Báo cáo khoa học: "The humus of a "Parabraunerde" (Orthic Luvisol) under Fagus sylvatica L and Quercus robur L and its modification in 25 years"

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Nội dung Text: Báo cáo khoa học: "The humus of a "Parabraunerde" (Orthic Luvisol) under Fagus sylvatica L and Quercus robur L and its modification in 25 years"

Original article The humus of a "Parabraunerde" (Orthic Luvisol) under Fagus sylvatica L and Quercus robur L and its modification in 25 years HP Blume U Irmler L Beyer 1 University of Kiel, Institute of Plant Nutrition and Soil Science, Hermann-Rodewald Strasse 2; 2 University of Kiel, Research Station of Ecosystems and Ecotechnics, Olshausenstrasse 40-60, 2 300 Kiel 1, Germany 18 July 1990; accepted 21 January 1991) (Received Summary— The humus of a loamy Orthic Luvisol containing a rich soil fauna formed on a boulder marl in the low-lying plain in the northwest of Germany near the Baltic sea under beech and oak with a mull humus was investigated in 1965 and 1986. Using a wet chemical procedure litter (proteins, polysaccharides, lignins) and humic components (fulvic and humic acids, humins) were separated. The results were combined with micro- and macromorphological observations and microbiotic and zootic investigations. The humus body has changed during the past 25 years. Decreasing bioturba- tion has induced a differentiation of the horizons in the organic layer, an accumulation of litter com- ponents and the development of an L- and an Oh-layer. The Of-layer has become tangled and lami- nated. The pH has decreased by half a unit. The translocation of fulvic acids has increased and the first signs of podzolization have been documented. The intensity of decomposition and humification has decreased during the past 25 years and therefore the humus form has changed from mull to moder. The main reason for this may be the decline of the earthworm population because of the lower pH and the deficiency of calcium as a consequence of the acid and proton input by air pollu- tion. / humus / Orthic Luvisol / soil acidification / humus transfor- humus morphology chemistry mation Résumé — L’humus d’un «Parabraunerde» (sol brun lessivé) sous hêtre (Fagus sylvatica L) (Quercus robur L) et son évolution au cours des 25 dernières années. et chêne rouvre L’humus du sol d’une hêtraie-chênaie à mull a fait l’objet de recherches et d’analyses comparées en 1965 et 1986. Il s’agit d’un sol brun lessivé limoneux, biologiquement actif, sur marnes morainiques d’une plaine basse de l’Allemagne du Nord près de la Baltique. On a procédé au fractionnement par voie humide des composés des litières (protéines, polysaccharides, lignine) et des composés hu- miques (acides fulvique et humiques, humines). Les résultats obtenus ont été confrontés avec les observations de micro- et macromorphologie, ainsi qu’avec les résultats des études microbilogiques et fauniques. Les humus se sont transformés au cours des 25 dernières années. La diminution de l’activité faunique a provoqué une différenciation plus marquée des horizons organiques, une accu- mulation en surface des composés de la litière, et enfin le développement d’une couche L et d’une couche Oh. La couche Of a pris l’aspect enchevêtré et laminé. Le pH a diminué d’une demi-unité. L’entraînement en profondeur des acides a augmenté et les premiers symptômes de la podzolisa- tion apparaissent. En raison du ralentissement de la décomposition des litières et de l’humification, * Correspondence and reprints
des 25 dernières années, le type d’humus est passé du mull au moder. La principale cause au cours de cette transformation semble résider dans la décroissance de la population de lonbrics, liée à la baisse du pH et au déficit en calcium, conséquence de l’apport des protons et de produits acides liés à la pollution atmosphèrique. morphologie de l’humus / chimie de l’humus / sol brun lessivé / acidification du sol / transfor- mation de l’humus INTRODUCTION in the Weichselian boulder marl over fluviogla- cial sands was investigated. It is located in the eastern hills in Schleswig-Holstein under a Meli- The soils in the mid-European forests co-Fagetum vegetation with Quercus robur. The have changed due to the deposition from mean age of the stand is ≈ 90 yr old. Soil acidifi- cation is very advanced (pH 3.6) and the 2 CaCl air pollution (Ulrich, 1989a). Soil acidifica- topsoil is poor in nutrients. Nevertheless, the tion is regarded as a primary reason for large