The long-term monitoring of long-lived trees allows us to understand how forest structure change over time as a consequence of 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. Even though many trees live more than 100 years, it is not easy to maintain the long-term dynamics plot and continue long-term monitoring, and therefore, even long-term monitoring beyond 50 years is quite rare.
In this study, we asked how forest structure changes over 50 years in a species-rich lowland rainforest in Pasoh, peninsular Malaysia. We focus on trees with stem diameters more than or equal to 10 cm in the 2-ha plot within the 6-ha long-term dynamics plot for which tree census data have existed since 1970. The 2-ha plot (100 x 200 m) is a primary forest but includes the logged area (20 x 100 m) in 1973 by the International Biological Program. We examine the change in aboveground biomass and trait-based species turnover from 1970 to 2023 and discuss how changes in forest structure differ between unlogged and logged areas.