Organic compounds in cryofolists developed on limestone under subalpine coniferous forest, Bavaria

Geoderma, 36 (1985) 145--157

145

Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

ORGANIC COMPOUNDS IN CRYOFOLISTS DEVELOPED ON LIMESTONE UNDER SUBAI~INE. CONIFEROUS FOREST, BAVARIA

R. BOCHTER and W. ZECH

Institute of Soil Science, University of Bayreuth, Postfach 3008, D-8580 Bayreuth (Federal Republic of Germany) (Received July 30, 1984; accepted after revision June 14, 1985)

ABSTRACT

Bochter, R. and Zech, W., 1985. Organic compounds in cryofolists developed on limestone under subalpine coniferous forest, Bavaria. Geoderma, 36:145--157. Five Lithic Cryofolists in the Nationalpark Berchtesgaden, southern Bavaria were studied. The soils have organic layers with total thicknesses between 2.5 and 63 cm, which directly overlie limestone. The site is occupied by a subalpine mixed needle forest (Picea abies, Larix decidua). According to the profile structure and the sequence of organic horizons, four different terrestrial humus types are distinguished: Mullmoder (L + O: 2.5 cm), Moder (L + O: 7.5 cm), Mor (L + O: 20 cm), and Tangelmor (L + O: 34 and 60 cm). In the Mullmoder, above-ground litter is the predominant source of organic substances, which are mineralized or transformed with depth, as shown by the decrease of lignin and cellulose. Microbes are believed to exert a decisive influence on these processes. Moder profiles are intermediate between Mullmoder and Mor or Tangelmor. In contrast to Mullmoder, Mor derives an important share of humus from root residues in addition to leaves and needles. In Mor and Tangelmor profiles, which differ from each other only in total thickness of organic layers (Tangelmor > 30 cm), two sections may be clearly distinguished. In the first section (as in Mullmoder), above-ground residues are transformed and the changes are attributed to microbial activities. In the second section, which is composed of densely aggregated O layers, root residues are dominant as the organic parent materials. Independently of the humus-type, all the Lithic-Cryofolists have a special horizon immediately above the chalky bedrock where mobile organic matter has been precipitated by calcium. This process is reversible and seems completely unaffected by microorganisms. Concentrations of undecomposed litter in these special horizons is very low.

INTRODUCTION A c c o r d i n g t o Soil T a x o n o m y ( S o i l S u r v e y S t a f f , 1 9 7 5 } , softs c o m p o s e d o f o r g a n i c m a t e r i a l r e s t i n g d i r e c t l y o n b e d r o c k are c l a s s i f i e d as F o l i s t s , if t h e soils are n e v e r s a t u r a t e d w i t h w a t e r f o r m o r e t h a n a f e w d a y s e a c h y e a r . D u r i n g e x t e n s i v e s t u d i e s o f soil d e v e l o p m e n t a t r e l a t i v e l y v i r g i n f o r e s t sites in the Nationalpark Berchtesgaden (Federal Republic of Germany}, Bochter

0016-7061/85/$03.30

© 1985 Elsevier Science Publishers B.V.

146

{1983) found that Lithic Borofolists, as well as Lithic Cryofolists, were widespread on limestone. The ages of single profiles, the processes forming the O-R-contact horizon {Oh, Ca) and problems arising from the integration of these soils into the German soil classification system have been reported elsewhere (Bochter, 1984a, b). The purpose of this paper is to present the differences in selected organic compounds with depth in five Lithic Cryofolists whose organic layers are 2.5 to 63 cm thick. M A T E R I A L S AND M E T H O D S

The research area is located in the Nationalpark Berchtesgaden, southern Bavaria {Fig. 1). The soils were developed on rock-slide-blocks of Dachsteinkalk, a very pure (> 99% CaCO3) and hard limestone. The site {1400 m a.s.l., N-aspect) is occupied by an open, mixed needle forest (Picea abies, Larix decidua) with dense shrub undergrowth of Vaccinium myrtillus, V. vitis-idaea, and Rhododendron hirsutum.

<~ VIENNA • MUNICH

~,,,_~'~

Alpennationalpark Berchtesgaden

~

Fig. 1. L o c a t i o n o f t h e research area.

