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(searched for: doi:10.1016/j.scitotenv.2017.09.251)
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, Anne Jansen-Willems, Christoph Müller, Peter Dörsch
Published: 18 May 2021
Soil Biology and Biochemistry, Volume 159; https://doi.org/10.1016/j.soilbio.2021.108303

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Wenjun Zhou, Dan Xi, Yunting Fang, Ang Wang, Liqing Sha, Qinghai Song, Yuntong Liu, Liguo Zhou, Ruiwu Zhou, Youxing Lin, et al.
Published: 25 March 2021
Journal: Catena
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Longfei Yu, , Hongli Ji, Xiaolong Bai, Youxing Lin, Yiping Zhang, Liqing Sha, Yuntong Liu, Qinghai Song, Peter Dörsch, et al.
Published: 9 February 2021
Science of the Total Environment, Volume 775; https://doi.org/10.1016/j.scitotenv.2021.145616

Abstract:
Forest soils in the warm-humid tropics significantly contribute to the regional greenhouse gas (GHG) budgets. However, spatial heterogeneity of GHG fluxes is often overlooked. Here, we present a study of N2O and CH4 fluxes over 1.5 years, along a topographic gradient in a rainforest catchment in Xishuangbanna, SW China. From the upper hillslope to the foot of the hillslope, and further to the flat groundwater discharge zone, we observed a decrease of N2O emission associated with an increase of soil water-filled-pore-space (WFPS), which we tentatively attribute to more complete denitrification to N2 at larger WFPS. In the well-drained soils on the hillslope, denitrification at anaerobic microsites or under transient water-saturation was the potential N2O source. Negative CH4 fluxes across the catchment indicated a net soil CH4 sink. As the oxidation of atmospheric CH4 is diffusion-limited, soil CH4 consumption rates were negatively related to WFPS, reflecting the topographic control. Our observations also suggest that during dry seasons N2O emission was significantly dampened (<10 μg N2O-N m−2 h−1) and CH4 uptake was strongly enhanced (83 μg CH4-C m−2 h−1) relative to wet seasons (17 μg N2O-N m−2 h−1 and 56 μg CH4-C m−2 h−1). In a post-drought period, several rain episodes induced exceptionally high N2O emissions (450 μg N2O-N m−2 h−1) in the groundwater discharge zone, likely driven by flushing of labile organic carbon accumulated during drought. Considering the global warming potential associated with both GHGs, we found that N2O emissions largely offset the C sink contributed by CH4 uptake in soils (more significant in the groundwater discharge zone). Our study illustrates important topographic controls on N2O and CH4 fluxes in forest soils. With projected climate change in the tropics, weather extremes may interact with these controls in regulating forest GHG fluxes, which should be accounted for in future studies.
Danni Xie, Gaoyue Si, Ting Zhang, Jan Mulder,
Published: 28 September 2018
Environmental Pollution, Volume 243, pp 1818-1824; https://doi.org/10.1016/j.envpol.2018.09.113

Abstract:
Nitrous oxide (N2O) is a major greenhouse gas, with elevated emission being reported from subtropical forests that receive high nitrogen (N) deposition. After 10 years of monthly addition of ammonium nitrate (NH4NO3) or sodium nitrate (NaNO3) to a Mason pine forest at Tieshanping, near Chongqing city in Southwest China, the simulated N deposition was stopped in October 2014. The results of soil N2O emissions monitoring in different seasons during the nitrogen application period showed that nitrogen addition significantly increased soil N2O emission. In general, the N2O emission fluxes were positively correlated to nitrate (NO3) concentrations in soil solution, supporting the important role of denitrification in N2O production, which was also modified by environmental factors such as soil temperature and moisture. After stopping the application of nitrogen, the soil N2O emissions from the treatment plots were no longer significantly higher than those from the reference plots, implying that a decrease in nitrogen deposition in the future would cause a decrease in N2O emission. Although the major forms of N deposition, NH4+ and NO3, had not shown significantly different effects on soil N2O emission, the reduction in NH4+ deposition may decrease the NO3 concentrations in soil solution faster than the reduction in NO3 deposition, and thus be more effective in reducing N2O emission from N-saturated forest soil in the future.
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