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1.
Biochar application to soils may increase carbon (C) sequestration due to the inputs of recalcitrant organic C. However, the effects of biochar application on the soil greenhouse gas (GHG) fluxes appear variable among many case studies; therefore, the efficacy of biochar as a carbon sequestration agent for climate change mitigation remains uncertain. We performed a meta‐analysis of 91 published papers with 552 paired comparisons to obtain a central tendency of three main GHG fluxes (i.e., CO 2, CH 4, and N 2O) in response to biochar application. Our results showed that biochar application significantly increased soil CO 2 fluxes by 22.14%, but decreased N 2O fluxes by 30.92% and did not affect CH 4 fluxes. As a consequence, biochar application may significantly contribute to an increased global warming potential (GWP) of total soil GHG fluxes due to the large stimulation of CO 2 fluxes. However, soil CO 2 fluxes were suppressed when biochar was added to fertilized soils, indicating that biochar application is unlikely to stimulate CO 2 fluxes in the agriculture sector, in which N fertilizer inputs are common. Responses of soil GHG fluxes mainly varied with biochar feedstock source and soil texture and the pyrolysis temperature of biochar. Soil and biochar pH, biochar applied rate, and latitude also influence soil GHG fluxes, but to a more limited extent. Our findings provide a scientific basis for developing more rational strategies toward widespread adoption of biochar as a soil amendment for climate change mitigation. 相似文献
2.
Animal manure application as organic fertilizer does not only sustain agricultural productivity and increase soil organic carbon (SOC) stocks, but also affects soil nitrogen cycling and nitrous oxide (N 2O) emissions. However, given that the sign and magnitude of manure effects on soil N 2O emissions is uncertain, the net climatic impact of manure application in arable land is unknown. Here, we performed a global meta‐analysis using field experimental data published in peer‐reviewed journals prior to December 2015. In this meta‐analysis, we quantified the responses of N 2O emissions to manure application relative to synthetic N fertilizer application from individual studies and analyzed manure characteristics, experimental duration, climate, and soil properties as explanatory factors. Manure application significantly increased N 2O emissions by an average 32.7% (95% confidence interval: 5.1–58.2%) compared to application of synthetic N fertilizer alone. The significant stimulation of N 2O emissions occurred following cattle and poultry manure applications, subsurface manure application, and raw manure application. Furthermore, the significant stimulatory effects on N 2O emissions were also observed for warm temperate climate, acid soils (pH < 6.5), and soil texture classes of sandy loam and clay loam. Average direct N 2O emission factors (EFs) of 1.87% and 0.24% were estimated for upland soils and rice paddy soils receiving manure application, respectively. Although manure application increased SOC stocks, our study suggested that the benefit of increasing SOC stocks as GHG sinks could be largely offset by stimulation of soil N 2O emissions and aggravated by CH 4 emissions if, particularly for rice paddy soils, the stimulation of CH 4 emissions by manure application was taken into account. 相似文献
3.
A greenhouse experiment was conducted to determine the influence of cropping variables on nitrogen dynamics in a soil amended
with green manure. Surface soil from various long-term spring wheat rotations was amended with 15N-labelled legume green manure ( Lathyrus tingitanus) and subsequently cropped (canola [ Brassica napus] and spring wheat [ Triticum aestivum]) or incubated without a crop for 56 days in a greenhouse. Nitrogen mineralization from both the indigenous soil N and from
green manure was suppressed in cropped soil. Net N mineralization in the uncropped and cropped treatments averaged 73 and
43 mg kg −1, respectively. This difference was attributed, in part, to enhanced biological immobilization in the rhizosphere. Previous
cropping practices also had significant effect on N mineralization, largely by their influence on indigenous organic matter
quality. These observations suggest that short-term N mineralization is favored by fallowing soil after green manure application
whereas N retention in organic matter is favored by immediate cropping.
Contribution 3878873 相似文献
4.
