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1.
Argyro Zerva 《Soil biology & biochemistry》2005,37(11):2025-2036
We examined the effects of forest clearfelling on the fluxes of soil CO2, CH4, and N2O in a Sitka spruce (Picea sitchensis (Bong.) Carr.) plantation on an organic-rich peaty gley soil, in Northern England. Soil CO2, CH4, N2O as well as environmental factors such as soil temperature, soil water content, and depth to the water table were recorded in two mature stands for one growing season, at the end of which one of the two stands was felled and one was left as control. Monitoring of the same parameters continued thereafter for a second growing season. For the first 10 months after clearfelling, there was a significant decrease in soil CO2 efflux, with an average efflux rate of 4.0 g m−2 d−1 in the mature stand (40-year) and 2.7 g m−2 d−1 in clearfelled site (CF). Clearfelling turned the soil from a sink (−0.37 mg m−2 d−1) for CH4 to a net source (2.01 mg m−2 d−1). For the same period, soil N2O fluxes averaged 0.57 mg m−2 d−1 in the CF and 0.23 mg m−2 d−1 in the 40-year stand. Clearfelling affected environmental factors and lead to higher daily soil temperatures during the summer period, while it caused an increase in the soil water content and a rise in the water table depth. Despite clearfelling, CO2 remained the dominant greenhouse gas in terms of its greenhouse warming potential. 相似文献
2.
We examined net greenhouse gas exchange at the soil surface in deciduous forests on soils with high organic contents. Fluxes of CO2, CH4 and N2O were measured using dark static chambers for two consecutive years in three different forest types; (i) a drained and medium productivity site dominated by birch, (ii) a drained and highly productive site dominated by alder and (iii) an undrained and highly productive site dominated by alder. Although the drained sites had shallow mean groundwater tables (15 and 18 cm, respectively) their average annual rates of forest floor CO2 release were almost twice as high compared to the undrained site (1.9±0.4 and 1.7±0.3, compared to 1.0±0.2 kg CO2 m−2 yr−1). The average annual CH4 emission was almost 10 times larger at the undrained site (7.6±3.1 compared to 0.9±0.5 g CH4 m−2 yr−1 for the two drained sites). The average annual N2O emissions at the undrained site (0.1±0.05 g N2O m−2 yr−1) were lower than at the drained sites, and the emissions were almost five times higher at the drained alder site than at the drained birch site (0.9±0.35 compared to 0.2±0.11 g N2O m−2 yr−1). The temporal variation in forest floor CO2 release could be explained to a large extent by differences in groundwater table and air temperature, but little of the variation in the CH4 and N2O fluxes could be explained by these variables. The measured soil variables were only significant to explain for the within-site spatial variation in CH4 and N2O fluxes at the undrained swamp, and dark forest floor CO2 release was not explained by these variables at any site. The between-site spatial variation was attributed to variations in drainage, groundwater level position, productivity and tree species for all three gases. The results indicate that N2O emissions are of greater importance for the net greenhouse gas exchange at deciduous drained forest sites than at coniferous drained forest sites. 相似文献
3.
The effects of elevated CO2 supply on N2O and CH4 fluxes and biomass production of Phleum pratense were studied in a greenhouse experiment. Three sets of 12 farmed peat soil mesocosms (10 cm dia, 47 cm long) sown with P. pratense and equally distributed in four thermo-controlled greenhouses were fertilised with a commercial fertiliser in order to add 2, 6 or 10 g N m−2. In two of the greenhouses, CO2 concentration was kept at atmospheric concentration (360 μmol mol−1) and in the other two at doubled concentration (720 μmol mol−1). Soil temperature was kept at 15 °C and air temperature at 20 °C. Natural lighting was supported by artificial light and deionized water was used to regulate soil moisture. Forage was harvested and the plants fertilised three times during the basic experiment, followed by an extra fertilisations and harvests. At the end of the experiment CH4 production and CH4 oxidation potentials were determined; roots were collected and the biomass was determined. From the three first harvests the amount of total N in the aboveground biomass was determined. N2O and CH4 exchange was monitored using a closed chamber technique and a gas chromatograph. The highest N2O fluxes (on average, 255 μg N2O m−2 h−1 during period IV) occurred just after fertilisation at high water contents, and especially at the beginning of the growing season (on average, 490 μg N2O m−2 h−1 during period I) when the competition of vegetation for N was low. CH4 fluxes were negligible throughout the experiment, and for all treatments the production and oxidation potentials of CH4 were inconsequential. Especially at the highest rates of fertilisation, the elevated supply of CO2 increased above- and below-ground biomass production, but both at the highest and lowest rates of fertilisation, decreased the total amount of N in the aboveground dry biomass. N2O fluxes tended to be higher under doubled CO2 concentrations, indicating that increasing atmospheric CO2 concentration may affect N and C dynamics in farmed peat soil. 相似文献
4.
