Annual dynamics of soil gross nitrogen turnover and nitrous oxide emissions in an alpine shrub meadow

Publication date: Available online 12 September 2019Source: Soil Biology and BiochemistryAuthor(s): Xiaoxia Hu, Chunyan Liu, Xunhua Zheng, Michael Dannenmann, Klaus Butterbach-Bahl, Zhisheng Yao, Wei Zhang, Rui Wang, Guangmin CaoAbstractSoil nitrogen (N) transformations play a vital role in maintaining grassland productivity and influencing nitrous oxide (N2O) emissions. To reveal annual dynamics of soil gross N turnover and its effects on N2O emissions in typical grasslands, we conducted year-round measurements of soil gross N turnover rates, inorganic N pool sizes and N2O fluxes in an alpine shrub meadow of the Qinghai–Tibet Plateau. Gross ammonium (NH4+) and nitrate (NO3−) immobilization rates were calculated both by the “isotope dilution method” (i.e., based on the consumption rates) and the “reformed difference method” (i.e., based on the differences between gross and net turnover rates). The “reformed difference method” avoids additional measurements of net N turnover rates in unlabeled soils compared with the traditional “difference method”, and provides reliable estimates of NH4+ immobilization in soils with low ambient NH4+ pool sizes. The annual gross rates of mineralization, nitrification, NH4+ and NO3− immobilization amounted to 606 ± 43, 236 ± 27, 389 ± 24 and 82 ± 19 mg N kg−1 dry soil yr−1, respectively, in a topsoil of 10 cm. The soil gross N turnover rates during freezing and freeze–thaw periods contributed considerably to the ...

Source: Soil Biology and Biochemistry - September 13, 2019 Category: Biology Source Type: research