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1.
To evaluate the effect of land use change from a natural broadleaf evergreen forest to Moso bamboo plantations and their management
practices on soil N 2O efflux in a subtropical region of China, N 2O efflux was measured during June 2008 and May 2009 using static closed chamber method. The observed mean N 2O fluxes were 0.230, 0.102 and 0.093 mg N 2O/m 2/h from the intensively managed bamboo forest (IM), conventionally managed bamboo forest (CM), and broadleaf evergreen forest
(BL), respectively, and calculated annual cumulative N 2O were 15.8, 8.7 and 7.2 kg N 2O/ha, respectively. Soil temperature had significant influence on N 2O flux. Whereas there was no correlation between N 2O flux and soil water content. Conversion of the natural subtropical broadleaf evergreen forest to Moso bamboo did not increase
soil N 2O efflux, but intensive management practices such as regular tillage and fertiliser application, significantly increased soil
N 2O emission from bamboo soil. 相似文献
2.
Background and aims Changes in soil moisture availability seasonally and as a result of climatic variability would influence soil nitrogen (N) cycling in different land use systems. This study aimed to understand mechanisms of soil moisture availability on gross N transformation rates. Methods A laboratory incubation experiment was conducted to evaluate the effects of soil moisture content (65 vs. 100% water holding capacity, WHC) on gross N transformation rates using the 15N tracing technique (calculated by the numerical model FLUAZ) in adjacent grassland and forest soils in central Alberta, Canada. Results Gross N mineralization and gross NH 4 + immobilization rates were not influenced by soil moisture content for both soils. Gross nitrification rates were greater at 100 than at 65% WHC only in the forest soil. Denitrification rates during the 9 days of incubation were 2.47 and 4.91 mg N kg -1 soil d -1 in the grassland and forest soils, respectively, at 100% WHC, but were not different from zero at 65% WHC. In the forest soil, both the ratio of gross nitrification to gross NH 4 + immobilization rates (N/IA) and cumulative N 2O emission were lower in the 65 than in the 100% WHC treatment, while in the grassland soil, the N/IA ratio was similar between the two soil moisture content treatments but cumulative N 2O emission was lower at 65% WHC. Conclusions The effect of soil moisture content on gross nitrification rates differ between forest and grassland soils and decreasing soil moisture content from 100 to 65% WHC reduced N 2O emissions in both soils. 相似文献
3.
Restored forested wetlands reduce N loads in surface discharge through plant uptake and denitrification. While removal of reactive N reduces impact on receiving waters, it is unclear whether enhanced denitrification also enhances emissions of the greenhouse gas N 2O, thus compromising the water-quality benefits of restoration. This study compares denitrification rates and N 2O:N 2 emission ratios from Sharkey clay soil in a mature bottomland forest to those from an adjacent cultivated site in the Lower Mississippi Alluvial Valley. Potential denitrification of forested soil was 2.4 times of cultivated soil. Using intact soil cores, denitrification rates of forested soil were 5.2, 6.6 and 2.0 times those of cultivated soil at 70, 85 and 100% water-filled pore space (WFPS), respectively. When NO 3 was added, N 2O emissions from forested soil were 2.2 times those of cultivated soil at 70% WFPS. At 85 and 100% WFPS, N 2O emissions were not significantly different despite much greater denitrification rates in the forested soil because N 2O:N 2 emission ratios declined more rapidly in forested soil as WFPS increased. These findings suggest that restoration of forested wetlands to reduce NO 3 in surface discharge will not contribute significantly to the atmospheric burden of N 2O. 相似文献
4.
