The rate of soil nitrogen transformation decreased by the degradation of alpine grasslands in the Qinghai Tibet Plateau

doi:10.11686/cyxb2017291

Abstract

Abstract: Alpine meadow and alpine steppe were studied to explore the mechanisms of degradation in soil nitrogen transformation and the key factors that affect soil N transformation in grasslands of the Qinghai Tibet Plateau. The net nitrification rate and net ammonification rate, as well as the microbial aspects of nitrogen transformation, plant and soil factors, were investigated using the method of in situ incubation. The results showed that: 1) The net nitrification and ammonification rates were significantly reduced by degradation in alpine grassland ecosystems; 2) The number of nitrifiers and ammonifiers in the soil, soil urease and protease activities decreased in the degraded meadows and steppe. 3) NH₄-N and NO₃-N contents were significantly reduced and microbial biomass nitrogen (MBN) also decreased. Soil nitrification and ammonification rates were closely related to the number of ammonifiers and nitrifiers, microbial biomass, and the extent of protease and urease in soils. Plant biomass, soil water, organic carbon and total nitrogen content were the main factors affecting soil N transformation by influencing the number of microbes, microbial biomass and enzyme activities. In conclusion, soil N transformation rates and the supply of available nitrogen in soils declined in degraded alpine grassland due to reductions in nitrogen transformation microbes and soil enzyme activities.

Key words: grassland degradation, nitrification rate, ammonification rate, nitrogen transformation microbes, alpine grassland

WANG Xue-xia, DONG Shi-kui, GAO Qing-zhu, ZHANG Yong, HU Guo-zheng, LUO Wen-rong. The rate of soil nitrogen transformation decreased by the degradation of alpine grasslands in the Qinghai Tibet Plateau[J]. Acta Prataculturae Sinica, 2018, 27(6): 1-9.

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