Plateau pika disturbance indirectly controls the temperature sensitivity of microbial respiration through soil organic carbon quality in alpine grasslands

Abstract

Understanding the spatial variations in the temperature sensitivity (Q₁₀) of soil microbial respiration is crucial for predicting the carbon cycle-climate feedbacks in the context of global warming. However, the response of Q₁₀ to soil heterogeneity, particularly that caused by bioturbation, and the underlying regulatory mechanisms remain poorly understood. In this study, a paired design experiment was conducted across 9 sites with varying disturbance gradients within alpine grasslands to compare plant and soil properties, soil respiration, and Q₁₀ values between pika-disturbed and pika-undisturbed areas. To accurately assess the levels of pika disturbance, we developed a multivariate index by applying principal component analysis to reduce the dimensionality of variables related to pika disturbance. Our results showed that low disturbance exhibited a significant positive effect on plant species richness and soil microbial respiration (R_H). Conversely, high disturbance significantly reduced plant vegetation cover, aboveground biomass, diversity, as well as soil water content, bulk density, pH, SOC, the ratio of SOC to total nitrogen, microbial biomass carbon and nitrogen, R_H, and SOC quality. The Q₁₀ value increased significantly with escalating pika disturbance gradients and displayed a rising trend from meadow to steppe grassland. Plateau pika disturbance indirectly influenced Q₁₀ through SOC quality in pika-disturbed grasslands, whereas SOC quality regulated Q₁₀ via soil microbial respiration in pika-undisturbed areas. Overall, our findings emphasize the importance of considering the impacts of pika disturbance, soil substrate quality and availability on the Q₁₀ in degraded alpine grasslands under future warming scenarios.