Nitrous oxide (N 2O) is one of the three main biogenic greenhouse gases (GHGs) and agriculture represents close to 30 % of the total N 2O net emissions. In agricultural soils, N 2O is emitted by two main microbial processes, nitrification and denitrification, both of which can convert synthetic nitrogen fertilizer into N 2O. Legume-rhizobia symbiosis could be an effective and environmental-friendly alternative to nitrogen fertilization and hence, to mitigate soil N 2O emissions. However, legume crops also contribute to N 2O emissions. A better understanding of the environmental factors involved in the emission of N 2O from nodules would be instrumental for mitigating the release of this GHG gas. In this work, in vivo N 2O emissions from nodulated soybean roots in response to nitrate (0, 1, 2 and 4 mM) and flooding have been measured. To investigate the contribution of rhizobial denitrification in N 2O emission from nodules, plants were inoculated with B. japonicum USDA110 and napA and nosZ denitrification mutants. The results showed that nitrate was essential for N 2O emissions and its concentration enhanced N 2O fluxes showing a statistical linear correlation, being the highest N 2O fluxes obtained with 4 mM nitrate. When inoculated plants grown with 4 mM nitrate were subjected to flooding, a 150- and 830-fold induction of N 2O emission rates from USDA110 and nosZ nodulated roots, respectively, was observed compared to non-flooded plants, especially during long-term flooding. Under these conditions, N 2O emissions from detached nodules produced by the napA mutant were significantly lower ( p?<?0.05) than those produced by the wild-type strain (382 versus 1120 nmol N 2O h ?1 g ?1 NFW, respectively). In contrast, nodules from plants inoculated with the nosZ mutant accumulated statistically higher levels of N 2O compared to wild-type nodules (2522 versus nmol 1120 N 2O h ?1 g ?1 NFW, p?<?0.05). These results demonstrate that flooding is an important environmental factor for N 2O emissions from soybean nodules and that B. japonicum denitrification is involved in such emission. 相似文献
5.
Increasing demand for food and fibre by the growing human population is driving significant land use (LU) change from forest into intensively managed land systems in tropical areas. But empirical evidence on the extent to which such changes affect the soil-atmosphere exchange of trace gases is still scarce, especially in Africa. We investigated the effect of LU on soil trace gas production in the Mau Forest Complex region, Kenya. Intact soil cores were taken from natural forest, commercial and smallholder tea plantations, eucalyptus plantations and grazing lands, and were incubated in the lab under different soil moisture conditions. Soil fluxes of nitrous oxide (N 2O), nitric oxide (NO) and carbon dioxide (CO 2) were quantified, and we approximated annual estimates of soil N 2O and NO fluxes using soil moisture values measured in situ. Forest and eucalyptus plantations yielded annual fluxes of 0.3–1.3 kg N 2O–N ha ?1 a ?1 and 1.5–5.2 kg NO–N ha ?1 a ?1. Soils of commercial tea plantations, which are highly fertilized, showed higher fluxes (0.9 kg N 2O–N ha ?1 a ?1 and 4.3 kg NO–N ha ?1 a ?1) than smallholder tea plantations (0.1 kg N 2O–N ha ?1 a ?1 and 2.1 kg NO–N ha ?1 a ?1) or grazing land (0.1 kg N 2O–N ha ?1 a ?1 and 1.1 kg NO–N ha ?1 a ?1). High soil NO fluxes were probably the consequence of long-term N fertilization and associated soil acidification, likely promoting chemodenitrification. Our experimental approach can be implemented in understudied regions, with the potential to increase the amount of information on production and consumption of trace gases from soils. 相似文献
6.
Nitrous oxide (N 2O) is a potent greenhouse gas with a high contribution from agricultural soils and emissions that depend on soil type, climate,
crops and management practices. The N 2O emissions therefore need to be included as an integral part of environmental assessments of agricultural production systems.
An algorithm for N 2O production and emission from agricultural soils was developed and included in the FASSET whole-farm model. The model simulated
carbon and nitrogen (N) turnover on a daily basis. Both nitrification and denitrification was included in the model as sources
for N 2O production, and the N 2O emissions depended on soil microbial and physical conditions. The model was tested on experimental data of N 2O emissions from grasslands in UK, Finland and Denmark, differing in climatic conditions, soil properties and management.
