Tree species richness as an important biotic factor regulates the soil phosphorus density in China’s mature natural forests

Phosphorus (P) is one of the most important limiting nutrients in terrestrial ecosystems. The soils represent the largest P reserve (He et al., 2021a), which P storage determines the form and supply of soil P to plants, potential affecting the function of forest ecosystems. However, our understanding of the drivers of soil P pattern is still lacking, particularly the biotic drivers, which hinders us to better improve the prediction of Earth models that represents the P cycle.

Tree species richness has been recognized as an underlying driving factorfor regulating soil phosphorus (P) status in many site-specific studies. However, it remains poorly understood whether this is true at broad scales where soil P strongly rely on climate, soil type and vegetation type. Researchers from South China Botanical Garden of Chinese Academy of Sciences analyzed the impact of tree species richness on soil P density of China’s mature natural forests (deciduous coniferous forest, DCF; evergreen coniferous forest, ECF; deciduous broad-leaved forest, DBF; evergreen broad-leaved forest, EBF; and mixed coniferous and broad-leaved forest, MF), based on the data of 946 mature natural forest sites from a nationwide field survey in China.

Results demonstrate that tree species richness has a greater importance than the soil type and vegetation type in regulating China’s mature natural forest soil P density. On the one hand, tree species richness had positive effects on ANPP, which might promote the plant P uptake from the soil, thereby decreasing the soil P density. On the other hand, tree species richness could decline the litter P concentration, which could inhibit the plant P return to the soil, thus decreasing the soil P density.

These results indicate that tree species richness plays an important role in regulating the soil P density of China’s mature natural forests through promoting the plant P uptake and decreasing the plant P return to the soil. This study could help to better understand the pattern and mechanisms of forest P cycle, and provide comprehensive measured P datasets of China’s mature natural forest for the Earth model improvement.

This work has been published online in Science of the Total Environment, entitled ‘Tree species richness as an important biotic factor regulates the soil phosphorus density in China’s mature natural forests’. Dr. Xujun Liu and associated Prof. Xuli Tang are the co-first authors of this paper, and Prof. Juxiu Liu is corresponding author. For further reading, please refer to: http://dx.doi.org/10.1016/j.scitotenv.2022.157277

Figure 1. Locations of the sampling sites (a), ranking of variable importance of biotic and abiotic 

factor on soil P density for Random Forests regression model (b), 

and structural equation model of biotic and abiotic factors on soil P density (c).