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1.
Soil food webs are mainly based on three primary carbon (C) sources: root exudates, litter, and recalcitrant soil organic matter (SOM). These C sources vary in their availability and accessibility to soil organisms, which could lead to different pathways in soil food webs. The presence of three C isotopes (12C, 13C and 14C) offers an unique opportunity to investigate all three C sources simultaneously. In a microcosm experiment we studied the effect of food web complexity on the utilization of the three carbon sources. We choose an incomplete three factorial design with (i) living plants, (ii) litter and (iii) food web complexity. The most complex food web consisted of autochthonous microorganisms, nematodes, collembola, predatory mites, endogeic and anecic earthworms. We traced C from all three sources in soil, in CO2 efflux and in individual organism groups by using maize grown on soil developed under C3 vegetation and application of 14C labelled ryegrass shoots as a litter layer. The presence of living plants had a much greater effect on C pathways than food web complexity. Litter decomposition, measured as 14CO2 efflux, was decreased in the presence of living plants from 71% to 33%. However, living plants increased the incorporation of litter C into microbial biomass and arrested carbon in the litter layer and in the upper soil layer. The only significant effect of food web complexity was on the litter C distribution in the soil layers. In treatments with fungivorous microarthropods (Collembola) the incorporation of litter carbon into mineral soil was reduced. Root exudates as C source were passed through rhizosphere microorganisms to the predator level (at least to the third trophic level). We conclude that living plants strongly affected C flows, directly by being a source of additional C, and indirectly by modifying the existing C flows within the food web including CO2 efflux from the soil and litter decomposition.  相似文献   

2.
The effect of barley plants on the rate of decomposition of soil organic matter over a 6-week period was studied using soil that had been previously labelled by incubation with 14C-labelled ryegrass for 1 year. The plants reduced the loss of 14CO2, from soil by 70 per cent over 42 days. About half of the reduction was accounted for by the uptake of labelled C by the plant roots, very little 14C label being associated with the shoot. Chemical fractionation of the root showed that the 14C was chemically incorporated into cell wall materials such as cellulose and holocellulose. The reduction in organic matter decomposition in the presence of plants has been explained by earlier workers in terms ofa reduction in microbial activity as a result of a soil moisture deficit caused by plant transpiration. This explanation does not account for all the reduction in decomposition noted in the present experiments. Control soil (without a plant, but amended with glucose or yeast extract to simulate the effect of root exudates) showed a small positive priming effect, the release of 14CO2, being increased. Thus the mechanism by which plants conserve organic matter is complex and cannot be explained merely by analogy to an increased level of nutrients available for microbial metabolism.  相似文献   

3.
The presence of plants induces strong accelerations in soil organic matter (SOM) mineralization by stimulating soil microbial activity – a phenomenon known as the rhizosphere priming effect (RPE). The RPE could be induced by several mechanisms including root exudates, arbuscular mycorrhizal fungi (AMF) and root litter. However the contribution of each of these to rhizosphere priming is unknown due to the complexity involved in studying rhizospheric processes. In order to determine the role of each of these mechanisms, we incubated soils enclosed in nylon meshes that were permeable to exudates, or exudates & AMF or exudates, AMF and roots under three grassland plant species grown on sand. Plants were continuously labeled with 13C depleted CO2 that allowed distinguishing plant-derived CO2 from soil-derived CO2. We show that root exudation was the main way by which plants induced RPE (58–96% of total RPE) followed by root litter. AMF did not contribute to rhizosphere priming under the two species that were significantly colonized by them i.e. Poa trivialis and Trifolium repens. Root exudates and root litter differed with respect to their mechanism of inducing RPE. Exudates induced RPE without increasing microbial biomass whereas root litter increased microbial biomass and raised the RPE mediating saprophytic fungi. The RPE efficiency (RPE/unit plant-C assimilated into microbes) was 3–7 times higher for exudates than for root litter. This efficiency of exudates is explained by a microbial allocation of fresh carbon to mineralization activity rather than to growth. These results suggest that root exudation is the main way by which plants stimulated mineralization of soil organic matter. Moreover, the plants through their exudates not only provide energy to soil microorganisms but also seem to control the way the energy is used in order to maximize soil organic matter mineralization and drive their own nutrient supply.  相似文献   