The model simulated the general time course of N 2O emissions and captured the observed effects of fertiliser and manure management on emissions. Scenario analyses for grazed
and cut grasslands were conducted to evaluate the effects of soil texture, climatic conditions, grassland management and N
fertilisation on N 2O emissions. The soils varied from coarse sand to sandy loam and the climatic variation was taken to represent the climatic
variation within Denmark. N fertiliser rates were varied from 0 to 500 kg N ha −1. The simulated N 2O emissions showed a non-linear response to increasing N rates with increasing emission factors at higher N rates. The simulated
emissions increased with increasing soil clay contents. N 2O emissions were slightly increased at higher temperatures, whereas increasing annual rainfall generally lead to decreasing
emissions. Emissions were slightly higher from grazed grasslands compared with cut grasslands at similar rates of total N
input (fertiliser and animal excreta). The results indicate higher emission factors and thus higher potentials for reducing
N 2O emissions for intensively grazed grasslands on fine textured soils than for extensive cut-based grasslands on sandy soils. 相似文献
7.
The effect of six Siberian tree species on two stages of denitrification—N 2O production and consumption—was studied. Broadleaf species (aspen and birch) proved to have lower rates of N 2O consumption compared to coniferous species. The factors influencing production and consumption of N 2O were also evaluated. The replacement of coniferous forests with broadleaf trees will double the N 2O/N 2 ratio in the denitrification end-products. Doubled N 2O emission from Siberian forest soils to the atmosphere can be expected due to changes in tree species composition of forest ecosystems even without considering changes in water and temperature regimes in soil. 相似文献
8.
N 2O production from denitrification in soils contributes to the enhanced greenhouse effect and the destruction of the stratospheric
ozone. Ungulate grazing affects denitrification and the production of N 2O. The short-term effect of grazing on denitrification and N 2O production has been examined in several grassland ecosystems. However, the effects of long-term grazing have rarely been
studied. We measured denitrification and N 2O production during the 2005 and 2006 growing seasons in a long-term (17 years) experiment that had five grazing intensities
(GI; 0.00, 1.33, 2.67, 4.00 and 5.33 sheep ha −1). We found that denitrification and N 2O production rates were seasonally variable during the measurement period, with higher values observed in summer and lower
values found in spring and autumn. The grazed treatments resulted in decreased denitrification and N 2O production, primarily due to the reduced soil nitrate concentration and organic N content under the long-term grazing. This
supported our hypothesis that long-term over-grazing suppresses denitrification and N 2O production. Although significant differences in denitrification and N 2O production were not found between the four GI, there was a general trend that cumulative denitrification and N 2O production decreased as grazing intensity increased, especially in 2006. Lower N losses via denitrification and N 2O production in the grazed plots, to some extent, may contribute to the mitigation of greenhouse gas emission and help to
preserve soil N and ameliorate the negative impacts of grazing on plant growth, productivity, and ecological restoration processes
in the temperate steppe in northern China. 相似文献
9.
大气氮沉降输入会增加森林生态系统氮素有效性,进而改变土壤N_2O产生与排放,然而有关不同氮素离子(氧化态NO_3~--N与还原态NH_4~+-N)沉降对土壤N_2O排放的影响知之甚少。以大兴安岭寒温带针叶林为研究对象,构建了3种类型(NH_4Cl、KNO_3、NH_4NO_3)和4个施氮水平(0、10、20、40 kg N hm~(-2)a~(-1))的增氮控制试验,利用流动化学分析仪和静态箱-气相色谱法4次/月测定凋落物层和矿质层土壤无机氮含量、土壤-大气界面N_2O净交换通量以及相关环境因子,分析施氮类型和剂量对土壤氮素有效性、土壤N_2O通量的影响探讨氮素富集条件下土壤N_2O通量的环境驱动机制。结果表明:施氮类型和剂量均显著影响土壤无机氮含量,土壤NH_4~+-N的积累效应显著高于NO_3~--N。施氮一致增加寒温带针叶林土壤N_2O排放,NH_4NO_3促进效应最为明显,增幅为442%-677%,高于全球平均水平(134%)。土壤N_2O通量与土壤温度、凋落物层NH_4~+-N含量正相关,且随着施氮水平增加而增加。结果表明大气氮沉降短期内不会导致寒温带针叶林土壤NO_3~--N大量流失,但会显著促进土壤N_2O的排放。此外,外源性NH_4~+和NO_3~-输入对土壤N_2O排放的促进作用具有协同效应,在未来森林生态系统氮循环和氮平衡研究中应该区分对待。 相似文献
10.
