1,721,115 research outputs found
Methane and nitrous oxide fluxes of soils in pure and mixed stands of European beech and Norway spruce
No full textTree species can affect the sink and source strength of soils for atmospheric methane and nitrous oxide. Here we report soil methane (CH4) and nitrous oxide (N2O) fluxes of adjacent pure and mixed stands of beech and spruce at Solling, Germany. Mean CH4 uptake rates ranged between 18 and 48 mu g C m(-2) hour(-1) during 2.5 years and were about twice as great in both mixed and the pure beech stand as in the pure spruce stand. CH4 uptake was negatively correlated with the dry mass of the O horizon, suggesting that this diminishes the transport of atmospheric CH4 into the mineral soil. Mean N2O emission was rather small, ranging between 6 and 16 mu g N m(-2) hour(-1) in all stands. Forest type had a significant effect on N2O emission only in one mixed stand during the growing season. We removed the O horizon in additional plots to study its effect on gas fluxes over 1.5 years, but N2O emissions were not altered by this treatment. Surprisingly, CH4 uptake decreased in both mixed and the pure beech stands following the removal of the O horizon. The decrease in CH4 uptake coincided with an increase in the soil moisture content of the mineral soil. Hence, O horizons may maintain the gas diffusivity within the mineral soil by storing water which cannot penetrate into the mineral soil after rainfall. Our results indicate that conversion of beech forests to beech-spruce and pure spruce forests could decrease soil CH4 uptake, while the long-term effect on N2O emissions is expected to be rather small
Laboratory estimates of trace gas emissions following surface application and injection of cattle slurry
No full textApplying cattle slurry to soil may induce emissions of the greenhouse gases N2O and CH4. Our objective was to determine the effects of different application techniques (surface application and slit injection) of cattle (Bostaurus) slurry on the decomposition of slurry organic matter and the emissions of N2O and CH4. The effects of slurry application (43.6 m(3) ha(-1)) were studied for 9 wk under controlled laboratory conditions using a soil microcosm system with automated monitoring of the CO2, N2O, and CH4 fluxes, The soil used was a silty loam (Ap horizon of a cambisol) with a constant water-filled pore space of 67% during the experiment. About 38% of the organic matter applied with the slurry was decomposed within 9 wk. Production of CO2 was not affected by the application technique. Emissions of N2O and CN4 from the injected slurry were significantly higher than from the surface-applied slurry, probably because of restricted aeration at the injected-slurry treatment. Total N2O-N emissions were 0.2% (surface application) and 3.3% (slit injection) of the slurry N added, Methane emission occurred only during the first Few days followimg application. The total net nux of CH4-C for 2 wk was -12 g ha(-1) for the control (CH4 uptake), 2 g ha(-1) far the surface-applied slurry, and 39 g ha(-1) for the injected slurry. Slurry injection, which is recommended to reduce NH3 volatilization, appears to increase emissions of the greenhouse gases N2O and CH4 from the fertilized fields
Influence of soil acidity on depth gradients of microbial biomass in beech forest soils
No full textThe objectives of the study were to investigate mineral soil profiles as a living space for microbial decomposers and the relation of microbial properties to soil acidity. We estimated microbial biomass C on concentration (mu g g(-1) DW) as well as on volume basis ( g m(-2)) and the microbial biomass C to soil organic C ratio along a vertical gradient from L horizon to 20 cm in the mineral soil and along a gradient of increasing acidity at five beech forest stands in Germany. Microbial biomass C concentration ranged from 17,000 - 34,000 mu g C-mic g(-1) DW in the litter layer and decreased dramatically down the profile to 29 - 264 mu g C-mic g(-1) DW at 15 - 20 cm depth in the mineral soil. This represents depth gradients of microbial biomass C concentrations ranging from a factor of 65 in slightly acidic and up to 875 in acidic soils. In contrast, microbial biomass C calculated on a volume basis ( g C-mic m(-2)) showed a different pattern since a considerable part of the microbial biomass C was located in the mineral soils. In the soil profile 22-34% of the microbial biomass C was found in the mineral soil at strictly acidic sites and as much as 64 - 88% in slightly acidic soils. The microbial biomass C to soil organic carbon ratios decreased in general down from the L horizon in the forest floor to 0 - 5 cm depth in the mineral soils. In strongly acidic mineral soils however, the C to soil organic carbon ratio increased with depth, suggesting a positive relation to increasing pH. We conclude from depth gradients of soil pH and microbial biomass C to soil organic carbon ratio that pH affects this ratio at acidic sites. The inter-site comparison indicates that acidity restricts microbial biomass C in the mineral soils