nutrient reserves in the subsoil result in this process (von Zezschwitz, 1985). How- highly productive beech trees, whose roots ever, base saturation and pH value have reach the boulder marl containing carbonates. an effect on rooting (Ulrich, 1989b), the The soil and the site have been described by humification of organic matter (Abraham- Blume et al (1986) and Duchaufour (1987). The annual precipitation is 560 mm and the average sen et al, 1980; Baath et al, 1980; Ulrich, temperature is 8.4 °C. 1989a) and the formation of the humus In early October 1960 and 1986 sampling for Zezschwitz, body (Diagne, 1982; von humus characterization (area 1 m was carried ) 2 1989). out before the main litter fall and after mapping At the 13th Congress of the Internatio- the humus form and the typical sequence of the nal Society of Soil Science in Hamburg in horizons in the organic layer of this beech stand. The morphology of a typical profile was de- 1986, an Orthic Luvisol under beech and scribed according to Brewer and Sleeman oak was shown during an excursion in (1960), Schlichting and Blume (1966) and AK Schleswig-Holstein. Its humus composition Standortskartierung (1982). In order to deter- was presented by using data from 1960 mine the litter and humus component groups, (Blume et al, 1986). The investigations air-dried soil samples were analysed wet chemi- were based on extensive macro- and mi- cally according to Schlichting and Blume (1966). Fat and waxes were extracted with ethanol/ cromorphological observations and wet benzene; sugar and starch with 0.05 N H 4 SO 2 chemical investigations (Blume, 1965). (the amounts of this fraction were always « 1 % Due to the discussion about "forest de- of C and were therefore added to the hemicel- org cline" it seemed very interesting to com- lulose fraction); hemicellulose with 0.6 N HCl, cellulose with 27 N H mobile fulvic acids ; 4 SO 2 pare the results from 1960 with those from with 0.05 N H and fulvic and humic acids 4 SO 2 1986 at the same site. We hoped to dem- with 0.1 N NaOH and 0.1 N H alternately. 4 SO 2 onstrate changes in the humus body and Proteins were estimated as α-NH x 6.25 by -N 2 the retardation of litter decay caused by determination of α-NH by hydrolysis with 6 N -N 2 the soil acidification. HCl and 1 N HCOOH. Lignins were estimated as OCH x 10.5 by determination of OCH by 3 3 using the ZeisI-PregI method. The determina- tion of carbon in the solution was carried out us- MATERIALS AND METHODS ing Ströhlein apparatus. The determination of carbon and nitrogen in the solid state was car- ried out in the CHN analyser; for a more detailed (Typische Parabrau- A Orthic Luvisol loamy nerde, Typic Hapludalf, Sol brun lessivé) formed description of the analyses, see Beyer (1989).
The thickness of the organic layer was meas- Ah2 (5-16) ured every 6 wk (10 replicates). The litter fall loam with crumb struc- Grey-brown sandy was estimated quantitatively every month from ) g/cm 3 (1.4 . ture an area of 1 m (5 replicates). The soil respira- 2 tion was measured fortnightly using Lundegardh Alv (16-47) cylinders (5 replicates); for further information Closely packed, brown loam (1.6 g/cm ) 3 see Beyer (1989). The soil fauna was ascer- with a subpolyhedric to polyhedric struc- tained in 3 layers (3 replicates): the soil surface ture with asepic to sepic plasma. and soil vegetation (vacuum trap), the litter layer (hand selection or expulsion in Kempson- Tullgren apparatus) and the topsoil (expulsion in Kempson-Tullgren apparatus). The litter decom- position was observed using net bags (mesh size 0.5 cm) which were filled with 8 g autumnal leaf litter. The determination of dry weight was carried out on 3 of the net bags at 2-month inter- vals (sampling at 8 dates with 3 replicates). The rate of decomposition was calculated according to Olson (1963). RESULTS Humus morphology In October 1960 the humus horizons had the following morphology (see fig 1 a; the thickness of the horizon is in brackets): L/Of (3-1) 40% whole twigs and 60% wavy, nibbled leaves and leaf pieces (0.03 g/cm ). 3 Of (1-0) Broken, skeletal leaf pieces, fruit shells and twig pieces with faeces (0.13 g/cm ). 3 The leaf surfaces are covered with faeces. OAh (0-2) twig pieces and 70% arthro- 30% leaf and and worm faeces. The earth worm pod faeces contain ≈ 50% mineral particles. Ah1 (2-5) Sandy loam, little litter and many animal faeces (0.26 g/cm The worm faeces (giv- ). 3 ing a crumb structure) contain only 20% or- ganic matter.
