Pedosphere 30(2): 214--225, 2020
ISSN 1002-0160/CN 32-1315/P
©2020 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Responses of soil microbial communities and functions associated with organic carbon mineralization to nitrogen addition in a Tibetan grassland
Ruyi LUO1,2, Jiafa LUO3, Jianling FAN1, Deyan LIU1, Jin-Sheng HE4, Nazia PERVEEN1, Weixin DING1
1State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
2University of Chinese Academy of Sciences, Beijing 10049 (China)
3AgResearch Limited, Ruakura Research Centre, Hamilton 3240 (New Zealand)
4Department of Ecology, College of Urban and Environmental Sciences, Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871 (China)
      Alpine grasslands with a high soil organic carbon (SOC) storage on the Tibetan Plateau are experiencing rapid climate warming and anthropogenic nitrogen (N) deposition; this is expected to substantially increase the soil N availability, which may impact carbon (C) cycling. However, little is known regarding how N enrichment influences soil microbial communities and functions relative to C cycling in this region. We conducted a 4-year field experiment on an alpine grassland to evaluate the effects of four different rates of N addition (0, 25, 50, and 100 kg N ha-1 year-1) on the abundance and community structure (phospholipid fatty acids, PLFAs) of microbes, enzyme activities, and community level physiological profiles (CLPP) in soil. We found that N addition increased the microbial biomass C (MBC) and N (MBN), along with an increased abundance of bacterial PLFAs, especially Gram-negative bacterial PLFAs, with a decreasing ratio of Gram-positive to Gram-negative bacteria. The N addition also stimulated the growth of fungi, especially arbuscular mycorrhizal fungi, reducing the ratio of fungi to bacteria. Microbial functional diversity and activity of enzymes involved in C cycling (β-1,4-glucosidase and phenol oxidase) and N cycling (β-1,4-N-acetyl-glucosaminidase and leucine aminopeptidase) increased after N addition, resulting in a loss of SOC. A meta-analysis showed that the soil C/N ratio was a key factor in the response of oxidase activity to N amendment, suggesting that the responses of soil microbial functions, which are linked to C turnover relative to N input, primarily depended upon the soil C/N ratio. Overall, our findings highlight that N addition has a positive influence on microbial communities and their associated functions, which may reduce soil C storage in alpine grasslands under global change scenarios.
Key Words:  alpine grassland,C cycling,C turnover,community level physiological profiles (CLPP),enzyme activity,microbial community composition,microbial function,N input
Citation: Luo R Y, Luo J F, Fan J L, Liu D Y, He J S, Perveen N, Ding W X. 2020. Responses of soil microbial communities and functions associated with organic carbon mineralization to nitrogen addition in a Tibetan grassland. Pedosphere. 30(2): 214-225.
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