Impact of grazing on germination trait selection in an alpine grassland on the Tibet Plateau

Previous studies indicated that grazing can cause significant changes in abiotic and biotic environment in grassland. However, how these changes impact germination trait selection in grassland has not been well studied. Thus, we aimed to explore whether grazing can significantly change germination trait diversity and composition of grasslands community. We measured the germination traits of species in the laboratory, and compared their performance in grazed and nongrazed grasslands. Then, we compared the community-weighted means of germination traits and functional diversity of grazed and nongrazed grasslands based on these germination traits to know whether grazed and nongrazed grasslands differed in their germination trait structures. At the species level, we found that the changes of abundance in grazed and nongrazed grasslands were not related to species' germination traits. However, at the community level, compared with nongrazed grasslands, species in the grazed grasslands generally exhibited a higher seed germination percentage. Moreover, seed germination response in grazed grasslands was more positively related to alternating temperature than in nongrazed grasslands, and breadth of the germination temperature niche was narrower in grazed than in nongrazed grasslands. Compared with nongrazed grasslands, seed germination trait diversity was increased and germination trait evenness decreased in grazed grasslands. Grazing can change microhabitat conditions, thereby changing germination trait selection by environmental filtering, resulting in a significant difference in germinate trait composition at the community level.