Microbes drive global soil nitrogen mineralization and availability
2019
Li, Zhaolei | Tian, Dashuan | Wang, Bingxue | Wang, Jinsong | Wang, Song | Chen, Han Y. H. | Xu, Xiaofeng | Wang, Changhui | He, Nianpeng | Niu, Shuli
Soil net nitrogen mineralization rate (Nₘᵢₙ), which is critical for soil nitrogen availability and plant growth, is thought to be primarily controlled by climate and soil physical and/or chemical properties. However, the role of microbes on regulating soil Nₘᵢₙ has not been evaluated on the global scale. By compiling 1565 observational data points of potential net Nₘᵢₙ from 198 published studies across terrestrial ecosystems, we found that Nₘᵢₙ significantly increased with soil microbial biomass, total nitrogen, and mean annual precipitation, but decreased with soil pH. The variation of Nₘᵢₙ was ascribed predominantly to soil microbial biomass on global and biome scales. Mean annual precipitation, soil pH, and total soil nitrogen significantly influenced Nₘᵢₙ through soil microbes. The structural equation models (SEM) showed that soil substrates were the main factors controlling Nₘᵢₙ when microbial biomass was excluded. Microbe became the primary driver when it was included in SEM analysis. SEM with soil microbial biomass improved the Nₘᵢₙ prediction by 19% in comparison with that devoid of soil microbial biomass. The changes in Nₘᵢₙ contributed the most to global soil NH₄⁺‐N variations in contrast to climate and soil properties. This study reveals the complex interactions of climate, soil properties, and microbes on Nₘᵢₙ and highlights the importance of soil microbial biomass in determining Nₘᵢₙ and nitrogen availability across the globe. The findings necessitate accurate representation of microbes in Earth system models to better predict nitrogen cycle under global change.
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