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  • 1
    Language: English
    In: Agricultural and Forest Meteorology, January 2015, Vol.201, pp.701-702
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.agrformet.2015.12.021 Byline: Xunhua Zheng Author Affiliation: Institute of Atmospheric Physics, Chinese Academy of Sciences, Hall 40, Huayanli, Chaoyang District, Beijing, CHINA
    Keywords: Agriculture ; Meteorology & Climatology
    ISSN: 0168-1923
    E-ISSN: 1873-2240
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  • 2
    Language: English
    In: Atmospheric Environment, Oct, 2014, Vol.96, p.201(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.atmosenv.2014.07.040 Byline: Chunyan Liu, Zhisheng Yao, Kai Wang, Xunhua Zheng Abstract: The remarkable expansion of fertilization and irrigation may stimulate nitrous oxide (N.sub.2O) emissions from cropping systems in northern China. High-resolution measurements were conducted in irrigated cotton and wheat-maize rotational systems in Shanxi Province, P.R. China, between 2007 and 2010 (three year-round crop cycles, hereinafter referred to as Y1, Y2 and Y3) to investigate the impacts of natural inter-annual variations and agricultural management on annual N.sub.2O emissions and direct emission factors (EFs). Overall, N.sub.2O emissions fluctuated diurnally, seasonally and inter-annually in the fertilized treatments. The hourly N.sub.2O fluxes closely followed the daily air temperature patterns. The daily mean fluxes corresponded to these hourly fluxes, which were observed between 09:00-10:00 and 19:00-20:00. An optimized sampling protocol could improve the reliability of discrete measurements when estimating cumulative emissions. The N.sub.2O emissions for the fertilized treatments were 2.7 [+ or -] 0.2 (Y1) and 1.6 [+ or -] 0.1 kg N ha.sup.-1 yr.sup.-1 (Y2) from the cotton field and 6.2 [+ or -] 0.4 (Y1), 4.5 [+ or -] 0.3 (Y2) and 4.5 [+ or -] 0.2 kg N ha.sup.-1 yr.sup.-1 (Y3) from the wheat-maize field. Peak N.sub.2O emissions after fertilization and irrigation/rainfall lasted one to three weeks and accounted for 16-55% of the annual emissions. Leaching losses were estimated at 10.4 [+ or -] 3.0 (Y1) and 12.5 [+ or -] 3.4 kg N ha.sup.-1 yr.sup.-1 (Y2), which accounted for 16-17% of the fertilizer-N applied to the cotton field. Annual N.sub.2O emissions did not increase with increasing fertilization rates or water inputs because significant amounts of fertilizer-N were lost through leaching. Background emissions amounted to one-third to one-half of the total N.sub.2O emissions from the fertilized treatments. The direct EFs were 2.2 [+ or -] 0.3% (Y1) and 0.9 [+ or -] 0.2% (Y2) in the cotton field and 1.3 [+ or -] 0.2% (Y1), 0.8 [+ or -] 0.1% (Y2) and 0.7 [+ or -] 0.1% (Y3) in the wheat-maize field. The large inter-annual variations in N.sub.2O emissions and direct EFs emphasize the importance of multiple-year continuous observations. Author Affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China Article History: Received 28 April 2014; Revised 16 July 2014; Accepted 19 July 2014
    Keywords: Planetary Boundary Layer -- Measurement ; Planetary Boundary Layer -- Environmental Aspects ; Emissions (Pollution) -- Measurement ; Emissions (Pollution) -- Environmental Aspects ; Atmospheric Physics -- Measurement ; Atmospheric Physics -- Environmental Aspects ; Atmospheric Chemistry -- Measurement ; Atmospheric Chemistry -- Environmental Aspects ; Fertilizers -- Measurement ; Fertilizers -- Environmental Aspects ; Cropping Systems -- Measurement ; Cropping Systems -- Environmental Aspects ; Corn -- Measurement ; Corn -- Environmental Aspects ; Nitrous Oxide -- Measurement ; Nitrous Oxide -- Environmental Aspects
