Species richness increases vegetation carbon sequestration but decreases soil carbon storage in temperate grasslands of China

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S0167880926002045

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Authors: Yingjia Su, Junyu Pu, Jing Huang et al.

07 April 2026

https://doi.org/10.1016/j.agee.2026.110417

Highlights

•Species richness increased carbon density in all vegetation layers.

•Different species contributed to above- and belowground carbon increases.

•Species richness enhanced vegetation carbon but reduced soil carbon density.

•Soil carbon loss was due to accelerated decomposition of original organic matter.

Abstract

Biodiversity is fundamental to sustaining ecosystem functions and regulating carbon storage, yet the mechanisms by which species richness influences carbon density across different vegetation fractions and soil carbon components remain poorly understood. Here, using a diversity simulation platform comprising four dominant forage species (Leymus chinensis, Elymus dahuricus, Festuca rubra, and Poa pratensis) in the steppe of northern China, we examined changes in vegetation and soil carbon densities under varying levels of species richness during the second growing season. Results showed that species richness significantly enhanced the carbon density of aboveground living herbage, plant litter, and belowground living roots, through complementarity effects. Moreover, different species contributed differently to the increase in the distribution of vegetation carbon density. Aboveground carbon accumulation was primarily driven by Leymus chinensis and Elymus dahuricus, whereas Festuca rubra and Poa pratensis played a dominant role in belowground carbon accumulation. However, increasing species richness led to a decline in soil organic carbon density, particularly that of particulate organic carbon (POC), possibly due to priming effects induced by high-quality litter inputs. In contrast, mineral-associated organic carbon (MAOC) density showed less pronounced variation across richness levels. It indicated that diverse plant communities might rapidly enhance vegetation biomass carbon, but soil carbon sequestration might require longer timeframes to offset initial losses. Our findings underscore the dual role of biodiversity as both a driver of vegetation carbon capture and a regulator of soil carbon turnover, with important implications for grassland management and climate change mitigation.

Source: ScienceDirect