We evaluated the spatial structures of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) fluxes in an Acacia mangium plantation stand in Sumatra, Indonesia, in drier (August) and wetter (March) seasons. A 60 × 100-m plot was established in an A. mangium plantation that included different topographical elements of the upper plateau, lower plateau, upper slope and foot slope. The plot was divided into 10 × 10-m grids and gas fluxes and soil properties were measured at 77 grid points at 10-m intervals within the plot. Spatial structures of the gas fluxes and soil properties were identified using geostatistical analyses. Averaged N2O and CO2 fluxes in the wetter season (1.85 mg N m−2 d−1 and 4.29 g C m−2 d−1, respectively) were significantly higher than those in the drier season (0.55 mg N m−2 d−1 and 2.73 g C m−2 d−1, respectively) and averaged CH4 uptake rates in the drier season (−0.62 mg C m−2 d−1) were higher than those in the wetter season (−0.24 mg C m−2 d−1). These values of N2O fluxes in A. mangium soils were higher than those reported for natural forest soils in Sumatra, while CO2 and CH4 fluxes were in the range of fluxes reported for natural forest soils. Seasonal differences in these gas fluxes appears to be controlled by soil water content and substrate availability due to differing precipitation and mineralization of litter between seasons. N2O fluxes had strong spatial dependence with a range of about 18 m in both the drier and wetter seasons. Topography was associated with the N2O fluxes in the wetter season with higher and lower fluxes on the foot slope and on the upper plateau, respectively, via controlling the anaerobic-aerobic conditions in the soils. In the drier season, however, we could not find obvious topographic influences on the spatial patterns of N2O fluxes and they may have depended on litter amount distribution. CO2 fluxes had no spatial dependence in both seasons, but the topographic influence was significant in the drier season with lowest fluxes on the foot slope, while there was no significant difference between topographic positions in the wetter season. The distributions of litter amount and soil organic matter were possibly associated with CO2 fluxes through their effects on microbial activities and fine root distribution in this A. mangium plantation. 相似文献
5.
Tjaša Danev?i? Bla? Stres David Stopar Janez Hacin 《Soil biology & biochemistry》2010,42(9):1437-1446
Peatlands play an important role in emissions of the greenhouse gases CO2, CH4 and N2O, which are produced during mineralization of the peat organic matter. To examine the influence of soil type (fen, bog soil) and environmental factors (temperature, groundwater level), emission of CO2, CH4 and N2O and soil temperature and groundwater level were measured weekly or biweekly in loco over a one-year period at four sites located in Ljubljana Marsh, Slovenia using the static chamber technique. The study involved two fen and two bog soils differing in organic carbon and nitrogen content, pH, bulk density, water holding capacity and groundwater level. The lowest CO2 fluxes occurred during the winter, fluxes of N2O were highest during summer and early spring (February, March) and fluxes of CH4 were highest during autumn. The temporal variation in CO2 fluxes could be explained by seasonal temperature variations, whereas CH4 and N2O fluxes could be correlated to groundwater level and soil carbon content. The experimental sites were net sources of measured greenhouse gases except for the drained bog site, which was a net sink of CH4. The mean fluxes of CO2 ranged between 139 mg m−2 h−1 in the undrained bog and 206 mg m−2 h−1 in the drained fen; mean fluxes of CH4 were between −0.04 mg m−2 h−1 in the drained bog and 0.05 mg m−2 h−1 in the drained fen; and mean fluxes of N2O were between 0.43 mg m−2 h−1 in the drained fen and 1.03 mg m−2 h−1 in the drained bog. These results indicate that the examined peatlands emit similar amounts of CO2 and CH4 to peatlands in Central and Northern Europe and significantly higher amounts of N2O. 相似文献
6.