Litter inputs are expected to have a strong impact on soil N 2O efflux. This study aimed to assess the effects of the litter decomposition process and nutrient efflux from litter to soil on soil N 2O efflux in a tropical rainforest. A paired study with a control (L) treatment and a litter-removed (NL) treatment was followed for 2 years, continuously monitoring the effects of these treatments on soil N 2O efflux, fresh litter input, decomposed litter carbon (LCI) and nitrogen (LNI), soil nitrate (NO 3 ?–N), ammonium (NH 4 +–N), dissolved organic carbon (DOC), and dissolved nitrogen (DN). Soil N 2O flux was 0.48 and 0.32 kg N 2O–N ha ?1 year ?1 for the L and NL treatments, respectively. Removing the litter caused a decrease in the annual soil N 2O emission by 33%. The flux values from the litter layer were higher in the rainy season as compared to the dry season (2.10 ± 0.28 vs. 1.44 ± 0.35 μg N m ?2 h ?1). The N 2O fluxes were significantly correlated with the soil NO 3 ?–N contents ( P < 0.05), indicating that the N 2O emission was derived mainly from denitrification as well as other NO 3 ? reduction processes. Suitable soil temperature and moisture sustained by rainfall were jointly attributed to the higher soil N 2O fluxes of both treatments in the rainy season. The N 2O fluxes from the L were mainly regulated by LCI, whereas those from the NL were dominated jointly by soil NO 3 ? content and temperature. The effects of LCI and LNI on the soil N 2O fluxes were the greatest in the 2 months after litter decomposition. Our results show that litter may affect not only the variability in the quantity of N 2O emitted, but also the mechanisms that govern N 2O production. However, further studies are still required to elucidate the impacting mechanisms of litter decomposition on N 2O emission from tropical forests. 相似文献
11.
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
12.
BackgroundThe greenhouse gas (GHG) mitigation is one of the most important environmental benefits of using bioenergy replacing fossil fuels. Nitrous oxide (N2O) and methane (CH4) are important GHGs and have drawn extra attention for their roles in global warming. Although there have been many works of soil emissions of N2O and CH4 from bioenergy crops in the field scale, GHG emissions in large area of marginal lands are rather sparse and how soil temperature and moisture affect the emission potential remains unknown. Therefore, we sought to estimate the regional GHG emission based on N2O and CH4 releases from the energy crop fields.ResultsHere we sampled the top soils from two Miscanthus fields and incubated them using a short-term laboratory microcosm approach under different conditions of typical soil temperatures and moistures. Based on the emission measurements of N2O and CH4, we developed a model to estimate annual regional GHG emission of Miscanthus production in the infertile Loess Plateau of China. The results showed that the N2O emission potential was 0.27 kg N ha?1 year?1 and clearly lower than that of croplands and grasslands. The CH4 uptake potential was 1.06 kg C ha?1 year?1 and was slightly higher than that of croplands. Integrated with our previous study on the emission of CO2, the net greenhouse effect of three major GHGs (N2O, CH4 and CO2) from Miscanthus fields was 4.08 t CO2eq ha?1 year?1 in the Loess Plateau, which was lower than that of croplands, grasslands and shrub lands.ConclusionsOur study revealed that Miscanthus production may hold a great potential for GHG mitigation in the vast infertile land in the Loess Plateau of China and could contribute to the sustainable energy utilization and have positive environmental impact on the region. 相似文献
13.