4.
The input of labeled C into the pool of soil organic matter, the CO2 fluxes from the soil, and the contribution of root and microbial respiration to the CO2 emission were studied in a greenhouse experiment with continuous labeling of oat plants with 13CO2 using the method of the natural 13C abundance in the air. The carbon of the microbial biomass composed 56 and 39% of the total amounts of 13C photoassimilates in the rhizosphere and in the bulk soil, respectively. The contribution of root respiration to the CO2 emission from the soil reached 61–92%, including 4–23% of the rhizomicrobial respiration. The contribution of the microbial respiration to the total CO2 emission from the soil varied from 8 to 39%. The soil organic matter served as the major carbon-containing substrate for microorganisms in the bulk soil and in the rhizosphere: 81–91% of the total amount of carbon involved in the microbial metabolism was derived from the soil organic matter.  相似文献   

5.
The Turnover of Plant Roots during the Growth Period and its Influence on “Soll Respiration” Mustard and wheat plants were grown under 14CO2, their roots being tightly separated from the shoot sphere. Root formation, root respiration, and root decomposition could thus be followed during the plant development by radiometric methods. The total quantity of organic root matter in soil at harvest time turned out to be 20–50% larger than the amount of root residues as determined by ordinary washing procedures. Depending on the plant and duration of the experiment, an additional amount of up to three times more than this remaining root carbon was already mineralized during the vegetation period. Only one fifth of this 14CO2-production could be attributed to the respiration of living root tissue, all the remainder seemed to be due to the microbial decomposition of dead roots, root residues and root excretions. Root respiration and root decomposition together produced almost four fifths of the total evolving CO2-quantity, whilst the contribution from soil organic matter breakdown did not exceed one fourth of it. According to these data, the total rhizo-deposition amounts to 3–4 times as much organic substance than what can be found as root residues at harvest time. This rich supply of readily decomposable organic matter leads to a most intensive turnover in the rhizosphere, which should be of considerable influence on the dynamic processes in soil.  相似文献   

6.
《Soil biology & biochemistry》2001,33(7-8):1067-1075
Placement of plant residues in conventional tillage (CT) and no-tillage (NT) soils affects organic matter accumulation and the organization of the associated soil food webs. Root-derived C inputs can be considerable and may also influence soil organic matter dynamics and soil food web organization. In order to differentiate and quantify C contributions from either roots or litter in CT and NT soils, a 14C tracer method was used.To follow root-derived C, maize plants growing in the field were 14C pulse-labeled, while the plant litter in those plots remained unlabeled. The 14C was measured in NT and CT soils for the different C pools (shoots, roots, soil, soil respiration, microbial biomass). Litter-derived C was followed by applying 14C labeled maize litter to plots which had previously grown unlabeled maize plants. The 14C pools measured for the litter-derived CT and NT plots included organic matter, microbial biomass, soil respiration, and soil organic C.Of the applied label in the root-derived C plots, 35–55, 6–8, 3, 1.6, and 0.4–2.4% was recovered in the shoots, roots, soil, cumulative soil respiration, and microbial biomass, respectively. The 14C recovered in these pools did not differ between CT and NT treatments, supporting the hypothesis that the rhizosphere microbial biomass in NT and CT may be similar in utilization of root-derived C. Root exudates were estimated to be 8–13% of the applied label. In litter-derived C plots, the percentage of applied label recovered in the particulate organic matter (3.2–82%), microbial biomass (4–6%), or cumulative soil respiration (12.5–14.7%) was the same for CT and NT soils. But the percentage of 14C recovered in CT soil organic C (18–69%) was higher than that in NT (12–43%), suggesting that particulate organic matter (POM) leaching and decomposition occurred at a higher rate in CT than in NT. Results indicate faster turnover of litter-derived C in the CT plots.  相似文献   

7.
The utilization of plant- and soil-C by the microbial biomass in the rhizosphere of maize plants was investigated as a function of root proximity. The plants were cultivated in pots with divided root chambers and their shoots supplied with 14CO2 for 23 days. Subsequently the individual soil zones were analyzed for organic C, 14C, biomass C and biomass 14C. Plant roots induced a 197% increase in microbial biomass and a 5.4% decrease in soil organic C compared with an 1.2% decrease in the unplanted control soil. The contributions of plant- and soil-C to this increased microbial growth amounted to 68% and 32% respectively. Biomass-14C corresponded to 1.6% of the total photosynthetically fixed 14C, to about 15% of the organic 14C-input into the rhizosphere and to 58% of the plant carbon remaining in soil after the removal of roots. 20% of this biomass-14C was found outside the immediate root zone. These results demonstrate that growing roots are a significant C-source for the microbial biomass and render an additional fraction of soil-C available to microbial utilization. The efficiency of C-utilization by the rhizosphere biomass is lower than values obtained with liquid cultures in laboratory experiments. The supply of plant-C to the microbial biomass outside the immediate root vicinity indicates that the overall volume of the maize rhizosphere is greater than what has been supposed so far.  相似文献   