Climate and land‐use models project increasing occurrence of high temperature and water deficit in both agricultural production systems and terrestrial ecosystems. Episodic soil wetting and subsequent drying may increase the occurrence and magnitude of pulsed biogeochemical activity, affecting carbon (C) and nitrogen (N) cycles and influencing greenhouse gas (GHG) emissions. In this study, we provide the first data to explore the responses of carbon dioxide (CO 2) and nitrous oxide (N 2O) fluxes to (i) temperature, (ii) soil water content as percent water holding capacity (%WHC), (iii) substrate availability throughout, and (iv) multiple soil drying and rewetting (DW) events. Each of these factors and their interactions exerted effects on GHG emissions over a range of four (CO 2) and six (N 2O) orders of magnitude. Maximal CO 2 and N 2O fluxes were observed in environments combining intermediate %WHC, elevated temperature, and sufficient substrate availability. Amendments of C and N and their interactions significantly affected CO 2 and N 2O fluxes and altered their temperature sensitivities (Q 10) over successive DW cycles. C amendments significantly enhanced CO 2 flux, reduced N 2O flux, and decreased the Q 10 of both. N amendments had no effect on CO 2 flux and increased N 2O flux, while significantly depressing the Q 10 for CO 2, and having no effect on the Q 10 for N 2O. The dynamics across DW cycles could be attributed to changes in soil microbial communities as the different responses to wetting events in specific group of microorganisms, to the altered substrate availabilities, or to both. The complex interactions among parameters influencing trace gas fluxes should be incorporated into next generation earth system models to improve estimation of GHG emissions. 相似文献
5.
Miscanthus x giganteus's efficacy as an energy crop relies on maintaining low greenhouse gas (GHG) emissions. As demand for Miscanthus is expected to rise to meet bioenergy targets, fertilizers and composts may be employed to increase yields, but will also increase GHG emissions. Manipulation experiments are vital to investigate the consequences of any fertilizer additions, but there is currently no way to measure whole‐plant GHG fluxes from crops taller than 2.5 m, such as Miscanthus, at the experimental plot scale. We employed a unique combination of eddy covariance (EC), soil chambers and an entirely new automated chamber system, SkyBeam, to measure high frequency (ca. hourly) fluxes of carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2O) from a Miscanthus crop amended with green compost. Untreated controls were also monitored in a fully replicated experimental design. Net ecosystem exchange (NEE) of CO 2 was partitioned into soil respiration ( Rs), gross primary productivity (GPP) and ecosystem respiration, and the crop was harvested to determine the effect of compost on crop productivity. Compost increased NEE emissions by 100% ( p < .05), which was the result of a 20% increase of Rs ( p < .06) and a 32% reduction in GPP ( p < .05) and biomass of 37% ( p < .06). Methane fluxes were small and unaffected by compost addition. N 2O emissions increased 34% under compost during an emission event; otherwise, fluxes were low and often negative, even under dry conditions. Diurnal variation in N 2O fluxes, with uptake during the day and emission at night was observed. These fluxes displayed a negative relationship with soil temperature and a hitherto undescribed diurnal temperature hysteresis. We conclude that compost addition negatively affected the productivity and environmental effects of Miscanthus cultivation during the first year following application. 相似文献
6.
Wetland catchments are major ecosystems in the Prairie Pothole Region (PPR) and play an important role in greenhouse gases (GHG) flux. However, there is limited information regarding effects of land-use on GHG fluxes from these wetland systems. We examined the effects of grazing and haying, two common land-use practices in the region, on GHG fluxes from wetland catchments during 2007 and 2008. Fluxes of methane (CH 4), nitrous oxide (N 2O), and carbon dioxide (CO 2), along with soil water content and temperature, were measured along a topographic gradient every other week during the growing season near Ipswich, SD, USA. Closed, opaque chambers were used to measure fluxes of soil and plant respiration from native sod catchments that were grazed or left idle, and from recently restored catchments which were seeded with native plant species; half of these catchments were hayed once during the growing season. Catchments were adjacent to each other and had similar soils, soil nitrogen and organic carbon content, precipitation, and vegetation. When compared with idle catchments, grazing as a land-use had little effect on GHG fluxes. Likewise, haying had little effect on fluxes of CH 4 and N 2O compared with non-hayed catchments. Haying, however, did have a significant effect on combined soil and vegetative CO 2 flux in restored wetland catchments owing to the immediate and comprehensive effect haying has on plant productivity. This study also examined soil conditions that affect GHG fluxes and provides cumulative annual estimates of GHG fluxes from wetland catchment in the PPR. 相似文献
7.
