Abstract
Long-term forest dynamic studies are vital for revealing how forests function. We conducted tree-by-tree censuses on 2 plots located in a valley of a lowland rainforest at Nanjenshan, southern Taiwan, which is located at the northern border of the Paleotropics. All free-standing trees ≥ 1 cm diameter at breast height (DBH) were identified, measured, and mapped for Nanjenshan plot I in 1993, 2000, and 2008, and for Nanjenshan plot II in 1999 and 2008. In 2008, 10,581 individuals in total were recorded in the 2 plots, belonging to 106 species, 75 genera, and 41 families. The community similarity index (Motyka’s index of similarity) showed that the 2 plots had 93~95% similarities to prior census. During 2000~2008, individuals in plot I increased by 10.0%, but the basal area decreased by 1.6%, and the plot was dominated by the broken mode of death (46.3%). During a similar period (1999~2008), individuals in plot II only decreased by 0.4%, the basal area increased by 2.6%, and the plot was dominated by the standing mode of death (66.7%). In addition, a higher proportion of large trees had died and more pioneer species were recruited in the same period in plot I. These results indicate that during the 2000~2008 census period, plot I might have experienced an increased frequency of disturbances, which could be caused by typhoons. In the meantime, the relatively low-elevation, small-sized plot II might have been better sheltered and less influenced by the gap-edge effect. Advanced studies of canopy gaps before and after typhoon seasons can help elucidate the disturbance mechanisms of lowland rainforests in Taiwan.