammonium was always detected. As f a r as could be determined, n i t r i f y i n g duff m u l l s o i l s have f a i l e d to show any s i g n i -f i c a n t seasonal v a r i a t i o n . I t was d i f f i c u l t to e s t a b l i s h any c o r r e l a t i o n between t o t a l n i t r o g e n of s o i l s , t h e i r carbon/ n i t r o g e n r a t i o , and t h e i r c a p a c i t y f o r n i t r i f i c a t i o n . I t i s unders'tood that n i t r a t e s , are not the only source of n i t r o g e n f o r the metabolism of f o r e s t t r e e s ; nevertheless, n i t r a t e s should be regarded as an important e c o l o g i c a l f a c t o r in''"the. e v a l u a t i o n of f o r e s t s i t e s . In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of rny Department or by h i s r e p r e s e n t a t i v e . I t i s under-stood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission. Department of 1b>o£of^  eu^A "Solcvn^ The U n i v e r s i t y of B r i t i s h Columbia, Vancouver $, Canada. Date i v TABLE OF CONTENTS Page I INTRODUCTION 1 I I LITERATURE REVIEW 3 A. Nitrogen i n A g r i c u l t u r a l S o i l s 3 a. T o t a l n i t r o g e n i n a g r i c u l t u r a l s o i l s 3 b. Nitrogen of organic o r i g i n i n a g r i c u l t u r a l s o i l s 3 c. Nitrogen of inorganic f r a c t i o n . . . 5 B. Nitrogen Intake i n S o i l s i n General . . . 7 a. F i x a t i o n of n i t r o g e n by symbiotic b a c t e r i a 7 b. F i x a t i o n of n i t r o g e n by nonsymbiotic b a c t e r i a 9 c. F i x a t i o n of n i t r o g e n by other organisms 11 d. F i x a t i o n of n i t r o g e n by n o r i b l o l o g i c a l f a c t o r s 13 C. Nitrogen Transformations i n S o i l s . . . . II). a. Ammonification and d e n i t r i f i c a t i o n . l l f b. N i t r i f i c a t i o n 18 D. For e s t S o i l s . .21 a. M u l l and mor general c h a r a c t e r i s t i c s 21 b. M i c r o b i o l o g i c a l studies of f o r e s t s o i l s 2J4. c. Nitrogen i n f o r e s t s o i l s 26 Page-I l l . EXPERIMENTAL. PART 30 A. C h a r a c t e r i z a t i o n of S o i l s and Plants i n Habi t a t s Under I n v e s t i g a t i o n 30 a. E c o l o g i c a l a n a l y s i s of s i t e s 30 b. A n a l y s i s of some p l a n t s f o r the a b i l i t y to accumulate inorganic n i t r o g e n 37 c. Determination of organic matter and t o t a l N of s o i l s ]\.$ d. pH measurements of s o i l s ^2 e. Percentage moisture ^3 f . Q u a n t i t a t i v e s t u d i e s of s o i l micro-organisms of f o r e s t s o i l s . . . . . *~>l\. B. P r e l i m i n a r y Studies of N i t r i f i c a t i o n by P e r f u s i o n Technique £8 C. N i t r i f i c a t i o n i n Forest S o i l as Inves t i g a t e d by the P e r f u s i o n Technique 6 5 IV. CONCLUSIONS . 71 V. BIBLIOGRAPHY 73 VI. APPENDIX Includ i n g . . . . . 'Tables I - V I I I . . . . . Fig u r e s I - IX ACKNOWLEDGMENT The author wishes to thank Dr. V.J. K r a j i n a , Dr. D.G. L a i r d , and Dr. J.S. C l a r k f o r t h e i r ' a s s i s t a n c e and suggestions i n the c a r r y i n g out of t h i s study. He also wishes to acknowledge that he was supported by a Research Grant given by the U n i v e r s i t y of B r i t i s h Columbia f o r studies, d i r e c t e d by Dr. V.J. K r a j i n a . 1 I . INTRODUCTION Of f i f t e e n elements known to be- required f o r the n u t r i t i o n of p l a n t s , n i t r o g e n i s regarded as one of the most important of the macroelement group. Very o f t e n i t becomes a l i m i t i n g f a c t o r . For these reasons the n i t r o g e n c y c l e i n nature- arid i t s economy has been the subject of thorough studies e s p e c i a l l y i n a g r i c u l t u r a l s o i l s , i n which the constant removal of crops reduces the n i t r o g e n l e v e l of these s o i l s and t h e i r p r o d u c t i v i t y . In v i r g i n s o i l s under the f o r e s t s , a s t a t e of dynamic e q u i l i b r i u m has been e s t a b l i s h e d over time. Any n a t u r a l changes i n t h i s e q u i l i b r i u m are minor and occur only a f t e r r e l a t i v e l y long periods of time by very slow changes i n c l i m a t i c , g e o l o g i c a l , and b i o t i c f a c t o r s . On t h i s assumption, t h e r e f o r e , i t was presumed that there i s no immediate n e c e s s i t y f o r a s t r i c t c o n t r o l or p o s s i b l e cor-r e c t i o n s of the n i t r o g e n l e v e l i n these s o i l s . Recently, i n countries where the f o r e s t i s a major asset i n the n a t i o n a l economy, i t became obvious that the s o i l under the f o r e s t should not be considered of l e s s importance than the trees growing on i t . With the removal of trees-by logging or the d e s t r u c t i o n of most of the organic matter by f i r e or any other d r a s t i c .changes i n the environmental c o n d i t i o n s , i t i s l o g i c a l to assume tha t nature's long e s t a b l i s h e d n i t r o g e n e q u i l i b r i u m i n these s o i l s w i l l be 2 a l t e r e d . To continue, t h e r e f o r e , an expensive and laborious program of r e f o r e s t a t i o n without regard to the productive capacity of the s o i l might lead to unpredictable and d i s a p p o i n t i n g r e s u l t s . 3 I I . LITERATURE. REVIEW t A. Nitrogen -in ••Agricultural S o i l s Most of our knowledge of the i n t e r c h a n g e a b i l i t y of v a r i o u s forms of n i t r o g e n i n nature i s derived from studies of the n i t r o g e n c y c l e i n a g r i c u l t u r a l s o i l s . a. T o t a l Nitrogen i n A g r i c u l t u r a l S o i l s T o t a l n i t r o g e n i n s o i l s depends' mainly upon the amount of organic matter i n the s o i l and bears only a s l i g h t r e l a t i o n s h i p t'.o the . s o i l n i t r o g e n a v a i l a b l e f o r the growth of p l a n t s . In general,, the organic f r a c t i o n of s o i l n i t r o g e n i s very r e s i s t a n t to decomposition and t h e r e f o r e , r e l a t i v e l y u n a v a i l a b l e to the growing vegetation (96). According to Rremner (16), only 1% - 3$ of organic n i t r o g e n i s m i n e r a l i z e d during the growing .season. Recent work (2l|,33,76,106) performed by a number of i n v e s t i g a t o r s at the Iowa A g r i c u l t u r a l Experiment S t a t i o n suggests n i t r a t e s r a t h e r than t o t a l n i t r o g e n as a r e l a t i v e measure of the p o t e n t i a l n i t r o g e n supplying power of a g r i c u l t u r a l s o i l s . F or data showing the average values of t o t a l n i t r o g e n i n c e r t a i n a g r i c u l t u r a l s o i l s see Appendix (Table I ) . b. Nitrogen of Organic O r i g i n i n A g r i c u l t u r a l S o i l s Nitrogen i n the organic f r a c t i o n , c o n s i s t u t e s about 97 to 98 percent of t o t a l n i t r o g e n (96). Considerable v a r i a t i o n i n the n i t r o g e n content of humus, and of d i f f e r e n t organic residues renders d i f f i c u l t the establishment of an accurate q u a n t i t a t i v e r e l a t i o n s h i p between t o t a l n i t r o g e n and t o t a l organic m a t e r i a l i n s o i l ( i l l ] . ) . There i s some evidence to show that the carbon/nitrogen r a t i o decreases with depth i n the s o i l and w i t h the. degree of humus decomposition (96.,111].) . I t might be expected> t h e r e f o r e , that the value of t h i s r a t i o would f l u c t u a t e considerably w i t h d i f f e r e n t s o i l s , but according to R u s s e l l (96) ,- i n most a g r i c u l t u r a l s o i l s the carbon/nitrogen r a t i o "... i s s u r p r i s i n g l y constant and surprisingly'Independent of s o i l treatment." For the v a r i a t i o n s of percentage n i t r o -gen i n humus i n d i f f e r e n t .soils and some data regarding carbon-nitrogen ratio's, see Appendix (Tables II-, I I I ) . In general, a h i g h value of carbon/nitrogen r a t i o i m plies an undecomposed status of a humus. A carbon/nitrogen r a t i o of 10:1 or l e s s p o i n t s r a t h e r to an advanced humus degradation and the l i k e l i h o o d o f decreased m i c r o b i a l a c t i o n (ill].) . The chemical nature of the various forms of nitrogenous compounds In s o i l organic matter i s not ye.t w e l l understood (117). Kojima (16) and Bremner (16) have shown that the p r o t e i n f r a c t i o n of amino-acid polymers can account f o r not more than l\.0% of t o t a l n i t r o g e n i n s o i l . Waksman ( l l ? ) a n a l y z i n g some p r a i r i e s o i l s i n A l b e r t a , Saskatchewanj and Manitoba found average p r o t e i n values to l i e w i t h i n 33.3 to 37-k- percent of t o t a l organic matter. C l a r k (16) stated that the. n u c l e i c acid p o r t i o n of s o i l n i t r o g e n i s n e g l i g i b l e . The presence: of amino sugars was. v e r i f i e d by some workers and stated by Bremner ( 1 6 ) to account f o r 5> to 1 0 percent of s o i l n i t r o g e n As no other n i t r o g e n compounds have;, as yet, been i s o l a t e d i n reasonably s u b s t a n t i a l q u a n t i t i e s , the i d e n t i t y of approximately h a l f of the t o t a l organic f r a c t i o n of s o i l n i t r o g e n remains obscure. Work of Rod. ( 1 6 ) w i t h t r o p i c a l s o i l s suggests, that some of t h i s u n i d e n t i f i e d n i t r o g e n may be f i x e d ammonia i n close a s s o c i a t i o n w i t h c l a y minerals. Other i n v e s t i g a t o r s ( 1 6 ) , p o s t u l a t e an i n t e r a c t i o n between ammonia and ox i d i z e d l i g n i n s or amino groups and quinone r i n g s of some humic substances ( 1 6 ) . c• Nitrogen of the Inorganic F r a c t i o n The inorganic n i t r o g e n i n the. form of ammonium + (NH^), ammonia (NH^), n i t r i t e s ( M ) 2 ) y and n i t r a t e s ( N O 3 ) c o n s t i t u t e s approximately 2 to 3 percent of the t o t a l n i t r o g e n i n s o i l s ( I I I 4 . ) . The amounts of mi n e r a l i z e d n i t r o g e n and the prop o r t i o n s of d i f f e r e n t forms v a r i e s considerably depending upon changes In the process of formation and removal ( 1 6 ) . Ammonium i s u s u a l l y present i n only r e l a t i v e l y small q u a n t i t i e s of a few p a r t s per m i l l i o n ( 9 7 ) • i t i s i n t e r e s t i n g to note that i t s l e v e l i n arable s o i l s i s f a i r l y low but constant ( 9 6 ) . In grasslands ammonium comprises the main p o r t i o n of inorganic n i t r o g e n and i t s concentration i s unaffected by a r t i f i c i a l a d d i t i o n s 6 (9b). Whereas n i t r a t e s are t o t a l l y d i s s o l v e d i n s o i l water, ammonium i s held on the exchange surfaces of both m i n e r a l and organic s o i l f r a c t i o n s . There are d i f f e r e n c e s of opinion among some i n v e s t i g a t o r s regarding the. importance of ammonium absorption f o r n i t r i f i c a t i o n and the a v a i l a b i l i t y .of absorbed ammonium ions to o x i d i z i n g organisms and growing p l a n t s (2,1].,32) . R e l a t i v e concentrations of n i t r i t e s are u s u a l l y n e g l i g i b l e as t h e i r r a t e of formation i s l e s s than t h e i r rate: of o x i d a t i o n . R u s s e l l (96) s t a t e s that i n some desert s o i l s ' the accumulation of n i t r i t e s might reach l e v e l s d e t r i m e n t a l to the growing crop. I t has been reported (96) that s o i l s w ith low phosphate, content and h i g h amount of calcium carbonate are able to accumulate n i t r i t e s . S t e r i l i z a t i o n of a s o i l or treatment w i t h c h l o r i d e s w i l l prev.ent n i t r i t e o x i d a t i o n w i t h the consequent accumulation of n i t r i t e s . Gene r a l l y v- the. presence of n i t r i t e s i n s o i l s is. regarded as harmful to p l a n t s though some i n v e s t i g a t i o n (97) p o i n t s to a p o s s i b l e u t i l i z a t i o n by p l a n t s . The approximate q u a n t i t i e s of n i t r a t e i n arable s o i l s , were estimated to be from .2 to 60 mgm/Kg of s o i l (96) . The- concentration of n i t r a t e s accord-ing to R u s s e l l (96)>- v a r i e s considerable w i t h fallow,-season, type of growth, amount and nature of decomposed m a t e r i a l , percent moisture, temperature, and f e r t i l i z a t i o n practice's. C l a r k (10f?) concludes that f o r these reasons the r e l a t i v e concentration .of n i t r a t e in. a given s o i l sample should not be used as an index o f - s o i l f e r t i l i t y . More 7 recent i n v e s t i g a t o r s (129) c l a i m that n i t r a t e production occurs over a wide range of s o i l moisture w i t h an optimum temperature of "j>$°G + 1°C. Iowa workers ( 3 3 / T 6 , 1 0 6 , 1 2 9 ) regard these, v a r i a t i o n s as n e g l i g i b l e and state; that, n i t r a t e production,, together w i t h other information,- w i l l provide a r e l i a b l e i n d i c a t i o n of the n i t r o g e n - s u p p l y i n g power of the s o i l , whichj they c l a i m , remains unchanged f o r a perio.d of years. B. Nitrogen Intake i n .Soils i n General The f i x a t i o n of elemental n i t r o g e n by e i t h e r b i o t i c or n o n b i o t i c f a c t o r s i s indispensable to the n i t r o g e n economy of a g r i c u l t u r a l s o i l s . The gaseous i n e r t form of n i t r o g e n that i s p a r t of our atmosphere can be u t i l i z e d by p l a n t s only i n a combined form. Two general groups of nicroorganisms p a r t i c i p a t e i n the f i x a t i o n of atmospheric n i t r o g e n namely the symbiotic organisms and the s o - c a l l e d f r e e - l i v i n g n i t r o g e n f i x e r s . a. F i x a t i o n of Nitrogen by Symbiotic B a c t e r i a In . a g r i c u l t u r a l s o i l s the best known and the most important examples of t h i s group are the b a c t e r i a of the genus Rhizobium associated w i t h some higher p l a n t s of the f a m i l y Leguminosae. The: b a c t e r i a i n f e c t i n g these p l a n t s s t i m u l a t e the growth of c e l l s s c a t tered throughout the root tissue' of the host, r e s u l t i n g i n the formation of c h a r a c t e r i s t i c , nodules. Most of the species of the 8 f amily. Leguminosae have not- developed t h i s h a b i t of harbour-ing nodular b a c t e r i a (79). Among the i d e n t i f i a b l e b a c t e r i a found to c o l o n i z e the roots of the. few leguminous species that are s u s c e p t i b l e , c e r t a i n elements of . s p e c i f i c i t y have developed. According to Waksman and Starkey (115>),-. at l e a s t twelve d i f f e r e n t s t r a i n s or species -of legume b a c t e r i a have been e s t a b l i s h e d . Each s t r a i n i s able to invade only one or a few leguminous p l a n t s . The f i x a t i o n of atmospheric n i t r o g e n occurs only i n the union of a health y v i g o r o u s l y growing p l a n t - h o s t and a s p e c i f i c b a c t e r i a l symbiont. Neither the. p l a n t nor. the bacterium alone can f i x n i t r o g e n . Various claims f o r the f i x a t i o n of n i t r o g e n by excised nodules have been c r i t i c i s e d (111), and even, i f accepted .as tr.ue> the amounts f i x e d are small and almost i n s i g n i f i c a n t (82). The q u a n t i t i e s of n i t r o g e n f i x e d depend upon many f a c t o r s , among them the presence of molybdenum (66) and the s u f f i c i e n c y of the. sulphur supply. In f a c t , any n u t r i t i o n a l d e f i c i e n c y that, lowers the v i t a l i t y of the. host p l a n t w i l l hamper n i t r o g e n f i x a t i o n . S o i l s i n which leguminous p l a n t s are to be grown r e q u i r e an ample supply of Calcium, potassium, sulphate-, and phosphate (72) . The presence of r e a d i l y a v a i l a b l e .sources of inorganic n i t r o g e n , e s p e c i a l l y n i t r a t e s , i n such s o i l s , tends to decrease n o d u l a t i o n since the p l a n t s take up n i t r a t e s and ammonium p r e f e r e n t i a l l y (79). Leguminous b a c t e r i a , e s p e c i a l l y .Rhiz.obium t r i f o l i i . 