The influence of forest stand age in a Picea sitchensis plantation on (1) soil fluxes of three greenhouse gases (GHGs – CO 2, CH 4 and N 2O) and (2) overall net ecosystem global warming potential (GWP), was investigated in a 2‐year study. The objective was to isolate the effect of forest stand age on soil edaphic characteristics (temperature, water table and volumetric moisture) and the consequent influence of these characteristics on the GHG fluxes. Fluxes were measured in a chronosequence in Harwood, England, with sites comprising 30‐ and 20‐year‐old second rotation forest and a site clearfelled (CF) some 18 months before measurement. Adjoining unforested grassland (UN) acted as a control. Comparisons were made between flux data, soil temperature and moisture data and, at the 30‐year‐old and CF sites, eddy covariance data for net ecosystem carbon (C) exchange (NEE). The main findings were: firstly, integrated CO 2 efflux was the dominant influence on the GHG budget, contributing 93–94% of the total GHG flux across the chronosequence compared with 6–7% from CH 4 and N 2O combined. Secondly, there were clear links between the trends in edaphic factors as the forest matured, or after clearfelling, and the emission of GHGs. In the chronosequence sites, annual fluxes of CO 2 were lower at the 20‐year‐old (20y) site than at the 30‐year‐old (30y) and CF sites, with soil temperature the dominant control. CH 4 efflux was highest at the CF site, with peak flux 491±54.5 μg m −2 h −1 and maximum annual flux 18.0±1.1 kg CH 4 ha −1 yr −1. No consistent uptake of CH 4 was noted at any site. A linear relationship was found between log CH 4 flux and the closeness of the water table to the soil surface across all sites. N 2O efflux was highest in the 30y site, reaching 108±38.3 μg N 2O‐N m −2 h −1 (171 μg N 2O m −2 h −1) in midsummer and a maximum annual flux of 4.7±1.2 kg N 2O ha −1 yr −1 in 2001. Automatic chamber data showed a positive exponential relationship between N 2O flux and soil temperature at this site. The relationship between N 2O emission and soil volumetric moisture indicated an optimum moisture content for N 2O flux of 40–50% by volume. The relationship between C : N ratio data and integrated N 2O flux was consistent with a pattern previously noted across temperate and boreal forest soils. 相似文献
8.
Biochar as a carbon‐rich coproduct of pyrolyzing biomass, its amendment has been advocated as a potential strategy to soil carbon (C) sequestration. Updated data derived from 50 papers with 395 paired observations were reviewed using meta‐analysis procedures to examine responses of soil carbon dioxide (CO 2) fluxes, soil organic C (SOC), and soil microbial biomass C (MBC) contents to biochar amendment. When averaged across all studies, biochar amendment had no significant effect on soil CO 2 fluxes, but it significantly enhanced SOC content by 40% and MBC content by 18%. A positive response of soil CO 2 fluxes to biochar amendment was found in rice paddies, laboratory incubation studies, soils without vegetation, and unfertilized soils. Biochar amendment significantly increased soil MBC content in field studies, N‐fertilized soils, and soils with vegetation. Enhancement of SOC content following biochar amendment was the greatest in rice paddies among different land‐use types. Responses of soil CO 2 fluxes and MBC to biochar amendment varied with soil texture and pH. The use of biochar in combination with synthetic N fertilizer and waste compost fertilizer led to the greatest increases in soil CO 2 fluxes and MBC content, respectively. Both soil CO 2 fluxes and MBC responses to biochar amendment decreased with biochar application rate, pyrolysis temperature, or C/N ratio of biochar, while each increased SOC content enhancement. Among different biochar feedstock sources, positive responses of soil CO 2 fluxes and MBC were the highest for manure and crop residue feedstock sources, respectively. Soil CO 2 flux responses to biochar amendment decreased with pH of biochar, while biochars with pH of 8.1–9.0 had the greatest enhancement of SOC and MBC contents. Therefore, soil properties, land‐use type, agricultural practice, and biochar characteristics should be taken into account to assess the practical potential of biochar for mitigating climate change. 相似文献
9.