Forest clear-cutting followed by soil preparation means disturbance for soil microorganisms and disruption of N and C cycles.
We measured fluxes of N 2O and dissolved organic carbon (DOC) in upland soil (podzol) and adjacent peat within a clear-cut forest catchment. Both soil
types behaved in a similar way, showing net uptake of N 2O in the first year after the clear-cutting, and turning to net release in the second. The N 2O flux dynamics were similar to those of N content in logging residues, as reported from a nearby site. As organic matter
is used in the food web of the decomposers, we attempted to explain the dynamics of N 2O uptake and release by measuring the concurrent dynamics of the low molecular weight (LMW) fraction and the aromaticity of
DOC in a soil solution. The labile and most readily available LMW fractions of DOC were nearly absent in the year following
the clear-cutting, but rose after two years. The more refractory high molecular weight (HMW) fraction of DOC decreased two
years after the clear-cutting. The first year’s net uptake of N 2O could be accounted for by the growth of decomposer biomass in the logging residues and detritus from the degenerating ground
vegetation, resulting in immobilization of nitrogen. Simultaneously, the labile, LMW fraction of DOC became almost completely
exhausted. The low availability of the LMW fraction could retard the growth and cause the accumulated decomposer biomass to
collapse. During the following winter and summer the fraction of LMW clearly increased, followed by increased N 2O emissions. The presence of LMW DOC fractions, not the concentration of DOC, seems to be an important controller for N 2O liberation after a major disturbance such as clear-cutting and site preparation. The complex connection between DOC characteristics,
nitrification or denitrification merits further studies. 相似文献
14.
Nitrous oxide production was measured in intact cores taken from active pasture and old-growth forest Inceptisols in the Atlantic Lowlands of Costa Rica. Following additions of aqueous KNO 3 or glucose, or the two combined amendments, the cores were incubated in the laboratory to determine if N 2O production rates were either N-limited or C-limited in the two land use types. Differences in rates of denitrification (N2 2O + N 2 production) among amended forest and pasture soils were determined by addition of 10% C 2H 2.The forest soils were relatively insensitive to all amendment additions, including the acetylene block. Forest N 2O production rates among the treatments did not differ from the controls, and were consistently lower than those of the pasture soils. With the addition of glucose plus nitrate to the forest soils, production of N 2O was three times greater than the controls, although this increase was not statistically significant. On the other hand, the pasture soils were definitely nitrogen-limited since N 2O production rates were increased substantially beyond controls by all the amendments which contained nitrate, despite the very low N level (5 mg N kg –1 soil) relative to typical fertilizer applications. With respect to the nitrate plus glucose plus acetylene treatment, denitrification was high in the pasture soils; N 2O production in the presence of C 2H 2 was 150% of the rate of N 2O production measured in the absence of the acetylene block. The results are discussed in relation to the effects of agricultural land use practices and subsequent impacts of disturbance on N 2O release. 相似文献
15.
