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1.
Experiments addressing the role of plant species diversity for ecosystem functioning have recently proliferated. Most studies
have focused on plant biomass responses. However, microbial processes involved in the production of N 2O and the oxidation of atmospheric CH 4 could potentially be affected via effects on N cycling, on soil diffusive properties (due to changes in water relations and
root architecture) and by more direct interactions of plants with soil microbes. We studied ecosystem-level CH 4 and N 2O fluxes in experimental communities assembled from two pasture soils and from combinations of 1, 3, 6, 8 or 9 species typical
for these pastures. The soils contrasted with respect to texture and fertility. N 2O emissions decreased with diversity and increased in the presence of legumes. Soils were sinks for CH 4 at all times; legume monocultures were a smaller sink for atmospheric CH 4 than non-legume monocultures, but no effect of species richness per se was detected. However, both the exchange of CH 4 and N 2O strongly depended on plant community composition, and on the interaction of composition with soil type, indicating that
the functional role of species and their interactions differed between soils. N 2O fluxes were mainly driven by effects on soil nitrate and on nitrification while soil moisture had less of an effect. Soil
microbial C and N and N mineralisation rates were not altered. The driver of the interactive soil type×plant community composition-effects
was less clear. Because soil methanotrophs may take longer to respond to alterations of N cycling than the 1/2 year treatment
in this study, we also tested species richness-effects in two separate 5-year field studies, but results were ambiguous, indicating
complex interactions with soil disturbance. In conclusion, our study demonstrates that plant community composition can affect
the soil trace gas balance, whereas plant species richness per se was less important; it also indicates a potential link between the botanical composition of plant communities and global
warming. 相似文献
2.
Phytomanagement of trace element-contaminated soils can reduce soil toxicity and restore soil ecological functions, including the soil gas exchange with the atmosphere. We studied the emission rate of the greenhouse gases (GHGs) CO 2, CH 4, and N 2O; the potential CH 4 oxidation; denitrification enzyme activity (DEA), and glucose mineralization of a Cu-contaminated soil amended with dolomitic limestone and compost, alone or in combination, after a 2-year phytomanagement with a mixed stand of Populus nigra, Salix viminalis, S. caprea, and Amorpha fruticosa. Soil microbial biomass and microbial community composition after analysis of the phospholipid fatty acids (PLFA) profile were determined. Phytomanagement significantly reduced Cu availability and soil toxicity, increased soil microbial biomass and glucose mineralization capacity, changed the composition of soil microbial communities, and increased the CO 2 and N 2O emission rates and DEA. Despite such increases, microbial communities were evolving toward less GHG emission per unit of microbial biomass than in untreated soils. Overall, the aided phytostabilization option would allow methanotrophic populations to establish in the remediated soils due to decreased soil toxicity and increased nutrient availability. 相似文献
3.
The application of inorganic nitrogen (N) fertilizers strongly influences the contribution of agriculture to the greenhouse effect, especially by potentially increasing emissions of nitrous oxide (N 2O), carbon dioxide (CO 2) and methane (CH 4) from soils. The present microcosm-study investigates the effect of different forms of inorganic N fertilizers on greenhouse gas (GHG) emissions from two different agricultural soils. The relationship between greenhouse gas emissions and soil microbial communities, N transformation rates and plant ( Hordeum vulgare L. cv. Morex) growth were investigated. Repeated N fertilization led to increased N 2O emissions. In a parallel survey of functional microbial population dynamics we observed a stimulation of bacterial and archaeal ammonia oxidisers accompanied with these N 2O emissions. The ratio of archaeal to bacterial ammonium monooxygenase subunit A ( amoA) gene copies (data obtained from Inselsbacher et al., 2010) correlated positively with N 2O fluxes, which suggests a direct or indirect involvement of archaea in N 2O fluxes. Repeated N fertilization also stimulated methane oxidation, which may also be related to a stimulation of ammonia oxidizers. The fertilizer effects differed between soil types: In the more organic Niederschleinz soil N-turnover rates increased more strongly after fertilization, while in the sandy Purkersdorf soil plant growth and soil respiration were accelerated depending on fertilizer N type. Compared to addition of NH 4 + and NO 3 ? , addition of NH 4NO 3 fertilizer resulted in the largest increase in global warming potential as a summary indicator of all GHG related effects. This effect resulted from the strongest increase of both N 2O and CO 2 emission while plant growth was not equally stimulated, compared to e.g. KNO 3 fertilization. In order to decrease N losses from agricultural ecosystems and in order to minimize soil derived global warming potential, this study points to the need for interdisciplinary investigations of the highly complex interactions within plant-soil-microbe-atmosphere systems. By understanding the microbial processes underlying fertilizer effects on GHG emissions the N use efficiency of crops could be refined. 相似文献
4.