Organic matter decomposition and soil CO 2 efflux are both mediated by soil microorganisms, but the potential effects of temporal variations in microbial community
composition are not considered in most analytical models of these two important processes. However, inconsistent relationships
between rates of heterotrophic soil respiration and abiotic factors, including temperature and moisture, suggest that microbial
community composition may be an important regulator of soil organic matter (SOM) decomposition and CO 2 efflux. We performed a short-term (12-h) laboratory incubation experiment using tropical rain forest soil amended with either
water (as a control) or dissolved organic matter (DOM) leached from native plant litter, and analyzed the effects of the treatments
on soil respiration and microbial community composition. The latter was determined by constructing clone libraries of small-subunit
ribosomal RNA genes (SSU rRNA) extracted from the soil at the end of the incubation experiment. In contrast to the subtle
effects of adding water alone, additions of DOM caused a rapid and large increase in soil CO 2 flux. DOM-stimulated CO 2 fluxes also coincided with profound shifts in the abundance of certain members of the soil microbial community. Our results
suggest that natural DOM inputs may drive high rates of soil respiration by stimulating an opportunistic subset of the soil
bacterial community, particularly members of the Gammaproteobacteria and Firmicutes groups. Our experiment indicates that
variations in microbial community composition may influence SOM decomposition and soil respiration rates, and emphasizes the
need for in situ studies of how natural variations in microbial community composition regulate soil biogeochemical processes. 相似文献
10.
The spatial variation of soil greenhouse gas fluxes (GHG; carbon dioxide—CO 2, methane—CH 4 and nitrous oxide—N 2O) remains poorly understood in highly complex ecosystems such as tropical forests. We used 240 individual flux measurements of these three GHGs from different soil types, at three topographical positions and in two extreme hydric conditions in the tropical forests of the Guiana Shield (French Guiana, South America) to (1) test the effect of topographical positions on GHG fluxes and (2) identify the soil characteristics driving flux variation in these nutrient-poor tropical soils. Surprisingly, none of the three GHG flux rates differed with topographical position. CO 2 effluxes covaried with soil pH, soil water content (SWC), available nitrogen and total phosphorus. The CH 4 fluxes were best explained by variation in SWC, with soils acting as a sink under drier conditions and as a source under wetter conditions. Unexpectedly, our study areas were generally sinks for N 2O and N 2O fluxes were partly explained by total phosphorus and available nitrogen concentrations. This first study describing the spatial variation of soil fluxes of the three main GHGs measured simultaneously in forests of the Guiana Shield lays the foundation for specific studies of the processes underlying the observed patterns. 相似文献
11.
Several European countries have expanded the traditional use of anaerobic digestion, i.e. waste treatment, to energy generation through attractive incentives. In some countries, it is further promoted by additional payments to generate biogas from biomass. This review aims to summarise agronomic aspects of methane production from maize, to address resulting abiotic environmental effects and to highlight challenges and prospects. The opportunities of biogas production are manifold, including the mitigation of climate change, decreasing reliance on fossil fuels and diversification of farm income. Although the anaerobic digestion of animal manure is regarded as the most beneficial for reducing greenhouse gas (GHG) emission from manure storage, the energy output can be substantially enhanced by co-digesting manure and maize, which is the most efficient crop for substrate provision in many regions. Although first regarded as beneficial, the rush into biogas production strongly based on maize ( Zea mays ssp. mays) is being questioned in view of its environmental soundness. Main areas of concern comprise the spatial concentration of biogas plant together with the high amount of digestate and resulting pollution of surface and ground water, emission of climate-relevant gases and detrimental effects of maize cultivation on soil organic matter degradation. Key challenges that have been identified to enhance the sustainability of maize-based biogas production include (1) the design of regionally adapted maize rotations, (2) an improved management of biogas residues (BR), (3) the establishment of a more comprehensive data base for evaluating soil C fluxes in maize production as well as GHG emissions at the biogas plant and during BR storage and (4) the consideration of direct and indirect land use change impact of maize-based biogas production. 相似文献
12.