9 are present i n almost a l l a g r i c u l t u r a l s o i l s and the most favorable pH range, f o r these organisms i s i n r e g i o n of n e u t r a l i t y (86,11^). Furthermore* they are cold t o l e r a n t , even being able to withstand prolonged f r e e z i n g (6l). Plants i n symbiotic consortium w i t h such Rhizobium species are capable of u t i l i z i n g the b a c t e r i a l l y f i x e d n i trogen as i s the b a c t e r i a l a s s o c i a t e i t s . e l f . Remaining q u a n t i t i e s of n i t r o g e n compounds are excreted i n t o the' s o i l . Sloughing o f f and decay of leguminous root t i s s u e i s regarded as a more important source of n i t r o g e n than such root ex c r e t i o n s (22) . I t should be. understood that the presence of legumes does not n e c e s s a r i l y imply an increase i n s o i l nitrogen., and thi s , i s p a r t i c u l a r l y true In the' case of s o i l s already h i g h i n n i t r o g e n or those from which a crop has been r e c e n t l y harvested.. In a d d i t i o n , the species of host p l a n t and the age. of the stand of which i t . i s a p a r t w i l l a f f e c t the r e l a t i v e , amount Of f i x e d n i t r o g e n (70) . b; F i x a t i o n of Nitrogen by Nonsymbiot.ic B a c t e r i a S o i l may acquire a p a r t of i t s n i t r o g e n as a r e s u l t of the a c t i v i t i e s ' of f r e e - l i v i n g b a c t e r i a l i k e C l o s t r i d i u m , Azotobacter and some- photo s y n t h e t i c and chemo-syn t h e t i c organisms. The- organisms from the above groups are present i n varying combinations and amount. This may be p a r t l y due to the methods of i s o l a t i o n (6l). Azotobacter, known, to be ;' 10 of world-wide d i s t r i b u t i o n (absent only from the. a r c t i c s o i l s ) , i s g e n e r a l l y considered to be l e s s abundant than the anaerobic C l o s t r i d i u m species (.26,96.) . Lochhead (6l) estimated that there were from s e v e r a l hundred to a thousand .Azotobacter c e l l s per gram of s o i l , whereas the same amount of the .same s o i l might contain as many as one hundr.ed m i l l i o n b a c t e r i a of other types. Waksman (117) s t a t e s that i n gener a l , the number of anaerobic C l o s t r i d i u m species found i n one gram of s o i l i s greater than 1 0 0 , 0 0 0 ; he concludes that any q u a n t i t -a t i v e estimates of anaerobic n i t r o g e n - f i x i n g p o p u l a t i o n can only be regarded as approximate. That t h i s i s so i s due l a r g e l y to the f a c t t h a t only a few organisms of t h i s group can develop on a r t i f i c i a l media. Nitrogen f i x e d by Azotobacter i s mostly i n c o r p o r -ated as . c e l l m a t e r i a l and the amount of nitrogen f i x e d can be regard.ed as an index of c e l l growth and increase i n c e l l m a t e r i a l (11$) ; t h i s n i t r o g e n ,can be u t i l i z e d by p l a n t s only a f t e r the death of such b a c t e r i a . The process of decay of m i c r o b i a l p r o t e i n i s f a i r l y slow. F i x a t i o n of n i t r o g e n by Az;otobac.ter species i s influenced s t r o n g l y by f a c t o r s such as the presence of phosphate, molybdenum, r e a d i l y a v a i l a b l e carbohydrates, s u i t a b l e pH, and the absence of i n o r g a n i c n i t r o g e n . Jensen (1|3) states that molybdenum i s e s s e n t i a l only to some species of Azotobacter and then only i n c e r t a i n c o n d i t i o n s . The optimal pH range, w i t h but few exceptions, (Azotobacter indicum) i s 7.5! - 6 . 8 (1^3 ,117). Calcium i s regarded (66) only as a n e u t r a l i z i n g agent and not as an e s s e n t i a l element. Ammonium immediately i n h i b i t s n i t r o g e n f i x a t i o n . N i t r i t e s and n i t r a t e s have a s i m i l a r e f f e c t but, compared to that of ammonium, i t i s somewhat delayed (1 |3 ) . In the case of C l o s t r i d i u m species, Waksman (117) states t h a t they are more abundant i n ac i d s o i l s . B o g e l l (117) r e p o r t s , t h a t heavy r a i n s f a v o r anaerobic n i t r o g e n f i x a t i o n by C l o s t r i d i a .species. Waksman (117) f i n d s C l o s t r i d i u m butylicum to be present everywhere. In conclusion, Lochhead ( 6 l ) says that one i s e n t i t l e d to doubt the importance of Azotobacter as an important source of f i x e d n itrogen i n nature. Waksman (117) and Jensen (1)_3) observed a s t i m u l a t i o n i n the growth and n i t r o g e n - f i x i n g c a p a c i t y of" Azotobacter when grown i n a s s o c i a t i o n w i t h other organisms. Somewhat l a t e r , Jensen (1|3) concluded that the f i x a t i o n of n i t r o g e n by species of Azotobacter i n n a t u r a l environmental c o n d i t i o n s i s not w e l l understood. (See Appendix, Table V, f o r data of average values' of nit r o g e n f i x e d by nonsymbiotic b a c t e r i a ) . c. F i x a t i o n of Nitrogen by Other Organisms I t i s now a w e l l e s t a b l i s h e d f a c t that many species of blue-green algae belonging to the genera of Nostoc, Anabaena, A u l o s i r a and Cylindrospermum have the a b i l i t y to f i x atmospheric n i t r o g e n (96) . Fogg (2£) s t a t e s 12 t h a t , of f o r t y a l g a l species t e s t e d , only about h a l f have been found to be capable of f i x a t i o n . According to the same author (25>), t h i s process i s considerably slower with algae than w i t h b a c t e r i a since- i t u s u a l l y takes s e v e r a l weeks to accumulate 2 0 - 3 0 ug. N/'ml. According to R u s s e l l (96), f i x a t i o n of n i t r o g e n by algae does not depend on l i g h t , since i f supplied w i t h a source of carbohydrates., they are f u n c t i o n a l i n t h i s regard even i n the dark. In nature algae may l i v e i n some type of symbiosis w i t h liverworts,- f u n g i , and cycads. Scott (99) has demonstrated f i x a t i o n of n i t r o g e n by a species of Nostoc. l i v i n g i n symbiosis w i t h P e l t i g e r a  p r a e t e x t a t a ; he did not f i n d any f i x a t i o n w i t h Cladonia  impexa. In g e n e r a l , n i t r o g e n f i x a t i o n among blue-green algae becomes more important when we consider that these completely autotrophic organisms are u n i v e r s a l l y d i s -t r i b u t e d and are able to adapt themselves, to a great v a r i e t y of environmental conditions (96). Algae are regarded as " i n v a s i v e c o l o n i z e r s " , a c t i v e l y r e s p o n s i b l e f o r c o l o n i z a -t i o n of barren m i n e r a l s o i l s , burnt-over areas or. s a l i n e -lake bed s o i l s . T h e i r a b i l i t y to act as pioneer organisms i s the r e s u l t of t h i s unique a b i l i t y to synthesis t h e i r own n i t r o g e n . The presence of n i t r a t e s , n i t r i t e s , or ammonia i n h i b i t s f i x a t i o n by these organisms; molybdenum seems to-be required (96) . The f i x a t i o n of n i t r o g e n by Phoma species, u s u a l l y i n a s s o c i a t i o n w i t h r o o t s , has been reported i n many instances though without absolute c e r t a i n t y . F o s t e r (28) regards s o i l f u n g i as very a c t i v e agents i n n i t r o g e n f i x a t i o n , though of l e s s e r importance, i n t h i s regard, than b a c t e r i a . A fungus' associated w i t h the root system of the grass Lolium temulentum, has been reported to possess a f i x a t i v e a b i l i t y with regard to n i t r o g e n . Scott-Wilson H.W. (98) quotes Lipman as having found some pseudo-yeast Tulare Nol].6.b e x h i b i t i n g t h i s a b i l i t y . Hand l e y (35) concludes that the use of i s o t o p i c n i t r o g e n i n recent i n v e s t i g a t i o n s has made i t even more c e r t a i n that some fungi are able to f i x atmospheric n i t r o g e n . d. F i x a t i o n of Nitrogen by N o n b i o l o g i c a l F a c t o r s Apart from the b i o l o g i c a l f i x a t i o n of atmos-phe r i c n i t r o g e n , there are some f a c t o r s which c o n t r i b u t e r a t h e r small but constant supplies of n i t r o g e n to growing vege t a t i o n . There are some forms of f i x e d n i t r o g e n i n our atmosphere which o r i g i n a t e d e i t h e r from e l e c t r o -s t a t i c discharges or from i n d u s t r i a l p o l l u t i o n and v o l a t i l i z a t i o n of ammonia from c e r t a i n s o i l s . U s u a l l y two main forms of n i t r o g e n are recognized i n our atmosphere as being brought back to the s o i l by means of snow and r a i n . These are n i t r a t e s and ammonium. The amount of n i t r o g e n -c o n t a i n i n g compounds oc c u r r i n g i n snow and r a i n f l u c t u a t e s with the season of the year, geographical l o c a t i o n , and the the amount of p r e c i p i t a t i o n (see Appendix, Table V I ) . Prom some of the data a v a i l a b l e , i t seems safe to suggest that under a humid temperate c l i m a t e , the average annual amount of 5 l b . of n i t r o g e n ( i n form of ammonium and n i t r a t e s ) Is brought by p r e c i p i t a t i o n to every acre of land. This amount, according to Lyon (70) i s equivalent to about 31 l b . of commercial nitrat.e of soda, a r t i f i c i a l l y a p p l i e d . Reports of some I n v e s t i g a t o r s on the f i x a t i o n of atmospheric n i t r o g e n by p u r e l y physico-chemical or photo-chemical r e a c t i o n s o c c u r r i n g In s o i l i t s e l f s t i l l remains unconfirmed. Dhar, through h i s work, claimed that a f a i r l y l arge percentage of gaseous n i t r o g e n could be f i x e d by so . i l s . F a i r l y recent work i n t h i s l i n e seems to confirm e a r l i e r claims that l i g h t s u p p l i e s energy f o r the f i x a t i o n of atmospheric n i t r o g e n by c l a y p a r t i c l e s and that t h i s process i s catalyzed by glucose. C. Nitrogen Transformation i n S o i l s a. Ammonification and D e n i t r i f i c a t i o n A very large number of organisms among b a c t e r i a , f u n g i , and actinomycetes are able to produce ammonium from d i f f e r e n t nitrogenous compounds and under d i f f e r e n t environmental c o n d i t i o n s . The amount of ammonium produced v a r i e s and depends on: (a) the nature of m a t e r i a l being attacked; (b) the organism involved i n the decomposition; and (c) the environment. The, great m a j o r i t y of s o i l b a c t e r i a 15 that develop on p e t r i p l a t e s i s able to form ammonium from p r o t e i n s of animal or p l a n t o r i g i n ( 1 1 7 ) • G e l a t i n -l i q u e f y i n g organisms, able to induce greater p r o t e i n decomposition, c o n s t i t u t e l5 percent or more of the t o t a l number of s o i l bacteria.. According to Waksman ( 1 1 7 ) , p r o t e i n s make up 1 to 2 0 percent of a l l p l a n t r e s i d u e . P l a n t residues that are low i n n i t r o g e n form l i t t l e ammonium on decomposition, and then only a f t e r prolonged periods of b a c t e r i a l a c t i v i t y . Young p l a n t s decompose more r e a d i l y w i t h a higher production of ammonium than o l d e r (ll5) • The degradation of p l a n t p r o t e i n s i s c a r r i e d out i n d i f f -erent stages by d i f f e r e n t organisms with a v a r i e t y of end products ( 1 1 7 ) . The f i n a l amount of ammonium l i b e r a t e d may be as much as 50 to 8 0 percent of t o t a l p r o t e i n n i t r o -gen ( 1 1 7 ) . There i s no case known i n which the t o t a l organic n i t r o g e n present can be changed i n t o ammonium (115). N i t r a t e s can be reduced to ammonium by organisms such as C l o s t r i d i u m w e l c h i i and E s c h e r i c h i a c o l i ( 1 1 7 ) • In s o i l s saturated w i t h water and c o n t a i n i n g l a r g e amounts of organic matter, n i t r a t e s are reduced e i t h e r to n i t r i t e s or ammonium, and these s o i l s become more a l k a l i n e as a consequence ( 1 1 7 ) • Ammonification by b a c t e r i a occurs i n a r e l a t i v e l y narrow range of pH whereas f u n g i may be a c t i v e under both n e u t r a l and a c i d i c c o n d i t i o n s . In acid f o r e s t 1 6 s o i l s f u n g i are the organisms mainly r e s p o n s i b l e f o r the degradation and breakdown of p l a n t p r o t e i n s . The r a t e of fu n g a l growth and ammonia formation, according to Waksman ( 1 1 7 ) depends upon the nature of the proteinaceous m a t e r i a l , i t s n i t r o g e n content, the species, of f u n g i p a r t i c i p a t i n g i n decomposition and the nature of the carbon compounds or p r o t e i n carbon. I n the absence of carbon sources, a fungus such as A s p e r g i l l u s n i g e r u t i l i z e s p r o t e i n s f o r i t s carbon and n i t r o g e n requirements ( 1 1 7 ) . Actinomycetes, as a r u l e , p r e f e r p r o t e i n s to carbohydrates as a source of carbon and, according to Waksman ( 1 1 6 ) , i n the presence of both w i l l a t t a c k pre-f e r e n t i a l l y p r o t e i n s w i t h considerable l i b e r a t i o n of ni t r o g e n i n form of ammonium. Waksman ( 1 1 7 ) , comparing the decomposition of p r o t e i n s by pure c u l t u r e s of b a c t e r i a , f u n g i , and actinomycetes, states that the r e l a t i v e amount of l i b e r a t e d ammonium i s highest i n the case of b a c t e r i a because they themselves synthesize l e s s . In a d d i t i o n * Waksman s t a t e s that the presence of an excessive amount of carbohydrates has a depressing e f f e c t on the l i b e r a t i o n of ammonium from any s o i l . Q u a n t i t a t i v e l y , ammonia or ammonium present i n s o i l s i s u s u a l l y i n the range of few p a r t s per m i l l i o n ( 9 7 ) . Arable s o i l s have a f a i r l y low but constant amount of ammonium. In. the case of grass l a n d , the main p o r t i o n of inorganic n i t r o g e n i s i n the form of ammonium and n i t r a t e s ( 9 6 ) . The f u n c t i o n of ammoniacal n i t r o g e n i n s o i l s v a r i e s as f o l l o w s : a. i t i s used by many s o i l organisms and the ammonifiers themselves; b. i t can be a c t i v e l y absorbed by most higher plants-, e s p e c i a l l y those that are i n the e a r l y stages of growth ( 1 ) . c. a considerable amount i s used i n n i t r i f i -c a t i o n . d. p o r t i o n s may be adsorbed on s o i l p a r t i c l e s or l o s t to the atmosphere. Waksman and Wilson (122) state, that ammonium i s the simple n i t r o g e n source f o r many bacteria,, y e a s t s , and moulds. Autotrophic Nitrosomonas can o x i d i z e ammonium to n i t r a t e and u t i l i z e the obtained energy f o r the a s s i m i l a t i o n of carbon d i o x i d e (8.2) . Many h e t e r o t r o p h i c organisms w i l l grow on ammonium s a l t s as the sole source of energy (82). Perhman (83) states that many actinomycetes are able to u t i l i z e ammonium and n i t r a t e s f o r t h e i r n i t r o g e n requirements. In the case of higher p l a n t s , ammonium i s r e a d i l y .absorbed from s o i l by ro o t system of the p l a n t s , e s p e c i a l l y In moderately aerated s o i l s w i t h a s u f f i c i e n t supply of carbohydrates (72) . This absorption may be d i r e c t or mostly through the m y c o r r h i z a l f u n g i .