Impact of annual plant prevalence on soil carbon storage through root turnover and productivity

Background and aims

Comprehending the mechanisms of soil organic carbon (SOC) accumulation is essential for maintaining soil fertility and combating climate change. However, the potential processes and roles of plant life cycle traits in regulating SOC accumulation over broad geographic scales remain unclear.

Methods

We generated a map of annual plant prevalence using occurrence/absence records of 4,837 vascular species, integrated with species distribution models. Based on 51 field observations across the Qinghai–Tibetan Plateau (QTP) and a structural equation model, we systematically investigated the direct effects of climate and annual plant prevalence on SOC versus the indirect effects mediated by root turnover and productivity.

Results

We found that annual plants accounted for only 8.9% of plant species on the QTP. The proportion of annual plants increases with higher temperatures and lower precipitation, indicating that annual plants are more competitive than perennials in arid environments. Furthermore, annual plant prevalence exerted both direct and indirect positive effects on SOC, with indirect effects mediated by changes in belowground net primary productivity, belowground biomass carbon, and root turnover time. Importantly, the higher annual plant prevalence can offset the negative impact of warming on SOC storage.

Conclusion

Our findings indicate that maintaining a high annual plant prevalence would enhance soil carbon storage and may help offset carbon losses due to global warming. The findings underscore the importance of adequately managing the vegetation of fragile ecosystems like those of the QTP for enhancing soil C sequestration, thereby contributing to climate change mitigation.