Maßstabsabhängige räumliche Variabilität mikrobieller Bodenkenngrößen in einem Buchenwald

Scale-dependent spatial variability of microbiological characteristics in soil of a beech forest The spatial variability of the microbial biomass content (C_mic), the microbial respiration rate (basal respiration) and the metabolic quotient (qCO₂) was analyzed in sandy Cambisols and Luvisols in a beech forest in Northern Germany. Highest variability of microbiological features and, thus, the distance of independent samples was around 10 m that is discussed with reference to spatial hierarchy. Structural changes between the 10 m and 50 m grid were suggested for the Ah horizon due to the break of correlations of C_mic content and the contents of C_org and plant-available Ca, Mg, K and N_t. The C_mic content correlated with the C_org content close to tree trunks and ecotones like borders of the forest and clearings. The qCO₂ did not generally increase with declining pH value. High H⁺ concentrations and C_org content in the litter layer near to the tree trunk indicated retarded microbial mineralization rates. High proportion of microorganisms that are resistant to low pH value and adjusted ro readily-degradable substrates seems to dominate in the soil close to the tree.     

Effect of forest and soil type on microbial biomass carbon and respiration

The aim of study was to evaluate the variation of soil microbial biomass carbon (C_mic) and microbial respiration (M_R) in three types soil (Chromic Cambisols, Chromic Luvisols and Eutric Leptosols) of mixed beech forest (Beech- Hornbeam and Beech- Maple). Soil was randomly sampled from 0–10 cm layer (plant litter removed), 90 soil samples were taken. C_mic determined by the fumigation-extraction method and M_R by closed bottle method. Soil C_org, N_tot and pH were measured. There are significant differences between the soil types concerning the C_mic content and M_R. These parameters were highest in Chromic Cambisols following Chromic Luvisols, while the lowest were in Eutric Leptosols. A similar trend of C_org and N_tot was observed in studied soils. Two-way ANOVA indicated that soil type and forest type have significantly effect on the most soil characteristics. Chromic Cambisols shows a productive soil due to have the maximum C_mic, M_R, C_org and N_tot. In Cambisols under Beech- Maple forest the C_mic value and soil C/N ratio were higher compared to Beech-Hornbeam (19.5 and 4.1 mg C g^–1, and 16.3 and 3.3, respectively). This fact might be indicated that Maple litter had more easy decomposable organic compounds than Hornbeam. According to regression analysis, 89 and 68 percentage of C_mic variability could explain by soil C_org and N_tot respectively.     

Quantitative und qualitative Veränderungen im A-Horizont von Sandböden nach Umwandlung von Dauergrünland in Ackerland

Quantitative and qualitative changes in soil properties of A- horizons of sandy soils caused by conversion of grassland to arable land Changes in physical soil properties and in soil organic matter of the A-horizons due to the conversion of permanent grassland to arable land are quantified and described as a function of time for sandy soils. The study was carried out in an area northeast of Hannover. A decrease of about 100 t/ha C_org (- 57%), 5 – 6 t/ha N_org (- 58%) and 1 t/ha S_t (- 58%) was measured for a period of 2 – 4 years after grassland conversion. Thereby the quality of the soil organic matter remains unchanged (no changes of the C/N ratio and of the distribution of N_org in 5 N-fractions). However, an increase of soil bulk density from 1.0 to 1.3 g/cm³ and a decrease of total pore volume from 0.59 to 0.47 were observed. The fast mineralization of soil organic matter in the A-horizon following the conversion of grassland soils results in a temporary heavily increased nitrate input into the groundwater. Furthermore mineralization and leaching of nitrate and sulfate induces an acidification push in the soil by a proton release in the order of 350 keq/ha during a 2 – 4 years period. However, this proton production is compensated quantitatively by several applications of lime or marl by farmers and by the buffering of bases cations released from mineralized soil organic matter.     

