Given the severe anthropogenic pressure on tropical forests and the high demand for field observations of ecosystem characteristics, it is crucial to collect such data both in pristine tropical forests and in the converted deforested land cover classes. To gain insight into the ecosystem characteristics of pristine tropical forests, regrowth forests, and cashew plantations, we established an ecosystem monitoring site in Phnom Kulen National Park, Cambodia. Here, we present observed datasets of forest inventories, leaf area index, leaf traits of woody species, a fraction of intercepted photosynthetically active radiation, and edaphic and meteorological conditions. We examined how land-use and land-cover change affect species and functional diversity, stand structure, and edaphic conditions among the three land-cover classes. We further investigated relationships between diameters at breast height and tree height, estimated aboveground biomass (<em>AGB</em>), and explored relationships between ecosystem characteristics and <em>AGB</em>. We uncovered some key differences in ecosystem characteristics among the land-cover classes. We also demonstrated the feasibility of locally updating AGB estimates using power law functions. These datasets and findings can contribute to filling data gaps in tropical forest research, addressing global environmental challenges, and supporting sustainable forest management.