Nitrogen availability in soil controls uptake of different nitrogen forms by plants
Min Liu, Xingliang Xu, Wolfgang Wanek, Jian Sun, Richard D. Bardgett, Yuqiang Tian, Xiaoyong Cui, Lili Jiang, Zeqing Ma, Yakov Kuzyakov, Hua Ouyang, Yanfen Wang
Abstract
Summary Nitrogen (N) uptake by plant roots from soil is the largest flux within the terrestrial N cycle. Despite its significance, a comprehensive analysis of plant uptake for inorganic and organic N forms across grasslands is lacking. Here we measured in situ plant uptake of 13 inorganic and organic N forms by dominant species along a 3000 km transect spanning temperate and alpine grasslands. To generalize our experimental findings, we synthesized data on N uptake from 60 studies encompassing 148 plant species world‐wide. Our analysis revealed that alpine grasslands had faster NH 4 + uptake than temperate grasslands. Most plants preferred NO 3 − (65%) over NH 4 + (24%), followed by amino acids (11%). The uptake preferences and uptake rates were modulated by soil N availability that was defined by climate, soil properties, and intrinsic characteristics of the N form. These findings pave the way toward more fully understanding of N cycling in terrestrial ecosystems, provide novel insights into the N form‐specific mechanisms of plant N uptake, and highlight ecological consequences of chemical niche differentiation to reduce competition between coexisting plant species.