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
5.
In this study, we quantify the impacts of climate and land use on soil N 2O and CH 4 fluxes from tropical forest, agroforest, arable and savanna ecosystems in Africa. To do so, we measured greenhouse gases (GHG) fluxes from 12 different ecosystems along climate and land‐use gradients at Mt. Kilimanjaro, combining long‐term in situ chamber and laboratory soil core incubation techniques. Both methods showed similar patterns of GHG exchange. Although there were distinct differences from ecosystem to ecosystem, soils generally functioned as net sources and sinks for N 2O and CH 4 respectively. N 2O emissions correlated positively with soil moisture and total soil nitrogen content. CH 4 uptake rates correlated negatively with soil moisture and clay content and positively with SOC. Due to moderate soil moisture contents and the dominance of nitrification in soil N turnover, N 2O emissions of tropical montane forests were generally low (<1.2 kg N ha ?1 year ?1), and it is likely that ecosystem N losses are driven instead by nitrate leaching (~10 kg N ha ?1 year ?1). Forest soils with well‐aerated litter layers were a significant sink for atmospheric CH 4 (up to 4 kg C ha ?1 year ?1) regardless of low mean annual temperatures at higher elevations. Land‐use intensification significantly increased the soil N 2O source strength and significantly decreased the soil CH 4 sink. Compared to decreases in aboveground and belowground carbon stocks enhanced soil non‐CO 2 GHG emissions following land‐use conversion from tropical forests to homegardens and coffee plantations were only a small factor in the total GHG budget. However, due to lower ecosystem carbon stock changes, enhanced N 2O emissions significantly contributed to total GHG emissions following conversion of savanna into grassland and particularly maize. Overall, we found that the protection and sustainable management of aboveground and belowground carbon and nitrogen stocks of agroforestry and arable systems is most crucial for mitigating GHG emissions from land‐use change. 相似文献
6.
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
7.
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
9.
Warming can accelerate the decomposition of soil organic matter and stimulate the release of soil greenhouse gases (GHGs), but to what extent soil release of methane (CH 4) and nitrous oxide (N 2O) may contribute to soil C loss for driving climate change under warming remains unresolved. By synthesizing 1,845 measurements from 164 peer‐reviewed publications, we show that around 1.5°C (1.16–2.01°C) of experimental warming significantly stimulates soil respiration by 12.9%, N 2O emissions by 35.2%, CH 4 emissions by 23.4% from rice paddies, and by 37.5% from natural wetlands. Rising temperature increases CH 4 uptake of upland soils by 13.8%. Warming‐enhanced emission of soil CH 4 and N 2O corresponds to an overall source strength of 1.19, 1.84, and 3.12 Pg CO 2‐equivalent/year under 1°C, 1.5°C, and 2°C warming scenarios, respectively, interacting with soil C loss of 1.60 Pg CO 2/year in terms of contribution to climate change. The warming‐induced rise in soil CH 4 and N 2O emissions (1.84 Pg CO 2‐equivalent/year) could reduce mitigation potential of terrestrial net ecosystem production by 8.3% (NEP, 22.25 Pg CO 2/year) under warming. Soil respiration and CH 4 release are intensified following the mean warming threshold of 1.5°C scenario, as compared to soil CH 4 uptake and N 2O release with a reduced and less positive response, respectively. Soil C loss increases to a larger extent under soil warming than under canopy air warming. Warming‐raised emission of soil GHG increases with the intensity of temperature rise but decreases with the extension of experimental duration. This synthesis takes the lead to quantify the ecosystem C and N cycling in response to warming and advances our capacity to predict terrestrial feedback to climate change under projected warming scenarios. 相似文献
10.