Because all profiles must be classified as Lithic Cryofolists, the humus type designations of Bochter (1983) are introduced as relevant and pertinent features for additional characterization of these organic soils. He defines individual humus types by the sequence of L and O subhorizons as shown in Table I for the humus types Mullmoder {profile 1), Moder {profile 2), and Mor (profile 3). If L and O layers together attain a thickness of at least 30 cm, the prefix "Tangel" is added (Tangelmor, profiles 4 and 5). The symbols for layers and horizons (Table I) are defined as follows (for detailed definitions, see Bochter, 1984b):

147

(1) L: > 90% (by volume) of above-ground plant residues, no roots. (a) Ln: (n = new) freshly fallen unaggregated litter. (b) Lv: (v = varied, altered) aged unaggregated litter, still transportable by wind. (c) Ld: (d = dense} litter pressed into dense packages consisting of at least five individual leaf or needle layers; packages are easily separated from the underlying O-horizon. (2) O: < 90% (by volume) of leaf or needle residues. (a) Of: 50--90% above-ground plant residues. (b) Ohf: 30--50% above-ground plant residues. (c) Ofh: < 30% above-ground plant residues but plant residues still identifiable with the naked eye. (d) Oh: above-ground plant residues no longer distinguishable. (e) Odf, Odhf, Odfh, Odh: (d = dense), same as Of, Ohf, Ofh, Oh but in addition densely aggregated, i.e. material may be cut into sharp-edged stable fragments using a knife and has the following chemical properties: pH < 4.0 and MnE 50 I.tg/g (MnE = EDTA-extractable Mn). (f) Oh, Ca: (Ca = EDTA-extractable calcium) black horizon in contact with chalky bedrock and with the following chemical properties: pronounced TABLE I Morphological characterization of the profiles: Lithic Cryofolists on Dachsteinkalk under subalpine c o n i f e r o u s f o r e s t (see t e x t f o r q u a l i t a t i v e a n d q u a n t i t a t i v e d e f i n i t i o n s o f o r g a n i c h o r i z o n s ) Layer

Thickness (cm)

Aboveground

plant residues (% b y volume)

Lvd

Living roots (% b y volume)

Dead coarse roots (=>1 c m ) (% b y volume)

1

99

0

Of

1

60

2

0

Ofh,Ca

0.5

10

5

0

R

0

1. M u l l m o d e r Unaggregated (50%) or dense packages (50%) of g r e y - b r o w n u n b r o k e n n e e d l e s o f Picea abies and L a r i x decidua; t r a c e s o f f a e c a l p a r t i c l e s ( ~ 1 m m ) ; b l a c k m y c e l / u m o f H e r p o t r i c h i a nigra. Half broken, half unbroken dark grey needles, fine s u b s t a n c e in 0 . 5 - - 3 m m p a r t i c l e s . Black particles (1--3 mm), dark-gzey needle fragments.

bedrock(limestone)

Lv

0.5

100

0

0

Ld

1.5

99

0

0

Of

2

60

20

0

Ohf

2

40

40

0

Ofh,Ca

1.5

10

20

0

R

Additional description

bedrock (limestone)

2. M o d e r L e a v e s o f R h o d o d e n d r o n h i r s u t u m a n d Vaccin i u m vitis-idaea (SO%), b r o w n , u n b r o k e n n e e d l e s o f Picea abies a n d Larix deeidua ( 2 0 % ) . G r e y - b r o w n p l a n t r e s i d u e s : 5 0 % s h r u b leaves ( 1 / 4 as s k e l e t a l f r a g m e n t s ) , n e e d l e s u n b r o k e n . U n b r o k e n n e e d l e s ( 5 0 % ) a n d ( 1 0 % ) s h r u b leaves (2/3 skeletal fragments); dark-brown fine subs t a n c e in 0 . 5 - - 2 m m p a r t i c l e s . D a r k g r e y n e e d l e s ( 1 / 2 as f r a g m e n t s ) ; fine s u b s t a n c e s a m e as in Of. B l a c k fine s u b s t a n c e ( p a r t i c l e s 1 - - 3 r a m ) ; n e e d l e fragments.

