Foraging tunnel disturbances created by small subterranean herbivores enhance soil organic carbon stability but reduce carbon sequestration in different alpine grassland types

Abstract

Foraging tunnel disturbances by small subterranean herbivores can alter soil properties and nutrient dynamics in grasslands, potentially altering soil organic carbon (SOC). Examining the impact of foraging tunnel disturbances on mineral-associated organic carbon (MAOC) and particulate organic carbon (POC) is crucial for understanding SOC changes and its stability. However, the effects of these disturbances on POC and MAOC are not well documented. This study uses the plateau zokor (Eospalax baileyi) as a focal subterranean herbivore to investigate the effects of foraging tunnel disturbances on POC and MAOC in alpine steppes, alpine meadows, and alpine meadow steppes. Ninety paired quadrats were used for soil and plant sampling across three alpine grassland types. Results show that foraging tunnel disturbances consistently reduced POC concentrations across all grassland types, with reductions of 44.01 % in alpine steppes, 20.86 % in alpine meadows, and 29.58 % in alpine meadow steppes. MAOC concentrations decreased by 16.49 % in alpine steppes, while no significant changes in MAOC were observed in alpine meadows and alpine meadow steppes. The reduction in the POC to MAOC ratio indicates increased SOC stability. However, despite this increased stability, the change may lead to a decrease in overall carbon sequestration potential, as the total SOC in the soil declines. The main factors influencing POC and MAOC were soil moisture, belowground biomass, and microbial biomass carbon, with their influences varying by grassland type. The findings demonstrate that foraging tunnel disturbances by plateau zokors can lead to substantial modifications in SOC composition, influencing both its stability and sequestration potential. The disturbances necessitate tailored management strategies to mitigate their impacts, considering the unique characteristics of each grassland type to preserve carbon sequestration potential. This study contributes to a deeper understanding of the ecological role of small subterranean herbivores in the carbon cycle of alpine grassland ecosystems.

Keywords: Alpine grassland; Foraging tunnel disturbances; Mineral-associated organic carbon; Particulate organic carbon; Small subterranean herbivore; Soil organic carbon stability.