tunnels containing Oh and Of material; In October 1986 the humus horizons are had the following morphology (see fig 1b); Enchytraeidae faeces are dominant, as are the thickness of the horizon is in brackets). cavities containing worm faeces. L Ah2 (2.5-11) (5.5-3.5) 50% whole twigs and wavy, 50% nibbled Strong loamy sand with crumb to fine poly- leaves and leaf pieces (0.05 g/cm The ). 3 small amount of lit- hedric structure and a (1.1 g/cm ). 3 leaf surfaces are covered with Collembola ter faeces. Alv (11-47) Of (3.5-1.5) Sandy loam (1.62 g/cm with coarse poly- ) 3 hedric structure with asepic to skel- and 20% fibrous twigs and skeletal leaf pieces. mosepic plasma. The leaf pieces and the Enchytraeidae and Oribatidae faecal pellets are stored in The litter was composed of leaves, alternate layers (0.02 g/cm ). 3 twigs, fruits and their involucres and leaf- bud hulls of trees and necrotic herb vege- Oh (1.5-0.0) tation. The thickness of the litter layer and Compact fine humus and mineral particles the litter supply of varied greatly during the (0.21 g/cm plant tissue is almost com- ); 3 annual cycle (fig 2). Earthworms especially pletely decomposed and humified; Oribati- caused intensive bioturbation in this Luvi- dae faeces, an increased amounts of En- sol. The Enchytraeidae participated in the chytraeidae faeces and small amounts of decomposition of litter. They caused the worm faeces are also present. characteristic fine crumbs (natural Ø < 1 Ah1 (0-2.5) mm; fig 1), whereas earthworm activity re- bleached sand with fine sulted in the formation of crumbs (natural Loamy, slightly crumb structure (1.1 g/cm the remains ); 3 0 1-10 mm, fig 1).Nevertheless there were also many soil animals, which did not of the litter are less humified, and there
substances increased in contrast to the lit- alter this soil in such a remarkable way (fig 3), but stimulated decomposition by the mi- ter. Fulvic acids were dominant. Most of cro-organisms (see soil respiration in fig 2). the humins were probably humic acids The largest part of the litter was incorporat- fixed in clay-humus complexes (Blume, ed and broken down within a year, so that 1965). Therefore we have looked at the ha the litter layer remained thin (fig 3), but + hu/fa ratio (tables I, IV) instead of the ha/ each of the organic layers was to be found fa ratio. the whole year round. COMPARISON OF THE Humus chemistry INVESTIGATIONS IN 1960 AND 1986 The results of the chemical investigations The carbon content in the soil was similar of the humus are shown in figure 4, and in for both investigations with ≈ 8.5 kg/m (ta- 2 tablesI and II. ble II, 2), but the nitrogen content was higher in 1986 (table II, 1).However, it was With increasing depth the litter compo- not fixed in proteins, as these were not as (fig 4: hc + cel + lig) decreased. Lig- nents high in 1986 (table II, 3). The largest nitro- nins were found to explain a large part of gen content was to be found in the Alv, the carbon (fig 4), because they were where it was fixed in humic substances present in fine roots. The increase of pro- and also probably as NH in the clay min- + 4 teins caused by presence of micro- was eral layers. In 1960 it was not possible to protein in the mineral soil. Humic organism
rizons was more difficult in 1960, because document a real litter layer, which is why the horizons runs smoothly into one an- in the LOf humified material was to be other due to the intensive bioturbation. In found (fig 4). In 1960 there was less litter the O horizon, humic substances which in the soil than in 1986 (table II, 4). The contain nitrogen were rebuilt and mixed proportion of litter (fig 4) was lower in 1960 with material from the Ah. This is the rea- in the Of; in 1986 however, the lowest pro- son for a dilution in the mineral soil. Higher portion was to be found in the Ah1- nitrogen levels in the Ah illustrate that this horizon. In 1960 the bulk density of the Of process was not as intensive in 1986. This was 0.13 g/cm it contained only 9% twigs ; 3 reduction of the C/N ratio in the Ah horizon and arthropod faeces. In 1986 the bulk