    ISSN: 1352-2310
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Atmospheric Environment, Dec, 2013, Vol.81, p.642(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.atmosenv.2013.09.046 Byline: Jia Deng, Zaixing Zhou, Xunhua Zheng, Changsheng Li Abstract: Intensive nitrogen (N) fertilizer application in the vegetable fields of China has commonly occurred during recent decades and may substantially increase both nitrous oxide (N.sub.2O) and nitric oxide (NO) emissions. However, the quantification of N.sub.2O and NO emissions from vegetable fields has been rare due to both the lack of long-term field measurements and reliable methods for extrapolating these measurements. Using a unique dataset from a four-year measurement study of an intensively managed conventional vegetable field in southeastern China, we tested a process-based biogeochemical model, denitrification-decomposition (DNDC), for its applicability for quantifying the impact of fertilizer management practices on emissions of N trace gases from vegetable production. The results from the model validation indicate that the simulations of vegetable yields and seasonal cumulative N.sub.2O and NO emissions are consistent with the observations. In addition, DNDC can generally capture the measured temporal pattern of daily N.sub.2O and NO fluxes. The modeled impacts of fertilization alternatives can be summarized as follows: (a) both the type and application rate of N fertilizers play important roles in regulating N.sub.2O and NO emissions as well as vegetable growth; (b) reducing the N application rate to 75% of the conventional amount decreased N.sub.2O and NO emissions by 31% and showed little impact on vegetable biomasses, suggesting that reducing the N dose to a reasonable level would be advisable for both the mitigation of N gases emissions and the maintenance of vegetable production; and (c) replacing synthetic fertilizer under the conventional management practices with organic manure may significantly stimulate N.sub.2O emission by 62% while decreasing vegetable yields. The results from this modeling study may provide useful information for the ongoing debate regarding the optimization of fertilizer use strategies in China. This study also demonstrates the potential of utilizing process-based models, such as DNDC, to quantify and mitigate N.sub.2O and NO emissions from intensive vegetable production through interpreting, integrating, and extrapolating field observations. Author Affiliation: (a) State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, PR China (b) Earth Systems Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, 39 College Road, Durham, NH 03824, USA Article History: Received 3 June 2013; Revised 21 August 2013; Accepted 20 September 2013
    Keywords: Vegetables -- Models ; Vegetables -- Environmental Aspects ; Vegetables -- Analysis ; Planetary Boundary Layer -- Models ; Planetary Boundary Layer -- Environmental Aspects ; Planetary Boundary Layer -- Analysis ; Nitric Oxide -- Models ; Nitric Oxide -- Environmental Aspects ; Nitric Oxide -- Analysis ; Denitrification -- Models ; Denitrification -- Environmental Aspects ; Denitrification -- Analysis ; Nitrous Oxide -- Models ; Nitrous Oxide -- Environmental Aspects ; Nitrous Oxide -- Analysis ; Atmospheric Physics -- Models ; Atmospheric Physics -- Environmental Aspects ; Atmospheric Physics -- Analysis ; Atmospheric Chemistry -- Models ; Atmospheric Chemistry -- Environmental Aspects ; Atmospheric Chemistry -- Analysis ; Organic Fertilizers -- Models ; Organic Fertilizers -- Environmental Aspects ; Organic Fertilizers -- Analysis
    ISSN: 1352-2310
