Abstract

Karst forest is a special forest ecosystem with rich biodiversity. In the Karst forest in Maolan National Nature Reserve, Guizhou Province, we investigated the quantitative characteristics of major tree species in forest gaps and non-gap stands, and the changes in species diversity and life forms during various gap phases. Our result showed that the forest gap stands were dominated by species such as Carpinus pubescens, Sapium rotundifolium, Platycarya longipes, Pistacia chinensis, and Celtis sinensis, whereas non-gap stands were dominated by Quercus glauca, Cladrastis platycarpa, Litsea verticillata, Photinia davidsoniae, and Machilus rehderi.These trees could be classified into three groups: negative response, positive response, and non sensitive. Most evergreen tree species regenerated in the non-gap stands; most deciduous tree and shrub species regenerated in the gap stands; and most understory small trees regenerated in both gap and non-gap stands. The species diversity in different gap phases ranked as follows: mid phase gaps (15-30 yr) > early phase gaps (<15 yr) > late phase gaps (>30 yr)> non-gap stands. Species diversity in gap stands was higher than that in non-gap stands, and the mid phase gap was a key period for maintaining species diversity. In the early gap phase, the species number of evergreen trees was less than deciduous trees. In the middle gap phase, both evergreen and deciduous tree species increased markedly, but deciduous species number increased more. In the late gap phase, evergreen trees species number continued to increase but deciduous tree species number decreased obviously. Shrubs dominated the stands during the early and middle gap phases, whereas trees dominated during the late gap phase. We conclude that the regeneration of gaps can enhance species richness and diversity in the Karst forest. Through the development of gaps, the structure of the plant community tends to be more stable.