Erosion of plateau pika mound caused the rapid loss of soil organic carbon and total nitrogen

The plateau pika (Ochotona curzoniae) burrows in loose soil and creates a bare mound, which is prone to erosion and causes loss of soil organic carbon (SOC) and total nitrogen (TN). Our understanding of the quantified contribution of pika mound erosion and its effect on SOC and TN remains limited owing to the lack of in-situ observations. In this study, fixed observations were conducted in four types of selected alpine grasslands in the source region of the Shule River Basin in the Qilian Mountains between 2021 and 2023. Our focus was to analyze the pika mound volume, quantify its erosion rate and the erosion-induced SOC and TN losses, and eventually establish a regression model between the volume and soil of the pika mound (y=ax + b). Compared to 2021, in 2023 the major and minor axes and the height of the pika mound decreased by 3.60～11.00, 0.33～6.28 and 0.85～2.88 cm, respectively. However, the major axis of the pika mound on the alpine meadow increased by 2.33 cm. Pika mound soils in four types of grasslands ranged from 1.64 to 3.74 kg in 2021, and 0.49 to 2.36 kg in 2023, suggesting that the erosion rate was 0.45～0.69 kg annually. Consequently, erosion of the pika mound caused an approximately 38%～70% loss of SOC and TN. The estimated pika mound soil based on the established regression model had a significantly positive correlation with the observed pika mound soil, indicating that the pika mound soil could be estimated by measuring its volume.