Nitrogen availability in soil controls uptake of different nitrogen forms by plants

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 NH₄ ⁺ uptake than temperate grasslands. Most plants preferred NO₃ ^- (65%) over NH₄ ⁺ (24%), followed by amino acids (11%). The uptake preferences and uptake