Wastewater treatment plants are known to be important point sources for nitrous oxide (N 2O) in the anthropogenic N cycle. Biofilm based treatment systems have gained increasing popularity in the treatment of wastewater, but the mechanisms and controls of N 2O formation are not fully understood. Here, we review functional groups of microorganism involved in nitrogen (N) transformations during wastewater treatment, with emphasis on potential mechanism of N 2O production in biofilms. Biofilms used in wastewater treatment typically harbour aerobic and anaerobic zones, mediating close interactions between different groups of N transforming organisms. Current models of mass transfer and biomass interactions in biofilms are discussed to illustrate the complex regulation of N 2O production. Ammonia oxidizing bacteria (AOB) are the prime source for N 2O in aerobic zones, while heterotrophic denitrifiers dominate N 2O production in anoxic zones. Nitrosative stress ensuing from accumulation of NO 2 ? during partial nitrification or denitrification seems to be one of the most critical factors for enhanced N 2O formation. In AOB, N 2O production is coupled to nitrifier denitrification triggered by nitrosative stress, low O 2 tension or low pH. Chemical N 2O production from AOB intermediates (NH 2OH, HNO, NO) released during high NH 3 turnover seems to be limited to surface-near AOB clusters, since diffusive mass transport resistance for O 2 slows down NH 3 oxidation rates in deeper biofilm layers. The proportion of N 2O among gaseous intermediates (NO, N 2O, N 2) in heterotrophic denitrification increases when NO or nitrous acid (HNO 2) accumulates because of increasing NO 2 ?, or when transient oxygen intrusion impairs complete denitrification. Limited electron donor availability due to mass transport limitation of organic substrates into anoxic biofilm zones is another important factor supporting high N 2O/N 2 ratios in heterotrophic denitrifiers. Biofilms accommodating Anammox bacteria release less N 2O, because Anammox bacteria have no known N 2O producing metabolism and reduce NO 2 ? to N 2, thereby lowering nitrosative stress to AOB and heterotrophs. 相似文献
16.
Abstract Nitrogen fixation was measured in a Corsican pine (Pinus laricio Poiret) forest in Calabria (Southern Italy). Acetylene reduction activity (ARA) and CO 2 production levels were determined by incubation of litter and superficial (0–5 cm) soil layer samples in the field, at monthly intervals. ARA variations were not correlated to those of substrate moisture, air temperature and microbial respiration. In fact N 2 fixation presented phases of different intensity which irregularly followed each other. Both litter and soil showed similar rates of N 2 fixation. Based on a C 2H 2:N 2 ratio of 3:1 0.8 Kg N ha –1 y –1 in each layer are fixed in the Pinus laricio forest, thus contributing to the N status of the soil in this nutrient–poor forest. 相似文献
17.
The deposition of nitrogen (N) is high in subtropical forest in South China and it is expected to increase further in the
coming decades. To assess effects of increasing deposition on N cycling, we investigated the current N status of two selected
40–45-year-old masson pine-dominated Chinese subtropical forest stands at Tieshanping (TSP, near Chongqing City) and Caijiatang
(CJT in Shaoshan, Hunan province), and explored the applicability of several indicators for N status and leaching, suggested
for temperate and boreal forest ecosystems. Current atmospheric N deposition to the systems is from 25 to 49 kg ha −1 year −1. The concentration of total N in the upper 15 cm of the soil is from as low as 0.05% in the B 2 horizon to as high as 0.53% in the O/A horizon. The concentration of organic carbon (C) varies from 0.74 (B 2) to 9.54% (O/A). Pools of N in the upper 15 cm of the soils range from 1460 to 2290 kg N ha −1, where 25–55% of the N pool is in the O/A horizon (upper 3 cm of the soil). Due to a lack of a well-developed continuous
O horizon (forest floor), the C/N ratio of this layer cannot be used as an indicator for the N status, as is commonly done
in temperate and boreal forests. The net N mineralization rate (mg N g −1 C year −1) in individual horizons correlates significantly with the C/N ratio, which is from as high as 18.2 in the O/A horizon to
as low as 11.2 in the B 2 horizon. The N 2O emission flux from soil is significantly correlated with the KCl extractable NH 4+–N in the O/A horizon and with the net nitrification in the upper 15 cm of the soil. However, the spatial and temporal variation
of the N 2O emission rate is high and rates are small and often difficult to detect in the field. The soil flux density of mineral N,
defined as the sum of the throughfall N input rate and the rate of in situ net N mineralization in the upper 15 cm of the
soil, i.e., the combination of deposition input and the N status of the system, explains the NO 3− leaching potential at 30 cm soil depth best. The seasonality of stream water N concentration at TSP and CJT is climatic and
hydrologically controlled, with highest values commonly occurring in the wet growing season and lowest in the dry dormant
season. This is different from temperate forest ecosystems, where N saturation is indicated by elevated NO 3− leaching in stream water during summer. 相似文献
18.
