The dataset consists of tree diameter at breast height (DBH) of all trees > 1 cm DBH in 16 parcels of 15 m x 15 m in the tropical heath forest of the Kabili-Sepilok Forest Reserve (Sabah, Malaysia). Also included are the tropical heath forest trees’ leaf element concentration. Tree DBH has been measured three times, one before (2016) and two after (2017 and 2018) the experimental application of Nitrogen fertiliser and CaCO3 to the forest floor. The leaves were collected before (2016) and after (January 2017; July 2017; June 2018) the application of experimental nitrogen and CaCO3 fertilisation. The experimental setting consists of four replicate parcels for the control plots, four replicates for the Nitrogen treatment, four replicates for the CaCO3 treatment and four replicates the Nitrogen and CaCO3 treatments combined. Full details about this dataset can be found at https://doi.org/10.5285/d5ea9e2c-f053-4631-aead-a8a5557488c6