Control of nitrous oxide emissions in European beech, Norway spruce and Scots pine forests
No full textElevated nitrogen deposition has increased tree growth, the storage of soil organic matter, and nitrate leaching in many European forests, but little is known about the effect of tree species and nitrogen deposition on nitrous oxide emission. Here we report soil N(2)O emission from European beech, Scots pine and Norway spruce forests in two study areas of Germany with distinct climate, N deposition and soils. N(2)O emissions and throughfall input of nitrate and ammonium were measured biweekly during growing season and monthly during dormant season over a 28 months period. Annual N(2)O emission rates ranged between 0.4 and 1.3 kg N ha(-1) year(-1) among the stands and were higher in 1998 than in 1999 due to higher precipitation during the growing season of 1998. A 2-way-ANOVA revealed that N(2)O fluxes were significantly higher (p< 0.001) at Solling than at Unterlub while tree species had no effect on N(2)O emissions. Soil texture and the amount of throughfall explained together 94% of the variance among the stands, indicating that increasing portions of silt and clay may promote the formation of N(2)O in wet forest soils. Moreover, cumulative N(2)O fluxes were significantly correlated (r(2) = 0.60, p< 0.001) with cumulative NO(3)(-) fluxes at 10 cm depth as an indicator of N saturation, however, the slope of the regression curve indicates a rather weak effect of NO(3)(-) fluxes on N(2)O emissions. N input by throughfall was not correlated with N(2)O emissions and only 1.6 - 3.2% of N input was released as N(2)O to the atmosphere. Our results suggest that elevated N inputs have little effect on N(2)O emissions in beech, spruce and pine forests
Soil respiration in pure and mixed stands of European beech and Norway spruce following removal of organic horizons
No full textSoil respiration was measured in adjacent pure and mixed stands of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) at Soiling, Germany. Forest type had a significant effect on soil respiration, which was highest in the pure beech stand and lowest in the pure spruce stand. Both throughfall and soil temperature increased with the proportion of beech. Additionally, microbial respiration and biomass in the organic (O) horizons increased sequentially from the pure spruce to the pure beech stand, suggesting that abiotic and biotic factors enhanced the decomposition of litter under beech. Because the spruce litter decomposition rate was low, carbon (C) stocks of the O horizons increased with the proportion of spruce, from 1.6 to 5.1 kg C(.)m(-2). The removal of the O horizons decreased soil respiration by 31%-45%, indicating a large contribution of the mineral soil and roots to total soil respiration. Turnover times of organic C in the O horizons ranged between 5.5 years in the pure beech stand and 20.6 years in the pure spruce stand. Our results suggest that tree species conversion may alter the turnover of soil organic matter, and thus the sequestration of organic C in the O horizons
Estimating water retention curves of forest soils from soil texture and bulk density
No full textForest soils differ significantly from the arable land in their distribution of the soil bulk density and humus content, but the water retention parameters are primarily derived from the data of agricultural soils. Thus, there is a need to relate physical parameters of forest soils with their water retention characteristics and compare them with those of agricultural soils. Using 1850 water retention curves from forest soils, we related the following soil physical parameters to soil texture, bulk density, and C content: air capacity (AC), available water capacity (AWC), and the permanent wilting point (PWP). The ACs of forest soils were significantly higher than those of agricultural soils which were related to the low bulk densities of the forest soils, whereas differences in AWCs were small. Therefore, for a proper evaluation