148 TABLE I (continued) Layer

Thickhess (cm)

Aboveground plant residues (% b y volume)

Living roots (% b y volume)

Dead coarse roots (>1 em) (% oy volume )

Lv

1

100

0

0

Ld

2

95

0

0

Of

2

70

10

0

Odhf

3

40

2O

0

Odfh Odh

4 5

10 0

20 10

0 20

Oh,Ca

3

0

10

0

100

0

0

Additional description

3. M o r L e a v e s o f V a c c i n i u m myrtillus ( 8 0 % ) , b r o w n u n b r o k e n n e e d l e s of Picea abies a n d Larix decidua ( 2 0 % ) ; t r a c e s o f H e r p o t r i c h i a nigra. V a c c i n i u m leaves (25%, 2 / 3 as s k e l e t a l fragments), unbroken needles (70%); grey brown. Only u n b r o k e n dark grey needles; dark b r o w n f i n e p a r t i c l e s (<:0.5 r a m , r a r e l y to 1 r a m ) . D a r k - b r o w n fine p a r t i c l e s (<:0.5 r a m ) ; n e e d l e fragments. S a m e as O d h f . Dark-brown to reddish-brown fine p a r t i c l e s

(<:0.5 m m ) . R

mm), partly subangular-

bedrock (limestone)

Lv

0.2

Ld

1

95

0

0

Of

1

60

5

0

Odhf

2

30

20

0

Odfh

1.5

10

2O

0

Odhl

8

0

IO

0

Odh2 Odh3 Oh~Ca

8 8 6

0 0 0

0 0 20

10 20 0

R

Black particles (0.5--3 blocky aggregated.

4. T a n g e l m o r U n b r o k e n n e e d l e s ( 5 0 % ) o f Picea abies a n d Larix decidua, leaves ( 5 0 % ) o f V a c c i n i u m myrtillus ( 2 / 3 as s k e l e t a l f r a g m e n t s ) ; b r o w n ; t r a c e s o f H e r p o triehia nigra. Grey-brown u n b r o k e n needles (90%) and skeletal f r a g m e n t s o f s h r u b l e a v e s (5%); t r a c e s o f fine particles (<:0.5 m m ) ; m y c e l i u m of H e r p o t r i c h i a nigra. D a r k g r e y n e e d l e s ( 1 / 2 as f r a g m e n t s ) , b r o w n f i n e p a r t i c l e s (<:0.5 r a m , r a r e l y to 1 r a m ) . B r o w n to r e d d i s h - b r o w n fine p a r t i c l e s (<:0.5 r a m , n e e d l e f r a g m e n t s ; y e l l o w i s h m y c e l i u m o f Cort i t i u m bicolor (5%). R e d d i s h - b r o w n f i n e s u b s t a n c e ( p a r t i c l e s <: 0 . 5 ram), needle fragments; traces of Cortitium bicolor R e d d i s h - b r o w n fine s u b s t a n c e , single p a r t i c l e s <:0.5 m m . S a m e as O d h l . S a m e as O d h l . Black f i n e s u b s t a n c e in 1--3 m m p a r t i c l e s , p a r t l y subangular-blocky aggregated.

bedrock (limestone)

Ln

0.1

100

0

0

Lv

0.5

100

0

0

Ld

1

95

0

0

Of

0.5

60

10

0

Odhf

4

30

30

0

Odfh

4

10

50

0

Odhl

10

0

50

0

Odh2 Odh3 Odh4 Odh,Ca

10 10 15 8

0 0 0 0

10 0 0 20

20 10 10 0

R

b e d r o c k (Limestone)

5. T h i c k Tangelrnor O n e l a y e r o f u n b r o k e n V a c c i n i u m myrtillus leaves; b r o w n , p a r t l y g r e e n . V a c c i n i u m leaves (70%, 1 / 2 a s s k e l e t a l f r a g m e n t s ) , u n b r o k e n n e e d l e s o f Picea abies a n d Larix decidua ( 3 0 % ) ; b r o w n . G r e y - b r o w n u n b r o k e n needles (75%), skeletal f r a g m e n t s o f s h r u b leaves ( 2 0 % ) . D a r k g r e y n e e d l e s ( 1 / 4 as f r a g m e n t s ) , t r a c e s of leaf s k e l e t o n s ; fine s u b s t a n c e in 0 . 5 - - 1 m m particles. D a r k - g r e y n e e d l e f r a g m e n t s ; r e d - b r o w n fine subs t a n c e (single p a r t i c l e s <:0.5 r a m ) . As O d h f , t r a c e s o f t h e y e l l o w i s h m y c e h u m o f C o r t i t i u m bicolor. R e d d i s h - b r o w n fine p a r t i c l e s <:0.5 r a m ; t r a c e s o f Cortitiurn bicolor. R e d d i s h - b r o w n fine p a r t i c l e s <:0.5 r a m . S a m e as O d h 2 . S a m e as O d h 2 . Black particles (0.5--1 ram), partly subangularblocky aggregated.