8.
Priming effects: Interactions between living and dead organic matter   总被引：1，自引：0，他引：1  
In this re-evaluation of our 10-year old paper on priming effects, I have considered the latest studies and tried to identify the most important needs for future research. Recent publications have shown that the increase or decrease in soil organic matter mineralization (measured as changes of CO2 efflux and N mineralization) actually results from interactions between living (microbial biomass) and dead organic matter. The priming effect (PE) is not an artifact of incubation studies, as sometimes supposed, but is a natural process sequence in the rhizosphere and detritusphere that is induced by pulses or continuous inputs of fresh organics. The intensity of turnover processes in such hotspots is at least one order of magnitude higher than in the bulk soil. Various prerequisites for high-quality, informative PE studies are outlined: calculating the budget of labeled and total C; investigating the dynamics of released CO2 and its sources; linking C and N dynamics with microbial biomass changes and enzyme activities; evaluating apparent and real PEs; and assessing PE sources as related to soil organic matter stabilization mechanisms. Different approaches for identifying priming, based on the assessment of more than two C sources in CO2 and microbial biomass, are proposed and methodological and statistical uncertainties in PE estimation and approaches to eliminating them are discussed. Future studies should evaluate directions and magnitude of PEs according to expected climate and land-use changes and the increased rhizodeposition under elevated CO2 as well as clarifying the ecological significance of PEs in natural and agricultural ecosystems. The conclusion is that PEs - the interactions between living and dead organic matter - should be incorporated in models of C and N dynamics, and that microbial biomass should regarded not only as a C pool but also as an active driver of C and N turnover.  相似文献   

9.
We investigated contributions of leaf litter, root litter and root-derived organic material to tundra soil carbon (C) storage and transformations. 14C-labeled materials were incubated for 32 weeks in moist tussock tundra soil cores under controlled climate conditions in growth chambers, which simulated arctic fall, winter, spring and summer temperatures and photoperiods. In addition, we tested whether the presence of living plants altered litter and soil organic matter (SOM) decomposition by planting shoots of the sedge Eriophorum vaginatum in half of the cores. Our results suggest that root litter accounted for the greatest C input and storage in these tundra soils, while leaf litter was rapidly decomposed and much of the C lost to respiration. We observed transformations of 14C between fractions even when total C appeared unchanged, allowing us to elucidate sources and sinks of C used by soil microorganisms. Initial sources of C included both water soluble (WS) and acid-soluble (AS) fractions, primarily comprised of carbohydrates and cellulose, respectively. The acid-insoluble (AIS) fraction appeared to be a sink for C when conditions were favorable for plant growth. However, decreases in 14C activity from the AIS fraction between the fall and spring harvests in all treatments indicated that microorganisms consumed recalcitrant C compounds when soil temperatures were below 0 °C. In planted leaf litter cores and in both planted and unplanted SOM cores, the greatest amounts of 14C at the end of the experiment were found in the AIS fraction, suggesting a high rate of humification or accumulation of decay-resistant plant tissues. In unplanted leaf litter cores and planted and unplanted root litter cores most of the 14C remaining at the end of the experiment was in the AS fraction suggesting less extensive humification of leaf and root detritus. Overall, the presence of living plants stimulated decomposition of leaf litter by creating favorable conditions for microbial activity at the soil surface. In contrast, plants appeared to inhibit decomposition of root litter and SOM, perhaps because of microbial preferences for newer, more labile inputs from live roots.  相似文献   