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, May, 2012, Vol.48, p.10(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.soilbio.2012.01.007 Byline: Feng Cui, Guangxuan Yan, Zaixing Zhou, Xunhua Zheng, Jia Deng Abstract: Nitrogen amendment followed by flooding irrigation is a general management practice for a wheat-maize rotation in the North China Plain, which may favor nitrification and denitrification. Consequently, high emissions of nitrous oxide (N.sub.2O) and nitric oxide (NO) are hypothesized to occur. To test this hypothesis, we performed year-round field measurements of N.sub.2O and NO fluxes from irrigated wheat-maize fields on a calcareous soil applied with all crop residues using a static, opaque chamber measuring system. To interpret the field data, laboratory experiments using intact soil cores with added carbon (glucose) and nitrogen (nitrate, ammonium) substrates were performed. Our field measurements showed that pulse emissions after fertilization and irrigation/rainfall contributed to 73% and 88% of the annual N.sub.2O and NO emissions, respectively. Soil moisture and mineral nitrogen contents significantly affected the emissions of both gases. Annual emissions from fields fertilized at the conventional rate (600 kg N ha.sup.-1 yr.sup.-1) totaled 4.0 [+ or -] 0.2 and 3.0 [+ or -] 0.2 kg N ha.sup.-1 yr.sup.-1 for N.sub.2O and NO, respectively, while those from unfertilized fields were much lower (0.5 [+ or -] 0.02 kg N ha.sup.-1 yr.sup.-1 and 0.4 [+ or -] 0.05 kg N ha.sup.-1 yr.sup.-1, respectively). Direct emission factors (EF.sub.ds) of N.sub.2O and NO for the fertilizer nitrogen were estimated to be 0.59 [+ or -] 0.04% and 0.44 [+ or -] 0.04%, respectively. By summarizing the results of our study and others, we recommended specific EF.sub.ds (N.sub.2O: 0.54 [+ or -] 0.09%; NO: 0.45 [+ or -] 0.04%) for estimating emissions from irrigated croplands on calcareous soils with organic carbon ranging from 5 to 16 g kg.sup.-1. Nitrification dominated the processes driving the emissions of both gases following fertilization. It was evident that insufficient available carbon limited microbial denitrification and thus N.sub.2O emission. This implicates that efforts to enhance carbon sink in calcareous soils likely increase their N.sub.2O emissions. Author Affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, PR China Article History: Received 30 September 2011; Revised 10 January 2012; Accepted 11 January 2012
    Keywords: Silt -- Environmental Aspects ; Denitrification -- Environmental Aspects ; Nitric Oxide -- Environmental Aspects ; Glucose -- Environmental Aspects ; Atmospheric Chemistry -- Environmental Aspects ; Atmospheric Physics -- Environmental Aspects ; Nitrification -- Environmental Aspects ; Nitrous Oxide -- Environmental Aspects ; Nitrogen Oxides -- Environmental Aspects ; Soil Carbon -- Environmental Aspects ; Anesthetics -- Environmental Aspects ; Cropping Systems -- Environmental Aspects ; Emissions (Pollution) -- Environmental Aspects ; Soils -- Environmental Aspects ; Soil Moisture -- Environmental Aspects ; Planetary Boundary Layer -- Environmental Aspects
    ISSN: 0038-0717
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Plant and Soil, 2014, Vol.383(1), pp.401-414
    Description: Background and aims High nitrous oxide ([N.sub.2]O) emissions may occur during the non-rice growing season of Chinese rice-upland crop rotation systems. However, our understanding of [N.sub.2]O emission during this season is poor due to a scarcity of available field [N.sub.2]O measurements. Methods Using the static manual chamber-GC technique, seasonal [N.sub.2]O emissions during the non-rice growing season were simultaneously measured at two adjacent rice-wheat and rice-rapeseed fields in southwest China for three consecutive annual rotation cycles (May 2005 to May 2008). Results Compared to the control, N fertilizer applications significantly enhanced soil [N.sub.2]O emissions from both wheat and rapeseed systems. Seasonal cumulative [N.sub.2]O fluxes from wheat systems were on average 2.6 kg N ha for the recommended practice (RP [150 kg N [ha.sup.