has already been described by von density was only 0.02 g/cm it contained ; 3 Zezschwitz (1985). The increased propor- 26% twigs and there were no faeces in tion of carbon in the Ah confirms the this horizon. This is the reason for the change in the humus form (von Zezsch- large difference in C (table I, 1) and the org witz, 1980). In 1986 it was not possible to completely different composition of the hu- separate the organic horizons exactly, but mus and litter components (table II). neverthless a L-Of-Oh chronology was to Whereas in 1986 the Of was more similar be found the whole year round. to the LOf, in 1960 it was more like an Ohf horizon. In contrast to 1986, a real Oh was In 1986 the soil solution contained solu- not be found in 1960. It was interesting ble organic carbon (Beyer, 1989). This car- that this horizon had the same carbon con- bon belonged to the mobile fulvic acids tent as the Of in 1960. The OAh from 1960 group, because the soil solution was yel- was really an Ah, because it contained low-brown coloured and water-soluble only 16% humus (table II : 2 x and polysaccharides were not important (see ) org C Methods). In 1960 these mobile fulvic ac- was comparable with the Ah1 recorded in ids peaked in the Ah1 and slowly in- 1986. A clear separation of the organic ho-
few years. The N input is at the lower end creased with increasing depth (fig 4). In of the input levels described by Kreutzer 1986 this peak was located in the Ah2 at a (1989), but according to Blume et al (1985) much higher level. The humic acid + hu- in Schleswig-Holstein the largest part of min/fulvic acid ratio decreased continuous- the input is caused by NH emission from ly (table II, 4). The translocation of humic 3 agriculture, due to intensive fertilization us- substances reached deeper horizons and ing slurry. The correlation between high N was intensified. Morphologically the initial input and the decrease in the base satura- podzolization was documented by observ- tion (table II, 7) and the simultaneous in- ing bleached mineral particles in the Ah1- crease of N supply (table II, 1) was docu- horizon. Von Zezschwitz (1979) has al- mented by Kreutzer (1989) in spruce ready described this in forest soils in west forests, but the same rule should apply to Germany. the beech site. Hallbäcken and Tamm The humus form has developed from a (1986) were able to verify a decrease of F-mull to a moder, poor in fine humus. pH in Swedish forest soils, which depends on the development of the trees after clear-felling. In 1960 the beech trees in DISCUSSION Siggen were fully developed and already 50-60 yr old and during the past few cen- turies the site has only been used for for- The decrease of the pH in the A horizon estry. This is why the changes in the envi- from 4.0 to 3.2 and the base saturation ronmental conditions are only negligible: from 40 to 13% (table I, 5+7) in the past 25 the shading of the soil, this means that the yr has probably influenced the biocenosis water and heat regimes, which are the of this soil ecosytem (Hartmann et al, most important parameters of decomposi- 1989). Especially in the beech forest, tion and humification, were similar during which has only moderate resistance to ac- the past 25 years. ids, a higher aluminium concentration causes the mortality of fine roots (Ulrich et The change in the humus form from al, 1984). At a base saturation of below mull to moder and the development of an 10-15% (table I,8) the damage to beech organic layer was probably induced by a roots is possible because of an acidic soil decrease in the earthworm population. In solution (Ulrich et al, 1989). This is why a 1987, 19 earthworms/m were recorded 2 permanent regeneration of fine roots is (table III). In a neighbouring site 2 yr ago necessary. This means that an accumula- the pH was increased by liming, so that the tion of litter due to necrotic roots is one pH value was the same as in 1960 (table reason for the higher proportion of litter in III). This caused an abundance of these 1986 (table II, 4). soil animals which was 5 times higher. The Lumbricidae