Changes in aboveground biomass and diversity between different stages of secondary succession of a karst vegetation in Guangxi, China

Widespread deforestation in karst region has led to an increase in secondary forest, shrubs and grasses in the tropics and subtropics. By 2000, 60-70% of forests in karst areas were cut and converted to secondary forest, shrubs or grasses in southwest China. This study focuses on the variation in vegetation composition, species diversity, and aboveground biomass in the different stages of secondary succession in the karst regions of Guangxi province of China. The different succession stage in karst vegetation has different dominant species and composition. The dominator in herbaceous stage was pioneer species H. contortus, N. reynaudiana, while in shrubs and young forest stage the composition will change into sub-pioneer species V. negundo, P. guajava, C. cinerascens and transition species H. trichosperma, P. heterophyllum, T. tonkinensis. These dominant species is replaced with sub-climax species C. glauca,L. rhodostegia, C. saxatile, C. saichkii, D. conferiifloura and climax species E. hsienmu, G. paucinervis in mature forest stage and climax stage. Species richness, Shannon-wiener index, Simpson index and Evenness index of the different succession stages increased with positive succession. There were significant differences in aboveground biomass between the different succession stages (p=0.008-0.000) except between herbaceous stage and shrubs stage (p=0.562). The aboveground biomass of climax stage was significantly higher than those in other stages. The secondary vegetation in tropical karst region appears to recover faster in aboveground biomass with in subtropical karst region.