Schwefelformen in Waldböden SO2-belasteter Standorte des Fichtelgebirges

Sulfur fractions in forest soils of the SO₂-polluted Fichtelgebirge The sulfur status of a soil sequence (two Dystric Cambisols, Haplic Podzol, Eutric Cambisol) in SO₂-polluted coniferous and hardwood forests of the Fichtelgebirge (North-East Bavaria) is investigated. In the mineral soil layers S_t fluctuates between 37 to 943 ppm; 11–84% of S_t is S_p. Layers rich in clay contain up to 79%-S_E, whereas in sandy to silty substrates organic bound C?S-S dominates. The organic surface layers show 1.0–2.9‰ S_t, maximum in the Oh. 69–90% of S_t are C?S-S. S_p is low with a maximum in the L-horizons (9–19% of S_t). S_E is vice versa, because values increase from L (0–8% of S_t) to Oh (7–22% of S_t). The characterization of the sulfur status in a forest ecosystem by investigation of organic layers presumably is more reliable than the results of needle and mineral soil analyses.     

Above-Ground Sulfur Cycling in Adjacent Coniferous and Deciduous Forests and Watershed Sulfur Retention in the Georgia Piedmont,U.S.A.

Atmospheric deposition and above-ground cycling of sulfur (S) were evaluated in adjacent deciduous and coniferous forests at the Panola Mountain Research Watershed (PMRW), Georgia, U.S.A. Total atmospheric S deposition (wet plus dry) was 12.9 and 12.7 kg ha-¹ yr-¹ for the deciduous and coniferous forests, respectively, from October 1987 through November 1989. Dry deposition contributes more than 40% to the total atmospheric S deposition, and SO₂ is the major source (～55%) of total dry S deposition. Dry deposition to these canopies is similar to regional estimates suggesting that 60-km proximity to emission sources does not noticeably impact dry deposition at PMRW. Below-canopy S fluxes (throughfall plus stemflow) in each forest are 37% higher annually in the deciduous forest than in the coniferous forest. An excess in below-canopy S flux in the deciduous forest is attributed to leaching and higher dry deposition than in the coniferous forest. Total S deposition to the forest floor by throughfall, stemflow and litterfall was 2.4 and 2.8 times higher in the deciduous and coniferous forests, respectively, than annual S growth requirement for foliage and wood. Although S deposition exceeds growth requirement, more than 95% of the total atmospheric S deposition was retained by the watershed in 1988 and 1989. The S retention at PMRW is primarily due to SO₄ ²- adsorption by iron oxides and hydroxides in watershed soils. The S content in white oak and loblolly pine boles have increased more than 200% in the last 20 yr, possibly reflecting increases in emissions.     

Schwefelformen saurer Böden unter Nadelwald in Nordostbayern

Fractions of sulfur of four soils under coniferous forests in northeast Bavaria The sulfur status of four forest soils (Podsol-Regosol, Braunerde-Pseudogley, two Braunerde – soils) located in northeast Bavaria are investigated. Total sulfur, water-, chloride- and phosphate-extractable, Ester-SO₄-S and C-bonded S were determined in the organic and mineral layers. Total S, highest in the Oh-horizons, fluctuates between 68–1851 ppm. There are quite narrow correlation coefficients between total S and total organic carbon (r = 0,85) and between C-bonded S and total organic carbon (r = 0,82). However, phosphate-extractable S is correlated to the amounts of amorphous sesquioxids (r = 0,88). Therefore, the water-, chloride- and phosphate-soluble S added, accounts for only 8–23% of total S in the Podsol-Regosol, for 12–56% in the Braunerde-Pseudogley, but for 17–84% in the Braunerde-soils, rich on sesquioxides. In contrast, organic carbon bonded S is highest in the organic layers and in the Ah-horizons. Except of the Podsol-Regosol, this fraction decreases with increasing soil depth, whereas Ester-SO₄-S shows an increasing tendency. The carbon bonded S is correlated to both total organic C (r = 0,82) and total N (r = 0,87). Ester-SO₄-S has no clear pattern of distribution. Water soluble S is partly bound to organic colloids. The differences in the depth functions of the water soluble and of the Ester-SO₄-fractions in the organic layers may attribute to the influence of atmospheric sulfur input.     

