Tropical forests experience extensive gap formation throughout their age and the rate of formation has increased over the past several decades due to global anthropogenic disturbances. Gaps increased seedling establishment and sapling densities, but species richness per stem was identical in gaps and in non gap areas. The optimal size of gap which can restore seeds and saplings bank of neighboring trees is remained unknown. To determine the optimal size of gap, we investigate the natural growth patterns of trees around the gap and quantify the factors that permissible for the succession of pioneers. By using spatially explicit census data from 50ha tree demography plot of Pasoh, Malaysia, we investigate the formation of gaps throughout 25 years of inventories. We determine the relative gap phase (GP) by the function of total tree basal area and designed it into different categories. We calculate GP for 5x5m subplots (n=20,000) in the 50ha plot.  The gap size is determined by calculating the total area of neighboring subplots with the same category of GP. We categorize the species identified in the plot into 4 categories according to their growth and succession pattern. Relative abundance of pioneers and other species categories are used to investigate their distribution and dispersal at different gap sizes.

Results/Conclusions

There are significant changes of GP throughout the 25 years of records. GP are increasing through time and the probability of decreasing increased at high GP. The decreases in GP are generally of greater magnitude than increases. The influence of gap size to diversity and abundance of species is significant. Preliminary results show that the abundance pioneers have negative correlation with GP. We explored the relationship between category of species and their distribution in different gap sizes and it conclude that a relationship is significant where pioneers are highly abundance at large gaps compared to other categories. At a smaller gap, the number of pioneers is low. The optimal size of forest gap was determined when the present of species other than pioneers are significant at the minimum gap size. We conclude that the different sizes of gap play an important role in restoring seeds bank of the neighboring trees surrounding the gap area of tropical forests, and that quantifying the optimal size of gap will help improve our understanding of the factors driving changes in forest tree dynamics as well as the loss of species diversity respectively.