10.
Microbial response to the addition of glucose in low-fertility soils   总被引：1，自引：0，他引：1  
Addition of soluble organic substrates to soil has been shown to either increase or restrict the rate of microbial CO2–C evolution. This has been attributed to a priming effect resulting from accelerated or decreased turnover of the soil organic matter including the soil microflora. We investigated microbial responses to small glucose-C additions (10–50 μg C g1 soil) in arable soils either amended or not with cellulose. An immediate CO2–C release between 0 and 69 h (equivalent to 59% of glucose-C applied) was measured. However, only half of the CO2–C respired could be attributed to the utilisation of glucose-C substrate, based on the percentage of 14C–CO2 evolved after the addition of a 14C-labelled glucose tracer. Thus, although no evidence of an immediate release of ‘extra’ C above the rate applied as glucose-C was observed, the pattern of decomposition for 14C-glucose suggested utilisation of an alternate C source. Based on this, a positive priming effect (1.5 to 4.3 times the amount CO2–C evolved that was attributed to glucose-C decomposition) was observed for at least 170 h in non-cellulose-amended soil and 612 h in cellulose-amended soil. Two further phases of microbial activity in cellulose-amended soils were attributed to either activation of different microbial populations or end-product inhibition of cellulase activity after glucose addition. During these subsequent phases, a negative priming effect of between 0.1 and 1.5 times was observed. Findings indicate that the response of the microbial community to small additions of soluble organic C substrate is not consistent and support the premise that microbial response varies in a yet to be predicted manner between soil type and ecosystems. We hypothesise that this is due to differences in the microbial community structure activated by the addition of organic C and the timing of soluble organic substrate addition with respect to the current dissolved organic C status of the soil.  相似文献   

11.
We have aimed to quantify the effect of roots on the size of the soil microbial biomass, and their influence on the turnover of soil organic matter and on the extent of the rhizosphere. We sampled a sandy clay loam topsoil from two subplots with different treatment histories. One had a normal arable fertilization record, the other had received only inorganic nitrogen fertilizer but no phosphorus and potassium for 30 years. Glucose labelled with 14C was added to both samples which were then incubated for 4 weeks before the soil was packed in cylinders and planted with ryegrass. In both soils, microbial biomass at the root surface doubled during the first 8 days. At day 15, the microbial biomass had further increased in the fertile soil, and the rhizosphere effect had extended 2.5 mm into the fertile soil, but to only 1 mm in the infertile soil. The microbial 14C increased threefold near the roots in the fertile soil as a result of assimilation of previously formed microbial residues, but in the infertile soil there was no increase. There was a close relation between the increase in microbial 14C and a decrease in 14C soluble in 2 m KCl, indicating that the microbial residues were more weakly adsorbed in the fertile soil. We conclude that the increased microbial population living near the root surfaces re‐assimilated part of the 14C‐labelled microbial residues in the fertile soil. In the infertile soil, microbial residues resisted decomposition because they were more strongly sorbed on to soil surfaces.  相似文献   

12.
We show that both temperature and priming act differently on distinct C pools in a temperate grassland soil. We used SOM which was 14C-labelled in four different ways: by labelling soil with 14C-glucose, by adding leaf litter from plants pre-labelled with 14CO2, and by labelling in situ with 14CO2 applied to the ryegrass canopy either 6 or 18 months earlier. Samples of each type of 14C labelled soil were incubated at either 4, 10, 15, or 20 °C and the exponential loss of 14CO2 used to characterise treatment effects. 14C allocation to microbial fractions was greater, and so overall mineralization by microbes was greater, as temperature rose, but turnover of the microbial labile pool was temperature-insensitive, and the turnover of microbial structural material was reduced as temperature rose. The ability of the microbial population to degrade just one fraction of plant litter was increased greatly by temperature. A pool of SOM with a half-life of about 70 d was degraded faster at higher temperatures. Less tractable but abundant pools of SOM were not accessed more readily at higher temperatures by the microbial population. Priming with glucose or amino-acids only speeded the mineralization of recent SOM (probably from the living microbial biomass), and was not altered by temperature. These results have implications for the impacts of climate change on soil C cycling.  相似文献   

13.
The amounts of organic materials released into soil from roots during the first 4 weeks of growth were determined for 11 cultivars of wheat (Triticum aestivum L.). Carbon loss from roots was measured by supplying 14CO2 continuously to the shoots and measuring the 14C content of the roots, root-free soil, water-soluble material and CO2 flushed from the root chamber. Six cultivars were compared in each of two experiments, with the cultivar Condor common to both experiments. There were no significant differences between cultivars, relative to Condor, for 14C activity present in soil, roots, water-soluble material or rhizosphere CO2. There was a significant difference between cultivars in experiment 1, but not in experiment 2, for the variate log10 (14C lost from roots: 14C translocated to roots).There was evidence that a reduction in growth temperature, within the range 10–15°C, increased carbon loss from wheat roots into the rhizosphere.  相似文献   