of the water retention curves (WRCs) and the parameters derived from them, further subdivisions of the lowest (< 1.45 g cm(-3)) of the three bulk density classes was undertaken to the wide range of low soil densities in forest soils (giving a total of 5 bulk density classes). In Germany, 31 soil texture classes are used for the estimation of soil physical parameters' Such a detailed classification is not required because of insignificant differences in WRCs for a large number of these classes. Based on cluster analysis of AC, AWC, and PWP parameters, 10 texture collectives were obtained. Using 5 classes of bulk densities, we further calculated the ACs, AWCs, and the PWPs for these 10 classes. Furthermore, "van Genuchten parameters" (thetar, thetas, alpha, and n) were derived which described the average WRC for each designated class. In a second approach using multiple regression analysis, regression functions for AC, AWC, and PWP and for the van Genuchten parameter were calculated
Soil phosphorus status and turnover in central-European beech forest ecosystems with differing tree species diversity
No full textProblems in phosphorus (P) nutrition of forest trees raise questions concerning the soil P concentrations, pools and turnover in forests. In addition, it is not clear if, and to what extent, tree species diversity has an influence on the soil P status and turnover. The aim of this study was to investigate the P status and turnover in beech (Fagus sylvatica L.) -dominated forest ecosystems on loess over limestone and to elucidate what role heterogeneities in tree species diversity would play. The soils of mixed species stands contained more organically bound P (710-772 kg ha(-1)) than those of pure beech stands (378 kg ha(-1)), whereas the inorganic P content differed little between the stand types. A large proportion (44-55%) of the total soil P was organically bound. This fraction was mainly dependent on the clay content of the soils and not on the tree diversity. The P input with leaf litter (1.4-2.1 kg ha(-1) year(-1)) showed a tendency to increase with increasing diversity. The apparent P turnover times in the organic surface layers differed, with shorter turnover times in mixed species stands (2-3 years) than in pure beech stands (10 years). Possible explanations for the different turnover times were differences in the litter quality, interactions in mixed species litters and the soil pH and base saturation. Hence, the tree species mainly influence the apparent P turnover time in the organic surface layer, whereas the P concentrations and pools in the mineral soil are determined by the soil properties, particularly the clay content.German Research Council (DFG) [1086
Potential contribution of Lumbricus terrestris L. to carbon dioxide, methane and nitrous oxide fluxes from a forest soil
No full textPotential effects of earthworms (Lumbricus terrestris L.) inoculated into soil on fluxes of CO2, CH4 and N2O were investigated for an untreated and a limed soil under beech in open topsoil columns under field conditions for 120 days. Gas fluxes from L. terrestris, beech litter and mineral soil from soil columns were measured separately in jars at 17 degreesC. The inoculation with L. terrestris and the application of lime had no effect on cumulative CO2 emissions from soil. During the first 3-4 weeks earthworms significantly (P<0.05) increased CO2 emissions by 16% to 28%. In contrast, significantly lower (P<0.05) CO2 emission rates were measured after 11 weeks. The data suggest that earthworm activity was high during the first weeks due to the creation of burrows and incorporation of beech litter into the mineral soil. Low cumulative CH4 oxidation rates were found in all soil columns as a result of CH4 production and oxidation processes. L. terrestris with fresh feces and the beech litter produced CH4 during the laboratory incubation, whereas the mineral soil oxidised atmospheric CH4. Inoculation with L. terrestris led to a significant reduction (P<0.02) in the CH4 oxidation rate of soil, i.e. 53% reduction. Liming had no effect on cumulative CH4 oxidation rates of soil columns and on CH4 fluxes during the laboratory incubation. L. terrestris significantly increased (P<0.001) cumulative N2O emissions of unlimed soil columns by 57%. The separate incubation of L. terrestris with fresh feces resulted in rather high N2O emissions, but the rate strongly decreased from 54 to 2 mug N kg(-1) (dry weight) h(-1) during the 100 h of incubation. Liming had a marked effect on N2O formation and significantly (P<0.001) reduced cumulative N2O emissions by 34%. Although the interaction of liming and L. terrestris was not significant, N2O emissions of limed soil columns with L. terrestris were 8% lower than those of the control