-1]]) and 5.0 kg N [ha.sup.-1] for the conventional practice (CP [250 kg N [ha.sup.-1]]). Lower [N.sub.2]O emissions were observed from the adjacent rapeseed systems. Average cumulative seasonal [N.sub.2]O fluxes from rapeseed were 1.5 and 2.2 kg N [ha.sup.-1] for the RP and CP treatments, respectively. The first 3 weeks after N fertilization were the "hot moment" of [N.sub.2]O emissions for both the wheat and rapeseed systems. The lowest yield-scaled [N.sub.2]O fluxes for wheat were obtained at the RP treatment (mean: 0.81 kg N [Mg.sup.-1]) while for rapeseed the CP treatment produced the lowest yield-scaled fluxes (mean: 0.79 kg N Mg 1). On average, the direct [N.sub.2]O emission factors ([EF.sub.d]) for the wheat system (1.76%) were over two times higher than for the rapeseed system (0.73%). Conclusions Intercropping of rapeseed tends to result in lower [N.sub.2]O emissions than wheat for rice-upland crop rotation systems of southwest China, indicating that either the N fertilization or the cropping system need to be considered not only for improving the estimate of regional and/or national [N.sub.2]O fluxes but also for proposing the climate-smart agricultural management practice to reduce [N.sub.2]O emissions from agricultural soils. Keywords Nitrous oxide * Yield-scaled emission * Non-rice season * Wheat * Rapeseed
    Keywords: Nitrous oxide ; Yield-scaled emission ; Non-rice season ; Wheat ; Rapeseed
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 6
    In: Nature, 2010, Vol.464(7290), p.881
    Description: Atmospheric concentrations of the greenhouse gas nitrous oxide ([N.sub.2]O) have increased significantly since pre-industrial times owing to anthropogenic perturbation of the global nitrogen cycle (1,2), with animal production being one of the main contributors (3). Grasslands cover about 20 per cent of the temperate land surface of the Earth and are widely used as pasture. It has been suggested that high animal stocking rates and the resulting elevated nitrogen input increase [N.sub.2]O emissions (4-7). Internationally agreed methods to upscale the effect of increased livestock numbers on [N.sub.2]O emissions are based directly on per capita nitrogen inputs (8). However, measurements of grassland [N.sub.2]O fluxes are often performed over short time periods (9), with low time resolution and mostly during the growing season. In consequence, our understanding of the daily and seasonal dynamics of grassland [N.sub.2]O fluxes remains limited. Here we report year-round [N.sub.2]O flux measurements with high and low temporal resolution at ten steppe grassland sites in Inner Mongolia, China. We show that short-lived pulses of [N.sub.2]O emission during spring thaw dominate the annual [N.sub.2]O budget at our study sites. The [N.sub.2]O emission pulses are highest in ungrazed steppe and decrease with increasing stocking rate, suggesting that grazing decreases rather than increases [N.sub.2]O emissions. Our results show that the stimulatory effect of higher stocking rates on nitrogen cycling (4,7) and, hence, on [N.sub.2]O emission is more than offset by the effects of a parallel reduction in microbial biomass, inorganic nitrogen production and wintertime water retention. By neglecting these freeze-thaw interactions, existing approaches may have systematically overestimated [N.sub.2]O emissions over the last century for semi-arid, cool temperate grasslands by up to 72 per cent.