14.
Soil was freed of its organic matter by heating it to 400°C. Plants were grown in a 14CO2 atmosphere and from them a labelled “soil organic matter” (humus) was prepared by composting the plant material for more than 3 yr in the modified soil under laboratory conditions. The influence of small additions of unlabelled glucose on the decomposition of the labelled soil organic matter was studied. Shortly after the addition of glucose there was a small extra evolution of 14CO2, which lasted about 1 day. It is claimed that the extra evolution of 14CO2 was caused by conversion of labelled material in the living biomass and was not due to a real priming action, i.e. an accelerated decomposition of humic substances or dead cellular material.  相似文献   

15.
Although soil Collembola are known to contribute to soil carbon (C) cycling, their contribution to the mineralization of C sources that differ in bioavailability, such as soil organic C (SOC) and leaf litter, is unknown. Stable C isotopes are often used to quantify the effects of both soil C and litter C on C mineralization. Here, 13C-labeled litter was used to investigate the effects of Collembola (Folsomia candida) on the mineralization of both SOC and litter C in laboratory microcosms. The three microcosm treatments were soil alone (S); soil treated with δ13C-labeled litter (SL); and soil treated with δ13C-labeled litter and Collembola (SLC). The presence of Collembola did not significantly affect soil microbial biomass or litter mass loss and only had a small effect on CO2 release during the first week of the experiment, when most of the CO2 was derived from litter rather than from SOC. Later, during the experiment (days 21 and 63), when litter-derived labile C had been depleted and when numbers of Collembola had greatly increased, Collembola substantially increased the emission of SOC-derived CO2. These results suggest that the effect of Collembola on soil organic C mineralization is negatively related to C availability.  相似文献   

16.
Five microbial species (Aspergillus flavus, Trichoderma viride, Streptomyces sp., Arthrobacter sp., Achromobacter liquefaciens) were cultivated in liquid media containing 14C-labelled glucose. The decomposition of these microorganisms was recorded in four different soils after chloroform fumigation by a technique related to that proposed by Jenkinson and Powlson, to determine the mineralization rate of microbial organic matter (Kc coefficient). Three treatments were used: untreated soil, fumigated soil alone and fumigated soil supplied with 14C-labelled cells. Total evolved CO2 and 14CO2 were measured after 7 and 14 days at 28°C.The labelled microorganisms enabled the calculation of mineralization rate Kc (Kc = mineralized microbial carbon/supplied microbial carbon). The extent of mineralization of labelled microbial carbon depended on the type of soil and on the microbial species. Statistical analysis of results at 7 days showed that 58% of the variance is taken in account by the soil effect and 32% by the microorganism effect. Between 35 and 49% of the supplied microbial C was mineralized in 7 days according to the soil type and the species of microorganism. Our results confirmed that the average value for Kc = 0.41 is acceptable, but Kc variability according to soil type must be considered.The priming effect on organic C and native microbial biomass mineralization, due to microbial carbon addition was obtained by comparison between the amount of non-labelled CO2-C produced by fumigated soils with or without added labelled microorganisms: this priming effect was generally negligible.These results indicate that the major portion of the error of microbial biomass measurement comes from the Kc estimation.  相似文献   

17.
It is still unclear whether elevated CO2 increases plant root exudation and consequently affects the soil microbial biomass. The effects of elevated CO2 on the fate of the C and nitrogen (N) contained in old soil organic matter pools is also unclear. In this study the short and long-term effects of elevated CO2 on C and N pools and fluxes were assessed by growing isolated plants of ryegrass (Lolium perenne) in glasshouses at elevated and ambient atmospheric CO2 and using soil from the New Zealand FACE site that had >4 years exposure to CO2 enrichment. Using 14CO2 pulse labelling, the effects of elevated CO2 on C allocation within the plant-soil system were studied. Under elevated CO2 more root derived C was found in the soil and in the microbial biomass 48 h after labelling. The increased availability of substrate significantly stimulated soil microbial growth and acted as priming effect, enhancing native soil organic matter decomposition regardless of the mineral N supply. Despite indications of faster N cycling in soil under elevated CO2, N availability to plants stayed unchanged. Soil previously exposed to elevated CO2 exhibited a higher N cycling rate but again there was no effect on plant N uptake. With respect to the difficulties of extrapolating glasshouse experiment results to the field, we concluded that the accumulation of coarse organic matter observed in the field under elevated CO2 was probably not created by an imbalance between C and N but was likely to be due to more complex phenomena involving soil mesofauna and/or other nutrients limitations.  相似文献   

