Ecosystem engineering in alpine grasslands: Differential impacts of subterranean animals on ecosystem multifunctionality

Ecosystem engineers modify community structure and ecological functions through bioturbation, but how their activities modulate ecosystem multifunctionality (EMF) remains unclear, particularly when multiple engineers coexist. Here, we investigated the differential impacts of plateau zokor ( Eospalax baileyi ), plateau pika ( Ochotona curzoniae ), and ants ( Camponotus ) on aboveground (AEMF), belowground (BEMF), and overall EMF in alpine grasslands. Our results reveal contrasting effects of these three subterranean animals on AEMF, BEMF, and EMF through distinct mechanisms. AEMF and EMF were significantly lower in plateau zokor burrowing plots than in controls. By contrast, plateau pikas had minimal effects on both AEMF and BEMF, resulting in no net change to EMF. Ants nesting plots showed a functional trade-off that counterbalanced AEMF losses with BEMF gains, leaving overall EMF unchanged. Soil nitrogen dynamics emerged as the primary driver of EMF variation across all species. These findings highlight that the net impact of burrowing animals on ecosystem functioning arises from the integration and potential trade-offs between aboveground and belowground functional responses, challenging simplistic classifications of these species as either beneficial or detrimental. Our results underscore the need for species-specific management strategies and emphasize the importance of maintaining stable population densities to preserve ecosystem multifunctionality in alpine grasslands.