Warming-induced changes in precipitation regimes, coupled with anthropogenically enhanced nitrogen (N) deposition, are likely to increase the prevalence, duration, and magnitude of soil respiration pulses following wetting via interactions among temperature and carbon (C) and N availability. Quantifying the importance of these interactive controls on soil respiration is a key challenge as pulses can be large terrestrial sources of atmospheric carbon dioxide (CO 2) over comparatively short timescales. Using an automated sensor system, we measured soil CO 2 flux dynamics in the Colorado Desert—a system characterized by pronounced transitions from dry-to-wet soil conditions—through a multi-year series of experimental wetting campaigns. Experimental manipulations included combinations of C and N additions across a range of ambient temperatures and across five sites varying in atmospheric N deposition. We found soil CO 2 pulses following wetting were highly predictable from peak instantaneous CO 2 flux measurements. CO 2 pulses consistently increased with temperature, and temperature at time of wetting positively correlated to CO 2 pulse magnitude. Experimentally adding N along the N deposition gradient generated contrasting pulse responses: adding N increased CO 2 pulses in low N deposition sites, whereas adding N decreased CO 2 pulses in high N deposition sites. At a low N deposition site, simultaneous additions of C and N during wetting led to the highest observed soil CO 2 fluxes reported globally at 299.5 μmol CO 2 m −2 s −1. Our results suggest that soils have the capacity to emit high amounts of CO 2 within small timeframes following infrequent wetting, and pulse sizes reflect a non-linear combination of soil resource and temperature interactions. Importantly, the largest soil CO 2 emissions occurred when multiple resources were amended simultaneously in historically resource-limited desert soils, pointing to regions experiencing simultaneous effects of desertification and urbanization as key locations in future global C balance. 相似文献
13.
The effects of nitrogen (N) deposition on soil organic carbon (C) and greenhouse gas (GHG) emissions in terrestrial ecosystems are the main drivers affecting GHG budgets under global climate change. Although many studies have been conducted on this topic, we still have little understanding of how N deposition affects soil C pools and GHG budgets at the global scale. We synthesized a comprehensive dataset of 275 sites from multiple terrestrial ecosystems around the world and quantified the responses of the global soil C pool and GHG fluxes induced by N enrichment. The results showed that the soil organic C concentration and the soil CO 2, CH 4 and N 2O emissions increased by an average of 3.7%, 0.3%, 24.3% and 91.3% under N enrichment, respectively, and that the soil CH 4 uptake decreased by 6.0%. Furthermore, the percentage increase in N 2O emissions (91.3%) was two times lower than that (215%) reported by Liu and Greaver ( Ecology Letters, 2009, 12:1103–1117). There was also greater stimulation of soil C pools (15.70 kg C ha ?1 year ?1 per kg N ha ?1 year ?1) than previously reported under N deposition globally. The global N deposition results showed that croplands were the largest GHG sources (calculated as CO 2 equivalents), followed by wetlands. However, forests and grasslands were two important GHG sinks. Globally, N deposition increased the terrestrial soil C sink by 6.34 Pg CO 2/year. It also increased net soil GHG emissions by 10.20 Pg CO 2‐Geq (CO 2 equivalents)/year. Therefore, N deposition not only increased the size of the soil C pool but also increased global GHG emissions, as calculated by the global warming potential approach. 相似文献
14.
The effects of rainfall events on soil CO 2 fluxes were examined in a cool temperate Quercus/Betula forest in Japan. The soil CO 2 fluxes were measured using an open-flow gas exchange system with an infrared gas analyzer in the snow-free season from August 1999 to November 2000. Soil CO 2 flux showed no significant diurnal trend on days without rain. In contrast, rainfall events caused a significant increase in soil CO 2 flux. To determine the effect of rainfall events and to evaluate more precisely the daily and annual soil carbon flux, we constructed a multiple polynomial regression model that included two variables, soil temperature and soil water content, using the soil CO 2 flux data recorded on sunny days. Daily soil carbon fluxes on sunny days calculated by the model were almost the same as those determined by the field measurements. On the contrary, the fluxes measured on rainy days were significantly higher than those calculated daily from the soil carbon fluxes by the model. Annual soil carbon fluxes in 1999 and 2000 were estimated using models that both do and do not take rainfall effects into consideration. The result indicates that post-rainfall increases in soil CO 2 flux represent approximately 16–21% of the annual soil carbon flux in this cool temperate deciduous forest. 相似文献
15.
Background and aimsThe litter layer is a major source of CO2, and it also influences soil-atmosphere exchange of N2O and CH4. So far, it is not clear how much of soil greenhouse gas (GHG) emission derives from the litter layer itself or is litter-induced. The present study investigates how the litter layer controls soil GHG fluxes and microbial decomposer communities in a temperate beech forest. MethodsWe removed the litter layer in an Austrian beech forest and studied responses of soil CO2, CH4 and N2O fluxes and the microbial community via phospholipid fatty acids (PLFA). Soil GHG fluxes were determined with static chambers on 22 occasions from July 2012 to February 2013, and soil samples collected at 8 sampling events. ResultsLitter removal reduced CO2 emissions by 30 % and increased temperature sensitivity (Q10) of CO2 fluxes. Diffusion of CH4 into soil was facilitated by litter removal and CH4 uptake increased by 16 %. This effect was strongest in autumn and winter when soil moisture was high. Soils without litter turned from net N2O sources to slight N2O sinks because N2O emissions peaked after rain events in summer and autumn, which was not the case in litter-removal plots. Microbial composition was only transiently affected by litter removal but strongly influenced by seasonality. ConclusionsLitter layers must be considered in calculating forest GHG budgets, and their influence on temperature sensitivity of soil GHG fluxes taken into account for future climate scenarios. 相似文献
16.