The role of soil chemical properties,land use and plant diversity for microbial phosphorus in forest and grassland soils

Management intensity modifies soil properties, e.g., organic carbon (C_org) concentrations and soil pH with potential feedbacks on plant diversity. These changes might influence microbial P concentrations (P_mic) in soil representing an important component of the P cycle. Our objectives were to elucidate whether abiotic and biotic variables controlling P_mic concentrations in soil are the same for forests and grasslands, and to assess the effect of region and management on P_mic concentrations in forest and grassland soils as mediated by the controlling variables. In three regions of Germany, Schwäbische Alb, Hanich‐Dün, and Schorfheide‐Chorin, we studied forest and grassland plots (each n = 150) differing in plant diversity and land‐use intensity. In contrast to controls of microbial biomass carbon (C_mic), P_mic was strongly influenced by soil pH, which in turn affected phosphorus (P) availability and thus microbial P uptake in forest and grassland soils. Furthermore, P_mic concentrations in forest and grassland soils increased with increasing plant diversity. Using structural equation models, we could show that soil C_org is the profound driver of plant diversity effects on P_mic in grasslands. For both forest and grassland, we found regional differences in P_mic attributable to differing environmental conditions (pH, soil moisture). Forest management and tree species showed no effect on P_mic due to a lack of effects on controlling variables (e.g., C_org). We also did not find management effects in grassland soils which might be caused by either compensation of differently directed effects across sites or by legacy effects of former fertilization constraining the relevance of actual practices. We conclude that variables controlling P_mic or C_mic in soil differ in part and that regional differences in controlling variables are more important for P_mic in soil than those induced by management.     

Biological influences on the morphology and micromorphology of selected Podzols (Spodosols) and Cambisols (Inceptisols) from the eastern United States and north-east Scotland

Biological activities greatly influence the formation of many soils, especially forest soils under cool humid climates. The objective of this study was to investigate the effects of vegetation and soil biota on the formation of selected soils. Field morphology, micromorphology, and carbon and organic matter analysis were determined on six Podzols (Spodosols) and two Cambisols (Inceptisols) from the eastern United States and north-east Scotland. Humification of plant material by soil fauna and fungi occurs in all organic horizons. Thick organic coatings are observed on soil peds and rock fragments from the E1 to the Bs horizon in a Haplic Podzol from Clingmans Dome Mt., TN. Thin sections reveal large accumulations of root material in different stages of decomposition in the spodic horizons of a Haplic Podzol from Whiteface Mt., NY. Organic carbon ranges from 5.4 to 8.5% in the spodic B horizons of the Whiteface Mt. Podzol. Earthworms and enchytraeids have a great effect on the structure of the surface and subsurface horizons in the Dystric Cambisols from Huntly and Clashindarroch Forests, Scotland and a Cambic Podzol from the Corrie Burn Basin, Scotland. Podzols from Speymouth Forest, Scotland (Gleyic Podzol), Clingmans Dome Mt., and Whiteface Mt. have thick organic horizons. The Podzols from the Flatwoods in Georgia, the Pine Barrens in New Jersey, the Corrie Burn Basin, and the Cambisol from Huntly Forest have only A horizons at the surface. The Clashindarroch Forest soil has a very thin organic horizon. Warm and humid climates and sandy parent material are responsible for thick E horizons and lack of thick organic horizons in the Flatwoods (Carbic Podzol) and Pine Barrens (Ferric Podzol) soils. Earthworms and enchytraeids thrive in the Corrie Burn Basin and Huntly Forest soils due to the vegetation and the highly weathered basic parent material. The site at Clashindarroch once carried oak, and then birch forest, both of which produce a mild litter and also encourage earthworm and enchytraeids. This fauna is responsible for much mixing of the topsoil. The present conifer vegetation will eventually produce a deep litter and cause podzolization.     