(Hymenomycetes) ( 7 0 ) . I t Is a w e l l accepted f a c t that p l a n t s can u t i l i z e ammonium and, i n some cases* p r e f e r t h i s source of n i t r o g e n to n i t r a t e s (70). K r a j i n a ( l e c t u r e notes) f i n d s that hemlock Tares best w i t h ammonium as a ni t r o g e n source, whereas D o u g l a s - f i r grows best i n an ample supply of n i t r a t e s . b. N i t r i f i c a t i o n The l i t e r a t u r e on t h i s subject i s too volum-inous f o r a comprehensive r e p r e s e n t a t i o n . Most of the research on n i t r i f i c a t i o n has been done w i t h a g r i c u l t u r a l s o i l s . ¥ork w i t h f o r e s t s o i l s i s comparatively scanty and some of the r e s u l t s cannot be used now to any advantage as they contain no reference to the e c o l o g i c a l c o n d i t i o n s of the s o i l s s t u d i e d . N i t r i f i c a t i o n u n t i l very recent times was regarded as the most important l i n k i n the n i t r o g e n c y c l e because of the value of n i t r a t e s to the n u t r i t i o n of p l a n t s . Recently, however, some a u t h o r i t i e s (70) have come to regard n i t r i f i c a t i o n as an overemphasized phase of b a c t e r i a l physiology and a very weak l i n k i n the n i t r o g e n c y c l e due to the f a c t t h a t the n i t r i f y i n g b a c t e r i a are extremely s e n s i t i v e to environmental changes. N i t r i f i c a t i o n appears to be a two-stage pro-cess being c h a r a c t e r i z e d by a gradual disappearance of ammonium with a concurrent formation of n i t r i t e s . This i s f o l lowed by f u r t h e r o x i d a t i o n of n i t r i t e s and an accumulation of n i t r a t e s . Both stages are a f f e c t e d by only two groups of h i g h l y s p e c i f i c , s t r i c t l y a utotrophic s o i l 1 9 b a c t e r i a . G-obd a e r a t i o n , an adequate amount of moisture, the presence of b u f f e r i n g substances, an absence of l a r g e q u a n t i t i e s of s o l u b l e organic matter, a s u i t a b l e pH range (pH 7 Q ~ 9 0 ) and f a i r l y h i g h temperature are among the more important requirements of these organisms (15>,112,111].) . The s i x t h e d i t i o n of Bergey's. manual (15>) l i s t s f i v e genera of b a c t e r i a capable of o x i d i z i n g ammonia to n i t r i t e and two genera that o x i d i s e n i t r i t e s to n i t r a t e s . The o x i d a t i o n of ammonia to n i t r i t e and atmospheric carbon d i o x i d e are the r e s p e c t i v e energy and carbon sources fundamental to these organisms. Recent i n v e s t i g a t i o n s suggest certain:'hetero-t r o p h i c b a c t e r i a and other organisms to be a c t i v e l y engaged i n the process of transformation of ammonia n i t r o g e n i n t o n i t r a t e s . Kalinenko r e p o r t s that many h e t e r o t r o p h i c b a c t e r i a i s o l a t e d from water, sewage, and s o i l are capable, under c e r t a i n c o n d i t i o n s , of n i t r i f y i n g i n o r g a n i c n i t r o g e n . Quastel ( 9 0 ) i s o l a t e d three species of s o i l b a c t e r i a o x i d i z -ing oximes of p y r u v i c a c i d or c e r t a i n other alpha-keto acids to n i t r i t e s . Jensen (9l\.) r e p o r t s i s o l a t i o n of some actinomycetes species (Nocardia c o r a l l i n a ) producing n i t r i t e s from p y r u v i c a c i d oxime. Isenberg (Ij.2) states that a c e r t a i n organism of the genus Streptomyces o x i d i s e s ammonium to n i t r i t e s . . F i s h e r ( . 2 3 ) and Hutton ( 3 9 ) found various u n i d e n t i f i e d h e t e r o t r o p h i c and methane-oxidizing s o i l 2 0 b a c t e r i a capable of ammonium to n i t r i t e t ransformations. Schmidt ( 1 0 0 ) succeeded i n I s o l a t i n g a fungus ( A s p e r g i l l u s  f l a v u s ) capable of c a r r y i n g the n i t r i f i c a t i o n r e a c t i o n to completion w i t h the formation of n i t r a t e . The d i f f i c u l t y experienced by a number of i n v e s t i g a t o r s (78) In i s o l a t i n g n i t r i f y e r . s by conventional s e l e c t i v e c u l t u r e techniques l i e s i n suppressing hetero-tr o p h i c organisms i n primary enrichment or i s o l a t i o n . This pointed to the p o s s i b i l i t y of n i t r i f i c a t i o n as a .symbiotic phenomenon (lj . 0 , 7 ^ ) • A change i n the method of study of n i t r i f i c a -t i o n , from pot c u l t u r e methods ( 3 0 ) to s o i l - p e r f u s i o n techniques ( 8,19 , 5 ^ , 5 5 , 5 8 , 5 9,91)-), has provided much funda-mental i n f o r m a t i o n on s o i l n i t r i f i c a t i o n . The study of s o i l metabolism by p e r f u s i o n techniques i s advantageous' i n that the many u n c o n t r o l l a b l e v a r i a b l e s , by being included In each t e s t sample, are eliminated from comparative con-c l u s i o n s . Twenty to f i f t y grams of s o i l are placed i n a gl a s s tube i n such a way that a l i q u i d can be passed through the tube from the top, c o l l e c t e d i n a r e s e r v o i r at the bottom and a u t o m a t i c a l l y returned through the s o i l tube again. The device i s f a i r l y simple and permits of e x c e l l e n t c o n t r o l of a e r a t i o n and the r a t e of p e r f u s i o n ( 8 ) . From studies such as these, n i t r i f i c a t i o n appears to occur wholly at the s o i l c o l l o i d surface where ammonium i s adsorbed and the b a c t e r i a adhere { ^ k , ^ . The a d d i t i o n 21 of calcium ions diminishes the r a t e of n i t r i f i c a t i o n due to the displacement of ammonium from exchange surfaces by the d i v a l e n t base. The curve of the r a t e of n i t r i f i c a t i o n w i t h f r e s h s o i l samples i s sigmoid and i m p l i e s that n i t r i -f i c a t i o n i s e f f e c t e d by a c t i v e l y m u l t i p l y i n g " c e l l s . The importance of the base exchange phenomena i n n i t r i f i c a t i o n gave r i s e to c e r t a i n c o n f l i c t i n g views. Lees and Quastel (5Ij.,5j?,5>6) held that ammonium has to be adsorbed by s o i l p a r t i c l e s f o r i t to be a v a i l a b l e to n i t r i f y i n g b a c t e r i a . Bower (llj.) A l l i s o n (2,4) and Goldberg Indicated a p o s s i b l e d e t r i m e n t a l e f f e c t of surface phenomena on the process of n i t r i f i c a t i o n . According to Goldberg and Gaine.y (32) absorption of ammonium from the s o i l s o l u t i o n may reduce the r a t e of n i t r a t e accumulation as much as 70%; i t would seem t h e r e f o r e , that Quastel'-s (89) c l a i m to the almost complete recovery of n i t r o g e n as n i t r a t e from s o i l s c o n t a i n i n g ammonium s a l t s during continuous p e r f u s i o n , i s d o u b t f u l . D. F o r e s t S o i l s a. M u l l and Mor General C h a r a c t e r i s t i c s Many systems have been proposed f o r the c l a s s i -f i c a t i o n of f o r e s t s o i l s , based u s u a l l y on d i f f e r e n t s o i l p r o p e r t i e s such as s o i l m a t u r i t y ( p r o f i l e morphology), or s o i l forming processes. At one time, i t was not uncommon f o r p e d o l o g i s t s to disregard the surface humus as part of the s o i l . Suchting, f o r i n s t a n c e , stated emphatically that 22 humus was an i n s i g n i f i c a n t and unimportant f a c t o r i n s o i l a n a l y s i s . In 1879 and 1881+, M u l l e r (77) d i v i d e d the f o r e s t s o i l s of beech woods and oak f o r e s t s of Denmark i n t o two genera l , b i o l o g i c a l l y d i s t i n c t i v e groups un d e r l y i n g two d i f f e r e n t types of humus, m u l l and mor. He a l s o recognized c e r t a i n t r a n s i t i o n a l phases. Waksman (111}.) stated that the humus la y e r i s the important f a c t o r i n forest- s o i l develop-ment and concluded that M u l l e r ' s concept, w i t h some modi-f i c a t i o n s , f u l f i l l e d present needs i n f o r e s t s o i l c l a s s i -f i c a t i o n . Wilde (120) recognized three types of f o r e s t humus: i . E a r t h m u l l : (a) mixture of amorphous organic matter and mineral s o i l (A.). (b) pH range 5.0 - 8.0. (c) organic matter r a r e l y exceeding 10 percent. (d) predominantly o c c u r r i n g under hardwood stands. i i . Duff m u l l : (a) f r i a b l e organic remains of Ao and A-j_ horizons of hig h b i o l o g i c a l a c t i v i t y and abundant supply of r e a d i l y a v a i l -able n u t r i e n t s . (b) pH range 5.0 - 6 . 5 . (c) o c c u r r i n g mostly under mixed hardwood-coniferous stands. i i i . Mor or raw humus: (a) t h i c k organic l a y e r comprised of tenacious h o r i z o n of Ao interwoven w i t h mycelia of f u n g i o v e r l y i n g leached m i n e r a l s o i l . (b) pH range 3.0 - 5.0. (c) u s u a l l y supporting dense stands of northern • conifer's . Handley (35) u t i l i z e d t h i s c l a s s i f i c a t i o n e x t e n s i v e l y i n h i s c h a r a c t e r i z a t i o n of f o r e s t s o i l s . Handley ( 3 5 ) , studying f a c t o r s involved i n the formation of m u l l and mor c o n d i t i o n s , regarded these two types as' the extremes of the various b i o l o g i c a l .systems o c c u r r i n g i n f o r e s t s o i l s i n general. Prom a review of past l i t e r a t u r e , Handley concluded that there was i n s u f f i c i e n t evidence f o r assuming that any s i n g l e ,factor was c a u s a l i n the formation of m u l l or mor humus. K r a j i n a ( l e c t u r e n o t e s ) , i n h i s e c o l o g i c a l studies of hemlock and D o u g l a s - f i r f o r e s t s i n B r i t i s h Columbia, recognizes two main types of humus c o n d i t i o n , namely raw humus (mor) and duff m u l l . The " e a r t h m u l l " c o n d i t i o n , developed on some a l l u v i a l . s o i l s , r e s u l t s from frequent f l o o d i n g and mixing of organic matter w i t h s u b s o i l . Accord-ing to K r a j i n a , raw humus co n d i t i o n s are mo;st l i k e l y to develop i n areas w i t h a short v e g e t a t i v e p e r i o d , low temperature, h i g h p r e c i p i t a t i o n , and under heavy f o r e s t cover. Raw humus accumulates over longer periods of time than duff m u l l and may reach a thickness, of up to 1 f o o t . 2 1 | I t i s composed mainly of f r e e organic remains interwoven wi t h f u n g a l hyphae and i s compressed i n t o a matted Ao h o r i z o n o v e r l a y i n g a leached mineral s o i l which, only i n rare i n s t a n c e s , i s i n f i l t r a t e d by humates. I t s u s u a l pH range i s 3-5 ~ 5«0. Duff m u l l i n B r i t i s h Columbia c o a s t a l areas, develops e i t h e r on lime-stone s u b s t r a t a or igneous rocks of a b a s i c character. I t s development i s favored by base-saturated seepage water. I t i s formed where the p r e c i p i t a t i o n - e v a p o r a t i o n r a t i o i s s m a l l . In g e n e r a l , i t i s c h a r a c t e r i z e d by f r i a b l e organic remains i n t e r g r a d i n g i n t o a more or l e s s developed l a y e r w i t h incorporated humus. The a c t u a l humus l a y e r i s not very t h i c k (1 to 3 i n c h e s ) . Underneath duff m u l l there i s always a melanized l a y e r . P o d s o l i z a t i o n i n d u f f - m u l l s o i l s , i s n e g l i g i b l e . The pH range i s from 5.0 - 7.2.. K r a j i n a concludes that i n the c o a s t a l f o r e s t s of B r i t i s h Columbia, raw humus, as i t occurs i n s.alal a s s o c i a t i o n s . Is the c l i m a t i c climax c o n d i t i o n . Duff m u l l , on the other hand, i s more r e s t r i c t e d In occurrence and i s an edaphic climax. He f u r t h e r regards raw humus as being advantageous to hemlock but l e s s so f o r western red cedar or D o u g l a s - f i r . The most e x c e l l e n t s i t e s f o r D o u g l a s - f i r are those i n which duff m u l l condi-t i o n s p r e v a i l . b. M i c r o b i a l Studies of F o r e s t S o i l s Research i n the f i e l d of f o r e s t s o i l b a c t e r i o -logy, In comparison w i t h the amount of work of s i m i l a r 25 nature on a g r i c u l t u r a l s o i l s , i s of very meagre p r o p o r t i o n s . This s t a t e of a f f a i r s can, i n p a r t , be explained by d i f f i -c u l t i e s experienced i n f o r e s t s o i l . c l a s s i f i c a t i o n , i n d i s c r i m i n a t e terminology regarding humus types, and the mistaken viewpoint that there i s no p r e s s i n g and no p r a c t i -c a l value i n a more thorough study of f o r e s t s o i l s . P f e i l (8i|.), f o r in s t a n c e , a German a u t h o r i t y on f o r e s t manage-ment, has introduced the paradox: "The only general r u l e i n f o r e s t r y i s that there are no general r u l e s . " Suchting, too, has stated e m p h a t i c a l l y : " o n l y that f o r e s t humus i s be s t , which i s never formed." The m a j o r i t y of papers dea l i n g w i t h f o r e s t s o i l m icrobiology cannot be used now to any advantage as they contain no references to the e c o l o g i c a l c o n d i t i o n s surrounding the s o i l they seek to des c r i b e . Even today, I t i s a common occurrence to r e f e r to the s o i l under study as "Forest s o i l " , "Forest s o i l under hardwood" without any reference to humus c o n d i t i o n s , c l i m a t e , topography, h i s t o r y of the s i t e , and character-i s t i c p l a