The study was carried out at the experimental station of the Japan International Research Center for Agricultural Sciences to investigate gas fluxes from a Japanese Andisol under different N fertilizer managements: CD, a deep application (8 cm) of the controlled release urea; UD, a deep application (8 cm) of the conventional urea; US, a surface application of the conventional urea; and a control, without any N application. NO, N2O, CH4 and CO2 fluxes were measured simultaneously in a winter barley field under the maize/barley rotation. The fluxes of NO and N2O from the control were very low, and N fertilization increased the emissions of NO and N2O. NO and N2O from N fertilization treatments showed different emission patterns: significant NO emissions but low N2O emissions in the winter season, and low NO emissions but significant N2O emissions during the short period of barley growth in the spring season. The controlled release of the N fertilizer decreased the total NO emissions, while a deep application increased the total N2O emissions. Fertilizer-derived NO-N and N2O-N from the treatments CD, UD and US accounted for 0.20±0.07%, 0.71±0.15%, 0.62±0.04%, and 0.52±0.04%, 0.50±0.09%, 0.35±0.03%, of the applied N, respectively, during the barley season. CH4 fluxes from the control were negative on most sampling dates, and its net soil uptake was 33±7.1 mg m−2 during the barley season. The application of the N fertilizer decreased the uptake of atmospheric CH4 and resulted in positive emissions from the soil. CO2 fluxes were very low in the early period of crop growth while higher emissions were observed in the spring season. The N fertilization generally increased the direct CO2 emissions from the soil. N2O, CH4 and CO2 fluxes were positively correlated (P<0.01) with each other, whereas NO and CO2 fluxes were negatively correlated (P<0.05). The N fertilization increased soil-derived global warming potential (GWP) significantly in the barley season. The net GWP was calculated by subtracting the plant-fixed atmospheric CO2 stored in its aboveground parts from the soil-derived GWP in CO2 equivalent. The net GWP from the CD, UD, US and the control were all negative at −243±30.7, −257±28.4, −227±6.6 and −143±9.7 g C m−2 in CO2 equivalent, respectively, in the barley season. 相似文献
7.
Fluxes of CO2, CH4, and N2O in an alpine meadow affected by yak excreta on the Qinghai-Tibetan plateau during summer grazing periods 总被引:1,自引:0,他引:1
Xingwu Lin Shiping Wang Xiuzhi Ma Caiyun Luo Gaoming Jiang 《Soil biology & biochemistry》2009,41(4):718-725
To assess the impacts of yak excreta patches on greenhouse gas (GHG) fluxes in the alpine meadow of the Qinghai-Tibetan plateau, methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) fluxes were measured for the first time from experimental excreta patches placed on the meadow during the summer grazing seasons in 2005 and 2006. Dung patches were CH4 sources (average 586 μg m−2 h−1 in 2005 and 199 μg m−2 h−1 in 2006) during the investigation period of two years, while urine patches (average −31 μg m−2 h−1 in 2005 and −33 μg m−2 h−1 in 2006) and control plots (average −28 μg m−2 h−1 in 2005 and −30 μg m−2 h−1 in 2006) consumed CH4. The cumulative CO2 emission for dung patches was about 36-50% higher than control plots during the experimental period in 2005 and 2006. The cumulative N2O emissions for both urine and dung patches were 2.1-3.7 and 1.8-3.5 times greater than control plots in 2005 and 2006, respectively. Soil water-filled pore space (WFPS) explained 35% and 36% of CH4 flux variation for urine patches and control plots, respectively. Soil temperature explained 40-75% of temporal variation of CO2 emissions for all treatments. Temporal N2O flux variation in urine patches (34%), dung patches (48%), and control (56%) plots was mainly driven by the simultaneous effect of soil temperature and WFPS. Although yak excreta patches significantly affected GHG fluxes, their contributions to the whole grazing alpine meadow in terms of CO2 equivalents are limited under the moderate grazing intensity (1.45 yak ha−1). However, the contributions of excreta patches to N2O emissions are not negligible when estimating N2O emissions in the grazing meadow. In this study, the N2O emission factor of yak excreta patches varied with year (about 0.9-1.0%, and 0.1-0.2% in 2005 and 2006, respectively), which was lower than IPCC default value of 2%. 相似文献
8.