Genese und Klassifikation von Organomarschen der Wesermarsch

Formation and classification of humus-rich marshland soils of the Weser marshland, Germany The formation and classification of marshland soils are still controversial. To improve the knowledge on the formation of humus-rich marshland soils 11 soil profiles have been investigated. The soils mostly showed Phragmitis in the subsoil. The Gr-horizons began at low depths (40–60 cm). The clay content was often about 60% and the C_org content up to 480 g kg^?1. The amount of total sulfur was up to 29.6 g kg^?1, that of exchangeable sulfate up to 4608 mg kg^?1 and that of sulfate in the saturation extract 51.2 mg l^?1. With pH (H₂O) values between 2.0 and 7.4, Carbonate/S ratios < 3 and total sulfur contents > 7.5 g kg^?1 some soils showed “Actual Acid Sulfate Soil” (AASS) properties. The pH(per) values varied between 2.4 and 7.1, thus some profiles showed “Potential Acid Sulfate Soils” (PASS) properties. Brakish as well as marine environments with an intensive sulfur dynamics and carbonate leaching are likely within the geogenetic phase of soil development. Via the control of the water regime the pedogenetic phase is mainly of anthropogenic influence. We propose to classify humus-rich marshland soils into “Organomarsch” and “Thiomarsch” on the soil type level of the German systematics.     

Winterliche N-Mineralisation in sandigen Böden des ‘Fuhrberger Feldes’ (Hannover)

N mineralization in sandy soils of the ‘Fuhrberg well field’ (Hannover) during winter Net N mineralization was measured under field conditions during winter and spring 1991/92 in sandy arable soils (Gleyic Podzols, Mollic Gleysols, Gleyic Arenosols) of the ‘Fuhrberg well field’, a drinking water catchment north-east of Hannover. The aim was to assess leaching losses of nitrate from mineralization processes during the winter on soils formerly used as grassland. Two field procedures were used: the incubation of soil material in polyethylene bags at its original location and rain sheltered fallow plots. Between 6 and 40 (100) kg N ha^?1 were mineralized during 73 days from Dec., 17th to March, 2nd. Mineralisation rates were closely correlated to the organic N and C contents of the soils (r² ± 0.9). In the uncovered soils, the NO₃ was completely leached out. On five out of seven fields the process ‘N-mineralization during winter’ alone was sufficient to exceed the official limit for drinking water (50 mg 1^?1 NO₃^? ) in the uppermost groundwater. It is concluded that even 15 years after converting grassland into arable land the N_org and C_org levels in the soils had not reached a new equilibrium.     

Silicon fractions in Histosols and Gleysols of a temperate grassland site

The importance of silicon (Si) in nutrition is currently being recognized by its beneficial effects on many crops. Therefore, it is important to determine the soil Si status and to examine different extractants for testing plant‐available Si. Little information is available about the Si status of Histosols and C_org‐rich Gleysols in temperate climate. This study was undertaken (1) to characterize different Si pools in C_org‐rich groundwater soils of an experimental site and (2) to study the influences of small‐scale variability on element distribution. At the experimental site, the thickness of the C_org‐rich layer ranges between 4 and 5 dm overlying fine‐sandy fluvial sediments. Four extractants were evaluated: 0.01 M CaCl₂, 0.5 M acetic acid, 0.1 M sodium pyrophosphate, and 0.1 M Tiron (C₆H₄Na₂O₈S₂ · H₂O). Further, total element content was determined following HNO₃/HF digestion. Calcium chloride–soluble Si shows no significant relations to other parameters analyzed. On the basis of published data, the soils investigated could be classified as Si‐deficient. The Si fraction extracted with acetic acid displays relations to C_org content of the soil and a weak correlation to CaCl₂‐soluble Si, indicating that both solutions extract overlapping but not the same fractions. Sodium pyrophosphate extracts mainly organo‐mineral Fe and Al complexes in the soils studied, which is reflected in a highly positive correlation to C_org. Pyrophosphate‐soluble Si showed a negative relationship to C_org, which means a closer relation of this Si fraction to mineral matter than to C_org. The Tiron solution extracted most Si of all extractants, but this amounts only 1% of the total Si content. Taking into account the element‐specific relationship between pyrophosphate and Tiron‐extractable Fe, Al, and Si, it can be concluded that Tiron dissolves mainly the opaline silica present in Histosols and C_org‐rich Gleysols. The distribution of C_org and ash content shows clear spatial trend at the experimental site, which is correlated to pyrophosphate‐extractable as well as total Si. This small‐scale variability of soil parameters itself is related to a distinct microrelief.     

