Disturbance by grazing and the presence of rodents facilitates the dominance of the unpalatable grass Achnatherum inebrians in alpine meadows of northern China

Abstract

Unpalatable plants reportedly serve as a biodiversity refuge. However, few studies have been conducted to evaluate how unpalatable plants impact vegetation composition in alpine ecosystems. In the present study we investigated alpine meadows at four sites in four different prefectures on the eastern Qinghai-Tibetan Plateau of Qinghai Province, China. The study sites included meadows grazed by livestock (AO) and others in the vicinity colonised by the unpalatable grass, Achnatherum inebrians (AI), which the livestock avoided. The results showed: (1) palatable graminoid species were significantly different in the two groups: AO plots were dominated by Kobresia spp. (sedges), whereas AI plots were dominated by Poa pratensis and Elymus nutans (grasses); (2) graminoid diversity was significantly higher in AI than in AO plots; (3) grasses had significantly more seeds in AI than in AO plots. We suggest a three-step process for the invasion of A. inebrians into overgrazed alpine meadows in Northern China. First, soil is disturbed by rodents. Second, disturbed soil is invaded by A. inebrians. Third, the A. inebrians community is colonised by palatable grasses such as Elymus, Poa, Leymus and Stipa spp.