Tropical forests on upland soils are assumed to be a methane (CH 4) sink and a weak source of nitrous oxide (N 2O), but studies of wetland forests have demonstrated that tree stems can be a substantial source of CH 4, and recent evidence from temperate woodlands suggests that tree stems can also emit N 2O. Here, we measured CH 4 and N 2O fluxes from the soil and from tree stems in a semi‐evergreen tropical forest on upland soil. To examine the influence of seasonality, soil abiotic conditions and substrate availability (litter inputs) on trace greenhouse gas (GHG) fluxes, we conducted our study during the transition from the dry to the wet season in a long‐term litter manipulation experiment in Panama, Central America. Trace GHG fluxes were measured from individual stem bases of two common tree species and from soils beneath the same trees. Soil CH 4 fluxes varied from uptake in the dry season to minor emissions in the wet season. Soil N 2O fluxes were negligible during the dry season but increased markedly after the start of the wet season. By contrast, tree stem bases emitted CH 4 and N 2O throughout the study. Although we observed no clear effect of litter manipulation on trace GHG fluxes, tree species and litter treatments interacted to influence CH 4 fluxes from stems and N 2O fluxes from stems and soil, indicating complex relationships between tree species traits and decomposition processes that can influence trace GHG dynamics. Collectively, our results show that tropical trees can act as conduits for trace GHGs that most likely originate from deeper soil horizons, even when they are growing on upland soils. Coupled with the finding that the soils may be a weaker sink for CH 4 than previously thought, our research highlights the need to reappraise trace gas budgets in tropical forests. 相似文献
17.
The first full greenhouse gas (GHG) flux budget of an intensively managed grassland in Switzerland (Chamau) is presented. The three major trace gases, carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2O) were measured with the eddy covariance (EC) technique. For CO 2 concentrations, an open‐path infrared gas analyzer was used, while N 2O and CH 4 concentrations were measured with a recently developed continuous‐wave quantum cascade laser absorption spectrometer (QCLAS). We investigated the magnitude of these trace gas emissions after grassland restoration, including ploughing, harrowing, sowing, and fertilization with inorganic and organic fertilizers in 2012. Large peaks of N 2O fluxes (20–50 nmol m ?2 s ?1 compared with a <5 nmol m ?2 s ?1 background) were observed during thawing of the soil after the winter period and after mineral fertilizer application followed by re‐sowing in the beginning of the summer season. Nitrous oxide (N 2O) fluxes were controlled by nitrogen input, plant productivity, soil water content and temperature. Management activities led to increased variations of N 2O fluxes up to 14 days after the management event as compared with background fluxes measured during periods without management (<5 nmol m ?2 s ?1). Fluxes of CO 2 remained small until full plant development in early summer 2012. In contrast, methane emissions showed only minor variations over time. The annual GHG flux budget was dominated by N 2O (48% contribution) and CO 2 emissions (44%). CH 4 flux contribution to the annual budget was only minor (8%). We conclude that recently developed multi‐species QCLAS in an EC system open new opportunities to determine the temporal variation of N 2O and CH 4 fluxes, which further allow to quantify annual emissions. With respect to grassland restoration, our study emphasizes the key role of N 2O and CO 2 losses after ploughing, changing a permanent grassland from a carbon sink to a significant carbon source. 相似文献
18.