CH4 oxidation and emissions of CH4 and N2O from Lolium perenne swards under elevated atmospheric CO2
Emissions of N2O and CH4 and CH4 oxidation rates were measured from Lolium perenne swards in a short-term study under ambient (36 Pa) and elevated (60 Pa) atmospheric CO2 at the Free Air Carbon dioxide Enrichment experiment, Eschikon, Switzerland. Elevated pCO2 increased (P<0.05) N2O emissions from high N fertilised (11.2 g N m−2) swards by 69%, but had no significant effect on net emissions of CH4. Application of 13C-CH4 (11 μl l−1; 11 at.% excess 13C) to closed chamber headspaces in microplots enabled determination of rates of 13C-CH4 oxidation even when net CH4 fluxes from main plots were positive. We found a significant interaction between fertiliser application rate and atmospheric pCO2 on 13C-CH4 oxidation rates that was attributed to differences in gross nitrification rates and C and N availability. CH4 oxidation was slower and thought to be temporarily inhibited in the high N ambient pCO2 sward. The most rapid CH4 oxidation of 14.6 μg 13C-CH4 m−2 h−1 was measured in the high fertilised elevated pCO2 sward, and we concluded that either elevated pCO2 had a stimulatory effect on CH4 oxidation or inhibition of oxidation following fertiliser application was lowered under elevated pCO2. Application of 14NH415NO3 and 15NH415NO3 (10 at.% excess 15N) to different replicates enabled determination of the respective contributions of nitrification and denitrification to N2O emissions. Inhibition of CH4 oxidation in the high fertilised ambient pCO2 sward, due to competition between NH3 and CH4 for methane monooxygenase enzymes or toxic effects of NH2OH or NO2− produced during nitrification, was hypothesised to increase gross nitrification (12.0 mg N kg dry soil−1) and N2O emissions during nitrification (327 mg 15N-N2O m−2 over 11 d). Our results indicate that increasing atmospheric concentrations of CO2 may increase emissions of N2O by denitrification, lower nitrification rates and either increase or decrease the ability of soil to act as a sink for atmospheric CH4 depending on fertiliser management. 相似文献
9.
Mette S. Carter Per Ambus Klaus S. Larsen Anders Priemé Claus Beier 《Soil biology & biochemistry》2011,43(8):1660-1670
In temperate regions, climate change is predicted to increase annual mean temperature and intensify the duration and frequency of summer droughts, which together with elevated atmospheric carbon dioxide (CO2) concentrations, may affect the exchange of nitrous oxide (N2O) and methane (CH4) between terrestrial ecosystems and the atmosphere. We report results from the CLIMAITE experiment, where the effects of these three climate change parameters were investigated solely and in all combinations in a temperate heathland. Field measurements of N2O and CH4 fluxes took place 1-2 years after the climate change manipulations were initiated. The soil was generally a net sink for atmospheric CH4. Elevated temperature (T) increased the CH4 uptake by on average 10 μg C m−2 h−1, corresponding to a rise in the uptake rate of about 20%. However, during winter elevated CO2 (CO2) reduced the CH4 uptake, which outweighed the positive effect of warming when analyzed across the study period. Emissions of N2O were generally low (<10 μg N m−2 h−1). As single experimental factors, elevated CO2, temperature and summer drought (D) had no major effect on the N2O fluxes, but the combination of CO2 and warming (TCO2) stimulated N2O emission, whereas the N2O emission ceased when CO2 was combined with drought (DCO2). We suggest that these N2O responses are related to increased rhizodeposition under elevated CO2 combined with increased and reduced nitrogen turnover rates caused by warming and drought, respectively. The N2O flux in the multifactor treatment TDCO2 was not different from the ambient control treatment. Overall, our study suggests that in the future, CH4 uptake may increase slightly, while N2O emission will remain unchanged in temperate ecosystems on well-aerated soils. However, we propose that continued exposure to altered climate could potentially change the greenhouse gas flux pattern in the investigated heathland. 相似文献
10.