149 T A B L E II A d d i t i o n a l c h e m i c a l c h a r a c t e r i z a t i o n of t h e profiles: L i t h i c C r y o f o l i s t s o n D a c h s t e i n k a l k u n d e r s u b a l p i n e c o n i f e r o u s f o r e s t ( n o n e o f t h e h o r i z o n s c o n t a i n s (CaCO3)

Layer

Corg

(%)

1. Mullmoder Lvd 48 Of 45 Ofh,Ca 41

TFA-hydrolyzable = noncellulosic polysaccharides (%)

Ca E (rag/g)

glu

man

xyl

gal

arab

4.0 4.0 3.0

3.8 3.6 1.8

2.1 2.1 0.8

3.9 3.6 2.1

3.6 2.8 1.4

13 25 37

2.Moder Lv Ld Of Ohf O~,Ca

48 47 44 47 41

5.5 4.2 4.9 5.2 5.1

2.0 1.6 1.9 1.6 1.5

2.4 1.6 1.6 2.1 1.9

4.2 2.7 2.8 2.5 2.0

2.5 1.9 1.9 1.1 1.2

15 19 19 13 27

3. Mor Lv Ld Of Odhf Odfh Odh Oh,Ca

50 50 49 49 47 50 40

4.6 5.2 6.4 7.4 7.3 6.4 4.4

3.6 2.7 3.5 3.2 2.1 1.9 1.2

2.2 1.9 2.5 2.2 1.7 1.5 0.8

2.8 2.9 3.3 3.1 2.3 2.1 1.5

1.6 2.2 2.1 1.5 0.9 0.6 0.6

4 5 6 5 7 10 35

3.6 4.8 4.1 5.0 5.0 5.0 4.6 4.5 3.8

1.5 2.5 1.8 2.2 2.0 2.2 1.8 1.5 1.1

3.2 3.3 1.5 1.8 1.8 2.0 1.9 1.5 0.8

2.0 3.5 2.2 2.6 2.6 2.2 1.9 1.6 1.2

1.8 2.0 1.5 0.8 0.7 1.0 0.5 0.4 0.3

4 6 6 4 4 6 8 9 29

6.7 5.0 4.5 4.4 4.5 4.7 4.7 4.3 3.7 3.6 3.0

2.7 1.9 2.3 2.2 2,1 2.1 2.2 1.9 1.2 1.1 1.0

3.0 3.3 2.9 2.1 2.0 1.9 1.9 1.8 0.7 0.6 0.7

3.5 2.6 2.8 2.6 2.1 1.9 2.O 1.8 1.2 1.0 1.0

1.7 1.7 2.0 1.9 1.5 1.0 O.9 0.9 0.7 0.7 0.9

2 5 6 5 4 6 6 6 8 11 26

4. Tangelmor Lv Ld Of Odhf Odfh Odhl Odh2 Odh3 Oh,Ca

50 49 49 49 50 49 49 49 44

5. Thick Tangelmor Ln Lv Ld Of Odhf Odfh Odhl Odh2 Odh3 Odh4 Odh,Ca

49 50 50 50 49 49 49 51 53 51 46

150 maxima in the depth functions of mobile (= oxalate-extractable) organic matter (Co) as well as EDTA-extractable Ca (Ca E ). (g) Ofh,Ca: as Oh,Ca but above-ground plant residues still identifiable (< 30%). As far as possible, samples were freed from coarse branches and living roots in the field. After air-drying (25°C), they were ground to < 0.75 mm in a sieve mill. The following techniques were used to analyse the samples to obtain the data in Table II: Corg, Nt, pH and mobile (= oxalate-extractable) organic matter (Co) were determined according to Schlichting and Blume (1966). EDTA-extractable cations were obtained by the method of Farmer et al. (1980). After extraction with ethanol-H20 (1:1 v/v; 1 g/20 ml, shaking time 16 h), free ninhydrine-positive-N (free Nin-N) was determined according to Stevenson and Cheng (1970). Lignin was extracted with dioxane/ H20 (100/4) and analysed semiquantitatively by phloroglucinol/HC1 (Bochter, 1981). Non-cellulosic polysaccharides (hemicellulose, pectic substances, microbial polysaccharides, etc.) were hydrolyzed 2 h by 2 N trifluoroacetic acid (TFA) at 120°C and total polysaccharides by treatment with 72% H2SO4 for 16 h at room temperature and after dilution to 2 N H2SO4 by boiling at 100°C for 5 h. Monosaccharides (gal = galactose, glu = glucose, man = mannose, arab = arabinose, xyl = xylose) were determined by highperformance, thin-layer chromatography (HPTLC). The cellulose content was calculated by the difference glut - glUTFA. For details of sugar hydrolysis and determination see Bochter (1984a). RESULTS AND DISCUSSION The chemical analyses are presented in Table II and Figs. 2--6.

