Excessive nitrogen addition accelerates N assimilation and P utilization by enhancing organic carbon decomposition in a Tibetan alpine steppe

Qiuyu Chen; Yanli Yuan; Yilun Hu; Jian Wang; Guicai Si; Ri Xu; Jizhong Zhou; Chuanwu Xi; Ang Hu; Gengxin Zhang

doi:10.1016/j.scitotenv.2020.142848

Excessive nitrogen addition accelerates N assimilation and P utilization by enhancing organic carbon decomposition in a Tibetan alpine steppe

Sci Total Environ. 2021 Apr 10:764:142848. doi: 10.1016/j.scitotenv.2020.142848. Epub 2020 Oct 9.

Authors

Qiuyu Chen¹, Yanli Yuan¹, Yilun Hu², Jian Wang³, Guicai Si⁴, Ri Xu¹, Jizhong Zhou⁵, Chuanwu Xi⁶, Ang Hu⁷, Gengxin Zhang⁸

Affiliations

¹ CAS Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100101, China.
² CAS Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100101, China.
³ Land and Resources College, China West Normal University, Nanchong 637009, Sichuan, China.
⁴ Lanzhou Center for Oil and Gas Resources, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
⁵ Institute for Environmental Genomics and Department of Microbiology and Plant Biology, University Oklahoma, Norman, OK 73019, USA; State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
⁶ Department of Environmental Health Sciences, School of Public Health, University of Michigan, Ann Arbor, MI 48109, USA.
⁷ College of Resources and Environment, Hunan Agricultural University, Changsha 410128, China.
⁸ CAS Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100101, China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China. Electronic address: zhangg@itpcas.ac.cn.

PMID: 33268263
DOI: 10.1016/j.scitotenv.2020.142848

Abstract

High amounts of deposited nitrogen (N) dramatically influence the stability and functions of alpine ecosystems by changing soil microbial community functions, but the mechanism is still unclear. To investigate the impacts of increased N deposition on microbial community functions, a 2-year multilevel N addition (0, 10, 20, 40, 80 and 160 kg N ha^-1 year^-1) field experiment was set up in an alpine steppe on the Tibetan Plateau. Soil microbial functional genes (GeoChip 4.6), together with soil enzyme activity, soil organic compounds and environmental variables, were used to explore the response of microbial community functions to N additions. The results showed that the N addition rate of 40 kg N ha^-1 year^-1 was the critical value for soil microbial functional genes in this alpine steppe. A small amount of added N (≤40 kg N ha^-1 year^-1) had no significant effects on the abundance of microbial functional genes, while high amounts of added N (>40 kg N ha^-1 year^-1) significantly increased the abundance of soil organic carbon degradation genes. Additionally, the abundance of microbial functional genes associated with NH₄⁺, including ammonification, N fixation and assimilatory nitrate reduction pathways, was significantly increased under high N additions. Further, high N additions also increased soil organic phosphorus utilization, which was indicated by the increase in the abundance of phytase genes and alkaline phosphatase activity. Plant richness, soil NO₂^-/NH₄⁺ and WSOC/WSON were significantly correlated with the abundance of microbial functional genes, which drove the changes in microbial community functions under N additions. These findings help us to predict that increased N deposition in the future may alter soil microbial functional structure, which will lead to changes in microbially-mediated biogeochemical dynamics in alpine steppes on the Tibetan Plateau and will have extraordinary impacts on microbial C, N and P cycles.

Keywords: Alpine steppe; Carbon cycle; Microbial functional genes; Multilevel N additions; Nitrogen cycle; Phosphorus cycle.

MeSH terms

Carbon* / analysis
Grassland
Nitrogen* / analysis
Soil
Soil Microbiology
Tibet

Substances

Soil
Carbon
Nitrogen