E.G. Gregorich D.W. Hopkins A.D. Sparrow P. Novis P. Rochette 《Soil biology & biochemistry》2006,38(10):3120-3129
We measured soil profile concentrations and emission of CO2, CH4 and N2O from soils along a lakeshore in Garwood Valley, Antarctica, to assess the extent and biogeochemical significance of biogenic gas emission to C and N cycling processes. Simultaneous emission of all three gases from the same site indicated that aerobic and anaerobic processes occurred in different layers or different parts of each soil profile. The day and location of high gas concentrations in the soil profile corresponded to those having high gas emission, but the pattern of concentration with depth in the soil profile was not consistent across sites. That the highest gas concentrations were not always in the deepest soil layer suggests either limited production or gas diffusion in the deeper layers. Emission of CO2 was as high as 47 μmol m−2 min−1 and was strongly related to soil temperature. Soil respiration differed significantly according to location on the lakeshore, suggesting that factors other than environmental variables, such as the amount and availability of O2 and nutrients, play an important role in C mineralization processes in these soils. High surface emission (maximum: 15 μmol m−2 min−1) and profile gas concentration (maximum: 5780 μL L−1) of CH4 were at levels comparable to those in resource-rich temperate ecosystems, indicating an active indigenous population of methanogenic organisms. Emission of N2O was low and highly variable, but the presence of this gas and NO3 in some of the soils suggest that denitrification and nitrification occur there. No significant relationships between N2O emission and environmental variables were found. It appears that considerable C and N turnover occurs in the lakeshore soils, and accurate accounting will require measurements of aerobic and anaerobic mineralization. The production and emission of biogenic gases confirm the importance of these soils as hotspots of biological activity in the dry valleys and probable reservoirs of biological diversity. 相似文献
11.
While experimental addition of nitrogen (N) tends to enhance soil fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), it is not known if lower and agronomic-scale additions of urea-N applied also enhance trace gas fluxes, particularly for semi-arid agricultural lands in the northern plains. We aimed to test if this were true at agronomic rates [low (11 kg N ha−1), moderate (56 kg N ha−1), and high (112 kg N ha−1)] for central North Dakota arable and prairie soils using intact soil cores to minimize disturbance and simulate field conditions. Additions of urea to cores incubated at 21 °C and 57% water-filled pore space enhanced fluxes of CO2 but not CH4 and N2O. At low, moderate, and high urea-N, CO2 fluxes were significantly greater than control but not fluxes of CH4 and N2O. The increases in CO2 emission with rate of urea-N application indicate that agronomic-scale N inputs may stimulate microbial carbon cycling in these soils, and that the contribution of CO2 to net greenhouse gas source strength following fertilization of semi-arid agroecosystems may at times be greater than contributions by N2O and CH4. 相似文献
12.
To determine the sum of ‘direct’ and ‘indirect’ effects of climatic change on enchytraeid activity and C fluxes from an organic soil we assessed the influence of temperature (4, 10 and 15 °C incubations) on enchytraeid populations and soil CO2 and CH4 fluxes over 116 days. Moisture was maintained at 60% of soil dry weight during the experimental period and measurements of enchytraeid biomass and numbers, and CO2 and CH4 fluxes were made after 3, 16, 33, 44, 65, 86 and 116 days. Enchytraeid population numbers and biomass increased in all temperature treatments with the greatest increase produced at 15 °C (to over threefold initial values by day 86). Results also showed that enchytraeid activity increased CO2 fluxes by 10.7±4.5, 3.4±4.0 and 26.8±2.6% in 4, 10 and 15 °C treatments, respectively, with the greatest CO2 production observed at 15 °C for the entire 116 day incubation period (P<0.05). The soil respiratory quotient analyses at lower temperatures (i.e. 4-10 °C) gave a Q10 of 1.7 and 1.9 with and without enchytraeids, respectively. At temperatures above 10 °C (i.e. 10-15 °C) Q10 significantly increased (P<0.01) and was 25% greater in the presence of enchytraeids (Q10=3.4) than without (Q10=2.6). In contrast to CO2 production, no significant relationships were observed between net CH4 fluxes and temperature and only time showed a significant effect on CH4 production (P<0.01).Total soil CO2 production was positively linked with enchytraeid biomass and mean soil CO2-C production was 77.01±6.05 CO2-C μg mg enchytraeid tissue−1 day−1 irrespective of temperature treatment. This positive relationship was used to build a two step regression model to estimate the effects of temperature on enchytraeid biomass and soil CO2 respiration in the field. Predictions of potential CO2 production were made using enchytraeid biomass data obtained in the field from two upland grassland sites (Sourhope and Great Dun Fell at the Moor House Nature Reserve, both in the UK). The findings of this work suggest that a 5 °C increase in atmospheric temperature above mean ambient temperature could have the potential to produce a significant increase in enchytraeid biomass resulting in a near twofold increase in soil CO2 release from both soil types. The interaction between temperature and soil biology will clearly be an important determinant of soil respiration responses to global warming. 相似文献
13.