n t a s s o c i a t i o n s i n h a b i t i n g these s o i l s , it M u l l e r (77) was one of the f i r s t to d i s t i n g u i s h between mor and mu l l l a r g e l y on the b a s i s of b i o l o g i c a l d i f f e r e n c e s . He p a r t i c u l a r l y stressed the s t r i k i n g d i f f e r e n c e s i n b a c t e r i a l and animal l i f e abundantly present i n m u l l and absent i n mor. Romell (92), from f a i r l y extensive s t u d i e s , came to the co n c l u s i o n again that m u l l humus i s d e f i n i t e l y c h a r a c t e r i z e d by a more a c t i v e fauna 26 than mor. P l i c e ( 8 5 ) , i n h i s study of f o r e s t s o i l s , s t a t e s t h a t , though b a c t e r i a and f u n g i i n h a b i t -both humus forms, b a c t e r i a predominate i n m u l l , and f u n g i In mor humus. Handley (35) , reviewing the subject of m i c r o b i a l p o p u l a t i o n of m u l l and mor, concludes that there Is i n s u f f i c i e n t i n f o r m a t i o n to enable one to say that b a c t e r i a are r e s -t r i c t e d to m u l l and f u n g i to mor. Works of Vandecaveye (123, 12k., 125) , Mitrofanova (75) , and Ambroz (5,6) have accumulated a f a i r l y l arge amount of evidence p o i n t i n g to the p o s s i b i l i t y that each s o i l process has i t s own c h a r a c t e r i s t i c m i c r o b i a l p o p u l a t i o n . M i s h u s t i n (7^-), i n h i s work, even goes as f a r as to say t h a t there i s a c l e a r c o r r e l a t i o n between the d i r e c t i o n of the s o i l forming process and the composition of the s o i l m i c r o f l o r a . He s t a t e s , with emphasis, that the m i c r o b i a l p o p u l a t i o n of d i f f e r e n t s o i l s i s no l e s s , " s p e c i f i c than the n a t u r a l vege-t a t i o n of higher p l a n t s . He i m p l i e s , t h e r e f o r e , that the s o i l c o n d i t i o n can be determined from a study of the s o i l micro-populations of d i f f e r e n t groups of micro-organisms present and the number of t h e i r component speci e s . c. Nitrogen i n F o r e s t S o i l s . Most of the n i t r o g e n i n f o r e s t s o i l s i s present In organic form. Waksman (ill).) s t a t e s that there Is no c o r r e l a t i o n between q u a n t i t y of n i t r o g e n and the amount of organic matter; but a d e f i n i t e r e l a t i o n has been demon-str a t e d between n i t r o g e n content of humus and i t s r e a c t i o n . A l k a l i n i t y favors humus decomposition and a consequent r e d u c t i o n of the carbon/nitrogen r a t i o . In g e n e r a l , the carbon/nitrogen r a t i o of f o r e s t s o i l s i s wider than i n a g r i c u l t u r a l s o i l s but i t becomes narrower w i t h i n c r e a s i n g depth (see Appendix, Table V I I ) . The amount of humus In f o r e s t s o i l s v a r i e s c o n s i d e r a b l y and, according to M u l l e r (quoted by Waksman, lli+) > true m u l l contains l e s s than 10 percent, m u l l - l i k e 30-6.0 percent and raw humus around 60 percent organic matter. This organic p a r t of f o r e s t s o i l develops from p l a n t d e b r i s that v a r i e s i n n i t r o g e n content (see Appendix, Table V I I I ) . Handley (35) reviewing the t o p i c of the n i t r o g e n content of f o r e s t l i t t e r , stated that percent n i t r o g e n i n p l a n t residues v a r i e s w i t h species and I t i s d i f f i c u l t to r e l a t e t h i s v a r i a t i o n to the type of s o i l on which p l a n t s grow. This conclusion leads Handley to the q u a l i t a t i v e r a t h e r than q u a n t i t i v e consider-a t i o n of ni t r o g e n i n f o r e s t organic d e b r i s . F u r t h e r on, he hypothesizes that nitrogenous m a t e r i a l i n mor i s character-i s t i c a l l y r e s i s t a n t to breakdown due to the presence of t a n n i n - l i k e m a t e r i a l s that are re s p o n s i b l e f o r the s t a b i l i z a t i o n of l e a f p r o t e i n s . This f i x a t i o n of p l a n t p r o t e i n i n mor humus lowers the l e v e l of a v a i l a b l e n i t r o g e n f o r microorganisms. The i n o r g a n i c forms of n i t r o g e n are consider-a b l y l e s s abundant i n f o r e s t s o i l s than i n a g r i c u l t u r a l s o i l s . Waksman (lll|-) s t a t e s that humus at pH 3 .5 - 5 .0 contains mostly ammonium as the p r i n c i p a l form of 28 i n o r g a n i c n i t r o g e n . L i t t l e or no n i t r a t e s are found at a pH below 3 - 9 . In raw humus, n i t r o g e n transformations culminate i n the production of ammonium. As ammonium i s p r a c t i c a l l y independent of organic matter accumulation, n i t r a t e s are t o t a l l y absent when the organic content of a s o i l exceeds 7 0 percent. For the surface e i g h t inches of v i r g i n f o r e s t s o i l , Wilde ( 1 2 0 ) puts the maximal l e v e l s of n i t r a t e s and ammonium at 2^ and 70 p a r t s per m i l l i o n r e s p e c t i v e l y . R u s s e l l (96) s t a t e s that mor s o i l s , because of t h e i r a c i d i t y , contain no n i t r a t e s , whereas mulls have a higher concentration of* both ammonium and n i t r a t e s . This p a r t i c u l a r c h a r a c t e r i s t i c i s regarded by many workers as the most c o n s i s t e n t and s t r i k i n g d i f f e r e n c e between raw-humus and d u f f - m u l l f o r e s t s o i l s . F i x a t i o n of atmospheric n i t r o g e n i n f o r e s t s o i l s by both b i o t i c and n o n b i o t i c f a c t o r s has not yet been Investigated s u f f i c i e n t l y . The presence of Azotobacter i n raw humus i s u n l i k e l y because of the low pH range common to such m a t e r i a l . Optimal pH co n d i t i o n s f o r Azotobacter are i n the 6 . 8 - 7 - 5 range. The l a c k of p r o t e o l y t i c enzymes and a very feeble deaminating a b i l i t y w i l l exclude Azotobacter from h i g h l y organic surface l a y e r s of any f o r e s t s o i l s . Furthermore, the presence of ammonium i n raw humus w i l l p r e f e r e n t i a l l y i n h i b i t n i t r o g e n f i x a t i o n by these organisms, as i t do.es i n c u l t u r e s ( k 3 , 8 6 ) . The same assumptions might apply to the anaerobic C l o s t r i d i u m species which are i n h i b i t e d by the presence of f i x e d n i t r o g e n compounds ( 8 6 ) . The very extensive root systems i n f o r e s t s o i l s w i l l undoubtedly create unfavorable c o n d i t i o n s f o r the establishment of Azotobacter, as has been shown to be the case w i t h other p l a n t s ( k 8 , 6 3 ) • The r o l e of f r e e - l i v i n g n i t r o g e n - f i x e r s other than Azotobacter and C l o s t r i d i u m i s not known. Nitrogen f i x a t i o n by Pseudomonas-like s o i l b a c t e r i a ( 7 ) , s e v e r a l s t r a i n s of Azotobacter aerogenus ( 3 k ), many photosynthetic b a c t e r i a , purple and green sulphur b a c t e r i a , and auto-t r o p h i c anaerobic sulphate-reducing b a c t e r i a ( 6 6 ) , p o i n t only to the p o s s i b i l i t y that n i t r o g e n f i x a t i o n , i n ge n e r a l , might be a very common and widespread phenomenon. F i x a t i o n of atmospheric n i t r o g e n by f u n g i , algae, and symbiosis of non-leguminous p l a n t s w i t h t h e i r r e s p e c t i v e microorganisms ( 7 9 , l l 5 ) s u b s t a n t i a t e s the previous statement and makes us r e a l i z e that t h i s might be a missing l i n k i n the n i t r o g e n cycle of f o r e s t s o i l s . 30 I I I . EXPERIMENTAL PART A. C h a r a c t e r i s a t i o n of Habitats Under I n v e s t i g a t i o n a. E c o l o g i c a l A n a l y s i s of S i t e s S o i l s used f o r the experimental p a r t of t h i s work were c o l l e c t e d from two very w e l l defined f o r e s t a s s o c i a t i o n s : 1. Pseudotsuga m e n z i e s i i - Thu.ja p l i c a t a -Polystichum muniturn a s s o c i a t i o n w i t h c h a r a c t e r i s t i c duff m u l l c o n d i t i o n s of t h i s ' f o r e s t s o i l . 2 . Pseudotsuga m e n z i e s i i - Tsuga h e t e r o p h y l l a - G-aultherla s h a l l o n a s s o c i a t i o n w i t h c h a r a c t e r i s t i c raw humus co n d i t i o n s of t h i s f o r e s t s o i l . Both s i t e s are located on the U n i v e r s i t y of B r i t i s h Columbia Endowment Lands. P l o t s i z e used f o r f l o r i s t i c a n a l y s i s of the two a s s o c i a t i o n s was l/5> of an acre. The r e l a t i v e abundance and dominance of the pl a n t species present was evaluated. ( E c o l o g i c a l a n a l y s i s of both s i t e s was done wit h the help and under the s u p e r v i s i o n of Dr. V.J. K r a j i n a . ) 31 TABLE OF SCALES ADAPTED FOR ECOLOGICAL DESCRIPTION OF SITES I . Wind exposure s c a l e : strong exposure to wind: !! moderately strong exposure: ! intermediate exposure: + + s l i g h t exposure: + w e l l sheltered from wind: 0 I I . .Scale f o r the e s t i m a t i o n of t o t a l abundance and dominance: + quite s o l i t a r y , dominance very small 1 seldom 2 very s c a t t e r e d , dominance small 3 scattered k often dominating l/20 - l / l O of area 5> often dominating l / l O - l / 5 of area 6 dominating l / 5 _ l / 3 of area 7 -. 11 - 1/3 - 1/2 8 - " - 1/2 - 3/1+ 9 - 11 - over 3/k 10 - " - 100$. I I I . Vigor i s expressed by f i g u r e s , attached as exponents to the f i g u r e s expressing the t o t a l estimate of abundance and dominance. The f o l l o w i n g i s the scale used f o r v i g o r : 3 most vigorous growth 2 growth moderately vigorous 1 poor v i g o r , but the p l a n t may reach a considerable age 0 v i g o r non, p l a n t may vegetate only f o r a short time n _ it _ it _ 3 2 ECOLOGICAL DESCRIPTION OF STUDIED FOREST ASSOCIATIONS I. Pseudotsuga m e n z i e s i i - Thuja p i l e a t a - Polystichum muniturn a s s o c i a t i o n General e c o l o g i c a l c h a r a c t e r i z a t i o n : 1. Date: September 18, 1 9 5 6 . 2 . P l a c e : U.B.C. Endowment Lands, SW of the proposed s i t e f o r the Fo r e s t Product Laboratory. 3 . A l t i t u d e : 260 f e e t above sea l e v e l . I4.. Exposure: south, i n the center of a c o l . 5 . S l o p i n g : 20 - 30 degrees. 6 . Wind exposure: at the ground: + ( i n the p r o x i m i t y of the sea l e v e l ) . at the top of the tree l a y e r : ! 7. Snow cover p e r i o d : u s u a l l y 2 , weeks, o c c a s i o n a l l y 5 - 6 weeks. 8 . Depth of f i n e weathered s o i l : over 1 meter. 9 . S o i l : g l e y of a l l u v i a l m a t e r i a l . 1 0 . P l o t s i z e : l / 5 acre. 11. T o t a l coyer of v e g e t a t l o n a l l a y e r s : A: 2 0 - 2 5 $ (dominant & codominant trees) A: 75-80% (intermediate & suppressed trees) B: 60$ ( t a l l shrubs & small t r e e s , 2 - 2 0 meters). B: 25$ (shrubs 2 0 - 2 0 0 cm.) C: 6 5 - 7 0 $ (herbs) D: 2$ (mosses) 1 2 . L i s t of p l a n t s : A: Pseudotsuga m e n z i e s i i 6 -> Thuja p l i c a t a l 2 Abies grandis +c-A: Acer macrophyllum 7 " " p Thu.ia p l i c a t a 3 p-n Alnus rubra 2 ^ u Abie s grand i s + B: Sambucus pub ens 7 Rubus s p e c t a b i l i s 3~k^ 1 — 0 Acer ma c r ophy1lum 3 33 2(-3) -pi Tsuga h e t e r o p h y l l a (on decaying wood) 1 2 1-2 Thu.ia p l i c a t a 1-2 Abies grand i s + ^ 2(-3) B: Sambucus pubens k Rubus p a r v i f l o r u s k ^ °^  Rubus s p e c t a b i l i s k 2  Ribes l a c u s t r e + 2 2 Symphpricarpos r i v u l a r i s + I l e x a q u i f o l i u m +"'" 2- 3 C : Polystichum muniturn 7 ~ 8 T i a r e l l a t r i f o l i a t a k-£ 2 " 3 , 2-0 Rubus v i t i f o l i u s 3-k 2 D r y o p t e r i s a u s t r i a c a 3 2-3 Bromus v u l g a r i s 3 1-2 Sambucus pubens 2-3 P—o Rubus p a r v i f l o r u s 2-3 2 Rubus s p e c t a b i l i s 2 2( -^1 C l a y t o n i a s i b i r i c a 2 v ->' T e l l i m a . g r a n d i f l o r a 2 ^"^ 2-1 Athyrium f i l i x - f e m i n a 1-2 2 - 1 Galium t r i f l o r u m 1 + 1 - 2 T r i e n t a l i s l a t i f o l i a + p Equisetum t e l m a t e i a + 1 - 2 Geum macrophyllum .+ 2 - 1 Carex leptopoda + Acer macrophyllum + ^ ^ 1 - 2 D i c e n t r a formosa + Cinna l a t i f o l i a + 1 - 2 1 - 2 V i c i a americana + 0 Sorbus s i t c h e n s i s + Polypodium vulgare var. occidentale (on decaying p wood & bark) + 2 - 3 Adenocaulon b i c o l o r + 2 - ^ Ranunculus b o n g a r d i i + -> 2 - 3 Osmorhiza c h i l e n s i s + 2 S t e l l a r i a c r i s p a + Eurhynchium s t o k e s i i 2 2 Mnium insigne 1 - 2 1 - 2 Brachythecium asperrlmum + 3£ I I . Pseudotsuga menzie'sii - Tsuga h e t e r o p h y l l a - C a u l t h e r l a s h a l l o n a s s o c i a t i o n General e c o l o g i c a l c h a r a c t e r i z a t i o n : 1. Date: September 18, 1956. 2 . Place: U.B.C. Endowment Lands, Secondary-f o r e s t on the p l a t e a u south of 16th Ave. 3 . A l t i t u d e : 300 f e e t above sea l e v e l , k. Exposure: W 7^ E. 5- S l o p i n g : 0-5 degrees. 6. Wind exposure: at the ground, 0 at the tops of the tree l a y e r , ++ . 7. Snow cover p e r i o d : 3 ("k) weeks; o c c a s i o n a l l y 6~7 weeks. .8. Depth of the f i n e s o i l : over 1 meter. 9. Podzol (A2 Layer r a t h e r t h i n , |—3 cm. t h i c k ) . 10. P l o t s i z e : 1/5 acre. 11. T o t a l cover of v e g e t a t i o n a l l a y e r s : A (dominant & codominant trees) 95-100$ A (intermediate & suppressed t r e e s ) B. 10$ ( t a l l shrubs & small t r e e s , 2-20 meters). B. 85-90$ (shrubs 20-200 cm.) C 10 - l 5$(herbs) D. 10$ (mosses) 12. L i s t of p l a n t s : 1-2 A. Pseudotsuga m e n z i e s l i 3 2 Tsuga h e t e r o p h y l l a 9 .Thuja p l i c a t a 1"^  2-1 Cornus n u t t a l l i i + 1 Tsuga h e t e r o p h y l l a 2 Thuja p l i c a t a 2-3 1 ^ - 0 ^ Cornus n u t t a l l i i  Sorbus s i t c h e n s i s  Malus d i v e r s i f o l i a + 1" 1 0  Prunus emarginate 1-2 Tsuga h e t e r o p h y l l a /j.-5> 2 G a u l t h e r i a s h a l l o n 9-10 2( Vaccinium p a r v i f o l i u m £ Thuja p l i c a t a 1-2 1 2 Mahohla nervosa + 2-3 Rosa gymnocarpa + Vaccinium o v a l i f o l i u m + Abies grandis p Mahonia nervosa .1-2 2 P t e r i d i u m a q u i f o l i u m 3 Rubus v i t i f o l i u s 3 1 - 2 Tsuga h e t e r o p h y l l a 3"*" Vaccinium p a r v i f o l i u m 2-3 2-3 G-aultheria s h a l l o n  Thuja p l i c a t a +^ 1-2 Moneses u n i f l o r a + Acer c i r c i n a t u m + ^ Blechnum sp l e a n t + 37 D r y o p t e r i s .austriaca +^ Polystichum muni turn +^ 2 D. Plagiothecium undulatum k L e p i d o z i a reptans (on decaying wood) 1 2 Dicranum scoparium 1 2 Scapania b o l a n d e r i (on decaying wood) + Hypnum c i r c i n a l e +^ b. ANALYSIS OF SOME PLANTS FOR THE ABILITY TO ACCUMULATE  INORGANIC NITROGEN 1. Determination of the Presence of N i t r a t e s i n P l a n t Tissue  by Diphenylamine Reagent ( l ) Experimental part  Reagents: (1) Diphenylamine Reagent f o r N i t r a t e s . D i s s o l v e 0.7 grams of diphenylamine i n a mixture of 60 cc. of concentrated HgSO^ and 28.8 cc. of d i s t i l l e d ( n i t r a t e f r e e ) water. A f t e r c o o l i n g the mixture, 11.3 cc. of concentrated HCL i s added and the reagent i s l e f t overnight. (2) Trommsdorf's Reagent f o r N i t r i t e s . Add slowly a b o i l i n g s o l u t i o n of 20 grams of zinc c h l o r i d e i n 100 cc. of d i s t i l l e d water to a mixture of k grams of s t a r c h i n water, and continue to heat u n t i l the s o l u t i o n i s n e a r l y c l e a r . 