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High frequency of extreme precipitation increases Stipa grandis biomass by altering plant and microbial nitrogen acquisition
Biology and Fertility of Soils  (IF6.432),  Pub Date : 2021-12-23, DOI: 10.1007/s00374-021-01608-7
Wen, Shuhai, Tian, Yuqiang, Ouyang, Shengnan, Song, Minghua, Li, Xiaobing, Zhang, Yong, Gao, Si, Xu, Xingliang, Kuzyakov, Yakov

Climate changes are altering precipitation to more frequent extreme precipitation events that have strong impacts on the structure and functions of grassland ecosystems. We conducted a rain simulation experiment combined with in situ 15 N labeling of three nitrogen (N) forms (NO3, NH4+, glycine) to investigate how the frequency of extreme precipitation influences plant productivity and N acquisition (N uptake, 15 N recovery, and preference for N form) by the dominant species Stipa grandis and soil microorganisms in the temperate steppe. Extreme precipitation had three frequencies (1, 3, and 6 events for low, medium, and high frequency) with the same total rain amount in 1-month cycle. The low frequency reduced the S. grandis biomass by 39%, whereas the high ones raised the S. grandis biomass by 43% and increased plant and microbial N uptake up to 6.3-fold and 5.1-fold of those under ambient precipitation, respectively. Plants preferred NO3 and microorganisms preferred NH4+ under low frequency, but they showed similar preference for three N forms, leading to chemical niche overlap for NO3, NH4+, and glycine under high frequency. This indicated that high precipitation frequency effectively reduced the proportion of each N form, which plants and microorganisms competed for as the available N pool increased. Overall, the increase of precipitation frequency (decreasing intensity) shifted the extreme (low frequency but high intensity) to optimal conditions for plant productivity and N acquisition by plants and microorganisms in the temperate steppe. These findings provide new insights for understanding the diverse responses of ecosystem functions to extreme climate events.