Mullmoder In the Mullmoder (profile 1, Table I, Fig. 2) cellulose decreases markedly from the Lvd {8.5%) to the Of (1.9%) and Ofh,Ca (0.5%) layers. On the other hand, for glUTFA (derived from non-cellulosic polysaccharides) only a slight decrease occurred (Lvd and Of: 4.0%; Ofh,Ca: 3.0%). The same is true for other TFA-hydrolyzed monosaccharides (Table II). Apparently cellulose, which is the major constituent of the secondary wall at the surface of the cell wall, is quickly attacked. Only part of the cellulose is completely decomposed; the remainder is transformed into oxycellulose (Blume, 1966). This oxycellulose portion can be hydrolysed by T F A {Bochter, 1984a) and thus appears as glUTFA. The mycelia ofHerpotrichia nigra (Table I) loosely connect the needle litter of the L horizon. Such saprophytic fungi excrete cellulases (Mirchink and Demkina, 1977). This may explain the marked decrease of cellulose from Lvd to Of horizons. When compared with cellulose, the decomposition of hemicellulosic sugars is delayed, be-

151

cause the hemicellulosic components of the primary cell wall can be attacked only after the secondary cell wall of cellulosic components is partially or completely removed. Similar results were reported earlier by Babel (1972) from microscopic examination of organic materials. {35

1,0

J

1,5

I

~/oNt

3,0

4,0

5,0

60

pH

I

. . . . . . .. -. '~pH Co " ' - - ~ . ~

o,,,c°i

....;:.:: 100 10 I

" ......... 200

30 I

300 50 I

pg/g freeNin-N 7L0~bcellulose,01UTF A

5'0

100 50 I

150 100 I

ABSx1000/g CO hgnin 150ABSx1000/gh ~W

Of orb,Ca

/

,,"glu TFA

2'0

3~

4~

c/N

Fig. 2. Depth functions of profile 1 : Mullmoder.

Extractable lignin and C/N ratio show maxima in the Lvd layer and then decrease uniformly (Fig. 2). Possible reasons for the increase in total nitrogen from Lvd (1.2%) to Of (1.7%) and Ofh,Ca (2.4%) will be discussed later. The m a x i m u m of free Nin-N is found in the Lvd layer. These soluble N-compounds are derived either from enzymatically hydrolysed proteins or directly from microbial biomass (which cannot be excluded from chemical analysis) and are easily washed out of the profile; only by incorporation into living organisms is free Nin-N retained. Therefore, the determination of free Nin-N is believed to offer a simple method for comparison of microbial activity in various organic layers (Ln is an exception: see below). Moder

As shown by both morphological and chemical properties, Moder profiles are intermediate between Mullmoder and Mor. Lignin and the C/N ratio stop decreasing between the Of and Ofh layers (Fig. 3). Cellulose decreases markedly from the Lv (5.7%) to Ld (2.5%) horizons but only slightly between Ld, Of (2.3%) and Ofh (2.1%) horizons. In the horizon in contact with bedrock (Ofh,Ca), cellulose is not found. O n the other hand, the glUzzA depth function shows a secondary m a x i m u m in the Ofh horizon. This supports the statement that cellulose is partly decomposed and partly transformed to oxycellulose. The Ofh horizon is penetrated extensively by roots (40% by volume, Table I), which helps to explain

