The influence of disturbance by humans on biodiversity

The influence of disturbance by humans on biodiversity is discussed from the aspects of fragmentation of landscape, history of conservancy, dispersal mechanism and population size to provide more effective methods for protecting biodiversity and restoring ecological environment. Generally intermediate levels of disturbance promote higher biodiversity. The results of studies from the effects of disturbance on the higher plants growing in the Castanopsis eyrei forests in Wuyishan national nature reserve showed that the index of species richness of higher plants in the disturbed forest was 76.32% higher more than that in the closing stable forest, whereas the community dominance index (C) of the disturbed forest was excessively lower than the C of the closing stable forest. According to these results, we proposed that the increase of species diversity is an adapting manner for the ecosystem to disturbing and a stratagy of ecosystem to recover the stability. The high levels of disturbance will not only lead to reduced diversity, but also restrain the reconstitution of the ecosystem. In the course of organisms evolving and adapting, many species, such as the Coptis chinensis and the Coptis chinensis var.brevisepala,due to their generalization or specialization of niches, only are confined to a narrow habitats where local populations have become extinct. Other species distributing sparsely, such as the Camellia chekiangoleosa, Rubus pinnatisepalus, and some species of Goodyera, Lasianthus and Ardisia, are also vulnerable to extinction when their ranges become smaller and smaller or their habitats change. Older communities in evolutionary time scales or being protected have more species than younger ones.The subtropical rain forest in Hexi, Fujian, China, where the forests have being protected at least 700 years, is rich in higher plants. Other subtropical rain forest in Dinghushan and surrounding area of Hexi contains fewer species in this same zone. Many species, which dispersed by animals, are in danger of extinction by loss of animals diversity or change of habitats. Some species can reach to new area, but cannot complete their life history effectively. The living things with small local population size are vulnerable to extinction.