Abstract: This paper reviewed the concept,formation and function of gap and developed a new concept,canopy riftIt refers to the small 1-25m ²rift in the canopy caused by the different distribution pattern of the canopy species or breakage,standing death and treefallCanopy gap,mainly caused by small scale disturbances including natural disturbance regime and human disturbance regime,is an important phase in the forest regeneration cycleIt plays a leading role in the formation and maintenance of the patches mosaic structure in a forest community Corresponding to the three phases of the forest regeneration cycle,patches can be classified into three types:gap phase,building phase and mature forestMany factors may contribute to the maintenance of biodiversityHere we divided them into ① intrinsic factors,mainly including the biological and ecological characteristics of the species and ② external factors,the heterogeneity of habitatThe formation of gaps leads to the diversification of micro environment,and changes the type and magnitude of understoryGap impacts the forest micro environment,community structure and dynamic processGap causes different status of renewal between pioneer species and climax species,and generates the patch which is the different in the constitute of woods,population dynamic and growing speedIt leads to the diversity of community difference and species component,which is the difference of species between community patchesGap is of great significance in enhancing and maintaining species diversity for it may enhance habitat heterogeneity.

Key words: dynamic global vegetation model, vegetation functional type, terrestrial ecosystem model.