Yak and Tibet sheep grazing ingestion restrain seed germination of two Saussurea species in Tibetan meadow.

Abstract

Grazing disturbance had been defined as an important mechanism that allows the maintenance of species diversities in plant communities. To help understand effect of grazing on seed germination characteristics, we conducted a laboratory germination experiment with two Saussurea species, which were dominant species in alpine meadow communities of the Qinghai-Tibetan Plateau, and yak and Tibet sheep rumen juices. Results showed that yak rumen juices completely restrained seed germination for two species. Tibet sheep rumen juices significantly decreased seed germination percentage, germination index and weighted germination index, prolonged first germination time and mean germination time for two species. Saussurea japonica showed a significantly higher germination percentage, germination index and weighted germination index, but a significantly shorter first germination time and mean germination time than Saussurea iodostegia . Our study suggests that yak and Tibet sheep grazing ingestion may affect species population dynamic by significantly restraining seed germination in alpine area of the Qinghai-Tibetan Plateau. Key words : Rumen juices, seed germination, Saussurea iodostegia , Saussurea japonica.