Soil water limitation intensity alters nitrogen cycling at the plant-soil interface in Scots pine mesocosms

TL;DR

This study shows how drought affects nitrogen cycling in soil and plants, with severe drought slowing nitrogen release and altering microbial activity.

Contribution

The study provides empirical evidence on how progressive water limitation alters nitrogen cycling at the plant-soil interface in Scots pine ecosystems.

Findings

Severe water limitation reduces nitrogen release from decomposing litter and impairs plant nitrogen uptake.

Moderate drought has minimal impact on microbial nitrogen cycling genes and plant nitrogen uptake.

Severe drought increases microbial genes linked to water stress tolerance and decreases mineralization and nitrification genes.

Abstract

More intense episodes of drought are expected to affect terrestrial nitrogen (N) cycling by altering N transformation rates, the functioning of soil microorganisms, and plant N uptake. However, there is limited empirical evidence of how progressive water loss affects N cycling at the plant-soil interface.

We adopted 15N tracing techniques and metagenomic analyzes of microbial genes involved in N cycling to assess how different levels of soil water availability influenced the fate of N derived from decomposing litter in mesocosms with Scots pine saplings.

With increasing water limitation, the release of N from decomposing litter into the soil declined rapidly. However, moderate levels of water limitation barely affected the microbial metagenome associated with N cycling and the uptake of N by the saplings. Comparatively, severe levels of water limitation impaired plant N uptake, and increased the prevalence of microbial N-cycling genes potentially involved in mechanisms that protect against water stress. Genes associated with the uptake and release of N during mineralization and nitrification declined under low soil water contents.

When soil water becomes largely unavailable, the cycling of N at the plant-soil interface is slowed down, and microbial and plant tolerance mechanisms may prevail over N uptake and microbial decomposition.

The online version contains supplementary material available at 10.1007/s11104-025-07758-z.

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