Atmospheric sulfur deposition for a red soil broadleaf forest in southern China

A two-year study in a typical red soil region of Southern China was conducted to determine 1) the dry deposition velocity (Vd) for SO2 and particulate SO4^2- above a broadleaf forest, and 2) atmospheric sulfur fluxes so as to estimate the contribution of various fractions in the total. Using a resistance model based on continuous hourly meteorological data, atmospheric dry sulfur deposition in a forest was estimated according to Va and concentrations of both atmospheric SO2 and particulate SO2^4-. Meanwhile, wet S deposition was estimated based on rainfall and sulfate concentrations in the rainwater. Results showed that about 99% of the dry sulfur deposition flux in the forest resulted from SO2 dry deposition.In addition, the observed dry S deposition was greater in 2002 than in 2000 because of a higher average concentration of SO2 in 2002 than in 2000 and not because of the average dry deposition velocity which was lower for SO2 in 2002. Also,dry SO2 deposition was the dominant fraction of deposited atmospheric sulfur in forests, contributing over 69% of the total annual sulfur deposition. Thus, dry SO2 deposition should be considered when estimating sulfur balance in forest ecological systems.     

Fluoreszenzmikroskopisch bestimmte mikrobielle Biomasse und deren Beziehung zum Gesamtkohlenstoffgehalt und zur Dehydrogenaseaktivität in ausgewählten Bodenproben

Microbial biomass measured by fluorescence microscopy and its relation to total organic carbon and dehydrogenase activity in selected soil samples Techniques for direct observation of microbial biomass with epifluorescence microscopy, which have proved reliable in aquatic microbiology, were applied for investigation of soils. The procedure for measurement of microbial biomass consisted of ultrasound treatment, filtration with nuclepore-filters, registration of cell-size classes and separate counting of small bacteria. Microbial biomass of an arable A_p (Slu = silty loamy sand) was nearly twice as high with ultrasonication as with untreated samples. In 16 root-free samples removed from different mineral soils, bacterial biomass ranged from 0,22 to 7,50 mg C/g soil, surpassing fungal biomass in general by the factor 2 to 35. Up to 98% of the total organic carbon (C_org) in soil was present in microbial biomass. In uncultivated topsoils dehydrogenase activity was highly correlated with C_org and microbial biomass (n = 7, r_mult. = 0,972, α = 0,001).     

Pore‐system characteristics of pavement seam materials of urban sites

The original light‐brown sandy seam filling of pavements in urban areas turns dark and changes its properties by the time due to various inputs of urban dust. Deposited C_org inputs do mostly not have natural characteristics but are man‐made, e.g., diesel dust. Thus, properties of the seam material are not predictable from experiences with forest or agricultural soils. Semiperviously sealed urban areas are sites of contaminant deposition as well as groundwater recharge. For an assessment of the resulting groundwater‐contamination risk in these areas, the properties of the seam material, which influences transport processes, must be known. The aim of this study was to investigate the pore‐system build‐up, which includes size distribution and fractal character in the seam material of urban sites. The investigated samples were taken from pavements adjacent to roads in Berlin and Warsaw. The micropore parameters (nanometer range) were characterized using water‐vapor desorption isotherms, mesopore parameters (micrometer range) were estimated from mercury‐intrusion porosimetry and macropore parameters (millimeter range) from water‐retention curves. Particle density, dry bulk density, and particle‐size distribution were measured using standard methods. Volumes of micro‐ and mesopores as well as particle densities and dry bulk densities correlated with C_tot contents. However, no such relation was found for macropore volumes. Compared to the original sandy seam filling, the altered seam material shows significantly higher C_org contents and higher amounts of micro‐ and mesopores. Therefore, the available water capacity increases by 0.05–0.11 m³ m^–3, as compared to the original sandy seam filling. Compared to natural sandy soils having similar C_org contents, the seam material shows similar macropore volumes, but the volume of mesopores and micropores is a few times smaller. That is mainly because of the particulate character of the organic matter.     

