The data represent the growth rates and carbon accumulation among different tree species. Tree censuses were conducted in November 2020, September 2021, and September 2022. Carbon accumulation data are available for 2021 and 2022. Data were collected from 15 plots across Wytham Woods, near Oxford in southern England, to measure the accumulation of carbon (MgC/ha/year) among tree species and size classes from three experimental plot types (15 plots in total, five plots per type). The plot types include ash dominated (AD), ash dominated where ash trees have been girdled (ADG), and non-ash dominated (NAD) plots. The data contributed to a project on the ecological impact of ash dieback and were used to quantify the growth rates, and carbon accumulation, among habitats with varying levels of ash dieback represented by different treatments. Full details about this dataset can be found at https://doi.org/10.5285/fc00dbd0-bf3d-495e-9895-190919f8e5e8