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

Area of Science:

• Plant biology
• Ecology
• Biogeochemistry

Background:

• Nitrogen (N) uptake by plant roots is a major terrestrial N cycle flux.
• Comprehensive analysis of plant uptake for diverse inorganic and organic N forms in grasslands is lacking.

Purpose of the Study:

• To analyze plant uptake of 13 inorganic and organic N forms across temperate and alpine grasslands.
• To synthesize global data on N uptake for 148 plant species.
• To understand N form-specific uptake mechanisms and ecological consequences.

Main Methods:

• In situ measurements of N uptake by dominant grassland species along a 3000 km transect.
• Synthesis of data from 60 published studies on plant N uptake.
• Analysis of factors modulating N uptake, including soil N availability and N form characteristics.

Main Results:

• Alpine grasslands exhibited faster ammonium (NH₄⁺) uptake than temperate grasslands.
• Plant N uptake preference: nitrate (NO₃^-) (65%) > ammonium (NH₄⁺) (24%) > amino acids (11%).
• Uptake rates and preferences were modulated by soil N availability, climate, soil properties, and N form characteristics.

Conclusions:

• Findings enhance understanding of N cycling in terrestrial ecosystems.
• Novel insights into plant N uptake mechanisms and chemical niche differentiation.
• Highlights ecological consequences of N form-specific uptake and competition reduction.