    Keywords: Biogeochemical Cycles -- Observations ; Nitrous Oxide -- Environmental Aspects ; Atmospheric Carbon Dioxide -- Properties ; Grasslands -- Natural History ; Greenhouse Gases -- Properties ; Livestock Industry -- Environmental Aspects ; Air Pollution Research -- Methods;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 7
    Language: English
    In: Chemosphere, November 2013, Vol.93(11), pp.2848-2853
    Description: The gas-flow-soil-core (GFSC) technique allows to directly measure emission rates of denitrification gases of incubated soil cores. However, the technique was still suffering some drawbacks such as inadequate accuracy due to asynchronous detection of dinitrogen (N ) and other gases and low measurement frequency. Furthermore, its application was limited due to intensive manual operation. To overcome these drawbacks, we updated the GFSC system as described by by (a) using both a chemiluminescent detector and a gas chromatograph detector to measure nitric oxide (NO), (b) synchronizing the measurements of N , NO, nitrous oxide (N O), carbon dioxide (CO ) and methane (CH ), and (c) fully automating the sampling/analysis of all the gases. These technical modifications significantly reduced labor demands by at least a factor of two, increased the measurement frequency from 3 to 6 times per day and resulted in remarkable improvements in measurement accuracy (with detection limits of 0.5, 0.01, 0.05, 2.3 and 0.2 μg N or C h kg ds, or 17, 0.3, 1.8, 82, and 6 μg N or C m h , for N , N O, NO, CO , and CH , respectively). In some circumstances, the modified system measured significantly more N and CO and less N O and NO because of the enhanced measurement frequency. The modified system distinguished the differences in emissions of the denitrification gases and CO due to a 20% change in initial carbon supplies. It also remarkably recovered approximately 90% of consumed nitrate during incubation. These performances validate the technical improvement, and indicate that the improved GFSC system may provide a powerful research tool for obtaining deeper insights into the processes of soil carbon and nitrogen transformation during denitrification.
    Keywords: Denitrification ; Soil Emission Rates of Carbon and Nitrogenous Gases ; Gas-Flow-Soil-Core (Gfsc) Technique ; Dinitrogen (N2) and Nitric Oxide (No) Analysis ; Automatic Measurement ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 8
    Language: English
    In: Atmospheric Environment, Nov, 2013, Vol.79, p.641(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.atmosenv.2013.07.006 Byline: Zhisheng Yao, Xunhua Zheng, Rui Wang, Baohua Xie, Klaus Butterbach-Bahl, Jianguo Zhu Abstract: Crop residue incorporation and no-tillage are recommended as management practices and are being increasingly adopted in the agricultural sector. However, few studies have assessed the extent to which these practices integrate annual carbon and nitrogen trace gas fluxes and grain yield. We investigated the effect of wheat straw incorporation and no-tillage on nitrous oxide (N.sub.2O) and methane (CH.sub.4) fluxes from a rice-wheat system in southeast China, using year-round field measurements. Compared to the treatment with synthetic nitrogen fertilizers alone, the wheat straw incorporation reduced the N.sub.2O emissions by 38% (P 〈 0.05) and increased the CH.sub.4 emissions by 74% (P 〈 0.05) during the annual rotation cycle. Compared to the conventional tillage, no-tillage prior to wheat sowing enhanced the N.sub.2O emissions by an average of 61% (P 〈 0.05), irrespective of residue incorporation. The CH.sub.4-C emissions that were induced by the wheat straw comprised 6% of the residue-carbon incorporated during the rice season. As a result of the stimulating effect of wheat straw incorporation on CH.sub.4 fluxes, the annual aggregate emissions of N.sub.2O and CH.sub.4 with straw incorporation (10.7 Mg CO.sub.2-eq ha.sup.-1 yr.sup.-1 or 725 kg CO.sub.2-eq Mg.sup.-1 grain yield) were usually higher than those with no residue incorporation (7.6 Mg CO.sub.2-eq ha.sup.-1 yr.sup.-1 or 545 kg CO.sub.2-eq Mg.sup.-1 grain yield), irrespective of the tillage practice. Nevertheless, the changes in greenhouse gas emissions are notably only the transient response of the rice-wheat system after crop residue incorporation and tillage conversion, which may not necessarily represent equilibrium conditions for this agro-ecosystem over the long term. Author Affiliation: (a) State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, PR China (b) Institute for Meteorology and Climate Research, Atmospheric Environmental Research, Karlsruhe Institute of Technology, D-82467 Garmisch-Partenkirchen, Germany (c) State Key Laboratory of Soil and Sustainable Agriculture, Nanjing Institute of Soil Sciences, Chinese Academy of Sciences, Nanjing 21008, PR China Article History: Received 15 March 2013; Revised 28 June 2013; Accepted 2 July 2013
    Keywords: Planetary Boundary Layer ; Agroecosystems ; Agricultural Ecology ; Air Pollution ; Wheat Industry ; Atmospheric Carbon Dioxide ; Atmospheric Physics ; Methane ; Cropping Systems ; Wheat ; Greenhouse Gases ; Nitrogen (Chemical element) ; Nitrous Oxide ; Atmospheric Chemistry ; Pollution Control ; No-tillage ; Nitrogen Fertilizers
    ISSN: 1352-2310
    Source: Cengage Learning, Inc.
