<b>Intensified aridity hinders soil microbes from improving their nitrogen use efficienc</b><b>y</b>

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 18O and 15N isotope labelling techniques to investigate effects of climatic, edaphic and biotic factors on microbial N metabolism along a 2,200 km aridity gradient on the Tibetan Plateau.