Hot water extractable C and N in relation to microbiological properties of soils under beech forests
No full textHot water extraction is sometimes recommended as an easy method to estimate the readily mineralizable fractions of total C (C-t) and total N (N-t) in arable soils. However, the usefulness of this method for forest soils has not been adequately studied. The objectives of this study were to relate the hot water extractable C (C-hw) and N (N-hw) to microbiological and chemical properties of the forest soils under beech (Fagus sylvatica L.) stands and to test the ability of near infrared spectroscopy (NIRS) to predict chemical and microbial properties of these soils. Soils differing in humus type, soil type and soil texture were collected from five locations and five depths. In all soils the amount of C-hw was higher than the microbial biomass C (C-mic) indicating that a considerable part of C-hw was of non-microbial origin. The amount of C-hw in mineral soil correlated significantly (r =-0.30-0.53) with C-mic, basal respiration (BAS) and C-t/N-t ratio but was not related to C-mic/C-t ratio. The amount of N-hw was correlated with C-mic, BAS, C-mic/C-t ratio, and C-t/N-t ratio (r =-0.59-0.78). However, C-t and N-t values showed better relationships (r =-0.42-0.88) with all the parameters, indicating no advantage in using C-hw and N-hw in forest soils. NIRS predicted satisfactorily C-t, N-t, C-hw, N-hw, C-mic, C-mic/C-t ratio and BAS in the mineral soils [the regression coefficients (a) of linear regression (measured against predicted values) ranged from 0.84 to 1.17 and the correlation coefficients (r) ranged from 0.86 to 0.94] indicating the applicability of NIRS to estimate these properties
Use of C-13 and N-15 mass spectrometry to study the decomposition of Calamagrostis epigeios in soil column experiments with and without ash additions
No full textThe dynamics of C and N in terrestrial ecosystems are not completely understood and the use of stable isotopes may be useful to gain further insight in the pathways of CO2 emissions and leaching of dissolved organic carbon (DOC) and nitrogen (DON) during decomposition of litter. Objectives were (i) to study the decomposition dynamics of Calamagrostis epigeios, a common grass species in forests, using C-13-depleted and N-15-enriched plants and (ii) to quantify the effect wood ash addition on the decomposition and leaching of DOC and DON. Decomposition was studied for 128 days under aerobic conditions at 8 degrees C and moisture close to field capacity in a spodic dystric Cambisol with mor-moder layer. Variants included control plots and additions of (i) Calamagrostis litter and (ii) Calamagrostis litter plus 4 kg ash m(-2). Decomposition of Calamagrostis resulted in a CO2 production of 76.2 g CO2-C (10% of added C) after 128 days and cumulative DOC production was 14.0 g C m(-2) out of which 0.9 g C m(-2) was Calamagrostis-derived (0.1% of added C). The specific CO2 formation and specific DOC production from Calamagrostis were 6 times higher (CO2) and 4 times smaller (DOC) than those from the organic layer. The amount of Calamagrostis-derived total N (NH4+, NO3-, DON) leached was 0.7 g N m(-2) (4.8% of added N). Cumulative DON production was 0.8 g N m(-2) which was slightly higher than for the control. During soil passage, much of the DOC and DON was removed due to sorption or decomposition. DOC and DON releases from the mineral soil (17 cm depth) were 6.3 g C m(-2) and 0.5 g N m(-2). (ii) Addition of ash resulted in a complete fixing of CO2 for 40 days due to carbonatisation. Afterwards, the CO2 production rates were similar to the variant without ash addition. Production of DOC (98.6 g C m(-2)) and DON (2.5 g N m(-2)) was marked, mainly owing to humus decay. However, Calamagrostis-derived DOC and Calamagrostis-derived total N were only 3.9 g C m(-2) (0.5 % of added C) and 0.5 g m(-2) (3.4% of added N). The specific DOC production rate from the organic layer was 6 rimes higher than that from Calamagrostis. The results suggest that with increasing humification from fresh plant residues to more decomposed material (O-F and O-H layers) the production ratio of DOC/CO2-C increases. Addition of alkaline substances to the forest floor can lead to a manifold increase in DOC production
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