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  • 9
    Language: English
    In: Plant and Soil, 1 January 2011, Vol.340(1/2), pp.291-301
    Description: Sheepfolds represent significant hot spot sources of greenhouse gases (GHG) in semi-arid grassland regions, such as Inner Mongolia in China. However, the annual contribution of sheepfolds to regional GHG emissions is still unknown. In order to quantify its annual contribution, we conducted measurements of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes at two sheepfold sites in the Baiyinxile administrative region of Inner Mongolia for 1 year, using static opaque chamber and gas chromatography methods. Our data show that, at an annual scale, both sheepfolds functioned as net sources of CO2, CH4 and N2O. Temperatures primarily determined the seasonal pattern of CO2 emission; 60–84% of the CO2 flux variation could be explained by temperature changes. High rates of net CH4 emissions from sheepfold soils were only observed when animals (sheep and goats) were present. While nitrous oxide emissions were also stimulated by the presence of animals, pulses of N2O emissions were also be related to rainfall and spring-thaw events. The total annual cumulative GHG emissions in CO2 equivalents (CO2: 1; CH4: 25; and N2O: 298) were quantified as 87.4±18.4 t ha-1 for the sheepfold that was used during the non-grazing period (i.e., winter sheepfold) and 136.7±15.9 t ha-1 used during the grazing period (i.e., summer sheepfold). Of the annual total GHG emissions, CH4 release accounted for approximately 1% of emissions, while CO2 and N2O emissions contributed to approximately 59% and 40%, respectively. The total GHG emission factor (CO2+CH4+N2O) per animal for the sheepfolds investigated in this study was 30.3 kg CO2 eq yr-1 head-1, which translates to 0.3, 18.8 and 11.2 kg CO2 eq yr-1 head-1 for CH4, CO2 and N2O, respectively. Sheepfolds accounted for approximately 34% of overall N2O emissions in the Baiyinxile administrative region, a typical steppe region within Inner Mongolia. The contribution of sheepfolds to the regional CO2 or CH4 exchange is marginal.
