The long-term monitoring of long-lived trees allows us to understand how forest structure and function change over time due to demographic turnover under environmental changes. This basic information on forest dynamics is essential for estimating and conserving various forest functions, such as carbon stocks and biodiversity. Although it is necessary to predict changes in forest structure and function in the future more precisely based on information on demographic performances under various environmental conditions, such as disturbances, the long-term monitoring of disturbed and undisturbed forests over a longer time, such as more than 50 years, is quite rare.
This study examines differences in forest demographic performance changes over 50 years with/without disturbances in a species-rich lowland rainforest in Pasoh, peninsular Malaysia. The 2-ha permanent plot was established in 1970, and all trees with a stem diameter of more than 10 cm were recorded. The 20 x 100 m area of the 2-ha plot was disturbed by clear-cutting in 1973 by the International Biological Program. We expanded the permanent plot to the 6-ha forest dynamics plot (200 x 300 m) in 1994, and we repeatedly measured all living trees more than 5 cm in stem diameter since then. By combining these long-term monitoring datasets, we examine differences in demographic rates of relative growth rates and survival rates of trees more than 10 cm in stem diameter from 1970 and of trees more than 5cm in stem diameter from 1994 between undisturbed and disturbed forest stands. Then, we will discuss how disturbed forest stands differ from undisturbed ones in their structure and function.