Plant and soil elemental C:N:P ratios are linked to soil microbial diversity during grassland restoration on the Loess Plateau, China.

ABSTRACT

Plant and soil elemental ratios of carbon (C), nitrogen (N) and phosphorus (P) play a central role in shaping the composition and structure of microbial communities. However, the relationships between plant and soil elemental CNP ratios and microbial diversity are still poorly understood. Here, we evaluated the effects of CNP ratios in plant-soil systems on microbial diversity in a chronosequence of restored grasslands (1, 5, 10, 15, 25, and 30 years since restoration) on the Loess Plateau. We found that C and N concentrations, CN and CP ratios in leaf, root, soil and microbial biomass, bacterial and fungal diversity (Shannon-Wiener index) gradually increased with year since grassland restoration. Microbial CNP ratios ranged from 17.84.51 to 24.36.61, and CP ratio increased from 17.81 at the 1-year site to 24.31 at the 30-year site, indicating the increasing P limitation for soil microorganisms during grassland development. Soil microbial diversity increased with root, soil, and microbial C and N concentrations, and decreased with P concentration (p < 0.05). Structural equation modeling indicated that soil and microbial CN and NP ratios had the greatest influences on soil bacterial and fungal diversity, and elemental CNP ratios had a greater effect on soil fungal than bacterial diversity. Our findings emphasize the importance of elemental CNP ratios on soil microbial diversity, which is critical for formulating policies for sustainable biodiversity conservation in terrestrial ecosystems.