3'8 Then 2 grams of z i n c i o d i d e are added and the mixture i s d i l u t e d w i t h d i s t i l l e d water to the f i n a l volume of 1 l i t e r . A f t e r f i l t e r i n g , the reagent should be stored i n a w e l l -stoppered, dark b o t t l e . (3) N - P h e n y l a n t h r a r i i l i c Acid Reagent. Prepare 0-1$ s o l u t i o n of N - P h e n y l a n t h r a n i l i c acid i n hot methanol i n order to Insure complete d i s s o l u -t i o n . In t e s t i n g f o r n i t r i t e s and n i t r a t e s , concentrated H2S0^_ should be used. P o s i t i v e t e s t i s i n d i c a t e d by p i n k - v i o l e t c o l o r a t i o n . S u b s t i t u t i o n of concentrated HCl f o r concen-t r a t e d H2S0^ gives a p o s i t i v e t e s t f o r n i t r i t e s i n presence or absence of n i t r a t e s . Procedure: Analyses were' c a r r i e d out on a f a i r l y l a r g e number of p l a n t s taken from d u l l m u l l and raw humus h a b i t a t s . Parts of a l e a f or stem of the p l a n t to be tested were s l i g h t l y crushed or broken and then placed i n t o the porce-l a i n spot p l a t e . S e v e r a l drops of the diphenylamine reagent plus a f i x e d number of drops of concentrated s u l p h u r i c a c i d was used. A blue colour was taken as i n d i c a t i v e of the presence of n i t r a t e s . To a s c e r t a i n that a p o s i t i v e r e a c t i o n was riot due to the p o s s i b l e presence of n i t r i t e s , the Trommsdorf's reagent was used, f o l l o w i n g the same technique. 39 R e a l i z i n g that a diphenylamine reagent w i l l give a coloured r e a c t i o n w i t h a v a r i e t y of compounds-, the same t e s t was repeated using N - p h e n y l a n t h r a n i l i c acid (Chem. A b s t r a c t s 15630 f . , 1955)• ( i i ) R e s u l t s : Scale used: - NO^ absent 0 - N 0 3 " trace 1 t N 0 3 " i n s l i g h t cone. 2 - N 0 3 " In medium cone. 3 - NO^ i n l a r g e cone. 1+-5 ( E x a c t l y the same sc a l e i s used f o r n i t r i t e s concentrations.) N-PFENYLANTRRANILIC ACID REAGENT TEST FOR NITRATES IN LEAVES AND STEMS OF PLANTS Results of the t e s t f o r some p l a n t s taken from bothvduff m u l l and raw. humus s i t e s P l a n t s tested S i t e N-Phenanthra- N-Phenanthra- Diphenyla-n i l i c t e s t n i l i c ; . t e s t mine t e s t f o r NOo f o r NO, f o r NO" Alnus rubra duff mull 0 0 0 Polystichum muniturn raw humus 0 0 0 Mnium insigne duff m u l l 0 0 0 Sambucus pubens (leaves) 0 2 k Rubus s p e c t a b i l i s 0 2 3 T i a r e l l a t r i f o l i a t a 0 2 3 Galium t r i f l o r u m 0 1 2 Rubus p a r v i f l o r u s (leaves) 0 2 k G a u l t h e r i a s h a l l o n Raw humus 0 0 0 P t e r l d i u m aquilinum n 0 0 0 k-1 DIPHENYLAMINE SPOT TEST FOR THE PRESENCE OF NITRATES IN LEAVES AND STEMS OF PLANTS Scale used: -NO3 absent 0 - N O 3 t r a c e 1 -NO^ In s l i g h t cone. 2 -NO3 i n medium " 3 -NO" i n larg e " k-£ 1. Results of the Test f o r Some Plan t s C o l l e c t e d from the Duff M u l l S i t e Plant Test r e s u l t Alnus rubra 0 • Acer macrophyllum 0 Pseudotsuga m e n z i e s i i 0 Abies grandis 0 Thuia p l i c a t a 0 T.suga h e t e r o p h y l l a 0 Polystichum muniturn 0 Dry o p t e r i s a u s t r i a c a 0 Symphoricarpos r i v u l a r i s 0 I l e x aquiffblium 0 Equisetum t e l m a t e i a 0 Ranunculus b o n g a r d i i 0 V i c i a americana 0 Mnium i n s i g n e 0 Eurhynchium s t o k e s i i 0 Brachythecium asperulum 0 Sambucus pubens (seedling) 5 " " (leaves a d u l t " 11 (stem p l a n t ) 5 young pl a n t ) 1-2 C l a y t o n i a s i b i r i c a 2-k Geum macrophyllum 3 T i a r e l l a t r i f o l i a t a 4 - 5 Rubus s p e c t a b i l l s 3-k D i c e n t r a formosa k Cinna l a t i f o l i a k Carex leptopoda 4 " 5 Ribes l a c u s t r e 2-3 Bromus v u l g a r i s k Athyrium f i l i x - f e m i n a 2-3 T e l l i m a g r a n d i f l o r a 4 " 5 Galium t r i f l o r u m 3-k Rubus p a r v i f l o r u s (leaves) k-$ 11 11 (stem) 1-2 Rubus v i t i f o l i u s 3-k Adenocaulon b i c o l o r 4 " 5 Osmorhiza c h i l e n s i s 4 - 5 S t e l l a r i a c r i s p a 3 R e s u l t s of the Test f o r Some Plan t s C o l l e c t e d from the Raw Humus S i t e Pseudotsuga m e n z i e s i i 0 Thu.ia p l i c a t a 0 Tsuga h e t e r o p h y l l a 0 Abies grand i s 0 Cornus n u t t a l l i i 0 Sorbus s i t c h e n s i s 0 Malus d i v e r s i f o l i a 0 Prunus emarginatus 0 Vaccinium p a r v i f o l i u m 0 Vaccinium o v a l i f o l i u m 0 G a u l t h e r i a s h a l l o n 0 Rosa gymnocarpa 0 " " ( f r u i t s ) 0 Pteridi.um aquilinum 0 Polystichum muni turn 0 Rubus v i t i f o l i u s 0 Moneses u n i f l o r a 0 Lepidoz i a reptans 0 Dry o p t e r i s a u s t r i a c a 0 Dicranum scoparium 0 Blechum spi c a n t 0 Plagiothecium undulatum 0 ( i i i ) Discus sion Accepting the t e s t s as r e l i a b l e , the f o l l o w i n g con-c l u s i o n s can be drawn: 1. Some p l a n t s are able to accumulate a c e r t a i n amount of inorganic n i t r o g e n i n the form of n i t r a t e s , mostly i n the leaves. 2. This accumulation occurs only (as f a r as i t was p o s s i b l e to detect) i n p l a n t s growing on duff m u l l s o i l s . 3. I t appears that only c e r t a i n p l a n t s are able to accumulate n i t r a t e s i n t h e i r t i s s u e . I t i s i n t e r e s t i n g to note that the q u a n t i t y of n i t r a t e s , detected i n p l a n t t i s s u e by the methods des c r i b e d , seems to vary considerably during the' year. This was ascertained from a prolonged s e r i e s of t e s t s conducted throughout the year by the author and Dr. V.J. K r a j i n a . In view of the f a c t that n i t r a t e s were detected from the d i s t i l l e d water leachates of duff m u l l and "A" s o i l s (see experiments on n i t r i f i c a t i o n ) , one can dete c t , t h e r e f o r e , a c e r t a i n r e l a t i o n s h i p between the presence or absence of s o i l n i t r i f i c a t i o n and the a b i l i t y of some p l a n t s to accumulate n i t r a t e s i n t h e i r t i s s u e s . k'6 c. DETERMINATION OF ORGANIC MATTER AND TOTAL NIGROGEN OF SOILS 1. Determination of T o t a l Organic Matter ( i ) Experimental part ( m o d i f i c a t i o n of Walkley-Black method) References: "Methods of S o i l A n a l y s i s f o r S o i l - f e r t i l i t y I n v e s t i g a t i o n s " by Peech, M i c h e a l , L.T. Alexander, L.A. Dean, and J . F i e l d i n g Reed. U.S.D.A. C i r c u l a r No. 757. 1952. Reagents: (1) N- Potassium dichrornate. D i s s o l v e 98.06 gm. of K^Cr^O-j i n water and d i l u t e to 2 l i t e r s w i t h water. (2) S u l f u r i c a c i d , eon. (not l e s s than 9 6 $ ) . (3) O.^ N - Ferrous s u l f a t e . D i s s o l v e 278 gm. FeSO^ . 7H 2 0 i n water, add 80 ml. cone. H^S0^, c o o l , and d i l u t e to 2 l i t e r s . (k) Ortho - Phenanthroline Ferrous Sulphate i n d i c a t o r . Procedure: Dried s o i l s were sieved through a 20-mesh screen. Three 50 mgm. p o r t i o n s were used f o r h i g h l y organic s o i l s such as raw humus and duff m u l l , and three 100 mgm. p o r t i o n s f o r s u b s o i l s and garden s o i l . S o i l samples' -were placed i n 250 ml. Erlenmeyer f l a s k s and 5 ml. of N dichromate and 10 ml. of concentrated s u l f u r i c a c i d were added. F l a s k s were shaken for.about l 5 seconds and then l e f t standing f o r 30 minutes. Then 30 ml. of water and 2 drops of (Ortho)-Phenanthroline Ferrous Sulphate i n d i c a t o r were, added. T i t r a t i o n with standard Ferrous Sulphate was continued u n t i l there was a change of colour from green to brownish gray. As the potassium dichromate i s a reasonably s t a b l e s o l u t i o n , I t was taken as the standard. The f e r r o u s s u l -f a t e i s subject to o x i d a t i o n , hence, i t was standardized against the dichromate each time the s o l u t i o n s were used. S t a n d a r d i z a t i o n was as f o l l o w s : 5 ml. of the standard dichromate s o l u t i o n i n a 2$0 ml. f l a s k was mixed w i t h 10 ml. Of concentrated s u l f u r i c a c i d . Then 30 ml. of water and .2 drops of the (Qrtho)-Phenanthroline Ferrous .Sulphate i n d i c a t o r were added. T i t r a t i o n w i t h standard f e r r o u s sulphate was continued u n t i l the brownish gray endpoint was reached. Assuming the dichromate to be c o r r e c t , the n o r m a l i t y f a c t o r f o r the f e r r o u s sulphate was c a l c u l a t e d . C a l c u l a t i o n s : The mean recovery of carbon by t h i s method has been found to be 75$, hence, the c o r r e c t i o n f a c t o r , = 1 . 3 3 , should be a p p l i e d . fo organic matter i n s o i l sample = (ml. N"dichromate/reduced) X 0 .003 X 1 .33 X 1 .724 X 100 = (Wt. of sample (gms.) ) (ml. IT dichromate reduced) X 0.6.9 (Wt. of sample i n grams) .Notes: C h l o r i d e s i n t e r f e r e by reducing the dichromate; carbonates up to at l e a s t $0% of the s o i l do not i n t e r f e r e ; Mn0.2 does not i n t e r f e r e . ( i i ) R e s ults of the Organic Matter E s t i m a t i o n i n S o i l s ( S o i l Samples C o l l e c t e d from Duff M u l l and Raw Humus S i t e s of U n i v e r s i t y Area F o r e s t , Vancouver, B.C.) S o i l s Amount • % organic matter %. organic matter Mean of f o r Test I I s o i l f o r Test I I I s o i l values s o i l used (average) (average) % f o r t e s t G-ard en 50 mg. 18.90 17.25 18.07 Duff humus 50 mg. 23.70 18.35 21.02 A l 50 mg. 11.10 11.34 11.22 Raw humus 50 mg. 67.OO 62 .37 6k. 68 B 100 mg. k . 0 7 k.6.2 i . . 3 k • -( A l l estimates were made on dry weight bases) Note: Test I I and t e s t I I I s o i l s were used f o r n i t r i f i c a t i o n experiment; see page 6£. 2. DETERMINATION OP TOTAL NITROGEN (I) Experimental p a r t : Reference: (27) Reagents : (1) D i g e s t i o n mixture: 16 gm. sodium selenate 503.0 gm. Na 2S0^ . 10 H~20 17-ij- gm. Cu SO^ . H 2 0 667 ml. cone. H^ S.O^  (made up to two l i t e r s w i t h d i s t i l l e d water) (2) I n d i c a t o r : 33 mg. Brom-cresol green 66 mg. Methyl red 100 ml. 95$ e t h y l a l c o h o l (3) Absorption s o l u t i o n : Saturated (!(.$) b o r i c a c i d s o l u t i o n ( 4 ) Sodium hydroxide (1 l b . of Na OH per l i t e r of water) (5) Standard h y d r o c h l o r i c acid (0.1N). Procedure: With humus samples and w i t h subsoils,. 2 grams and 10 grams r e s p e c t i v e l y , of oven d r i e d samples wero used. S i x t y ml. of the d i g e s t i o n mixture i n an 800 ml. K j e l d a h l f l a s k , plus a given weight of s o i l sample, was heated g r a d u a l l y f o r 3 hours. A f t e r c o o l i n g , the mixture was d i l u t e d w i t h 100 ml. of d i s t i l l e d water and 100 ml. of k9 Na OH. (Before NaOH i s added s e v e r a l pieces of mozzy z i n c had been placed i n t o the f l a s k . ) A f t e r mixing the contents, the l i q u i d i n the f l a s k s was d i s t i l l e d over the saturated b o r i c s o l u t i o n , to which 1 ml. of the i n d i c a t o r s o l u t i o n had been added. The ammonia c o l l e c t e d was t i t r a t e d w i t h 0.1 N HCL a c i d . Prom the f a c t that the a l k a l i n e s o l u t i o n of t h i s mixture i s green and the acid red, the end p o i n t i s e a s i l y observed. C a l c u l a t i o n : Percentage n i t r o g e n + ^ T " B ) N x 1 , k W T •= volume of acid used w i t h s o i l B = " " " rt " blank N = n o r m a l i t y of a c i d ¥ = weight of dry s o i l used ( i i ) R esults of the t o t a l n i t r o g e n estimations 1. Values f o r s o i l s c o l l e c t e d from duff m u l l and raw humus s i t e s . ( U n i v e r s i t y area, Vancouver.) S o i l s % -N t e s t I I s o i l s (average) % - N t e s t I I I s o i l s (average) Mean values Garden s o i l 0.60k 0.687 0.6k5 Duff m u l l 0.567 0.598 0.583 A l 0.292 0.281 0.286. Raw humus 1.211 1.165 1.188 O .O78 0.091 0.08k Note: Regarding t e s t I I and t e s t I I I s o i l s , see page- 6i$. 2. Value f o r s o i l s c o l l e c t e d from U n i v e r s i t y Forest i n Haney * B.C. (Given as a d d i t i o n a l * comparative values only) S o i l s % - N (average) Raw humus 1.165 Hardwood m u l l 1.018 Black muck 1.425 • Lake peat 2.418 Table of Carbon/Nitrogen r a t i o f o r s o i l samples from U n i v e r s i t y Area, Vancouver S o i l s Percent Percent C/N C/N Average carbon carbon r a t i o r a t i o C/N s o i l s s o i l s s o i l s o i l r a t i o : t e s t . I I t e s t I I I t e s t I I t e s t I I I Garden s o i l 11 .0 10. .0 18.2 14 . 5 16 .3 Duff-humus 13 • 7 10, .6 24.2 17 •7 ' 20 .9 A l 6 •4 6. .6 21.4 23 . 5 22 •4 Raw humus . 38 .9 36, .2 3 2 . 2 31 .1 31 .6 B 2 .3 2, • 7 2 9.5 29 .7 29 .6 (Percent carbon was estimated on the assumption that : s o i l organic matter contains 58$ of carbon.) Ref. : (21) . Note: Regarding t e s t I I and t e s t I I I s o i l s , see page 6£. . 51 ( i i i ) D i s c u s s i o n S o i l c o l l e c t e d f o r these determinations were from the f o l l o w i n g depths: a. duff m u l l u s u a l depth from 0.5 to 1 . 0 i n c h . b. from 0.5 up to 7-0 inches. c. raw humus up to 30 inches. d . B up to 11 .0 inches. Before t a k i n g small samples f o r both t o t a l organic or t o t a l n i t r o g e n determinations, s o i l s were thoroughly-mixed to insure the u n i f o r m i t y of samples. The c a l c u l -ated carbon/nitrogen r a t i o s p o i n t to the f a c t that there-i s considerable v a r i a t i o n between raw humus and duff, m u l l s o i l s i n t h i s regard. I t would be d i f f i c u l t to p r e d i c t the f e r t i l i t y of the s o i l s from these two s i t e s , taking i n t o c o n s i d e r a t i o n only t o t a l n i t r o g e n or t o t a l organic matter present. D e s t r u c t i o n of the humus l a y e r , by f i r e or some other agency, i n raw humus s i t e s has a more d e t r i m e n t a l e f f e c t on growth than s i m i l a r d e s t r u c t i o n i n s o i l s o v e r l a i n by duff m u l l . The former s o i l type has a B h o r i z o n c h a r a c t e r i s t i -c a l l y low i n n i t r o g e n . The d i s t r i b u t i o n of t o t a l n i t r o g e n i n duff m u l l s o i l s i s more uniform. Considerably lower carbon/nitrogen r a t i o s a r e - i n d i c a t i v e of a more advanced type of humus degradation and l i k e w i s e a more i n t e n s i v e type of micro-b i a l a c t i o n . 