need calcium for their physio- The deposition of protons from the at- logy (Lee, 1985). The low supply of Ca (ta- mosphere into the soil (4-6 kg NO 7- -N, 3 ble I, 8) in the top soil reduces the earth- 14 kg NH 11-20 kg SO and 0.4 kg -N, 4 -S 4 activity. worm H in Schleswig-Holstein is not insignif- /ha) + icant (Blume et al, 1985). That is why we Soil degradation by the translocation of think that the natural process of acidifica- nutrient and humic substances to deeper tion has been intensified by air pollution soil horizons is stimulated by the beech and deposition into the soil during the past trees, because no light comes through the
REFERENCES tree canopy. This is why only a small amount of herb vegetation is present. The low C/N ratio of the necrotic herb vegeta- Abrahamsen G, Hovland J, Hagvar S (1980) Ef- tion would stimulate the soil animals (Dun- fects of artificial acid rain and liming on soil organisms and the decomposition of organic ger, 1983). The present bioturbation is not matter. In: Effects of Acid Precipitation on sufficient to counteract the observed trans- Terrestrial Ecosystems (Hutchinson TC, Ha- location. vas M, eds) Plenum Press, NY, 341-362 Liming at the soil surface with 3 t/ha of Forstliche Stan- AK Standortskartierung (1980) dolomite could moderate the soil acidifica- Münster- Landwirtschaft, dortsaufnahme. tion and stimulate the development of the Hiltrup, 4 Aufl soil herb vegetation. This would influence Berg B, Lohm U, Lundgren B, Lundk- Baath E, the soil animals (table III) and the litter de- vist, Rosswall B, Söderström B, Wiren A (1980) Effects of artificial acidification and composition in a positive way (fig 5). The liming on soil organisms and decomposition higher abundance of decomposers in- in a Scots pine forest. Pedobiologia 20, 85- duced by liming would cause an increase 100 in litter decay. 300 g/m of lime cause the 2 Beyer L (1989) Nutzungseinfluss auf die Stoffdy- decomposition time of litter to be reduced schleswig-holsteinischer Böden- namik by a third and 600 g/m cause it to be 2 Humusdynamik und mikrobielle Aktivität. halved. The decomposition of the fallen lit- Bodenkd Pflanzenernaehr Schriftenr Inst ter is stimulated by liming and hinders the Univ Kiel 6 formation of a permanent organic layer. (1965) Die Charakterisierung von Hu- Blume HP muskörpern durch Streu- und Humus- Stoffgruppenanalysen unter Berücksichti- gung ihrer morphologischen Eigenschaften. CONCLUSION Z Pflanzenernaehr Dueng Bodenkd 111, 95- 113 body of an Orthic Luvisol has The humus Blume HP, Lamp J, Schimming CG, Wiese D, changed during the past 25 years. The in- Zingk M (1985) Bodenbelastung aus der Luft? Publ Agric Fac Univ Kiel 67, 44-51 tensity of decomposition and humification has decreased and the humus form has Lamp J, Schnug E, Wiese D (1986) Blume HP, soils and landscapes in Holstein. Mitt Typical changed from mull to moder. The translo- Dtsch Bodenkundl Ges 51, 14-42 cation of fulvic acids has increased and Brewer R, Sleeman JR (1960) Soil structure and first signs of podzolization have been re- fabric. J Soil Sci 11, 172-185 corded. The main reason for this may be Diagne A (1982) Effects d’une fertilisation mine- the decline in the earthworm population rale sur l’humification, les cycles biologiques because of the lower pH and the deficien- et la productivité d’une hêtraie acidiphile sur cy of calcium as a consequence of the acid grès de l’est de la France. Thèse, Univ Nan- and proton input by air pollution. cy Duchaufour P (1987) Influence de la mise en culture sur les propriétés de deux sols foresti- ACKNOWLEDGMENTS ers du Holstein. CR Acad Agric Fr 73, 5-10 Tiere im Boden. Ziemsen, Wit- Dunger W (1983) tenberg The authors wish to thank P Duchaufour for translating the French parts of this paper. This Hallbäcken L, Tamm CO (1986) Changes in soil work has been supported financially by the Fed- acidity from 1927 to 1982-1984 in a forest eral Ministry of Research and Technology area of south-west Sweden. Scand J For Res (BMFT), Germany-Bonn-Bad Godesberg. 1, 219-232
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