Effects of plateau pikas’ foraging and burrowing activities on vegetation biomass and soil organic carbon of alpine grasslands

Abstract

Aims: Quantitatively assess the foraging and burrowing effects of plateau pikas (Ochotona curzoniae, hereafter pikas) on vegetation biomass and soil organic carbon at plot scale. Methods: Combining field surveys and aerial photographing, we investigated pikas density, vegetation biomass, soil organic carbon and total nitrogen at quadrat-scale in 82 grassland sites of the Qinghai-Tibetan Plateau. We then upscaled these variables to plot-scale and eventually quantified pikas’ foraging and burrowing effects on aboveground biomass and soil organic carbon. Results: Pikas have a wide distribution, with densities ranging from 40.29 to 71.40 ha−1. Under this density level, pikas consume approximate 21% to 40% of the total vegetation biomass, while their burrowing activity causes less than 1% vegetation biomass reduction. However, pikas burrowing transfers 1 to 5 T ha−1 of soil to the ground surface, which contains approximate 20 to 70 kg ha−1 of soil organic carbon and 2 to 5 kg ha−1 of total nitrogen. Conclusions: Vegetation biomass is susceptible to the foraging influence of pikas. Pikas burrowing activity has a potential impact on soil organic carbon loss and thus vegetation growth. These results are conducive to improve our understanding of the effects of pikas on regulating alpine grasslands. Unmanned aerial vehicle is a feasible and efficient tool to perform the monitoring extensiveness plots and study the role of pikas.