Emission of N2O and CH4 oxidation rates were measured from soils of contrasting (30-75%) water-filled pore space (WFPS). Oxidation rates of 13C-CH4 were determined after application of 10 μl 13C-CH4 l−1 (10 at. % excess 13C) to soil headspace and comparisons made with estimates from changes in net CH4 emission in these treatments and under ambient CH4 where no 13C-CH4 had been applied. We found a significant effect of soil WFPS on 13C-CH4 oxidation rates and evidence for oxidation of 2.2 μg 13C-CH4 d−1 occurring in the 75% WFPS soil, which may have been either aerobic oxidation occurring in aerobic microsites in this soil or anaerobic CH4 oxidation. The lowest 13C-CH4 oxidation rate was measured in the 30% WFPS soil and was attributed to inhibition of methanotroph activity in this dry soil. However, oxidation was lowest in the wetter soils when estimated from changes in concentration of 12+13C-CH4. Thus, both methanogenesis and CH4 oxidation may have been occurring simultaneously in these wet soils, indicating the advantage of using a stable isotope approach to determine oxidation rates. Application of 13C-CH4 at 10 μl 13C-CH4 l−1 resulted in more rapid oxidation than under ambient CH4 conditions, suggesting CH4 oxidation in this soil was substrate limited, particularly in the wetter soils. Application of and (80 mg N kg soil−1; 9.9 at.% excess 15N) to different replicates enabled determination of the respective contributions of nitrification and denitrification to N2O emissions. The highest N2O emission (119 μg 14+15N-N2O kg soil−1 over 72 h) was measured from the 75% WFPS soil and was mostly produced during denitrification (18.1 μg 15N-N2O kg soil−1; 90% of 15N-N2O from this treatment). Strong negative correlations between 14+15N-N2O emissions, denitrified 15N-N2O emissions and 13C-CH4 concentrations (r=−0.93 to −0.95, N2O; r=−0.87 to −0.95, denitrified 15N-N2O; P<0.05) suggest a close relationship between CH4 oxidation and denitrification in our soil, the nature of which requires further investigation. 相似文献
14.
Initial effects of elevated atmospheric CO2 concentration on N2O fluxes and biomass production of timothy/red clover were studied in the laboratory. The experimental design consisted of two levels of atmospheric CO2 (ca. 360 and 720 μmol CO2 mol−1) and two N fertilisation levels (5 and 10 g N m−2). There was a total of 36 mesocosms comprising sandy loam soil, which were equally distributed in four thermo-controlled greenhouses. In two of the greenhouses, the CO2 concentration was kept at ambient concentration and in the other two at doubled concentration. Forage was harvested and the plants fertilised three times during the basic experiment, followed by harvest, a fertilisation with the double amount of nitrogen and rise of water level. Under elevated CO2, harvestable and total aboveground dry biomass production of a mixed Trifolium/Phleum stand was increased at both N treatments compared to ambient CO2. The N2O flux rates under ambient CO2 were significantly higher at both N treatments during the early growth of mixed Phleum/Trifolium mesocosms compared to the N2O flux rate under elevated CO2. However, when the conditions were favourable for denitrification at the end of the experiment, i.e. N availability and soil moisture were high enough, the elevated CO2 concentration enhanced the N2O efflux. 相似文献
15.
Nitrous oxide research has generally focused directly on measuring fluxes of N2O from the soil surface. The fate of N2O in the subsoil has often been placed in the ‘too hard’ basket. However, determining the production, fate and movement of N2O in the subsoil is vital in fully understanding the sources of surface fluxes and in compiling accurate inventories for N2O emissions. The aim of this study was to generate and introduce into soil columns 15N labelled N2O, and to try and determine the consumption of the 15N2O and production of ambient N2O. Columns, 100 cm long by 15 cm diameter, were repacked with sieved soil (sampled from 0 to 5 cm depth) and instrumented with silicone rubber gas sampling ports. Nitrous oxide enriched with 15N was generated using a thermal decomposition process at 300 °C and then transferred to 2 l flasks. After equilibrating with SF6 tracer gas the 15N2O was introduced into the soil columns via passive diffusion. Gas samples from the soil profile and headspace flux were taken over a 12-day period. A watering event was simulated to perturb the 15N2O gas composition in the soil profile. Using the measured 15N enriched fluxes and the rate of decline in 15N in the N2O reservoir, from which the N2O diffused into the soil, we calculated an N2O sink (consumption plus absorption by water) equal to 0.48 ng N2O g−1 soil h−1. The decrease in the 15N enrichment between successive soil depths indicated N2O production in the soil profile and we calculated a net N2O production rate of 0.88 ng N2O g−1 soil h−1. This pilot study demonstrated the potential for simultaneously measuring both N2O consumption and production rates, using the 15N enrichment of the N2O measured. Further potential refinements of the methodology are discussed. 相似文献
16.
