Abstract

Plant communities in Beijing nature reserves are undergoing unprecedented disturbance due to city expansion. To examine the resistance of plant communities to disturbance is thus of both theoretical and practical significance. We surveyed 22 plant community plots in Labagoumen and Songshan nature reserves. A total of 213 plant species were recorded, and 33 plant functional traits were measured for each species. The functional implications of each trait to disturbance, such as potential for restoration, resistance to fire, grazing and exotic invasion, were quantified according to published information. We calculated a functional index for each species, growth form and plant association, respectively. Regression analysis was used to detect the relationship between species richness and functional index at the community level. We found that the plant restoration index ranged between 4.36 and 10.15, and was significantly higher for herbs than for woody plants, while index of resistance to disturbance by grazing ranged between 10.27 and 23.15, and was significantly higher for woody plants than for herbs. Resistance to fire ranged between 9.01 and 22.15, with trees showing greatest resistance followed, in turn, by shrubs and herbs, while resistance to exotic invasion ranged from 4.41 to10.54, and was again highest for trees. At the community level, plant associations with Populus davidiana as the dominant species were at the top position of a decreasing sequence as determined by functional index of each association. Species richness was not correlated with any functional index at the layer of trees and herbs, but was significantly and positively correlated with resistance index to fire, grazing and exotic invasion within the shrub layer. The information obtained from our research will be important to the future vegetation restoration and management of Beijing nature reserves. Although the functional index of a community is determined to a large extent by the dynamics of dominant species, species richness is fundamental to ecosystem stability. Species redundancy may be detectable in a specific community layer or under a given type of disturbance, but might not be so in all situations.