Effects of human disturbance on species diversity of Pinus massoniana plantation in Jiangyou district, Sichuan province

Over the last century, human disturbance plays an important role in the change of global climate and environment and consequently, the loss of global species diversity. Unsustainable use of forest resources is causing dramatic changes in the forest communities and poses a serious threat to biodiversity worldwide. Plant species diversity is an index reflecting the complexity and stability of forest community function. The effect of human disturbance on forest community can be directly reflected by the change of community structure and diversity. We hypothesize that community structure and plant species diversity varies with the different densities of human disturbance. In order to investigate the influences of different disturbances(slight disturbance and severe disturbance) on the characteristics of species composition and diversity of Pinus massoniana plantation in Jiangyou district, Sichuan Province, a field investigation was conducted. The species richness index D, Shannon-wienner index H, Simpson index H′, Pielou index Jsw are adopted to evaluate the level of species diversity in Pinus massoniana community. The results were as following,(1) 124 species, belonging to 56 families and 105 genera were found in 8 plots with a total area of 3200 m2. The number of species in different layer decreased with the increase of disturbance intensity.(2) In terms of the community structure, different densities of human disturbance leads to different community structure. The diameter class was normally distributed with severe disturbance and the peak value 26 was found in diameter class Ⅵ(7 cm≤DBH9 cm). The diameter class was not normally distributed with slight disturbance and the peak value 43 was found in diameter class Ⅶ(13 cm≤DBH15 cm). The height class was similar to the diameter class under both slight and severe disturbance. Individuals under slight disturbance were mainly distributed in small and medium height class(3≤H17), and individuals under severe disturbance were mainly distributed in medium and high height class(H≥13). As presented, the distribution of individuals under severe disturbance was relatively not even among different diameter and height classes and the low vertical diversity and instability of community structure were reflected.(3) Influenced by human disturbance, the richness index D, Shannon-wienner index H and Pielou index Jsw decreased and the Simpson index H′ increased with the increase of disturbance intensity, and a negative relation between human disturbance and species diversity was dedicated.