Changes in soil hydration status affect microbial community dynamics and shape key biogeochemical processes. Evidence suggests that local anoxic conditions may persist and support anaerobic microbial activity in soil aggregates (or in similar hot spots) long after the bulk soil becomes aerated. To facilitate systematic studies of interactions among environmental factors with biogeochemical emissions of CO 2, N 2O and CH 4 from soil aggregates, we remolded silt soil aggregates to different sizes and incorporated carbon at different configurations (core, mixed, no addition). Assemblies of remolded soil aggregates of three sizes (18, 12, and 6 mm) and equal volumetric proportions were embedded in sand columns at four distinct layers. The water table level in each column varied periodically while obtaining measurements of soil GHG emissions for the different aggregate carbon configurations. Experimental results illustrate that methane production required prolonged inundation and highly anoxic conditions for inducing measurable fluxes. The onset of unsaturated conditions (lowering water table) resulted in a decrease in CH 4 emissions while temporarily increasing N 2O fluxes. Interestingly, N 2O fluxes were about 80% higher form aggregates with carbon placement in center (anoxic) core compared to mixed carbon within aggregates. The fluxes of CO 2 were comparable for both scenarios of carbon sources. These experimental results highlight the importance of hydration dynamics in activating different GHG production and affecting various transport mechanisms about 80% of total methane emissions during lowering water table level are attributed to physical storage (rather than production), whereas CO 2 emissions (~80%) are attributed to biological activity. A biophysical model for microbial activity within soil aggregates and profiles provides a means for results interpretation and prediction of trends within natural soils under a wide range of conditions. 相似文献
11.
Nitrogen (N) deposition can alter the rates of microbial N- and C- turnover, and thus can affect the fluxes of greenhouse gases (GHG, e.g., CO 2, CH 4, and N 2O) from forest soils. The effects of N deposition on the GHG fluxes from forest soils were reviewed in this paper. N deposition to forest soils have shown variable effects on the soil GHG fluxes from forest, including increases, decreases or unchanged rates depending on forest type, N status of the soil, and the rate and type of atmospheric N deposition. In forest ecosystems where biological processes are limited by N supply, N additions either stimulate soil respiration or have no significant effect, whereas in “N saturated” forest ecosystems, N additions decrease CO 2 emission, reduce CH 4 oxidation and elevate N 2O flux from the soil. The mechanisms and research methods about the effects of N deposition on GHG fluxes from forest soils were also reviewed in this paper. Finally, the present and future research needs about the effects of N deposition on the GHG fluxes from forest soils were discussed. 相似文献
12.
Permafrost soils are large reservoirs of potentially labile carbon (C). Understanding the dynamics of C release from these soils requires us to account for the impact of wildfires, which are increasing in frequency as the climate changes. Boreal wildfires contribute to global emission of greenhouse gases (GHG—CO 2, CH 4 and N 2O) and indirectly result in the thawing of near-surface permafrost. In this study, we aimed to define the impact of fire on soil microbial communities and metabolic potential for GHG fluxes in samples collected up to 1 m depth from an upland black spruce forest near Nome Creek, Alaska. We measured geochemistry, GHG fluxes, potential soil enzyme activities and microbial community structure via 16SrRNA gene and metagenome sequencing. We found that soil moisture, C content and the potential for respiration were reduced by fire, as were microbial community diversity and metabolic potential. There were shifts in dominance of several microbial community members, including a higher abundance of candidate phylum AD3 after fire. The metagenome data showed that fire had a pervasive impact on genes involved in carbohydrate metabolism, methanogenesis and the nitrogen cycle. Although fire resulted in an immediate release of CO 2 from surface soils, our results suggest that the potential for emission of GHG was ultimately reduced at all soil depths over the longer term. Because of the size of the permafrost C reservoir, these results are crucial for understanding whether fire produces a positive or negative feedback loop contributing to the global C cycle. 相似文献
13.
