Global patterns and drivers of soil microbial nitrogen and phosphorus use efficiency

TL;DR

This study reveals global patterns in soil microbes' efficiency in using nitrogen and phosphorus, finding nitrogen use is nearly double phosphorus use, with soil carbon and climate playing key roles.

Contribution

The study quantifies global patterns of microbial nitrogen and phosphorus use efficiency and identifies soil organic carbon as a key driver.

Findings

Microbial nitrogen use efficiency (NUE) is nearly twice phosphorus use efficiency (PUE) globally.

Higher soil organic carbon is associated with greater nutrient use efficiency.

Tundra and boreal forest soils have significantly lower NUE compared to other regions.

Abstract

While nutrient use efficiency of soil microorganisms, the proportion of assimilated nutrients allocated into biosynthesis rather than invested in mineralization, is a critical microbial functional trait, its global patterns remain poorly quantified. Here, we estimate microbial nitrogen use efficiency (NUE, n = 2012) and phosphorus use efficiency (PUE, n = 3419) across terrestrial ecosystems using the ecoenzymatic stoichiometric approach. Globally, NUE (mean 0.60) is nearly twice as high as PUE (0.35). Soil organic carbon (SOC) is the strongest predictor of both, with higher SOC associated with greater nutrient use efficiency. Spatial upscaling shows that tundra and boreal forest soils have markedly lower NUE than other regions, suggesting high nitrogen investments in nutrient acquisition in cold ecosystems, whereas PUE is similar across biomes, implying pervasively low phosphorus acquisition capacity. Our study identifies potential nutrient cycling hotspots worldwide and offers critical parameters to refine large-scale predictions of soil carbon and nutrient dynamics.

Soil microbes recycle nutrients, but their global nutrient use efficiency is poorly understood. This study finds microbial nitrogen-use efficiency is nearly twice phosphorus-use efficiency, driven by soil carbon content, and is lowest in tundra and boreal forests.

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