Intensified Aridity Hinders Soil Microbes From Improving Their Nitrogen Use Efficiency
Jingyi Yang, Zitong Wang, Ziping Liu, Qing Chang, Bo Wang, Yangjian Zhang, Edith Bai
Abstract
ABSTRACT Microbial nitrogen (N) use efficiency (NUE) is crucial for retaining N in soils and supplying N to plants. However, how soil microbial NUE in N‐limited dryland responds to aridity remains poorly understood. Here we used 18 O and 15 N isotope labeling techniques to investigate the effects of climatic, edaphic, and biotic factors on microbial N metabolism along a 2200 km aridity gradient on the Tibetan Plateau. We found soil microbes could enhance their NUE to cope with N limitation, but this ability was hindered when aridity index (AI) < 0.12 (extremely dry conditions) where water limitation directly inhibited microbial growth. As water limitation weakened (AI > 0.12), microbes increased their NUE with decreasing aridity because they got more limited by N and temperature. The increase of microbial NUE increased microbial necromass N, contributing to the increase of soil total N. Our findings provide new insights into microbial N use strategies under water‐ and N‐limited conditions and their vital role in N retention in ecosystems. This helps to deploy microbial potential in conserving N in soils for higher productivity and to better predict soil N processes under global changes.