152 5

10

1.5

20

2.5 %N t

4.0

5.0

60

5'0

100

ABSxlOOO/g Co

i

L

i

pH

Lw Ld ,, s

Of

Ohf-

free

N,n~-N. . . . . . -

2'

~

Ofh,Ca 50

100 10

150 30

200

pg/g free Nm-N

50%cellutose,glUTF A

50

100 i

150 hgnmABSxl000/~

Lv / ,/

s -S

Ld

f~ Of ligninj . . J ,

Ohf-

Ofh,Ca~

J

..~

,,

1~0

20

310

C/N

Fig. 3. Depth functions of profile 2 : Moder. the shape of the curve in Fig. 2. Therefore, we postulate that root residues are responsible for the relatively high contents of cellulose, hemicellulose and lignin in the Ofh-layer. As shown later, the Odh horizons of the Mor and Tangelmor profiles clearly have maxima of these compounds. The highest concentrations of free Nin-N (Fig. 3) are found in the Ld (250 pg/g; pH: 5.6) and the neighboring Of {225 pg/g; pH: 6.0) horizons. Therefore, in these horizons, maximum microbial activity is assumed. This agrees well with the results of Meyer (1960), w h o analysed similar Moder profiles under Picea abies by counting bacterial colonies. He was able to establish maximum microbial activity in horizons which correspond with the Ld and Of of profile 2 ("obere Vermoderungsschicht"; Meyer, 1960), followed by a marked decrease in the underlying horizons. A similar decrease of free Nin-N can be observed in profile 2 (Ohf: 150 ~g/g, pH: 4.2; Ofh,Ca: 50 pg/g, pH: 5.2). The low concentrations at the O-R-contact horizon are unexpected, especially if one considers the increase in pH. Bochter (1983) investigated many similar profiles (Lithic Cryo- or Borofolists on limestone) and always found by far the lowest values of free Nin-N in organic horizons immediately above the bedrock, independent of pH values {3.7--7.5). We explain these findings as follows. Microorganisms prefer soluble compounds as sources of carbon and energy. During litter decomposition, however, soluble phenolic polymerization products, difficult to attack and degrade, are formed. These substances are washed through the profile and

153

finally precipitated by Ca, thereby enriching the O-R-contact layer (see Bochter, 1983 for a more detailed explanation of the processes involved). The pronounced maxima of Co and Ca~ (26--37 mg/g; Table II) in the Oh,Ca horizons of all Lithic Cryofotists (Table II) support this conclusion. Ca not only precipitates the organic substances; it also ties up the key functional groups within organic molecules where microbial degradation begins (such as phenolic and carboxylic groups), thereby further inhibiting microbial degradation. These processes satisfactorily explain the very low microbial activity within the Oh,Ca horizons. According to Duchaufour (1973), Chouliaras et al. (1975) and Muller and Vedy {1978), only slightly transformed organic matter ("humine residuelle") and fulvic acids accumulate in mineral A horizons of Rendolls. These authors explain their findings through the hypothesis that Ca precipitates the polyphenolic precursors of humic substances and the fulvic acids, thereby blocking biodegradation as well as further humification. Our findings are consistent with the earlier hypothesis. The same processes are believed to occur in organic layers of Folists immediately above the chalky bedrock. 0,5

1,0

1,5

I

2,0

I

I

% Nt

3,0 J

4,0

5,0

500

ABS x l O00/g Co

I

pH

l

LvLdOfOdhfOdfh-

l jr

f~rete'Nin-N ~ . .

OdhOh,Ca100

200

2,0j

LdOfOdhfOdfhOdhOh,Ca-

300

6,0t

pglg free Nin-N 10,0 % cellulose,glUTFk

100

300 1O0

200L

3~ lignin ABS x 1000/!

C/N "' ,,,\., I

, ' oluTFA s o

¢

2'0 Fig. 4. Depth functions of profile 3: Mor.

