Gap characteristics and natural regeneration in Mt. Makiling rainforest, the Philippines

This study was conducted to determine the characteristics of gaps and natural regeneration of trees on Mt. Makiling,the Philippines. Canopy gaps in or around two 1-ha permanent plots and on 3-km line transects were investigated. Mostof the gaps studied were formed or affected by Typhoon Milenyo, which hit the study site in September 2006. The mostfrequent mode of gap maker death was snap-off, whereas uprooting was relatively less important. The most frequentgap maker was balobo (Diplodiscus paniculatus) followed by magabuyo (Celtis luzonica) and katmon (Dillenia philippinensis).In contrast, the most frequent gap filler was magabuyo (C. luzonica). At the sapling layer, the most importantspecies was magabuyo (C. luzonica), but there was a high proportion of lianas and palms. Most of the gaps had leaf areaindex (LAI) values between 3 and 5. A clear trend of a decrease in gap size and an increase in LAI was observed for 2 yearsfrom 2007 to 2009. New seedlings emerged very abundantly during the same time period. The rapid changes in the gapswere partially due to the excellent capability of tropical trees to resprout after the crown or stem was damaged by thetyphoon. This study on gap dynamics may contribute to a better understanding of the natural regeneration process oftrees in tropical rainforests.