Asymmetric responses of abundance and diversity of N‐cycling genes to altered precipitation in arid grasslands

Summary

This 6-year precipitation manipulation experiment in arid grasslands combined metagenomic sequencing with field measurements to examine how altered rainfall affects soil microbial N-cycling gene abundance, diversity, and function. The authors found that increased precipitation enhanced gene abundance and accelerated N turnover, but paradoxically reduced diversity of ammonium assimilation genes, whilst decreased precipitation had minimal effect on gene pools. Gene abundance proved a reliable predictor of gross N transformation rates, suggesting that future precipitation increases in arid and semi-arid regions could substantially alter soil N cycling dynamics.

Regional applicability

The study was conducted in China's arid grasslands and may have limited direct applicability to United Kingdom conditions, which typically receive higher and more reliably distributed precipitation. However, the mechanistic findings regarding microbial gene responses to water availability could inform understanding of UK grassland resilience to increasingly variable precipitation patterns, particularly in drier regions of southern and eastern England.

Key measures

Abundance and diversity of N-cycling genes (ammonium assimilation, nitrification, denitrification, and related pathways); gross N transformation rates; soil depth (0–10 cm and 30–50 cm); precipitation manipulation treatments

Outcomes reported

The study quantified how altered precipitation (−30%, +30%, +50% relative to ambient) affected the abundance and diversity of soil N-cycling genes across two soil depths over 6 years, using metagenomic sequencing. Gross nitrogen transformation rates were measured and modelled against gene abundance data.

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