52 d. pH MEASUREMENTS OF SOILS ( i ) Experimental p a r t The pH of s o i l samples was determined immediately a f t e r t h e i r c o l l e c t i o n u s i n g approximately 25 cc. of each s o i l i n a 50 ml. beaker, and adding enough d i s t i l l e d water to each to produce a t h i c k paste. The beaker and i t s con-tents were allowed to stand f o r 30 minutes, p r i o r to any measurement, to permit the s o i l and water to come to equi-l i b r i u m . A po r t a b l e Beckman Model N pH-meter was used. ( i i ) R e s u l t s : S o i l s 15 t h of February 11th of May 26 t h of May 15 t h of June 26th of June 12th Average of values J u l y Garden s o i l 6.10 7 . 1 0 7 . 2 0 7 . 3 5 6 . 9 5 7.22 6 . 9 8 Duff m u l l k . 2 5 5-6.3 k.26 k.ko 5 . 3 0 k . 7 1 A l 6 . 2 5 6 . 0 5 6 . k 3 5 . 8 5 6 . k 3 5 . k 3 6 . 0 7 Raw humus 3.60 k.20 3 . 7 0 3 . 5 o 3 . 6 5 i+.3k 3 . 8 3 B 5 - 2 5 k . 8 8 5 . 0 8 k.60 5.08 1+.89 D i s t . water 5.80 5 . 8 5 -• 5.6.8 5 . 8 6 5 . 7 2 -(The values quoted are the average values of two : sample measurements per s o i l per horizon.) 53 e. SOIL MOISTURE (1) Procedure: S o i l s to be- analysed were c o l l e c t e d i n sealed g l a s s j a r s and weighed to the nearest m i l l i g r a m ; then d r i e d i n an oven at 105°C. to a constant weight, f o r n e a r l y 1+8 hours. The dr i e d samples were re-weighed and the percentage of moisture was c a l c u l a t e d as f o l l o w s : % moisture = (wt. l o s t ) x (100) Dry weight. ( i i ) R e s u l t s : Percent Moisture Values (Soils, c o l l e c t e d from U n i v e r s i t y Area, Vancouver, B.C.) S o i l 3rd l 5 t h 18th 11th l£th 12th Average of of of of of of values Dec. Jan. Mar. May June J u l y Garden 1+0.32 1+1.61 1+2.52 1+8.20 38.50 35-80 1+1.16 Duff mull 39.15 1+1.30 1+5.60 38.30 1+0.72 39.1+1 1+0.75 A 1 1+0.20 1+0.61 1+0.31 38.30 32.10 39.1+1 38.1+9 Raw humus 71.31 68.05 .69.50 61.20 66.52 61.28 66.31 B 11+.21+ 11.1+0 12.33 13.72 9.36 8.95 1.1.66 ( A l l f i g u r e s are the average values of two measurements per sample of s o i l . ) ( i i i ) D i s c u s s i o n : The highest amount of t o t a l moisture was found i n raw humus. This i s evidence of the f a c t that organic matter i s capable of r e t a i n i n g a considerable amount of water, and that s o i l s r i c h i n humus are l i k e l y to be l e s s subject to drought than humus d e f i c i e n t s o i l s . In the case of a d u f f - m u l l s o i l , moisture i s r e t a i n e d by both the organic matter and the not inco n s i d e r a b l e c o l l o i d a l f r a c t i o n of the u n d e r l y i n g m i n e r a l m a t e r i a l . In order to be able to obtain a more exact understanding of s o i l moisture, and s o i l - w a t e r r e l a t i o n -ships i n f o r e s t s o i l s , from d i f f e r e n t s i t e s , f i v e p r i n c i -p a l forms of s o i l water should be s t u d i e d , namely:-g r a v i t a t i o n a l , c a p i l l a r y , hygroscopic, water vapor and ground water. Determination of percent moisture-, as given i n t h i s work, serves only as an a d d i t i o n a l , and very general f a c t o r i n the c h a r a c t e r i z a t i o n of the s o i l s s t u d i e d . F. Q u a n t i t a t i v e Studies of S o i l Microorganisms i n Forest  S o i l s ( i ) Experimental Part The q u a n t i t a t i v e e s t i m a t i o n of aerobic popula-t i o n s i n duff m u l l and raw humus s o i l s was made accord-ing to the method of A.G-. Lochhead and R.H. Thexton (195>1), 55 w i t h some m o d i f i c a t i o n s . I t was found that the s o i l e x t r a c t agar, as described by Lochhead, gave smaller b a c t e r i a l counts than s o i l i n f u s i o n agar. The. s o i l i n f u s i o n agar p l a t e s were, prepared as f o l l o w s : 250 grams of s o i l was l e f t i n 250 ml. of d i s -t i l l e d water f o r 21+ hours at 3 7 C . ; then, .before f i l t r a -t i o n , the temperature, was r a i s e d to j u s t below b o i l i n g p o i n t , and the. i n f u s i o n was f i l t e r e d while hot; the "Case" n u t r i e n t agar was d i s s o l v e d i n the above s o i l e x t r a c t without any pH adjustments' being made. As a consequence, a separate i n f u s i o n agar medium was used w i t h the s o i l samples. There was no attempt made to c o n t r o l any p o s s i b l e occurrence of "spreaders," but r e l a t i v e l y few plate's were discarded on t h i s account. In order to group the microorganisms according to t h e i r morphology, 50 colonies were selected at random from acceptable p l a t e s and a microscopic examination made' of the gram-stained p r e p a r a t i o n s . (Table B.) ( i i ) R e s ults See Table A and Table' B. TABLE A. Results of P l a t e Counts, of Microorganisms by S o i l Horizons i n Forest S o i l s ( S o i l s c o l l e c t e d from the U n i v e r s i t y Area F o r e s t , Vancouver, B.C.) (Numbers given are i n hundred thousands per gram, oven-dry s o i l ) S o i l s . , pH . %. moisture B a c t e r i a Actlnomyc. and f u n g i Garden s o i l 0-l£cm. 7.2.0 kl..20 190.kO 31.80 Duff m u l l 0-10cm. 39.10 121 .83 k l . 2 l A 10~2£cm. 6.k3 38.70 126.33 38.20 Raw humus 0-l£cm. 3.70 6 3 . kO 13.81 97. k3 mostly f u n g i B .- - lj?-2£ cm. 5.08 lk.10 7.26 k0 . 3 8 mostly f u n g i -TABLE B. Morphological Groups .Present i n Each S o i l Horizon (Soils- c o l l e c t e d from the U n i v e r s i t y Area F o r e s t , Vancouver, B. C.) Gram p o s i t i v e c o c c i forms Gram p o s i t i v e spor.e-f ormlng b a c i l l i Gram negative B a c i l l i Spore formers Pleomorphic organisms Others: A c t i n o and Fungi Garden s o i l 18 31 1 23 10 17 Duff m u l l 6 38 h 32 10 10 A^ ho r i z o n k 32 3 37 14 10 Raw humus - 5 2 32 i|0 21 B hori z o n 1 k - 12 52 31 (Figures given are percent values c a l c u l a t e d from each p l a t e by p i c k i n g up 5>0 c o l o n i e s at random.) 58 ( i i i ) D i s c u s s i o n Prom the above r e s u l t s , i t i s obvious there i s a r e l a t i v e l y r i c h p o p u l a t i o n of b a c t e r i a i n garden, s o i l , duff m u l l , and A]_-hori.zori s o i l s . Conversely, few b a c t e r i a i n h a b i t raw humus and i t s immediate s u b s o i l . The f u n g a l p o p u l a t i o n , on the other hand, seems to be at a c o n s i d e r a b l y higher l e v e l i n raw humus. P l a t i n g methods, as a means of o b t a i n i n g a q u a n t i t a t i v e r e p r e s e n t a t i o n of s o i l m i c r o f l o r a , , are admittedly of dubious worth. Nevertheless., the above conclusions are i n accord w i t h those of others (77 , 8 5 ) . B. PRELIMINARY STUDIES OF NITRIFICATION BY PERFUSION  TECHNIQUES ( i ) Experimental Part P r e l i m i n a r y studies were c a r r i e d out on duff m u l l and raw humus (mor) s o i l s of the D o u g l a s - f i r f o r e s t comparing t h e i r r e l a t i v e n i t r i f y i n g and d e n i t r i -f y i n g c a p a c i t y . For t h i s purpose, p e r f u s i o n apparatuses were, set up according to the technique described by I . J . Audus (8) w i t h c e r t a i n m o d i f i c a t i o n s that improved considerably the a p p l i c a t i o n of t h i s apparatus f o r s o i l s t u d i e s . The change made was the use of a "by-pass tube" that obviated any p o s s i b i l i t y of overflowing or plugging, though s t i l l i n s u r i n g adequate s o i l a e r a t i o n (see Appendix, P i g . I and P i g . I I ) . This apparatus was i n continuous operation f o r more than t h i r t y days without any t e c h n i c a l d i f f i c u l t i e s . The s o i l s were C o l l e c t e d from two d i f f e r e n t l o c a l i t i e s i n s t e r i l e g l a s s j a r s . They were riot d r i e d or sieved, as was suggested by H. Lee.s and J.H. Q u a s t e l l (54)J but r a t h e r used i n t h e i r n a t u r a l s t a t e . Each s o i l sample was leached completely w i t h a s u f f i c i e n t amount of d i s t i l l e d water to in s u r e the removal of any detect-able t r a c e s of ammonium, n i t r i t e or nitrate:; then the leachates were replaced by 200 cc. of N/50 (NH^) 2 S0^. The p e r f u s i o n w i t h the above s o l u t i o n was continued f o r 2J4. days w i t h a r e g u l a r d a i l y check f o r the presence of ammonium, n i t r a t e s and n i t r i t e s . Adjustments f o r eva-p o r a t i o n were; made one' hour before removing 0.5 cc. of leachate f o r a n a l y s i s . The d e t e c t i o n and approximate q u a n t i t r y e estimations of ammonium, n i t r i t e s , and n i t r a t e s were made as f o l l o w s : a. F o r determination of ammonium-: one drop of Nessler*'s s o l u t i o n and one drop o f the s o l u t i o n to be tested were used i n a spot p l a t e . b. For determination of n i t r i t e s : Trommsdorf's reagent was used. 60 c. F o r determination of n i t r a t e s : one drop of diphenylamine reagent was added to one drop of leachate and two drops of concentrated s u l -p h u r i c a c i d . A l l reagents used and the method followed were- according to E.B. Fred and S.A. Waksman ( 3 0 ) . An a d d i t i o n a l t e s t was run on s o i l samples of raw humus and i t s s u b s o i l treated w i t h 0.5 percent c a l c i u m hydroxide (Ca(0H) 2) to r a i s e t h e i r pH. (from 3 .85 to 6.85 i n the case of raw humus and from k.20 to 7-05 i n the case of the "B" h o r i z o n . The i n t e n t i o n was to determine whether- any r e l a t i o n s h i p e x i s t s between the. low pH valuers c h a r a c t e r i s t i c of such media and the absence of n i t r i f i c a t i o n as a process' i n them. 61 RESULTS OF AMMONIUM OXIDATION ( S o i l samples c o l l e c t e d from U n i v e r s i t y Area F o r e s t , Vancouver, B.C.) No. Duff m u l l A^ Raw humus B Garden s o i l of _ , , _ _ , days NHJJ N0 2 NO3 NHj£ N0 2 NO3 NHj N0 2 NO3 NH^ N0 2 N.O3 NH.J N0 2 NO 1 Ipc - Ipc - X ipc - - .Ipc - - .Ipc - X 3 3x X 3x - l x Ipc - - Ipc - 3x x 2x 3x - Ix 2x - 2x ipc - - ipc - l x - 3x 7 2z 2x 2x X 3x ipc - - ipc - X - ipc 9 2x 2x l x . X 3x ipc - - ipc - X X Ipc 11 Ix 2x X - 3x ipc - - ipc - - X 4x 13 X 3x - - 3x Ipc - - Ipc - - • £ Ipc 15 X - 3x - - 3x Ipc - - ipc - - - Ipc 17 X - 3x - x 3x Ipc - - Ipc - - - Ipc 19 - - 3x - - 3x Ipc - - Ipc - - - Ipc 21 - - 3x - - 3x Ipc - - Ipc - - X Ipt 23, . -•. 3x. - - 3x ipc - - Ipc - - Ipc Scale used: ipc - maximum colour i n t e n s i t y of p o s i t i v e r e a c t i o n . 3x) 2x) - g r a d u a l l y decreasing i n t e n s i t y of co l o u r , l x ) x - s l i g h t l y detectable c o l o u r . :x - u n c e r t a i n . 62 RESULTS OP AMMONIUM O X I D A T I O N ( S o i l samples' c o l l e c t e d from Nanaimo R i v e r V a l l e y , V a n c o u v e r I s l a n d , B.C.) No. D u f f - m u l l An Raw- humus 1 B Garden 1 s o i l of NHiJ NO2 days N H J NO 2 : N 0 3 i NO3 N H J NO2 NO3 NHj NO2 NO3 NHjJ NO2 NO3 1 I+X - ipc - - i+x - - I+x - Ipc - -3 Ipc - X i+x - X ipc - r Ipc Ipc . . X X 5 Ipc - X i+x - X ipc - - .i+x - 3x X l x 7 3x - l x ipc - X ipc - - I+x - - 2x X 2x 9 3x - l x 3x - l x 4X - X l+x - - 2x X 2x 11 3x - l x 3x - 2x Ipc - - Ipc - - 2x - 3x 13 3x - 2x 2x . x 3x Ipc - - i+x - - 2x . X 3x 15 2x 2x 2x - 3x ipc . x i+x ". x - l x X 3x 17 2x 2x 2x - 3x l+x - - i+x - l x X i+x 19 2x 2x l x X 3x ipc X Ipc x - X '. . X i+x 21 l x 2x l x - 3x ipc - - i+x - - X X ipc 23 l x 3x x : x 3x Ipc I+x - - X X i+x 39-. ,2x - 2x Jpc - - I+x - - - 4x To s i m p l i f y the d a t a * r e a d i n g s , o r i g i n a l l y t a k e n d a i l y , a r e g i v e n above f o r e v e r y second day. S c a l e u s e d : ipc - maximum c o l o u r i n t e n s i t y o f p o s i t i v e r e a c t i o n • 3x) 2 x ) - g r a d u a l l y d e c r e a s i n g i n t e n s i t y o f c o l o u r , l x ) x - s l i g h t l y d e t e c t a b l e p r e s e n c e . :x - u n c e r t a i n . 63 RESULTS OF AMMONIUM OXIDATION FOR DEACIDIFIED SOILS ( S o i l samples, c o l l e c t e d from U n i v e r s i t y Area F o r e s t , Vancouver, B.C.) No. of days pH Raw. humus NHj^ NO g NO" pH B NHj NO2 NO^ pH Garden s o i l NEfJ N 0 2 NO" 1 6.85 kx - - 7.o5 kx - - 6.90 3x - X 2 k . 2 0 kx - - 6.80 kx - - 6.75 2x - 2x 3 k . 3 5 k x . - - J . l 5 kx - - 7 • 05 x - 3x k k . 6 5 kx - - 7.05 kx - - 7.00 x 3x 5 5 .o5 kx - - 7 .00 kx - - 7 .00 x 3x 6 5.85 ILX - - 6.95 kx - - 7.05 - 2x 7 5.70 kx - - 7 .00 kx - - 7.10 - - 3x 8 5.60 kx - - 7 .00 kx - - 7 .00 ;x kx 9 5.60 kx - - 7.00 kx - - 6.95 - - kx 10 5.65 kx - - - kx - - 6.90 - - kx 6k ( i i i ) - D i s c u s s i o n I t i s appreciated that the above analyses were only rough, q u a l i t a t i v e estimates. To obtain more r e l i a b l e data, q u a n t i t a t i v e microchemical a n a l y s i s should be used. Even wi t h t h i s r e s e r v a t i o n , i t appears evident from the present data that the n i t r i f y i n g c a p a c i t y of the duff m u l l and A-^  (melanized) horizons tested i s consider-able and i s comparable w i t h that of the garden s o i l . No ammonium o x i d a t i o n was observed i n any instances w i t h raw humus or i t s B ( s u b s o i l ) h o r i z o n , even I f the u s u a l a c i d i t y of these s o i l s was a r t i f i c i a l l y c o r r e c t e d . I t i s of f u r t h e r i n t e r e s t to note that raw humus was unable to b u i l d Up any a b i l i t y to o x i d i s e ammonium even when l e f t f o r a p e r i o d of more than f o r t y days. There i s a strong l i k e l i h o o d that n i t r i f y i n g b a c t e r i a are t o t a l l y absent from raw humus. An a n a l y s i s of the leachates c o l l e c t e d d i r e c t l y from the f r e s h s o i l s showed a complete absence of any detectable t r a c e s of n i t r i t e and n i t r a t e i n raw humus and i t s B horiz.on. The duff m u l l , A-^-horizon and. garden, s o i l leachates' had a f a i r amount of n i t r a t e s , the high-est concentration being i n the garden s o i l , the lowest i n the A_ h o r i z o n of f o r e s t s e l l . The. leachates from the raw humus, however, gave a p o s i t i v e t e s t f o r ammonium. 65 C. NITRIFICATION IN FOREST SOILS AS INVESTIGATED BY .THE PERFUSION TECHNIQUE (1) Experimental p a r t : S o i l s , used f o r these experiments were c o l l e c t e d i n s t e r i l e glass' j a r s and t r a n s f e r r e d immediately to the l a b o r a t o r y . Samples of s o i l s f o r the v a r i o u s t e s t s were c o l l e c t e d as f o l l o w s : S o i l s f o r t e s t I A p r i l 1 0 t h . " " " I I June 15 th . " " " I I I J u l y 12th . " " " IV January 2k. Small amounts of the s o i l samples were weighed f o r moisture and pH determinations. Remaining p o r t i o n s of s o i l s were a i r - d r i e d f o r 2k hours, then mixed thoroughly and passed through an 8-mesh s i e v e . 35 gram samples were used f o r garden and B-horizon s o i l s and 25 gram samples were used f o r duff m u l l , A-^  and raw humus s o i l s . lkO cc. of N/50 (NH^_)2 S0^ was added to garden and B-horizon s o i l s , and 100 cc. of N/50 ( N H ^ _ ) 2 SO^ to the other samples i n order to give approximately the same concentration of (NHj^) 2 S0^ per each gram of s o i l . Before p e r f u s i o n was .carried out each apparatus cont a i n i n g s o i l samples and perfusate was- weighed e x a c t l y to w i t h i n 0 . 