Global warming will likely enhance greenhouse gas (GHG) emissions from soils. Due to its slow decomposability, biochar is widely recognized as effective in long‐term soil carbon (C) sequestration and in mitigation of soil GHG emissions. In a long‐term soil warming experiment (+2.5 °C, since July 2008) we studied the effect of applying high‐temperature Miscanthus biochar (0, 30 t/ha, since August 2013) on GHG emissions and their global warming potential (GWP) during 2 years in a temperate agroecosystem. Crop growth, physical and chemical soil properties, temperature sensitivity of soil respiration ( Rs), and metabolic quotient (qCO 2) were investigated to yield further information about single effects of soil warming and biochar as well as on their interactions. Soil warming increased total CO 2 emissions by 28% over 2 years. The effect of warming on soil respiration did not level off as has often been observed in less intensively managed ecosystems. However, the temperature sensitivity of soil respiration was not affected by warming. Overall, biochar had no effect on most of the measured parameters, suggesting its high degradation stability and its low influence on microbial C cycling even under elevated soil temperatures. In contrast, biochar × warming interactions led to higher total N 2O emissions, possibly due to accelerated N‐cycling at elevated soil temperature and to biochar‐induced changes in soil properties and environmental conditions. Methane uptake was not affected by soil warming or biochar. The incorporation of biochar‐C into soil was estimated to offset warming‐induced elevated GHG emissions for 25 years. Our results highlight the suitability of biochar for C sequestration in cultivated temperate agricultural soil under a future elevated temperature. However, the increased N 2O emissions under warming limit the GHG mitigation potential of biochar. 相似文献
14.
Heterotrophic soil microorganisms rely on carbon (C) allocated belowground in plant production, but belowground C allocation (BCA) by plants is a poorly quantified part of ecosystem C cycling, especially, in peat soil. We applied a C balance approach to quantify BCA in a mixed conifer-red maple ( Acer rubrum) forest on deep peat soil. Direct measurements of CH 4 and CO 2 fluxes across the soil surface (soil respiration), production of fine and small plant roots, and aboveground litterfall were used to estimate respiration by roots, by mycorrhizae and by free-living soil microorganisms. Measurements occurred in two consecutive years. Soil respiration rates averaged 1.2 bm μmol m ? 2 s ? 1 for CO 2 and 0.58 nmol m ? 2 s ? 1 for CH 4 (371 to 403 g C m ? 2 year ? 1). Carbon in aboveground litter (144 g C m ? 2 year ? 1) was 84% greater than C in root production (78 g C m ? 2 year ? 1). Complementary in vitro assays located high rates of anaerobic microbial activity, including methanogenesis, in a dense layer of roots overlying the peat soil and in large-sized fragments within the peat matrix. Large-sized fragments were decomposing roots and aboveground leaf and twig litter, indicating that relatively fresh plant production supported most of the anaerobic microbial activity. Respiration by free-living soil microorganisms in deep peat accounted for, at most, 29 to 38 g C m ? 2 year ? 1. These data emphasize the close coupling between plant production, ecosystem-level C cycling and soil microbial ecology, which BCA can help reveal. 相似文献
15.
Soil aggregates, with complex spatial and nutritional heterogeneity, are clearly important for regulating microbial community ecology and biogeochemistry in soils. However, how the taxonomic composition and functional attributes of N-cycling-microbes within different soil particle-size fractions under a long-term fertilization treatment remains largely unknown. Here, we examined the composition and metabolic potential for urease activity, nitrification, N 2O production and reduction of the microbial communities attached to different sized soil particles (2000–250, 250–53 and <53 μm) using a functional gene microarray (GeoChip) and functional assays. We found that urease activity and nitrification were higher in <53 μm fractions, whereas N 2O production and reduction rates were greater in 2000–250 and 250–53 μm across different fertilizer regimes. The abundance of key N-cycling genes involved in anammox, ammonification, assimilatory and dissimilatory N reduction, denitrification, nitrification and N 2-fixation detected by GeoChip increased as soil aggregate size decreased; and the particular key genes abundance (e.g., ureC, amoA, narG, nirS/ K) and their corresponding activity were uncoupled. Aggregate fraction exerted significant impacts on N-cycling microbial taxonomic composition, which was significantly shaped by soil nutrition. Taken together, these findings indicate the important roles of soil aggregates in differentiating N-cycling metabolic potential and taxonomic composition, and provide empirical evidence that nitrogen metabolism potential and community are uncoupled due to aggregate heterogeneity. 相似文献
16.