The responses of soil-atmosphere carbon (C) exchange fluxes to growing atmospheric nitrogen (N) deposition are controversial, leading to large uncertainty in the estimated C sink of global forest ecosystems experiencing substantial N inputs. However, it is challenging to quantify critical load of N input for the alteration of the soil C fluxes, and what factors controlled the changes in soil CO 2 and CH 4 fluxes under N enrichment. Nine levels of urea addition experiment (0, 10, 20, 40, 60, 80, 100, 120, 140 kg N ha −1 yr −1) were conducted in the needle-broadleaved mixed forest in Changbai Mountain, Northeast China. Soil CO 2 and CH 4 fluxes were monitored weekly using the static chamber and gas chromatograph technique. Environmental variables (soil temperature and moisture in the 0–10 cm depth) and dissolved N (NH 4+-N, NO 3−-N, total dissolved N (TDN), and dissolved organic N (DON)) in the organic layer and the 0–10 cm mineral soil layer were simultaneously measured. High rates of N addition (≥60 kg N ha −1 yr −1) significantly increased soil NO 3−-N contents in the organic layer and the mineral layer by 120%-180% and 56.4%-84.6%, respectively. However, N application did not lead to a significant accumulation of soil NH 4+-N contents in the two soil layers except for a few treatments. N addition at a low rate of 10 kg N ha −1 yr −1 significantly stimulated, whereas high rate of N addition (140 kg N ha −1 yr −1) significantly inhibited soil CO 2 emission and CH 4 uptake. Significant negative relationships were observed between changes in soil CO 2 emission and CH 4 uptake and changes in soil NO 3−-N and moisture contents under N enrichment. These results suggest that soil nitrification and NO 3−-N accumulation could be important regulators of soil CO 2 emission and CH 4 uptake in the temperate needle-broadleaved mixed forest. The nonlinear responses to exogenous N inputs and the critical level of N in terms of soil C fluxes should be considered in the ecological process models and ecosystem management. 相似文献
19.
有机物料还田是提升农田土壤有机碳、培肥土壤的重要措施。为探讨不同有机物料的还田效果,采用室外培养方法,研究了在等碳输入条件下,施用水稻秸秆、紫云英、生物有机肥、猪粪和水稻秸秆生物炭对洞庭湖双季稻区潮土有机碳和活性有机碳组分含量的影响。结果表明: 经过180 d的培养试验,与不施用有机物料相比,施用有机物料提高了土壤活性有机碳含量。生物有机肥、猪粪和水稻秸秆生物炭处理分别使土壤有机碳含量显著提升了26.1%、9.7%和30.7%,水稻秸秆和紫云英对土壤有机碳含量的提升效应在试验期间并不显著。水稻秸秆和紫云英还田更有利于土壤可溶性有机碳和微生物生物量碳的积累,猪粪更有利于土壤可溶性有机碳的积累,生物有机肥更有利于土壤微生物生物量碳和易氧化有机碳的积累,水稻秸秆生物炭则更有利于土壤微生物生物量碳和轻组有机碳的积累。与水稻秸秆还田相比,紫云英、生物有机肥、猪粪和水稻秸秆生物炭还田使土壤碳库管理指数分别提高了31.8%、111.6%、62.2%和50.7%。从土壤固碳和土壤碳库管理指数来看,生物有机肥、猪粪和水稻秸秆生物炭的还田效果优于水稻秸秆和紫云英还田。 相似文献
20.
The impact of animal manure application on soil organic carbon (SOC) stock changes is of interest for both agronomic and environmental purposes. There is a specific need to quantify SOC change for use in national greenhouse gas (GHG) emission inventories. We quantified the response of SOC stocks to manure application from a large worldwide pool of individual studies and determined the impact of explanatory factors such as climate, soil properties, land use and manure characteristics. Our study is based on a meta‐analysis of 42 research articles totaling 49 sites and 130 observations in the world. A dominant effect of cumulative manure‐C input on SOC response was observed as this factor explained at least 53% of the variability in SOC stock differences compared to mineral fertilized or unfertilized reference treatments. However, the effects of other determining factors were not evident from our data set. From the linear regression relating cumulative C inputs and SOC stock difference, a global manure‐C retention coefficient of 12% ± 4 (95% Confidence Interval, CI) could be estimated for an average study duration of 18 years. Following an approach comparable to the Intergovernmental Panel on Climate Change, we estimated a relative SOC change factor of 1.26 ± 0.14 (95% CI) which was also related to cumulative manure‐C input. Our results offer some scope for the refinement of manure retention coefficients used in crop management guidelines and for the improvement of SOC change factors for national GHG inventories by taking into account manure‐C input. Finally, this study emphasizes the need to further document the long‐term impact of manure characteristics such as animal species, especially pig and poultry, and manure management systems, in particular liquid vs. solid storage. 相似文献
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