Energetic eco‐physiology of the soil microbiota in two landscapes of southern and northern Germany

Interactions between microbial communities and organic matter were analyzed for soils from the project regions ’︁Ecosystem Research in the Agricultural Landscape/FAM, Munich’ in southern Germany and ’︁Ecosystem Research in the Bornhöved Lake district’ from northern Germany using ratios between microbial biomass content (C_mic), microbial metabolic quotient (qCO₂) and organic carbon content (C_org). In the agricultural soils in southern Germany, the qCO₂/C_org ratio differed significantly with respect to agricultural management in contrast to ecophysiological C_mic/C_org ratio. In addition, C_mic/C_org ratio decreased from 39 to 21 mg C_mic g^—1 C_org and qCO₂/C_org ratio increased from 72 to 180 mg CO₂‐C g^—1 C_mic h^—1 (g C_org g^—1 soil)^—1 with increasing soil depth. For the upper soil horizons from the landscape in northern Germany the two quotients differed significantly with reference to land use showing highest microbial colonization under grassland and lowest under beech forest. In contrast, C use efficiency was lowest in arable field under maize monoculture and highest in a wet grassland having a high organic C content.     

Interactive effects of substrates and ectomycorrhizal colonization on growth of a poplar clone

A balsam poplar clone (Populus trichocarpa cv. Weser 6) was inoculated by two ectomycorrhizal strains (Laccaria bicolor MW 158 and Paxillus involutus 1444) in Kick‐Brauckmann‐pots. The substrates were two arable sandy soils (Cambisols) with different organic matter content and nutrient supply. One soil (WIL) was rich in organic matter (C_org = 1.6%) and total nitrogen (N_t = 0.14%), whereas the other soil (RIE) had low contents of C_org (0.8%) and N_t (0.08%). Leaf nutrient concentrations, shoot lengths, root and shoot biomass production and nitrogen accumulation in the biomass were determined to discover possible inoculation effects. Mycorrhization indices (% colonized fine roots) of 36% with Laccaria bicolor and 40% with Paxillus involutus were observed on the C_org rich soil (WIL) in contrast to 16% and 14% on the C_org poor soil (RIE), respectively. Inoculation of poplar on the soil WIL increased shoot length, biomass production, shoot:root ratio and total N uptake of the cuttings, whereas on the soil RIE only the shoot:root ratio increased and the N nutrition was improved. We conclude that interactions between soil and fungus should be tested when choosing ectomycorrhizal strains for inoculation.     

土壤中不同形态硫的生物有效性研究

在温室条件下连续种植 4茬玉米和水稻幼苗 ,分别研究好气和淹水条件下土壤无机硫(MCP-S)和有机硫包括酯键硫 (C-O-S)、碳键硫 (C-S)和未知态有机硫 (UO-S)的转化及生物有效性。结果表明 ,植物吸硫总量和植株含硫量从第一茬至第四茬逐渐下降 ,这与土壤MCP-S含量下降有关 ,而与土壤有机硫各组分的变化无关。种植期间土壤MCP-S的含量也是逐渐下降 ,种植水稻时下降的幅度小于种植玉米 ;土壤有机硫组分如C-O-S、C-S和UO-S从第一茬到第四茬逐渐下降 ,种植 4茬后 ,玉米和水稻的吸硫总量远大于土壤MCP-S的下降量 ,其高出部分来源于土壤有机硫的矿化。C-O-S、C-S和UO-S对植物都是有效的 ,各组分有机硫对玉米和水稻幼苗吸硫的表观贡献为:C-O-SC-SUO-S。淹水条件下有机硫对水稻的贡献大于好气条件下对玉米的贡献     

Diversity of microorganisms from forest soils differently polluted with heavy metals

Large accumulation of heavy metals in organic layers of forest soils may adversely affect the structure and diversity of microbial communities. The objective of this study was to assess the influence of different soil chemical properties on structure and diversity of microbial communities in soils polluted with different levels of heavy metals. The soil samples were taken at ten sites located in the vicinity of the cities of Legnica and Olkusz, differently polluted with Cu, Zn and Pb. The samples were measured for pH and the contents of organic C (C_org), total N (N_t), total S (S_t) and total Zn, Cu and Pb. The measured gross microbial properties included microbial biomass (C_mic) and soil respiration (RESP). The structure of soil microbial communities was assessed using phospholipid fatty acid (PLFA) analysis and the structure of soil bacterial communities using pyrosequencing of 16S rRNA genes. To assess diversity of the bacterial communities the Chao1 index was calculated based on the pyrosequencing data. For C_mic and RESP the most important factors were N_t and C_org, respectively. The structure and diversity of soil microbial communities revealed by PLFA profiles and pyrosequencing depended mainly on soil pH. The effect of high heavy metal contents on soil microbial properties was weaker compared with other soil properties. High concentrations of heavy metals negatively affected RESP and the Chao1 diversity index. The heavy metal pollution altered the structure of microbial communities measured with PLFA analysis, but the effect of heavy metal pollution was not observed for the structure of soil bacteria measured by pyrosequencing. The obtained results indicate that the use of soil microbial properties to study heavy metal effects may be difficult due to confounding influences of other environmental factors. In large-scale studies local variability of soil properties may obscure the effect of heavy metals.     