As surface temperatures are expected to rise in the future, ice‐rich permafrost may thaw, altering soil topography and hydrology and creating a mosaic of wet and dry soil surfaces in the Arctic. Arctic wetlands are large sources of CH 4, and investigating effects of soil hydrology on CH 4 fluxes is of great importance for predicting ecosystem feedback in response to climate change. In this study, we investigate how a decade‐long drying manipulation on an Arctic floodplain influences CH 4‐associated microorganisms, soil thermal regimes, and plant communities. Moreover, we examine how these drainage‐induced changes may then modify CH 4 fluxes in the growing and nongrowing seasons. This study shows that drainage substantially lowered the abundance of methanogens along with methanotrophic bacteria, which may have reduced CH 4 cycling. Soil temperatures of the drained areas were lower in deep, anoxic soil layers (below 30 cm), but higher in oxic topsoil layers (0–15 cm) compared to the control wet areas. This pattern of soil temperatures may have reduced the rates of methanogenesis while elevating those of CH 4 oxidation, thereby decreasing net CH 4 fluxes. The abundance of Eriophorum angustifolium, an aerenchymatous plant species, diminished significantly in the drained areas. Due to this decrease, a higher fraction of CH 4 was alternatively emitted to the atmosphere by diffusion, possibly increasing the potential for CH 4 oxidation and leading to a decrease in net CH 4 fluxes compared to a control site. Drainage lowered CH 4 fluxes by a factor of 20 during the growing season, with postdrainage changes in microbial communities, soil temperatures, and plant communities also contributing to this reduction. In contrast, we observed CH 4 emissions increased by 10% in the drained areas during the nongrowing season, although this difference was insignificant given the small magnitudes of fluxes. This study showed that long‐term drainage considerably reduced CH 4 fluxes through modified ecosystem properties. 相似文献
17.
We assessed the response of soil microbial nitrogen (N) cycling and associated functional genes to elevated temperature at the global scale. A meta‐analysis of 1,270 observations from 134 publications indicated that elevated temperature decreased soil microbial biomass N and increased N mineralization rates, both in the presence and absence of plants. These findings infer that elevated temperature drives microbially mediated N cycling processes from dominance by anabolic to catabolic reaction processes. Elevated temperature increased soil nitrification and denitrification rates, leading to an increase in N 2O emissions of up to 227%, whether plants were present or not. Rates of N mineralization, denitrification and N 2O emission demonstrated significant positive relationships with rates of CO 2 emissions under elevated temperatures, suggesting that microbial N cycling processes were associated with enhanced microbial carbon (C) metabolism due to soil warming. The response in the abundance of relevant genes to elevated temperature was not always consistent with changes in N cycling processes. While elevated temperature increased the abundances of the nirS gene with plants and nosZ genes without plants, there was no effect on the abundances of the ammonia‐oxidizing archaea amoA gene, ammonia‐oxidizing bacteria amoA and nirK genes. This study provides the first global‐scale assessment demonstrating that elevated temperature shifts N cycling from microbial immobilization to enhanced mineralization, nitrification and denitrification in terrestrial ecosystems. These findings infer that elevated temperatures have a profound impact on global N cycling processes with implications of a positive feedback to global climate and emphasize the close linkage between soil microbial C and N cycling. 相似文献
18.
Over the last 50 years, the most increase in cultivated land area globally has been due to a doubling of irrigated land. Long‐term agronomic management impacts on soil organic carbon (SOC) stocks, soil greenhouse gas (GHG) emissions, and global warming potential (GWP) in irrigated systems, however, remain relatively unknown. Here, residue and tillage management effects were quantified by measuring soil nitrous oxide (N 2O) and methane (CH 4) fluxes and SOC changes (ΔSOC) at a long‐term, irrigated continuous corn ( Zea mays L.) system in eastern Nebraska, United States. Management treatments began in 2002, and measured treatments included no or high stover removal (0 or 6.8 Mg DM ha ?1 yr ?1, respectively) under no‐till (NT) or conventional disk tillage (CT) with full irrigation ( n = 4). Soil N 2O and CH 4 fluxes were measured for five crop‐years (2011–2015), and ΔSOC was determined on an equivalent mass basis to ~30 cm soil depth. Both area‐ and yield‐scaled soil N 2O emissions were greater with stover retention compared to removal and for CT compared to NT, with no interaction between stover and tillage practices. Methane comprised <1% of total emissions, with NT being CH 4 neutral and CT a CH 4 source. Surface SOC decreased with stover removal and with CT after 14 years of management. When ΔSOC, soil GHG emissions, and agronomic energy usage were used to calculate system GWP, all management systems were net GHG sources. Conservation practices (NT, stover retention) each decreased system GWP compared to conventional practices (CT, stover removal), but pairing conservation practices conferred no additional mitigation benefit. Although cropping system, management equipment/timing/history, soil type, location, weather, and the depth to which ΔSOC is measured affect the GWP outcomes of irrigated systems at large, this long‐term irrigated study provides valuable empirical evidence of how management decisions can impact soil GHG emissions and surface SOC stocks. 相似文献
19.
