This dataset contains greenhouse gas flux data and vegetation survey data from an experiment based at Parsonage Down, UK. The vegetation survey comprises total species percentage cover and species richness data from four 50 cm by 50 cm quadrats. The greenhouse gas flux data comprises net ecosystem carbon dioxide exchange, photosynthesis and respiration data measured with an Infra-red Gas Analyser (IRGA); methane, carbon dioxide and nitrous oxide data measured using gas chromatography; and nitrate and ammonium from soil samples extracted with potassium chloride. The experiment investigated the effect of different plant groups on soil carbon stores and nutrient cycling, by using a mixture of hand weeding and herbicide spot spraying to create different plant communities on the species rich grassland at Parsonage Down. The resulting carbon and nutrient cycling rates were compared to the characteristics of the plant groups. The experiment ran from 2013 to 2015 and this dataset contains data from 2014 only. This experiment was part of the Wessex BESS project, a six-year (2011-2017) project aimed at understanding how biodiversity underpins the ecosystem functions and services that landscapes provide. Full details about this dataset can be found at https://doi.org/10.5285/e05b350f-3cf4-4f8d-aa3c-24d562ca756b