Bioturbation–elevation interactions mediate alpine soil carbon stability: Microbial necromass compensation and network robustness under plateau pika bioturbation

Alpine meadows harbor abundant soil organic carbon (SOC) but face pressures from climate change and biological disturbances. Although the plateau pika ( Ochotona curzoniae ) is recognized as an ecosystem engineer, how its disturbance-associated differences vary along elevational gradients and modulate SOC through belowground processes remains unresolved. We established paired high- and low-density pika-burrow plots across an elevational gradient (2869–4712 m) on the Qinghai-Tibet Plateau. We assessed plant diversity, SOC fractions, microbial necromass, microbial community structure, and co-occurrence networks. Continuous analysis detected no significant relationship between elevation and SOC ( p > 0.05). Regional comparisons showed that surface-soil SOC was 46% and 40% lower in high-density than in low-density plots in the low- and mid-elevation zones, respectively (both p < 0.001). At high elevations, SOC was 31% lower in high-density plots, but the difference was not significant ( p > 0.05). Pika bioturbation was also associated with altered microbial necromass accumulation. Bacterial necromass carbon (BNC) and total necromass carbon (TNC) showed significant disturbance × elevation 2 interactions ( p = 0.023 and p = 0.044, respectively), whereas the corresponding interaction for fungal necromass carbon was not significant ( p = 0.056). Intense disturbance was associated with a shift in necromass dominance from fungal to bacterial pathways. Structural equation modeling suggested a potential indirect pathway linking pika bioturbation to SOC through increased microbial necromass. However, this potential compensation did not offset disturbance-associated lower SOC content. These findings inform the management of pika outbreaks and belowground carbon-related functions in alpine meadows.