The maintenance of offspring diversity in response to land use: sexual and asexual recruitment in an alpine meadow on the Tibetan Plateau

Abstract

Human activities have caused dramatic land use changes, impacting plant community composition, diversity and function. Fertilization and grazing are the two most common land use modes in grasslands. To understand the effects of grazing and fertilization on sexual and asexual recruitment in alpine grasslands, we conducted a demographic field investigation of species recruitment in an alpine meadow on the Tibetan Plateau. Grazing and fertilization had different effects on the quantity and diversity of sexual and asexual recruitment. Sexual recruitment increased significantly in grazed plots, but decreased significantly in fertilized plots. Asexual recruitment increased significantly in fertilized plots, but decreased significantly in grazed plots. For functional groups, grazing significantly reduced offspring recruitment of graminoids, but significantly increased offspring recruitment of forbs and legumes; fertilization significantly reduced offspring recruitment of forbs and legumes, but significantly increased offspring recruitment of graminoids. Furthermore, offspring diversity from sexual recruitment was significantly higher than from asexual recruitment in grazed plots, and as compared to non-grazed and fertilized grasslands. Our studies indicate that moderate grazing disturbance has positive effects on seedling recruitment and offspring diversity, and fertilization has negative effects on offspring diversity, but may significantly increase asexual recruitment.