1 gram. (See Appendix.) 66 A c o n t i n u a l temperature check was maintained throughout experiment. Every day, one hour before t a k i n g the samples f o r determination of ammonium and n i t r a t e s , each of the: sets was adjusted f o r evaporation w i t h s t e r i l e d i s t i l l e d water. 1.. Determination of N i t r a t e s  Reagents: (1) Sodium hydroxide, 1 N s o l u t i o n (2) Phenoldisulphonic acid 15>0 ml. of concentrated H,, S0^ i n f l a s k to which 2^ gm. of pure white phenol and 75> ml. of fuming SO, i s added. Mixture i s heated 2 1+ at 100°C f o r 2 hours, cooled and s t o r e d . (3) Standard n i t r a t e s o l u t i o n c o n t a i n i n g 10 g NO^-NitrOgen/ml. (1+) I O N NaOH - EDTA s o l u t i o n D i s s o l v e 15 gm. of disodium EDTA i n 8 0 0 ml. of water. Add 1+00 gm. of NaOH, c o o l and make to 1 l i t e r . Procedure: 1 cc. of leachate was p i p e t t e d i n t o a $0 ml. beaker to which 1 ml. of I N NaOH was added, the contents were eva-porated to dryness at low temperature and then 2 ml. of phenoldisulphonic reagent was introduced i n such a way as to coyer a l l the r e s i d u e . Then 20 ml. of HgO and 10 ml. of NaOH - EDTA s o l u t i o n was added and the mixture cooled Colour was read on an AC Model F i s h e r E l e c t r o -photometer at k25 m i l l i m i c r o n s ( f i l t e r l\.2$-B) . 2. Determination of Ammonium  Reagents: (1) Sodium tartrate- 1 0 # (.2) Nessler's reagent: k£.5 g. of mercuric i o d i d e . 35>-0 g. of potassium i o d i d e are di s s o l v e d i n a 1000 ml. f l a s k i n as l i t t l e water as p o s s i b l e . Then 112 g. of K0H i s added, mixed, cooled and d i l u t e d to volume. Reagent should be: allowed to stand a. few days before, u s i n g . (3) Gum Acacia s o l u t i o n 10 g. of gum acac i a i s d i s s o l v e d i n 195 ml of d i s t i l l e d H 2 0 and 3 ml. of Nessler's s o l u t i o n i s added. (k) Standard s o l u t i o n of ammonium having 10 g NH^- nitrogen/ml. Procedure: 1 cc. of leachate was p i p e t t e d i n t o a t e s t tub i n t o which the. f o l l o w i n g amounts of d i f f e r e n t s o l u t i o n s were added: 68 20 cc. of d i s t i l l e d H"20 1 cc. of Sodium t a r t r a t e 1.5 cc. of Nessle.r'.s reagent 0.5 cc. of gum a c a c i a g i v i n g a t o t a l volume of 2J4..OO cc. . A f t e r a l l o w i n g l5 minutes f o r f u l l c olour development, colour was read on AC Model F i s h e r Electrophotometer at jj.25 m i l l i m i c r o n s ( f i l t e r 1+25-B) . ( i i i ) R e s u l t s : A l l values p l o t t e d on the attached graphs are amounts of ammonium and n i t r a t e n i t r o g e n In g/ml. of leachage. Graphed values were obtained from standard curves f o r ammonium and n i t r a t e s of known con c e n t r a t i o n s . A l l p l o t t e d values are mean values of two simultaneous runs and four estimates (two estimates per s o i l sample). 69 ( i i ) R e s u l t s : Amounts of N i t r a t e s and Ammonium Present i n D i s t i l l e d Water Leachates o f D u f f mull and Raw humus S o i l s Date Duff m u l l Raw humus A-^  B NO3 NH+ NO3 NH+ NO3 NH^ NO^ NH^ A p r i l 10 1.0 - - 1.0 1.0 June l5 1 . 5 - " 1.0 1.0 June 16 1 .5 " " 1.0 2 .5 J u l y 2k - 1 .5 1.5 January 18 - 2.0 1 .5 February .6 0 .5 - • - 1-5 2.0 ( A l l values using 1 cc. of s o i l ) given i n ug/ml. of leachate, of d i s t i l l e d water per 1 gram to f o l l o w page 69 TEST Ho I . CURVES SHOWING THE DISAPPEARANCE OF AMMONIUM. T 4 6 TIMK IN DAYS O GARDEN SOIL DUFF MULL "A," RAW HUMUS to f o l l o w page 69 TEST No I CURVES SHOWING THE ACCUMULATION OF NITRATES, 1 H 1 1 1 2 ^ 6 & io TIME IN DAYS • - GARDEN SOIL • - DUFF MULL - "A," to f o l l o w page 69 TEST Ho I I CURVES SHOWING THE DISAPPEARANCE GP AMMONIUM. 20 -1 IS -3 \ 10 S3 e M 5 -T M- 6 TIME IN DAYS GARDEN SOIL DUFF MULL O - MA,M - RAW HUMUS - "B" to f o l l o w page 69 TEST No I I CURVES SHOVING T H E A C C U M U L A T I O N OF N I T R A T E S . T : 1 1—: 1 1 2 4 6 8 to T I M E I N DAYS • - GARDEN S O I L - D U F F M U L L - "A," to f o l l o w page 69 TEST No III CURVES SHO/v'ING T H E D I S A P P E A R A N C E O F A M M O N I U M . 2 0 i Z 4 6 & »0 T I M E I N D A Y S • - G A R D E N S O I L A - D U F F M U L L • - "A;1 A - RAW H U M U S to f o l l o w page 69 TEST No III CURVES SHOWING THE ACCUMULATION OP NITRATES T r 2. h TIME IN DAYS Q - GARDEN SOIL A - DUPE MULL • - "A," A - RAW HUMUS O - " B M to f o l l o w page 69 TEST No I V CURVES SHOWING THE DISAPPEARANCE OF AlHiONIUM. 2 0 N TIME IN DAYS • - GARDEN SOIL A - DUFF MULL • - "A? ^ - RAW HUMUS O - "B" to f o l l o w page 69 • GARDEN SOIL DUFF MULL "A" ( i i i ) D i s c u s s i o n : These f o u r consecutive t e s t s show a complete absence of n i t r i f i c a t i o n i n raw humus s o i l s and t h e i r sub-s o i l s eg. B-horizon. This absence of n i t r i f i c a t i o n i n raw humus and the u n d e r l y i n g s o i l horizonz cannot be explained by the unfavorable pH c o n d i t i o n s . S o i l s that l a c k n i t r i f y i n g a b i l i t y w i l l not acquire i t when t h e i r a c i d i t y i s co r r e c t e d . A l l samples of duff m u l l and A-j_ h o r i z o n s o i l s show f a i r l y a c t i v e n i t r i f i c a t i o n . Prom the graphs, one can conclude that r a t e s of n i t r a t e accumulation and ammonium disappearance vary l i t t l e w i t h season. Tests of d i s t i l l e d water leachates' of f r e s h l y c o l l e c t e d s o i l s have shown c o n s t a n t l y detectable amounts of n i t r a t e s i n duff m u l l and A-^  - horizon s o i l s . Only raw humus has shown e a s i l y detectable q u a n t i t i e s of ammonium i n d i s t i l l e d water leachates. 71 CONCLUSIONS 1. A study of n i t r i f i c a t i o n i n the' two humus hor i z o n s , duff m u l l and raw humus, has i n d i c a t e d a close dependence of the process on the e c o l o g i c a l nature of the s i t e . The r e s u l t s lend weight to attempts by e c o l o g i s t s and others to amplify and enlarge c l a s s i c a l s o i l d e s c r i p -tions, by an account of the bi o c o e n o t i c environment t h a t has given r i s e , to them. 2. The two d i s t i n c t i v e humus types, and the e q u a l l y d i s t i n c t i v e ecotypes from which they o r i g i n a t e , have t h e i r own c h a r a c t e r i s t i c m i c r o f l o r a and they, i n turn,, have d e f i n i t e counterparts i n the f l o r i s t i c . s t r u c t u r e of the higher p l a n t s . 3. The r e s p e c t i v e m i c r o f l o r a l p o p u l a t i o n s , t y p i c a l of the two d i s t i n c t i v e and most widely o c c u r r i n g humus types, duff mull and raw humus, vary i n t h e i r a b i l i t y to o x i d i z e ammonium. The r e s u l t a n t forms of n i t r o g e n are s p e c i f i c a l l y s u i t e d to the growth of c e r t a i n s p e c i e s , whether t r e e , shrub, or herb. k. In the raw humus type there are no p l a n t s s t o r i n g n i t r a t e s i n t h e i r leaves, whereas i n the duff m u l l type some p l a n t s store rather- l a r g e q u a n t i t i e s of n i t r a t e s i n t h e i r leaves. Among p l a n t s that store n i t r a t e s , there are some ( n i t r o p h i l o u s p l a n t s ) that may grow w i t h 72 lower v i g o r i n other h a b i t a t s and not stor e n i t r a t e s . Others, mainly those that s t o r e r e l a t i v e l y large q u a n t i -t i e s of n i t r a t e s , are incapable of m i g r a t i o n to other h a b i t a t s ( o b l i g a t o r y n i t r d p h y t e s ) . 5>. B a c t e r i a are present i n greater q u a n t i t y i n du f f m u l l than i n raw humus, which has a markedly higher number of f u n g i per u n i t weight. 6. Studies of n i t r i f i c a t i o n can be considered as an index of s o i l f e r t i l i t y and the s u i t a b i l i t y of a s o i l f o r tree growth. I t i s known, f o r i n s t a n c e , that D o u g l a s - f i r p r e f e r s n i t r a t e s - r a t h e r than ammonium s a l t s as a source of n i t r o g e n supply, whereas western hemlock e x h i b i t s no such preference-. 7. As most transformations of n i t r o g e n i n t o the forms required by p l a n t s take p l a c e i n the organic increment of any s o i l , any d r a s t i c changes i n the nature of the humus (by f i r e or other means of de s t r u c t i o n ) w i l l a l t e r the long e s t a b l i s h e d e q u i l i b r i u m i n the n a t u r a l n i t r o g e n c y c l e o f these f o r e s t ecosystems. BIBLIOGRAPHY 73 1. Allison, F.E., "Forms of Nitrogen Assimilated by Plants." Quart. Rev. Biol.. 6:313-321, 1931. 2. , "Availability of Fixed Ammonia in Soils Containing Different Clay Minerals." Soil Sci;. 21'373-381, 1953-3. , "Does Nitrogen Applied to Crop Residues Produce More Humus." Soil Sci. Soc. Amer. Proc . 19_: 210-211, 1955. 4. , and Roller, E.M., "Fixation and Release of Ammonium Ions by Clay Minerals." Soil Sci.. 80:431-441, 1955-5. Ambroz, Z., "The Microbiological Characteristics of Certain Site Tjppes of the Mjonsi Virgin Forest Reserve, Jablunka Mts." Sborn. esl. Akad. Zemed. (Ser.A)26(6), 514-524, 1953. 6. , "Results of Microbiological Studies of the Carbon and Nitrogen Cycles in Different Forest Soils." Sborn. esl. Akad.Zemed.. (Ser.A)27(5), 385-400, 1954. 7. Anderson, G.R., "Nitrogen Fixation by Pseudomonas-like Soil Bacteria." Jour. Bact.. 20:129-133, 1955. 8. Audus, L.J., "A New Soil Perfusion Apparatus." Nature. 158:419. 1946. 9. Barrit, N.W., Bichem. Jour.. 25: 1965, 1931. 10. Bernat, J., "Mykoflora lesnych pod." Preslia, 26(3):277-284, 1954. 11. Boquel, G., Kauffman, J., and Toussaint, P., "Investigation of the Influence of Climate and Vegetation on Microflora of Tropical Soils." Agron.Trop.Nugent.. 8:476-481, 1953. 12. Boswell, J.G., "The Microbiology of Acid Soils.IV. Selected Sites in Northern England and Southern Scotland." New Phytol.. 54:311-319, 1955. 13. , and Sheldon, J., "The Microbiology of Acid Soils." New Phytol.. 50:172-17.8, 1951. 7k 14. Bower, S., Soil Sci. Soc. Amer. Proc, 12:199, 1951. 15. Breed, R.S., Murray, E.G.D., and Hitchens, A.P., Bergey's Manual of Determinative Bacteriology. Williams and Williams, Baltimore, Maryland, 1948. 16. Bremner, J.M., "Some Soil Organic Matter Problems." Soils and Fert.. 19_:115, 1956. 17. Chase, F.E., and Baker, G., "The Comparison of Microbial Activity in an Ontario Forest Soil under Pine, Hemlock, and Maple Cover." Jour. Microb.. 1 :45-54, 1954. 18. , "A Preliminary Report on the Use of the Lees and Quastel Soil Perfusion Technique in Determining the Nitrifying Capacity of Field Soils." Sci. A g r i c . 28:315-320, 1948. 19. Collins, F.M., and Sims, CM., "A Compact Soil Perfusion Apparatus." Nature Lond.. 128:1073-1074, 1956. 2 0 . Cobb, M.J., "A Quantitative Study of the Microorganic Population of a Hemlock and a Deciduous Forest S o i l . " Soil Sci., 3J:325-345, 1932. 21. Division of Chemistry, Science Service, Dep. of A g r i c , Canada, "Chemical Methods of Soil Analysis." Issued: Febr., 1946, Revised: January, 1946. 22. Feher, D., and Frank, M., "Research on Geographical Distribution of Soil Microflora." Bot. Inst, of the Hungarian Tech. Univ. in Sopron, 1947. 23. Fisher, T., and Fisher, E.J., Bacter.. 64:596, 1952. 24. F i t t s , J.W. Bartholomew, W.V. and Heidel, H., "Predicting Nitrogen F e r t i l i z e r Needs of Iowa Soils: I. Evaluation and Control of Factors in Nitrate Production and Analysis." Soil Sci. Soc. Amer. P r o c . 12 :69-73, 1955. 25. Fogg, G.E., "Nitrogen Fixation by Blue-Green Algae." Endeavour, 6:172-175, 1947. 26. , "Nitrogen Fixation." New Biology. 18:52-71 , 1955. 27. Forest Soil Committee of the Douglas F i r Region, "Sampling Procedures and Methods of Analysis of Forest Soils." . Univ. of Washington, College of Forestry, Seattle, March, 1953* 75 28. Foster, J.W., "Chemical A c t i v i t i e s of Fungi." Hew York. Academic Press. 1949. 29. Fowler, G.J., "An Introduction to the Biochemistry of Nitrogen Conservation." 30. Fred, E.B., and Waksman, S.A., Laboratory Manual of General Microbiology. McGraw-Hill Book Company, Inc., 1928. 31. Geoghegan, M.J., and Brian, R.C., "Aggregate Formation i n S o i l s . " Jour. Bichem.. 4^ : 5 , 1948. 32. Goldberg, S.S., and Gainey, P.L., "Role of Surface Phenomena i n N i t r i f i c a t i o n . " S o i l S c i . . 80:43-53, 1955. 33* Hanway, J . , and Dumenil, L., "Use of Nitrates Production Together with other Information as a Basis for Making Nitrogen F e r t i l i z e r Recommendation for Corn i n Iowa." S o i l S c i . Soc. Amer. P r o c 19_:77-80, 1955. 34. Hamilton, P.B., Magee, W.E., and Mortenson, L.W., Bact. P r o c . 82, 1953. 35. Handley, W.R.C., Mull and Mor Formation In Relation to Forest S o i l s . Forestry Commission B u l l e t i n No. 23, London, 1954. 36. Hesselman, H., "Studier Over barrskogens humustMcke, dess egenskaper och beroende av skogsvarden." Medd.SkogsfOrskOsanst. Stockh., No. 22, I69, 1925. 37. , "Studier Over salpeterbildingen i n naturliga jordmaner." Medd.Fran.Stat.SkogsfOrsOksanstalt. 13-14, 1917. 38. Hutchinson, G.E., "Nitrogen i n the Biochemistry of the Atmosphere." Amer. S c i e n t i s t . 32:178-195, 1944. 39. Hutton, W.E., and ZoBell, C.E., B a c t e r i o l . . 216, 1953. 4 0 . Imsenecki, A., "Symbiosis Between Myxobacteria and N i t r i f y i n g Bacteria." Nature. 157:877. 1946. 41. Isaac, L.A., and Hopkins, H.G., "The Forest Soils of the Douglas F i r Region, and Changes Brought Upon i t by Logging and Slash Burning." Ecology. 18, 1937. 76 4 2 . Isenberg, H.D., et a l . , Bact. Proc. Soc. Amer. Bact., Annual Meeting, A b s t r . 4 1 , 1952. 4 3 . Jensen, H.L., "The Azotobacteriaceae." Bact.Rev.. V o l . 1 8 , No.4, December, 1954 . 4 4 . . Jour. Gen. Microb.. 5:360, 1 9 5 1 . 4 5 . Kalinenko, V.O., (Heterotrophic B a c t e r i a as N i t r i f i e r s . ) , Pochvovedenie. (Pedology), 3 5 7 - 3 6 3 , 1948 . 4 6 . Katznelson, H., and Chase, P.E., " Q u a l i t a t i v e Studies on S o i l Microorganisms; V I , Influence of Season on Treatment on the Incidence of N u t r i t i o n a l Groups of B a c t e r i a . " S o i l S c i ; . 5 8 : 4 7 3 . 1944 . 4 7 . , et a l . , " S o i l Microorganisms and the Rhizosphere." Bot.Revs.. 14 , No.9, 5 4 3 , 1948 . 4 8 . , and Stevenson, I.L., "Observation on A c t i v i t y of the S o i l M i c r o f l o r a . " Can.Jour, of Microb.. V o l . 2 , October, 1956 . 4 9 . Kojima, R.T., " S o i l Organic Nitrogen: I . Nature o f the Organic Nitrogen i n a Muck S o i l from Geneva, New York." S o i l S c i . . 6 4 : 1 5 7 . 1 9 4 7 . 50. K r a j i n a , V.J., " E c o l o g i c a l C l a s s i f i c a t i o n of Hemlock F o r e s t , Columbia R i v e r B a s i n . " Mim. Copy, September, 1953. ( U n i v e r s i t y of B.C.) 51. , and S p i l s b u r y , R.H., "The E c o l o g i c a l C l a s s i f i c a t i o n of the D o u g l a s - f i r F o r e s t on Vancouver I s l a n d . " In manuscript, 1952. 