Changes in the organic matter forms in chernozems of the Kamennaya Steppe under different land uses, locations, and hydromorphism degrees

The soils of the Kamennaya Steppe (Voronezh oblast) were studied. The rate of changes in the contents of C_org and the particular forms of organic matter (labile, microbial, and stable) were revealed in the quasi-natural soils of the fallows and shelterbelt and in the arable soils (rainfed farming for 12, 55, 85, and 115 yrs and irrigated farming for 40 yrs) of different positions on the watersheds and slopes. The effect of the increased soil moistening in the recent decades was also studied. In the upper 50 cm of the fallow soils that were not plowed since 1882, the relative C_org accumulation in the recent 30 yrs has amounted to 5%. The soils of the shelterbelt planted in 1903 were similar to the fallow soils. As compared to the soil of the unmown fallow, the C_org loss from the 1-m soil layer under the shelterbelt and the 12-year-old cropland were less than 9%; the losses from the plowed soils (used for 55–115 yrs) were 21–27% on the watersheds and 37–46% on the slopes. In the first decade, the rate of the Corg losses in the 0- to 20-cm layer of the cultivated chernozem was 120 g C/m². With the increasing duration of the soil plowing (from 55 to 115 yrs), the C_org losses decreased from 45 to 28 g C/m² per yr in the watershed soils and from 51 to 35 g C/m² per yr in the soils on the slopes. The maximum loss of C_org was found for the soils on slopes, waterlogged soils, and irrigated soils. In the slope soils, the C_org loss due to erosion was 9–18% of the total. In the upper horizons of the old agrogenic soils, compared to the soil of the unmown fallow, the C_ha/C_fa increased, since the content of fulvic acids (FA) faster decreased than that of the humic acids (HA); the C content of the nonhydrolyzable residue was reduced. The slope and waterlogged soils differed from the watershed soils in the smaller amounts of HA and FA and in the greater content of humin carbon. In the 0- to 20-cm layer of the soils studied, the rate of the basal respiration (BR) was 0.2–0.5 μg C/g soil per h, the content of the microbial biomass (C_micr) was 326–1073 μg C/g, and the share of C_micr amounted to 1.0–1.9%. These values were minimal in the irrigated soil and maximal in the fallow ones. A high correlation coefficient (r = 0.88–0.92) was found between the C_micr content and the BR, between the contents of C_org and HA, and between the contents of C_org and mobile C. The correlation coefficient between the contents of C_org and FA and C_org and humin C was 0.67.     

Impact of the heatwave in 2003 on the summer CH4 budget of a spruce forest with large variation in soil drainage: A four‐year comparison (2001–2004)

Well‐aerated soils are sinks for atmospheric methane (CH₄) whereas hydromorphic soils act as sources. Both CH₄ oxidation and production are highly sensitive to variation in soil moisture. Significant changes of net CH₄ fluxes from soils can therefore be expected to accompany redistribution of precipitation in the course of climate change where more extreme events are predicted for the future. The extreme summer drought in 2003 offered the opportunity to study the impact of such events on methane fluxes under field conditions. The objective was to evaluate the impact of the summer drought in 2003 on net methane budget of a spruce‐forest ecosystem. We studied net CH₄ flux (bi‐)weekly during the summers of 2000–2004 using a closed‐chamber technique on six different soil types ranging from well‐aerated Cambisols, to poorly drained Gleysols and a wet Histosol in a cool‐humid spruce forest.