Abstract: Based on the investigation on gaps and non-gap stands of the Karst forest in Maolan National Nature Reserve, Guizhou Province , the changeable regular pattern of species composition , relationship of species and life form feature during gaps development were analyzed . The results showed that family, genera and species of plant in gaps increased gradually from 10 to 30 years and decreased after 40 years . The composition of family and genera in 40 years was equilibrated to those in non-gap stands , but species number increased continuously . It indicated that species diversity increased and community composition structure became complicated and diversified with gap development . Similarity analysis of family , genera and species showed that the dynamic changes of vegetation in gaps were somewhat continuous and gradual , the similarities between the neighboring stages were greater than those between non-neighboring stages during gaps development . With
gaps development , the percentage of phanerophytes and epiphytic plants increased , hemicryptophytes and therophytes decreased correspondingly , but the percentage of chamaephytes and cryptophytes did not change much . With gaps development, community structure became stable and ecological function was enhanced .

Key words: Karst forest