~o

4~

~o

C/N

154

Mor and Tangelmor Profiles 3, 4 and 5 (Mor and Tangelmor) will be discussed together, because there are no major differences between these soils, except for the thickness of the Odh layer (see Figs. 4, 5 and 6). As compared with the Moder profile (Fig. 3), all maxima and minima in the "S"-shaped depth function curves for lignin and C/N are intensified. Apparently, as in Mullmoder and Moder profiles, leaf and needle lignin decomposes rather quickly or at least some characteristic properties of lignin (extractability, color reactions ) are lost. On the other hand, in the densely aggregated red-brown O layers (Odh, Table I), root lignin is higher, leading to a clear secondary maximum. As in MuUmoder and Moder profiles, the cellulose of above1,5 I

1,0 I

2,0 I

2,5 I

°/oNt

Lv-

3,0 I

T

/ /

LdOf"

4,0 ]

5,0 I

pH

/

OdhfOdfhOdhlOdh2Odh3Oh,Ca-

......

140 1,0

200 4,0

300 82

polo freeNin-N ~ r,ellolo=e,oluTFk

1~0

2~0

340

100 I

200 I

300 A

,,,i

AeSxl0OO/gCo ligninABSxlO00/,

Ld L v - _ %"/t ~ cellulose Of-

OdhfOdfh-J ~

/ i oluTFA \, "*,,,

Odh3-

Oh,Ca-

2'o Fig. 5. Depth functions of profile 4 : Tangelrnor.

3'o

4'0

C/N

155

ground plant residues is readily attacked. But only part of the cellulose is mineralized; the remainder is largely transformed to oxycellulose as shown by the cellulose minimum and the glUTFA m a x i m u m in the same horizon (the glUTFA includes oxycellulose). The secondary cellulose maximum of the Odfh (profiles 3 and 4) or O d h l (profile 5) is attributed to the high root contents of these horizons (Table I). Therefore, we postulate that much fresh root litter is formed in this part of the profile. As with aboveground litter, root cellulose is quickly decomposed or transformed to oxycellulose. At the same time the secondary lignin maxima appear below the horizons with the secondary cellulose maxima, which implies that root lignin transformation ceases. Again high contents of free Nin-N mark the Ld and Of layers. Thus, within these two layers, the m a x i m u m of microbial activity can be assumed. 0,5

1,0

1,5

2,0

i

I

I

I

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Ld-

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4,0

I

J

Lv-

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32

I

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I

pH

/

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OdfhOdhl-

Odh2Odh3Odh4Odh,Ca-

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400 100 I

600 150 I

ABSxlOOO/gCo lignin 200 ABSx 10001 I

LnLvLdOf-

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/ 30

Fig. 6. Depth functions of profile

5 :

Thick Tangelmor.

,'0

~o

c,N

156

Profile 5 shows an Ln layer consisting of freshly fallen Vaccinium myrtillus leaves. Probably leaf proteases are still active after cell death and hydrolyse leaf protein, which could be responsible for the highest amounts of extractable free Nin-N (Fig. 6). The Lv horizon shows a characteristic minimum in free Nin-N; the water soluble organic substances could already have been leached from this layer. Lithic Cryofolists on limestone with the Mor or Tangelmor humus type can be divided into three main sections. (1) L-to-Odfh layers (or O d h l , profile 5). This section corresponds to the whole Mullmoder profile, except for the Ofh,Ca horizon immediately above the bedrock. Within the L-to-Odfh layers, leaves and needles are the dominant organic parent material for humus formation. These aboveground plant residues are either completely mineralized, are integrated within the microbial biomass or are transformed into humic substances and their precursors by active participation of microbes. As the concentrations of litter constituents decrease, the a m o u n t of humic material increases. This is consistent with an increase in the CEC from horizon to horizon (Bochter, 1983) a decrease in the C/N-ratio and an increase in N t (Figs. 4, 5 and 6). According to Ottow (1978), when large amounts of decomposition intermediates containing nitrogen are present, these N-constituents can be incorporated in greater amounts into humic substances. Microbial activity decreases due to a deficiency of easily mineralizable carbon. These conditions seem to prevail in the lower parts of the first section (Odhf, Odfh, and O d h l layers). (2) Odh layers. This second section is characteristic only for Mor and Tangelmor and absent in Mullmoder and Moder. Within it, there is a change in the organic parent material. Root residues dominate instead of aboveground plant residues, resulting in root cellulose being degraded or transformed. Lignin decomposition is markedly inhibited. As shown by Figs. 5 (Odh3) and 6 (Odh4), the largest C/N-ratios are obtained below the lignin maxima (Odh2). The shortage of nitrogen and the low pH are both unfavorable for humification. R o o t residues are poor in N, as evidenced by C/N-ratios as high as 55 (Fig. 6). (3) Oh, Ca layers. O-R-contact horizons clearly differ from the horizons of the upper two sections, not only in morphological features (Table I) but also in their chemical properties. High concentrations of mobile organic matter are reversibly precipitated by Ca as previously mentioned. Only minor amounts of lignin and polysaccharides are present; however, there is a marked increase in N t. We postulate that this nitrogen is bound to the mobile organic phase and therefore concentrated in the Oh,Ca layers by processes already described. ACKNOWLEDGEMENTS