52. Lawrence, D.P., Lawrence, E.G., and Hu l b e r t , L., "Growth S t i m u l a t i o n of Adjacent P l a n t s by Older and Lupine on Recent G l a c i e r Deposits i n South-Eastern Alaska." Science, January, 1 9 5 1 . 53. Leland, E.W., "Nitrogen and S u l f u r i n the P r e c i p i t a t i o n at Ithaca N.Y." Agron. Jour.. 4 4 : 1 7 2 - 1 7 5 , 1945 . 54 . Lees, H., and Quastel, J.H., "Biochemistry of N i t r i f i c a t i o n i n S o i l . " Biochem.Jour.. 4 0 : 803, 1946 . 55. , "Biochemistry of N i t r i f i c a t i o n i n S o i l , I I , The S i t e of S o i l N i t r i f i c a t i o n . " Biochem.Jour.. 4 0 : 8 1 5 - 8 2 3 , 1946 . , "Biochemistry of Nit r i f i c a t i o n in S o i l , III, Nitrific a t i o n of Various Organic Nitrogen Compounds." Blochem.Jour.. 40^824-828, 1946. , "Effect of Copper Enzyme Poisons on Soil Nitrification.?' Nature. 158:97, 1946. , "The Soil Percolating Technique." Plant and Soil Sci.. 3:221, 1949. , "A Percolating Respirometer." Nature. 166:118, 1950. , "Isolation of Nitrifying Organisms from Soils." Nature. 167:355, 1951. Lochhead, A.G., and Thexton, R.H., "A Four Year Quanti-tative Study of Nitrogen Fixing Bacteria in Soils of Different F e r t i l i z e r Treatment." Can.Jour.of Res.. 14:166-177, 1936. , and Taylor, C.B., "Qualitative Studies of Soil Microflora." Can.Jour.of Res.. 16:152-161, 1938. , "Qualitative Studies on So i l Microflora: III. Influence of Plant Growth on the Character of the Bacterial Flora." Can.Jour.of Res.. 18:42-53, 1940. , and Chase, F.E., "Qualitative Studies on Soil Microflora: V. Nutritional Requirements of the Predominant Bacterial.Flora." Soil Sci.. H:185-195, 1943. , "The Nutritional Classification of Soil Bacteria." Proc.Soc. for Applied Bact.. Vol . 1 5 , No.l, 1952. Lochhead, A.G., "Soil Microbiology." Annual Rev, of Microbiology. 6:185, 1952. , and Roualt, J.W., "The Rhizosphere Effect on the Nutritional Groups of Soil Bacteria." Soil Sci. Soc. Amer. Proc. 19:48-49. , and Thexton, R.H., "Vitamin B12 as a Growth Factor for So i l Bacteria." Nature. 167:1034. 1951. Lutz, H.J. and Chandler, R.F., Forest Soils. New York, John Wiley & Sons Inc., 194oT 78 7 0 . Lyttleton Lyon, T., Buckman, H.O., and Brady, N.C., The Nature and Properties of Soils. F i f t h Ed. New York, The Macmillan Co., 1 9 5 5 . 7 1 . Marbut, CF., "The Relation of Soil Type to Organic Matter." Jour.Amer.Soc.Agron., 2 1 : 9 4 3 - 9 5 0 . 7 2 . Meyer, S. and Anderson, D.B., Plant Physiology. New York, D.Van Nostrand Co. Inc., 195FT 7 3 . Millbank, J.W., "Estimation of Numbers of Nitrosomonas in Soi l and Culture." Nature, 122:848-849, 1 9 5 6 . 7 4 . Mishustin, E.N., "Law of Zonality and Study of Microbial Associations in the Soils." Usp.Sovremennoi Biol. 3 7 , No.l, 1 - 2 1 , Bot.Cent. Document.3, 1954. 7 5 . Mitrofanova, N.S., "Change in Steppe S o i l Microflora under the Influence of Tree Plantation." MikrobioIogi.1a, Moskwa, 2 2 ( 3 ) , ( 2 7 5 - 8 0 ) , 1 9 5 3 . 7 6 . Munson, R.D., and Stanford, G., "Evaluation of Nitrates Productivity as a Criterion of Nitrogen Availability." S o i l Sci.Soc.Amer.Proc., 19_:464-468, 1 9 5 5 . 77. Muller,. P.E.., "Studier over Skovjord, Som Bidrag t i l Skovdyrkningens Theori: I, OM Btfgemuld og Bjrfgemor paa Sand og Ler." Tidsskr. Skov.brug. 3, 1, I 8 7 9 . 7 8 . Nelson, D.H.., "The Isolation of Nitrosomonas and Nitrobacter by the Single Ce l l Technique." Science, Vol. LXXI, No.1847, 541-42, 1 9 3 0 . 7 9 . Nicol, H., Microbes and Us. Penguin Books Ltd., TCanada), 1 9 5 5 . 8 0 . Nikiforoff, CC., "Soil Organic Matter and Soil Humus.", Yearbook of Agriculture. U.S. Dep. of A g r i c , U.S. Govern.Print.Office, 1 9 3 8 . 8 1 . Norman, A.G., Advances in Agronomy. Volume 1, 8 2 . Oginski, E.L., and Umbreit, W.W., An Introduction to Bacterial Physiology. W.H. Freeman and Company, San Francisco, 1954. 8 3 . Perhman, D., "Physiological Studies on the Actinomycetes." Bot.Rev., Vol.19, No.l, January, 1 9 5 3 . 79 84. P f e i l , W., "Die Deutsche Holzzucht begrundet auf der Eigentumlichkeit der Forstholzer und ihr Verhalten zu dem verschiedenen Standorte", i860. 85. Plice,.M.J., "The Bionomics of Some Forest Soils." S o i l Sci. Soc. Amer. Proc. 4:346-352, 1939. 86. Porter, J.R., Bacterial Chemistry and Physiology. Wiley, New York, 1946. 87. Powers, W.L., and Bollen, W.B., "The Chemical and Biological Nature of Certain Forest Soils." Soil Sci.. 40:321-329, 1935. 88. Prianishnikow, D.N., trans, by S.A. Wilde, Nitrogen in the Life.of Plants. Kramer Business Service, Inc., Madison, Wis., 1950. 89. Quastel, J.H. and Schdefield, P.G., "Influence of Organic Nitrogenous Compounds on Nitr i f i c a t i o n in S o i l . " Nature. 164:1069, 1949. 90. _ , Scholefield, P.G., and Stevenson, J.W.,. "Oxidation of Pyruvic Oxime by Soil Organisms." Nature..166: 940-942, 1950. 91. Raunkiaer, B., "Nitratinholdet has Anemone nemorosa paa forskellige Standpladser. Det.Kgl.Dauske Videnskab. Selskab. Biol.Medd. 5, 1926. 92. Romell, L.G., "Ecological Problems of the Humus Layer in the Forest." Cornell Univ. Agric. Exp. Station Memoir, 170, 1935-93« » and Heiberg, S.O., "Types of Humus Layer in the Forest of Northeastern United States." Ecology, 12:567-608, 1931. 94. Rose, R.E., "The Soil.Perfusion Apparatus in Soil Micro-biological Studies." Sci.Rev.,.14:121-122. 1956. 95. Rost, CO., at a l . , "Some Properties of the Black Praries Soils of Minnesota." Proc.Soil Sci. Soc.Amer.. 8:388-395, 1943. 96. Russell, J.E., Soil Conditions and Plant Growth, Eight Ed., Longmans, Green & Co., 1950. 97. Schreiner, 0. and Brown, B.E., "Soil Nitrogen." Yearbook of Agriculture. U.S. Dep. of A g r i c , 1938. 98. Scott-Wilson, H.W., Aids to Bacteriology. Ba i l l i e ' r e , Tindall and Cov, London, 1952. 99. Scott, G.D., "Further Investigations of Some Lichens for Fixation of Nitrogen." New Phytol.. _\111-116, 1956. 100. Schmidt, E.L., "Nitrate Formation by a Soil Fungus." Science. 112:187-189, 1954. 101. Shibamato Takeo, F e r t i l i z i n g Forest Lands. Forest and Estate Mut. Foundation, Tokyo, Japan, 1957. 102. Site Evaluation Committee, Forest Soil Research, "Abstracts and Citations of Literature Published in the U.S.A." 103. Society for General Microbiology, Microbial Ecology"! Seventh Symposium held at the Royal Institution, London. Cambridge University Press, 1957* 104. Starkey, R.L., "Some Influences of the Development of Higher Plants upon the Microorganisms in the Soil:I. Historical and Introductory." Soil Sci.. 22:319, 1929. 105. , "Effects of Plants upon Distribution of Nitrates." Soil Sci.. 22:395, 1931. 106. Stanford, G. and Hanway, J., "A Simplified Technique for Determining Relative Nitrate Production in Soils." S o i l Sci. Soc.Amer.Proc.. 1^:74-77, 1955. 107. Stephenson, R.E., "Nitrification and Plant Nutrition." Soil Sci.. 41:187-197, 1936. 108. Stevenson, I.L., "Microbial Examination of Soils." Soil Sci.. 25:255, 1936. 109. Stiven, G., "Production of Antibiotic Substances by the Roots of Grass." Nature. London, 120:712-713, 1952. 110. Timonin, M.I., "The Interaction of Higher Plants and Soil Microorganisms." Can.Jour.of Res.. 18:307, 1940. 111. Tove, Shirley, R., Niss, H.F., and Wilson, P.W., "Fixation of Nl5 by Excised Nodules of Leguminous Plants." Jour.Biol.Chem., 184:77-82, 1950. 81 112. Waksman, S.A., Principles of Soil Microbiology. Second Edition, Baltimore, The Williams & Wilkins Co., 1932. 113. , "Chemical Nature of Soil Organic Matter, Methods of~Analysis, and the Role of Microorganisms in its Formation and Decomposition." Soil Sci.. 40:347-364, 1935. 114. , Humus, Second Edition, Baltimore, The Williams & Wilkins Co., 1938. 115. , and Starkey, R.L., The Soil and the Microbe. New York, John Wiley & Sons, Inc., 1 9 4 9 . 116. , Actinomycetes. Chronica Botanica Co., Waltham, Mass., 1950. 117. y , Soil Microbiology. John Wiley & Sons, Inc., New York, 1952. 118. Werkman, CH. and Wilson, P.W., Bacterial Physiology. Academic Press Inc. Publishers, New York, 1951. 119. Wilde, S.A., Forest Soils. Second Edition, Kramer Business Service Inc., Madison, Wise, 1942. 120. , Forest Soils and Forest Growth. Chronica Botanica Co., Waltham, Mass., 1946. 121. , and Voigt, G.K., Analysis of Soils and Plants for Foresters and Horticulturists. J.Ytf. Edwards, Publishers, Inc., Ann Arbor, Michigan, 1955. 122. Wilson, P.W., The Biochemistry of Symbiotic Nitrogen Fixation. The University of Wisconsin Press, Madison, 1940. 123. Vandecaveye, S.C., and Baker, G.O., "Microbial Activity in S o i l . III. Activity of Specific Groups of Microbes in Different Soils." Soil Sci.. 45:315, 1938. 124. , and Katznelson, H., "Microbial Activities in S o i l . IVT Microflora of Different Zonal Soil Types Developed Under Similar Climatic Conditions." Soil Sci.. 46:57, 1938. 125. , and Katznelson, H., "Microbial Activities in So i l . V. Microbial Activity and Organic Matter Transfor-mation in Palouse and Helmer Soils." Soil Sci.. 46:139, 1938. APPENDIX 82 LIST OF TABLES ATTACHED Table Nitrogen in Agricultural Soils I. Nitrogen Content of Soil Humus II. C/N Ratio of Soils III. Quantities of Nitrogen Fixed by Leguminosae and Rhizobia IV. Quantities of Nitrogen Fixed by Non-symbiotic Bacteria V. Quantities of Nitrogen in Precipitation VI. C/N Ratio of Forest Soils VII. Nitrogen Content of Forest Litter VIII. TABLE I. NITROGEN IN CERTAIN AGRICULTURAL SOILS 83 Soils % Nitrog. Ref. Marbut (1929) Prairies: Surface up to 6 inch. 0.05-0.15 (71) Depth up to 40 " 0.12 averag. Chernozem: Surface up to 6 inch. 0.15-0.30 (71) Depth up to 40 " 0.12 averag Rost (1943) Prairie soils (Minnesota) 0.17-0.35 (95) Average value 0.266 Dep. of Agric. Majority of agricultural (21) Canada (1949) soils in Canada 0.10-0.50 Peats and mucks 1.00-2.00 TABLE II. NITROGEN CONTENT OF SOIL HUMUS Soils % Nitrogen Ref. in humus Zacharow Russian soils (given as total range) 4.48-8.49 (114) Waksman American soils(given as total range) 2.57-8.03 (113) Allison Average value for agric. soils 5.5 (3) Undecomposed crop residue, (wheat and corn straw) 0.50-1.00 (3) TABLE III. 8k C/N RATIO OF SOILS AND CERTAIN ORGANIC RESIDUES C/N Ratio Ref. Lyttleton Lyon, Buckman arid Brady, (1952) Waksman (194-9) Deherain (1902) Stewart (1910) McLean (1930) Leighty (1930) Waksman (1952) Organic matter of the furrow-slice of arable soils . 10-12/1 (70) Plant material (Legumes) 20-30/1 Farm manure up to 90/1 Microorganisms 4-9/1 ( i t is narrower for bacteria and wider for fungi) Fungi (average) Bacteria (average) Actinomycetes (average) Cultivated soils of France Brown s i l t loam soils of I l l i n o i s : - surface - subsoil 10/1 (115) 5/1 6/1 9.5/1 (114) 12.1/1 8.9/1 Average for f i f t y British soils Most frequent range for sixty-three American soils: - surface - subsoil 10.0/1 8.5-11.4/1 (96) 5.5- 8..4/1 Average for sixteen cherno-zem soils (Alberta) 10/1 (117) Average for twenty-one cherno-zem soils (Manitoba) 11/1 Average for eighteen brown soils (Saskatchewan) 11/1 TABLE IV. QUANTITIES OF NITROGEN FIXED BY LEGUMINOSAE AND RHIZOBIA 85 N in lb/acre Ref. Lyttleton Lyon, Average crop of al f a l f a 200-250 (70) Buckman, and Brady (1952) " " " red clover 100-150 Mayer (1955) Good crop of a l f a l f a 400 (72) Nicol (1955) Good crop of lucerne 100 (79) Legume nodule bacteria 40-50 TABLE V. QUANTITIES OF NITROGEN FIXED BY NON-SYMBIOTIC BACTERIA Amount fixed Ref, Wilson (195D Waksman (1952) Jensen (1954) Waksman (1952) Lochhead Azotobacter in optimal conditions: 100-150 mg/ml in 24 hours. (122) Clostridium spp. Azotobacter Azotobacter 15-20 mg/per 1 gram carbohydrates. 10-12 mg/per 1 gram carbohydrates. 10 mg/per 1 gram (117) carbohydrates 15-16 mg/per 1 gram (43) carbohydrates Butyric bacteria In pure cultures: 2-3 mg/per 1 gram (117) carbohydrates Bact. asterosporus (facultative anaerobe): ~~ 1-3 mg/per 1 gram carbohydrates (Clostridium spp. when freshly isolated f i x more than Azotobacter) CI. pasterianum approaches Azotobacter in some cases. (66) 86 TABLE VI. QUANTITIES OF NITROGEN IN PRECIPITATION Nitrogen lb/acre/year Ref. Shutt (1917) Miller (1949) Leland (1949) Meyer and Anderson (1955) Lyttleton Lyon, Buckman, and Brady Fogg Nicol (1955) (1955) Average for 10 years for neighborhood of Ottawa, for 23.39 inch/year 6.583 Rain contains NH3, NO3 4.00 Average for 1931-49 for Ithaca N.Y., for 35.55 inch/year -NH3 4.02 - N O 3 1.25 Quotes data taken for 5 years in Rothamsted Exper. Stat. 4.4 Quoting a number of data gives an average 5«0 Rain may supply in average 1.0 In temperate climates the rain contributes about (41) (95) (53) 4.0 (72) (70) (26) (79) TABLE VII C/N RATIO OF FOREST SOILS 87 C/N Ratio Ref. Waksman Minnesota forest 19/1 (117) Alpine soils 9.7-34/1 Isaac and Douglas F i r Region (Pacific Hopkins Northwest): - average for duff (cut-over area) 57/1 (41) - mineral soils at depth of: G - 3 inches 27/1 3 - 6 " 24/1 6 - 1 2 " 22/1 12 - 3 0 » 21/1 - adjoining old-growth timber area: for duff mull 52/1 for rotten log 171/1 (common C/N ratio for agricultural soils) 10/1 TABLE VIII NITROGEN CONTENT OF FOREST LITTER Isaac and" Hopkins "Douglas Fir~RegTon (Pacific Northwest) - average for duff (cut-over area) - average for old growth timber area Surface 8-inch layer of virgin forest s o i l Nitrogen % ppm. Ref. Wilde 0 . 9 2 $ 0 . 8 7 $ 0.1-0.3$ (content of nitrates seldom exceeds 20 ppm. (content of ammonia may accumulate up to 7 0 ppm. (41) (119) 88 LIST OF FIGURES ATTACHED Figure Perfusion Apparatus . I. Set of Perfusion Apparatuses in Work . . . . II. Perfusion Apparatus Prepared for Weighing . . III. Pseudotsuga menziesii - Thu.ia plicata -Polystichum munitum association with duff mull humus IV. " " V. " " " » VI. Pseudotsuga menziesii - Tsuga heterophylla - Gaultheria shallon association with raw humus VII. " " " " VIII. " « » " IX. 89 t& of c o n t r o l dnd a d j u s t m e n t . A - Control o£ perfusate . B,C- Control oJ dir j"l P - Main riscrvoir. S - Soi I tuba- . T - B y - p a . * s t u b a . PERFUSION APPARATUS, SET OF PERFUSION APPARATUSES AT WORK. o Fie. I l l 91 P E R F U S I O N APPARATUS PREPARED FOR WEIGHING. Polvstichum muni-turn. Thuja p l i c a t a . Satabucus pubens Pseudotsuga m e n z i e s i i . Thu.ia p l i c a t a . Saoibucus pub ens. Rubus s p e c t a b i l i s . Rubus p a r v i f l o r u s . Polystichum muniturn Pseudotsuga m e n z i e s i i . Polystichum muniturn. Rubus p a r v i f l o r u s . Gaultheria shallon. Tsuga h e t e r o p h y l l a . Pseudotsuga m e n z i e s i i (stump), Thuja p l i c a t a , Cornus n u t t a l l i i , G a u l t h e r i a s h a l l o n , Vaccinium p a r v i f o l i u m , Vaccinium o v a l i f o l i u m , P t e r i d i u m a q u i f o l i u m . vo ON Tsuga h e t e r o p h i l s , Pseudotsuga m e n z i e s i i (in the background), G a u l t h e r i a s h a l l o n , Vaccinium P a r v i f o l i u m . 

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