The effects of differences in functional group diversity and composition on plant community productivity in four types of alpine meadow communities

Abstract

The relationship between species diversity and ecosystem function is one of the core problem of biodiversity research, and productivity is an important modality of ecosystem function. The species diversity of natural communities is often strongly related to their productivity. The grassland is an important component of terrestrial ecosystems and plays a significant role in the biodiversity and ecosystem function. Understanding of how to use natural vegetation to restore deteriorated grasslands is critical for protection of grassland ecosystems. Moreover, the relationship between species richness and productivity relies on scales. At some scales, productivity affects diversity, and at other scales, species diversity also affects productivity. Thus, it is necessary to know the relationship between plant functional diversity and productivity in different grassland types. In 2003 the differences in plant functional diversity, functional composition and productivity in different grassland types of alpine meadow were analyzed. Humans are modifying both the identities and the numbers of species in ecosystems. However, the impacts of such changes on ecosystem processes are still controversial. The effects of functional diversity and composition on plant community productivity were analyzed in four types of alpine meadows. The research results show:(1) the effects of the legume functional group on productivity was greater than other functional groups in Kobresia humlis meadow and Potentilla froticosa shrub. (2) Although the biomass of forbs, C 3 plants and sedge functional groups account for higher proportion of community productivity in Kobresia pygmaca meadow and K. tibetica swamp meadow, differences were not significantly different, indicating that the factors influencing community productivity were not only species diversity, but also the identity of species present and environmental resources. These factors were in turn mainly affected by species diversity and evenness among functional groups. That is, differences in functional group composition have a larger effect on ecosystem processes than functional group richness alone. (3) A significant correlation was found between the coverage per functional group and the primary productivity of communities in the four types of alpine meadows. (4) Changes in productivity with number of species per functional group showed a unimodal pattern, such that the maximum community productivity occured at an intermediate level of number of species per functional group.