Soil nutrient changes induced by the presence and intensity of plateau pika (Ochotona curzoniae) disturbances in the Qinghai-Tibet Plateau, China

Abstract

The plateau pika (Ochotona curzoniae), one of the main bioturbators, creates extensive disturbances in the soil of the alpine meadow of the Qinghai-Tibet Plateau (QTP). This study investigated the effects of the presence and intensity of plateau pika disturbances on the main soil nutrients of the Kobresia pygmaea meadow across three study sites in the QTP by using the method of counting the active burrow entrance densities of plateau pika in the field as a representation of the disturbance intensity. Our results showed that the presence of plateau pika significantly increased the soil total nitrogen (TN), soil organic carbon (SOC) and total phosphorus (TP) concentrations and decreased the available phosphorus (AP) concentrations across the three study sites. The presence of plateau pika increased the NO3−-N and NH4+-N concentrations in Luqu County and Maqu County, but had no significant effect on these concentrations in Gonghe County. The soil TN, SOC and TP concentrations showed a downward parabola and the NO3−-N, NH4+-N and AP concentrations showed an upward parabola as the intensity of the disturbances increased in Luqu County and Maqu County. These soil nutrients had a threshold (inflection point) of 475 (475±90) burrow entrances per ha. However, the soil TN, SOC and TP concentrations increased linearly while the NO3−-N, NH4+-N and AP concentrations decreased linearly with the increasing intensity of disturbances in Gonghe County (≤512 burrow entrances per ha). These results implied that the soil nutrient changes induced by plateau pika disturbances are not only related to their presence but are also related to the intensity of the disturbances, and that the most appropriate disturbance intensity (475 (475±90) burrow entrances per ha) of plateau pika was beneficial to the storage of soil carbon and nitrogen in the alpine meadow in the QTP.