Different levels of rainfall and trampling change the reproductive strategy of Kobresia humilis in the Qinghai-Tibet Plateau

Abstract

The sedge Kobresia humilis (C.A. Mey. ex Trautv.) Serg. is the dominant plant in the alpine meadows of China’s Qinghai-Tibet Plateau, which has experienced substantial grassland degradation due to reduced rainfall and overgrazing. In this study we sought to determine the reproductive strategy of K. humilis under three levels of rainfall and seven levels of trampling by Tibetan sheep and yaks with a two year simulation trial on the Plateau. With a reduction in rainfall and an increase in trampling intensity, there was a decrease in sexual reproduction indices, plant height and single leaf number. The highest rainfall promoted sexual reproduction, whereas average rainfall was conducive to vegetative reproduction, and the lowest rainfall inhibited reproduction. The reproductive strategy of K. humilis could be judged according to the average rainfall from July to August. Notably, after two years of low rainfall and a heavy trampling treatment, K. humilis produced more seeds with smaller size. The rainfall presented a two-way regulation function in the trampling effect on K. humilis reproductive characteristics.