18.
A greenhouse rhizobox experiment was carried out to investigate the fate and turnover of 13C‐ and 15N‐labeled rhizodeposits within a rhizosphere gradient from 0–8 mm distance to the roots of wheat. Rhizosphere soil layers from 0–1, 1–2, 2–3, 3–4, 4–6, and 6–8 mm distance to separated roots were investigated in an incubation experiment (42 d, 15°C) for changes in total C and N and that derived from rhizodeposition in total soil, in soil microbial biomass, and in the 0.05 M K2SO4–extractable soil fraction. CO2‐C respiration in total and that derived from rhizodeposition were measured from the incubated rhizosphere soil samples. Rhizodeposition C was detected in rhizosphere soil up to 4–6 mm distance from the separated roots. Rhizodeposition N was only detected in the rhizosphere soils up to 3–4 mm distance from the roots. Microbial biomass C and N was increased with increasing proximity to the separated roots. Beside 13C and 15N derived from rhizodeposits, unlabeled soil C and N (native SOM) were incorporated into the growing microbial biomass towards the roots, indicating a distinct acceleration of soil organic matter (SOM) decomposition and N immobilization into the growing microbial biomass, even under the competition of plant growth. During the soil incubation, microbial biomass C and N decreased in all samples. Any decrease in microbial biomass C and N in the incubated rhizosphere soil layers is attributed mainly to a decrease of unlabeled (native) C and N, whereas the main portion of previously incorporated rhizodeposition C and N during the plant growth period remained immobilized in the microbial biomass during the incubation. Mineralization of native SOM C and N was enhanced within the entire investigated rhizosphere gradient. The results indicate complex interactions between substrate input derived from rhizodeposition, microbial growth, and accelerated C and N turnover, including the decomposition of native SOM (i.e., rhizosphere priming effects) at a high spatial resolution from the roots.  相似文献   

19.
Biochar application to arable soils could be effective for soil C sequestration and mitigation of greenhouse gas (GHG) emissions. Soil microorganisms and fauna are the major contributors to GHG emissions from soil, but their interactions with biochar are poorly understood. We investigated the effects of biochar and its interaction with earthworms on soil microbial activity, abundance, and community composition in an incubation experiment with an arable soil with and without N-rich litter addition. After 37 days of incubation, biochar significantly reduced CO2 (up to 43 %) and N2O (up to 42 %), as well as NH4 +-N and NO3 ?-N concentrations, compared to the control soils. Concurrently, in the treatments with litter, biochar increased microbial biomass and the soil microbial community composition shifted to higher fungal-to-bacterial ratios. Without litter, all microbial groups were positively affected by biochar × earthworm interactions suggesting better living conditions for soil microorganisms in biochar-containing cast aggregates after the earthworm gut passage. However, assimilation of biochar-C by earthworms was negligible, indicating no direct benefit for the earthworms from biochar uptake. Biochar strongly reduced the metabolic quotient qCO2 and suppressed the degradation of native SOC, resulting in large negative priming effects (up to 68 %). We conclude that the biochar amendment altered microbial activity, abundance, and community composition, inducing a more efficient microbial community with reduced emissions of CO2 and N2O. Earthworms affected soil microorganisms only in the presence of biochar, highlighting the need for further research on the interactions of biochar with soil fauna.  相似文献   

20.
The biogas production process generates as side-products biogas residues containing microbial biomass which could contribute to soil organic matter formation or induce CO2 emissions when applied to arable soil as fertilizer. Using an isotope labelling approach, we labelled the microbial biomass in biogas residues, mainly G+ bacteria and methanogenic archaea via KH13CO3, and traced the fate of microbial biomass carbon in soil with an incubation experiment lasting 378 days. Within the first seven days, 40% of the carbon was rapidly mineralized and after that point mineralization continued, reaching 65% by the end of the experiment. Carbon mineralization data with 93% recovery could be fitted to a two-pool degradation model which estimated proportions and degradation rate constants of readily and slowly degrading pools. About 49% of the carbon was in the slowly degrading pool with a half-life of 1.9 years, suggesting mid-term contribution to living and non-living soil organic matter formation. Biogas residues caused a priming effect at the beginning, thus their intensive application should be avoided.  相似文献   

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