Nitrous oxide (N 2O) emissions from soil contribute to global warming and are in turn substantially affected by climate change. However, climate change impacts on N 2O production across terrestrial ecosystems remain poorly understood. Here, we synthesized 46 published studies of N 2O fluxes and relevant soil functional genes (SFGs, that is, archaeal amoA, bacterial amoA, nosZ, narG, nirK and nirS) to assess their responses to increased temperature, increased or decreased precipitation amounts, and prolonged drought (no change in total precipitation but increase in precipitation intervals) in terrestrial ecosystem (i.e. grasslands, forests, shrublands, tundra and croplands). Across the data set, temperature increased N 2O emissions by 33%. However, the effects were highly variable across biomes, with strongest temperature responses in shrublands, variable responses in forests and negative responses in tundra. The warming methods employed also influenced the effects of temperature on N 2O emissions (most effectively induced by open‐top chambers). Whole‐day or whole‐year warming treatment significantly enhanced N 2O emissions, but daytime, nighttime or short‐season warming did not have significant effects. Regardless of biome, treatment method and season, increased precipitation promoted N 2O emission by an average of 55%, while decreased precipitation suppressed N 2O emission by 31%, predominantly driven by changes in soil moisture. The effect size of precipitation changes on nirS and nosZ showed a U‐shape relationship with soil moisture; further insight into biotic mechanisms underlying N 2O emission response to climate change remain limited by data availability, underlying a need for studies that report SFG. Our findings indicate that climate change substantially affects N 2O emission and highlights the urgent need to incorporate this strong feedback into most climate models for convincing projection of future climate change. 相似文献
20.
为研究大兴安岭重度火烧迹地在不同恢复方式下林地土壤CO 2、CH 4和N 2O排放特征及其影响因素,采用静态箱/气相色谱法,在2017年生长季(6月-9月)对3种恢复方式(人工更新、天然更新和人工促进天然更新)林地土壤温室气体CO 2、CH 4、N 2O通量进行了原位观测。研究结果表明:(1)3种恢复方式林地土壤在生长季均为大气CO 2、N 2O的源,CH 4的汇;生长季林地土壤CO 2排放通量大小关系为人工促进天然更新((634.40±246.52)mg m -2 h -1) > 人工更新((603.63±213.22)mg m -2 h -1) > 天然更新((575.81±244.12)mg m -2 h -1),3种恢复方式间无显著差异;人工更新林地土壤CH 4吸收通量显著高于人工促进天然更新;天然更新林地土壤N 2O排放通量显著高于其他两种恢复方式。(2)土壤温度是影响3种恢复方式林地土壤温室气体通量的关键因素;土壤水分仅对人工更新林地土壤N 2O通量有极显著影响( P < 0.01);3种恢复方式林地土壤CO 2通量与大气湿度具有极显著的响应( P < 0.01);土壤pH仅与天然更新林地土壤CO 2通量显著相关( P < 0.05);土壤全氮含量仅与人工促进天然更新林地土壤CH 4通量显著相关( P < 0.05)。(3)基于100年尺度,由3种温室气体计算全球增温潜势得出,人工促进天然更新(1.83×10 4 kg CO 2/hm 2) > 人工更新(1.74×10 4 kg CO 2/hm 2) > 天然更新(1.67×10 4 kg CO 2/hm 2)。(4)阿木尔地区林地土壤年生长季CO 2和N 2O排放量为8.85×10 6 t和1.88×10 2 t,CH 4吸收量为1.05×10 3 t。 相似文献
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