BioDeNO x process, which combines the advantages of the chemical absorption and biological reduction processes, is regarded as a promising candidate for NO removal from the flue gas. In the BioDeNO x , N 2O was accumulated in the process of the biological reduction of Fe II(EDTA)-NO. In this work, the pathway of the Fe II(EDTA)-NO reduction was investigated and a mathematic model was developed to evaluate and predict the accumulation of N 2O. Furthermore, parametric tests such as the effects of the C/N ratio (molar ratio of carbon/nitrogen), electron donor, and sulfite concentrations on N 2O accumulation were investigated. Experimental results revealed that N 2O accumulation was inhibited with a high C/N ratio (2.4), sufficient electron donor, and a low sulfite concentration. In addition, compared with the inorganic electron donor (Fe II(EDTA)), the organic electron donor (glucose) was beneficial for microorganism metabolism and N 2O accumulation inhibition. This work will provide significant insight into the inhibition of N 2O accumulation during the operation of BioDeNO x and advance this novel process for the industrial application. 相似文献
19.
Tropical rainforest soils harbor a considerable diversity of soil fauna that contributes to emissions of N 2O. Despite their ecological dominance, there is limited information available about the contribution of epigeal ant mounds to N 2O emissions in these tropical soils. This study aimed to determine whether ant mounds contribute to local soil N emissions in the tropical humid rainforest. N 2O emission was determined in vitro from individual live ants, ant-processed mound soils, and surrounding reference soils for two trophically distinct and abundant ant species: the leaf-cutting Atta mexicana and omnivorous Solenopsis geminata. The abundance of total bacteria, nitrifiers (AOA and AOB), and denitrifiers ( nirK, nirS, and nosZ) was estimated in these soils using quantitative PCR, and their respective mineral N contents determined. There was negligible N 2O emission detected from live ant individuals. However, the mound soils of both species emitted significantly greater (3-fold) amount of N 2O than their respective surrounding reference soils. This emission increased significantly up to 6-fold in the presence of acetylene, indicating that, in addition to N 2O, dinitrogen (N 2) is also produced from these mound soils at an equivalent rate (N 2O/N 2?=?0.57). Functional gene abundance (nitrifiers and denitrifiers) and mineral N pools (ammonium and nitrate) were significantly greater in mound soils than in their respective reference soils. Furthermore, in the light of the measured parameters and their correlation trends, nitrification and denitrification appeared to represent the major N 2O-producing microbial processes in ant mound soils. The ant mounds were estimated to contribute from 0.1 to 3.7% of the total N 2O emissions of tropical rainforest soils. 相似文献
20.
The mixture of other broadleaf species into beech forests in Central Europe leads to an increase of tree species diversity, which may alter soil biochemical processes. This study was aimed at 1) assessing differences in gross rates of soil N cycling among deciduous stands of different beech ( Fagus sylvatica L.) abundance in a limestone area, 2) analyzing the relationships between gross rates of soil N cycling and forest stand N cycling, and 3) quantifying N 2O emission and determining its relationship with gross rates of soil N cycling. We used 15N pool dilution techniques for soil N transformation measurement and chamber method for N 2O flux measurement. Gross rates of mineral N production in the 0–5 cm mineral soil increased across stands of decreasing beech abundance and increasing soil clay content. These rates were correlated with microbial biomass which, in turn, was influenced by substrate quantity, quality and soil fertility. Leaf litter-N, C:N ratio and base saturation in the mineral soil increased with decreasing beech abundance. Soil mineral N production and assimilation by microbes were tightly coupled, resulting in low N 2O emissions. Annual N 2O emissions were largely contributed by the freeze-thaw event emissions, which were correlated with the amount of soil microbial biomass. Our results suggest that soil N availability may increase through the mixture of broadleaf species into beech forests. 相似文献
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