We thank Mrs. M. Detzer for able assistance with the analytical procedures, Mr. Th. Engelbrecht for drawing the figures and the Deutsche For-

157

schungsgemeinschaft for financial grant. The checking of the English manuscript by Dr. R. Malcolm, Geological Survey, Denver, Colorado is gratefully acknowledged. REFERENCES Babel, U., 1972. Moderprofile in W~ldern. Hohenheimer Arbeiten 60, Ulmer, Stuttgart. Blume, H.-P., 1966. Die Charakterisierung yon HumuskSrpern dutch Streu- und HumusStoffgruppenanalysen unter Beriicksichtigung ihrer morphologischen Eigenschaften. Z. Pflanzenern~/hr., Diing., Bodenkd., 111: 95--114. Bochter, R., 1981. Humusformen der m o n t a n e n und subalpinen Stufe des Alpennationalparks Berchtesgaden. Mitt. Dtsch. Bodenkd. Ges., 32: 593--598. Bochter, R., 1983. BSden naturnaher Bergwaldstandorte auf carbonatreichen Substraten Beitr~ge zu Genese, Okologie und Systematik. Diss. Universit~t Bayreuth; Nationalpark Berchtesgaden, Forschungsber. In press. Bochter, R., 1984a. Bestimmung cellulosisch und nichtcellulosisch gebundener Neutralzucker in Bodenhydrolysaten mit Hilfe yon Hochleistungsdfinnschichtchromatographie. Z. Pf]anzenern~hr. Bodenkd., 147: 203--209. Bochter, R., 1984b. Vorschlag zur Gliederung yon Humusprofilen auf Kalkfels in der Waldstufe der Alpen. Z. Pflanzenern~hr. Bodenkd., 147: 232--241. Bochter, R., 1984c. Bodenbildung auf Kalk- und GneisbergsturzblScken unter subalpinem Fichtenwald. Z. Pflanzenern~hr. Bodenkd., 147: 604--613. Chouliaras, N., Vedy, J.C. and Jacquin, F., 1975. Fractionnement et caract~risation de la mati~re organique dans les rendzines. Bull. E.S.N.A., 17: 65--73. Duchaufour, Ph., 1973. Action des cations sur les processus d'humification. Sci. Sol, 3: 151--163. Farmer, V.C., Russel, I.D. and Berrow, M.L., 1980. Imogolite and proto-imogolite allophane in spodic horizons: evidence for a mobile aluminium silicate complex in podzol formation. J. Soil Sci., 31: 673---684. Meyer, F.H., 1960. Vergleich des mikrobiellen Abbaus von Fichten- und Buchenstreu auf verschiedenen Bodentypen. Arch. Mikrobiol., 35 : 340--360. Mirchink, T.G. and Demkina, T.S., 1977. Ecology of darkcolored fungi in litter. Moscow Univ. Soil Sci. Bull., 32 (3): 44--48. Muller, I.C. and Vedy, J.C., 1978. Morphoscopie et fractionnement des mati~res organiques des rendzines sur craie. Sci. Sol, 8: 129--144. Ottow, J.C.G., 1978. Chemie und Biochemie des HumuskSrpers unserer BSden. Naturwissenschaften, 65: 413--423. Schlichting, E. and Blume, H.-P., 1966. Bodenkundliches Praktikum. Parey, Hamburg. Soil Survey Staff, 1975. Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys. U.S. Dept. Agric. Handbook 4 3 6 , 7 5 4 pp. Stevenson, F.J. and Cheng, C.N., 1970. Amino acids in sediments: Recovery by acid hydrolysis and quantitative estimation by a colorimetric procedure. Geochim. Cosmochim. Acta, 34: 77--88. -

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