Long-term grazing of Cervus elaphus kansuensis restrains expansion of Salix cupularis shrubs in the Eastern Qilian Mountains

Abstract

Alpine shrubland not only has significant ecological function and ecological value, but also is a grazing land for Tibetan livestock and a habitat for wild animals. However, the grazing livestock on a long-term scale has caused severe shrubization of the alpine shrubland. How to control the shrubization of grassland is very important. Therefore, the purpose was to explore the effects of long-term grazing and utilization patterns of different livestock on alpine shrubland. In this study, a collective pasture with basically the same grazing history, intensity and vegetation type was enclosed into two sample plots to graze by Cervus elaphus kansuensis (CEK), and mixed grazing by Bos grunniens (yak) and Ovis aries (Tibetan sheep) (YTS) from 1983 to 2019 respectively, and it provides an vital scientific basis for promoting the balanced development of grass and livestock and maintaining ecological balance. The results showed that, in 2018 and 2019, compared with grazing YTS, the biomass of the Salix cupularis in grazing CEK plot was 55.20% and 56.63% lower, the cluster height was 68.36% and 68.36% lower, the crown width was 75.34% and 76.00% lower, the coverage was 80.00% and 78.00% lower, and the difference was significant ( P < 0.05). The cluster height of Spiraea alpina was also 47.17% and 44.38% lower; The Shannon-Wiener index, Simpson index and evenness index of the shrub communities in the CEK plot were significantly higher than YTS ( P < 0.05); The leaf carbon storage of Salix cupularis in CEK was 26.48% and 18.44% lower, and the root carbon storage was 48.88% and 49.15% higher respectively. The contents of soil organic matter, total phosphorus, total potassium, available nitrogen and available potassium in CEK were higher than those in YTS. In 2018, the soil respiration rate among CEK shrubs was significantly lower than that of YTS by 46.81%; The diversity and wealth of the bacterial community between shrubs, and the wealth index of the fungal community under shrubs in the CEK plot were all lower than those of YTS plot. The relative abundance of saprophytic fungi and bacterial metabolism between and under shrubs in grazing CEK plot were higher than that of YTS, while the relative abundance of arbuscular mycorrhizal fungi, animal parasitic bacteria and human-related infectious disease bacteria were lower than YTS. Therefore, moderate long-time grazing of Cervus elaphus kansuensis can effectively inhibit the spread of alpine shrubs, facilitate the growth of herbaceous plants and achieve the balanced development of grass and livestock. It provides a strong support for the rational utilization and management of alpine shrubs.