This dataset provides photosynthesis data for the plant species Calluna vulgaris, Vaccinium myrtillus and Empetrum nigrum. Photosynthesis response curves were measured for Calluna vulgaris and Vaccinium myrtillus only. Photosynthesis was measured at the climate change field site Climoor which is located in Clocaenog forest, North East Wales. Photosynthesis measurements have been carried out in 2001, 2002, 2003, 2005 and 2007; photosynthesis light response curves and Net Carbon Dioxide (CO2) assimilation rate (A), versus calculated substomatal CO2 concentration (Ci), (A/Ci), responses have been measured in 2002 and 2003. In 2005, the effects of drought on photosynthesis of all three species has been measured. In 2007, the effect climate change (warming and drought) has been measured on healthy, fungal affected and herbivory affected Vaccinium myrtillus leaves. The experimental field site consists of three untreated control plots, three plots where the plant canopy air is artificially warmed during night time hours and three plots where rainfall is excluded from the plots at least during the plants growing season (March to September). Photosynthesis measurements were carried out by trained members of CEH Bangor staff. The Climoor field experiment intends to answer questions regarding the effects of warming and drought on ecosystem processes. Plot level photosynthesis measurements are important to investigate ecosystem carbon dynamics and changes in the soil carbon under the imposed climatic treatments. Full details about this dataset can be found at https://doi.org/10.5285/a17b3345-b769-426d-bccd-f3c8bd88dea1