Ryota Konda Seiichi Ohta Shigehiro Ishizuka Seiko Arai Saifuddin Ansori Nagaharu Tanaka Arisman Hardjono 《Soil biology & biochemistry》2008,40(12):3021-3030
We investigated spatial structures of N2O, CO2, and CH4 fluxes during a relatively dry season in an Acacia mangium plantation stand in Sumatra, Indonesia. The fluxes and soil properties were measured at 1-m intervals in a 1 × 30-m plot (62 grid points) and at 10-m intervals in a 40 × 100-m plot (55 grid points) at different topographical positions of the upper plateau, slope, and valley bottom in the plantation. Spatial structures of each gas flux and soil property were identified using geostatistical analysis. The means (±SD) of N2O, CO2, and CH4 fluxes in the 10-m grids were 0.54 (±0.33) mg N m−2 d−1, 2.81 (±0.71) g C m−2 d−1, and −0.84 (±0.33) mg C m−2 d−1, respectively. This suggests that A. mangium soils function as a larger source of N2O than natural forest soils in the adjacent province on Sumatra during the relatively dry season, while CO2 and CH4 emissions from the A. mangium soils were less than or consistent with those in the natural forest soils. Multiple spatial dependence of N2O fluxes within 3.2 m (1-m grids) and 35.0 m (10-m grids), and CO2 fluxes within 1.8 m (1-m grids) and over 65 m (10-m grids) was detected. From the relationship among N2O and CO2 gas fluxes, soil properties, and topographic elements, we suggest that the multiple spatial structures of N2O and CO2 fluxes are mainly associated with soil resources such as readily mineralizable carbon and nitrogen in a relatively dry season. The soil resource distributions were probably controlled by the meso- and microtopography. Meanwhile, CH4 fluxes were spatially independent in the A. mangium soils, and the water-filled pore space appeared to mainly control the spatial distribution of these fluxes. 相似文献
17.
A laboratory investigation was performed to compare the fluxes of dinitrogen (N2), N2O and carbon dioxide (CO2) from no-till (NT) and conventional till (CT) soils under the same water, mineral nitrogen and temperature status. Intact soil cores (0-10 cm) were incubated for 2 weeks at 25 °C at either 75% or 60% water-filled pore space (WFPS) with 15N-labeled fertilizers (100 mg N kg−1 soil). Gas and soil samples were collected at 1-4 day intervals during the incubation period. The N2O and CO2 fluxes were measured by a gas chromatography (GC) system while total N2 and N2O losses and their 15N mole fractions in the soil mineral N pool were determined by a mass spectrometer. The daily accumulative fluxes of N2 and N2O were significantly affected by tillage, N source and soil moisture. We observed higher (P<0.05) fluxes of N2+N2O, N2O and CO2 from the NT soils than from the CT soils. Compared with the addition of nitrate (NO3−), the addition of ammonium (NH4+) enhanced the emissions of these N and C gases in the CT and NT soils, but the effect of NH4+ on the N2 and/or N2O fluxes was evident only at 60% WFPS, indicating that nitrification and subsequent denitrification contributed largely to the gaseous N losses and N2O emission under the lower moisture condition. Total and fertilizer-induced emissions of N2 and/or N2O were higher (P<0.05) at 75% WFPS than with 60% WFPS, while CO2 fluxes were not influenced by the two moisture levels. These laboratory results indicate that there is greater potential for N2O loss from NT soils than CT soils. Avoiding wet soil conditions (>60% WFPS) and applying a NO3− form of N fertilizer would reduce potential N2O emissions from arable soils. 相似文献
18.