    Keywords: Physical sciences -- Chemistry -- Chemical compounds ; Biological sciences -- Biology -- Anatomy ; Environmental studies -- Atmospheric sciences -- Climatology ; Environmental studies -- Atmospheric sciences -- Climatology ; Biological sciences -- Agriculture -- Agricultural management ; Environmental studies -- Environmental quality -- Environmental degradation ; Biological sciences -- Agriculture -- Agricultural sciences ; Physical sciences -- Physics -- Matter ; Environmental studies -- Environmental quality -- Environmental degradation ; Environmental studies -- Environmental quality -- Environmental degradation
    ISSN: 0032079X
    E-ISSN: 15735036
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  • 10
    Language: English
    In: Plant and Soil, Jan, 2012, Vol.350(1-2), p.297(14)
    Description: Byline: Benjamin Wolf (1), Ralf Kiese (1), Weiwei Chen (2), Rudiger Grote (1), Xunhua Zheng (2), Klaus Butterbach-Bahl (1) Keywords: Freeze-thaw; Impedance concept; [N.sub.2]O; Steppe; Biogeochemical modelling; Grazing intensity Abstract: Aims Temperate grassland is one of the major global biome types and is widely used as rangeland. Typically, cold winters are followed by a transition period with soil thawing that may last from days to weeks. Pulse [N.sub.2]O emissions during freeze-thaw events have been observed in a range of temperate ecosystem types and may contribute significantly to annual [N.sub.2]O emissions. It was shown recently that spring thaw pulse [N.sub.2]O emissions dominated annual [N.sub.2]O emissions in a steppe region of Inner Mongolia. Even though biogeochemical models are increasingly used for up scaling of [N.sub.2]O emissions from terrestrial ecosystems, they still need to be further developed to be capable of both simulating pulse [N.sub.2]O emission during spring thaw and accounting for the impact of grazing on soil [N.sub.2]O emissions in general. Methods In this study, we modified an existing biogeochemical model, Mobile-DNDC, to allow an improved simulation of plant production, snow height, and soil moisture for steppe in Inner Mongolia exposed to different grazing intensities. The newly introduced routines relate maximum snow height to end-of-season biomass (ESSB), to account for decreased plant productivity due to grazing and consider the increase of resistance (impedance) of soil ice on the soil hydraulic conductivity. Results The implementation of the impedance concept, which means the consideration of decreased hydraulic conductivity in frozen soil, resulted in an improved simulation of soil water content and decreased simulated oxygen content in the top soil during freeze-thaw periods. Increased soil moisture and associated oxygen limitation stimulated [N.sub.2]O emission by enhanced denitrification. Based on observations in the field, maximum snow height was limited by ESSB, protecting snow against erosion by wind. Since grazing reduced biomass and thereby snow cover, water availability during spring thaw was smaller at grazed sites as compared to ungrazed sites. In agreement with field observations, lower water content and anaerobiosis resulted in decreased [N.sub.2]O emissions during spring thaw. Conclusions The introduction of the impedance concept into Mobile-DNDC is a major step forward in simulating pulse [N.sub.2]O emissions from soils during spring-thaw. Author Affiliation: (1) Institute for Meteorology and Climate Research (IMK-IFU), Karlsruher Institute of Technology, Kreuzeckbahnstrasse 19, 82467, Garmisch-Partenkirchen, Germany (2) State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute for Atmospheric Physics, Chinese Academy of Sciences (IAP-CAS), 100029, Beijing, China Article History: Registration Date: 07/07/2011 Received Date: 23/02/2011 Accepted Date: 07/07/2011 Online Date: 23/07/2011 Article note: Responsible Editor: Hans Lambers.
    Keywords: Biomes -- Analysis ; Biomes -- Models ; Biomes -- Environmental Aspects ; Soil Moisture -- Analysis ; Soil Moisture -- Models ; Soil Moisture -- Environmental Aspects ; Atmospheric Physics -- Analysis ; Atmospheric Physics -- Models ; Atmospheric Physics -- Environmental Aspects ; Planetary Boundary Layer -- Analysis ; Planetary Boundary Layer -- Models ; Planetary Boundary Layer -- Environmental Aspects ; Steppes -- Analysis ; Steppes -- Models ; Steppes -- Environmental Aspects ; Air Pollution Control -- Environmental Aspects ; Air Pollution Control -- Analysis ; Air Pollution Control -- Models ; Denitrification -- Analysis ; Denitrification -- Models ; Denitrification -- Environmental Aspects ; Terrestrial Ecosystems -- Analysis ; Terrestrial Ecosystems -- Models ; Terrestrial Ecosystems -- Environmental Aspects ; Hydrogeology -- Analysis ; Hydrogeology -- Models ; Hydrogeology -- Environmental Aspects ; Atmospheric Chemistry -- Analysis ; Atmospheric Chemistry -- Models ; Atmospheric Chemistry -- Environmental Aspects
    ISSN: 0032-079X
    Source: Cengage Learning, Inc.
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