Peatlands typically exhibit significant spatial heterogeneity which can lead to large uncertainties when catchment scale greenhouse gas fluxes are extrapolated from chamber measurements (generally <1 m2). Here we examined the underlying environmental and vegetation characteristics which led to within-site variability in both CH4 and N2O emissions and the importance of such variability in up-scaling. We also consider within-site variation in the controls of temporal dynamics. Net annual emissions (and coefficients of variation) for CH4 and N2O were 1.06 kg ha−1 y−1 (300%) and 0.02 kg ha−1 y−1 (410%), respectively. The riparian zone was a significant CH4 hotspot contributing ∼12% of the total catchment emissions whilst covering only ∼0.5% of the catchment area. In contrast to many other studies we found smaller CH4 emissions and greater uptake in chambers containing either sedges or rushes. We also found clear differences in the drivers of temporal CH4 dynamics across the site, e.g. water table was important only in chambers which did not contain aerenchymous plants. We suggest that depending on the heterogeneity of the site, flux models could be improved by incorporating a number of spatially distinct sub-models, rather than a single model parameterized using whole-catchment averages. 相似文献
19.
Chiara Bertora Petra C.J. van Vliet Jan Willem van Groenigen 《Soil biology & biochemistry》2007,39(2):632-640
Earthworm activity has been reported to lead to increased production of the greenhouse gas nitrous oxide (N2O). This is due to emissions from worms themselves, their casts and drilosphere, as well as to general changes in soil structure. However, it remains to be determined how important this effect is on N2O fluxes from agricultural systems under realistic conditions in terms of earthworm density, soil moisture, tillage activity and residue loads. We quantified the effect of earthworm presence on N2O emissions from a pasture after simulated ploughing of the sod (‘grassland renovation’) for different soil moisture contents during a 62-day mesocosm study. Sod (with associated soil) and topsoil were separately collected from a loamy Typic Fluvaquent. Treatments included low (L), medium (M) and high (H) moisture content, in combination with: only soil (S); soil+incorporated sod (SG); soil+incorporated sod+the anecic earthworm Aporrectodea longa (SGE). Nitrous oxide and carbon dioxide (CO2) fluxes were measured for 62 d. At the end of the incubation period, we determined N2O production under water-saturated conditions, potential denitrification and potential mineralization of the soil after removing the earthworms. Cumulative N2O and CO2 fluxes over 62 d from incorporated sod were highest for treatment HSGE (973 μg N2O-N and 302 mg CO2-C kg−1 soil) and lowest for LSG (64 μg N2O-N and 188 mg CO2-C kg−1 soil). Both cumulative fluxes were significantly different for soil moisture (p<0.001), but not for earthworm presence. However, we observed highly significant earthworm effects on N2O fluxes that reversed over time for the H treatments. During the first phase (day 3-day 12), earthworm presence increased N2O emissions with approximately 30%. After a transitional phase, earthworm presence resulted in consistently lower (approximately 50%) emissions from day 44 onwards. Emissions from earthworms themselves were negligible compared to overall soil fluxes. After 62 d, original soil moisture significantly affected potential denitrification, with highest fluxes from the L treatments, and no significant earthworm effect. We conclude that after grassland ploughing, anecic earthworm presence may ultimately lead to lower N2O emissions after an initial phase of elevated emissions. However, the earthworm effect was both determined and exceeded by soil moisture conditions. The observed effects of earthworm activity on N2O emissions were due to the effect of earthworms on soil structure rather than to emissions from the worms themselves. 相似文献
20.
Soil compaction and soil moisture are important factors influencing denitrification and N2O emission from fertilized soils. We analyzed the combined effects of these factors on the emission of N2O, N2 and CO2 from undisturbed soil cores fertilized with (150 kg N ha−1) in a laboratory experiment. The soil cores were collected from differently compacted areas in a potato field, i.e. the ridges (ρD=1.03 g cm−3), the interrow area (ρD=1.24 g cm−3), and the tractor compacted interrow area (ρD=1.64 g cm−3), and adjusted to constant soil moisture levels between 40 and 98% water-filled pore space (WFPS).High N2O emissions were a result of denitrification and occurred at a WFPS≥70% in all compaction treatments. N2 production occurred only at the highest soil moisture level (≥90% WFPS) but it was considerably smaller than the N2O-N emission in most cases. There was no soil moisture effect on CO2 emission from the differently compacted soils with the exception of the highest soil moisture level (98% WFPS) of the tractor-compacted soil in which soil respiration was significantly reduced. The maximum N2O emission rates from all treatments occurred after rewetting of dry soil. This rewetting effect increased with the amount of water added. The results show the importance of increased carbon availability and associated respiratory O2 consumption induced by soil drying and rewetting for the emissions of N2O. 相似文献