The data consists of, standing aboveground biomass, and belowground biomass measurements, from sites in the Conwy catchment. Standing aboveground biomass was measured at 7 sites and belowground biomass measurements were made at 8 sites. Data were collected in 2013 and 2014. The sites were chosen to represent habitat types and the terrestrial productivity gradient in Britain from intensive agriculturally managed lowland grasslands through to montane heath. Standing aboveground biomass (grams of dry mass per metre square) in habitats dominated by herbaceous biomass was measured on 1x1 metre quadrats in four plots per site. Standing aboveground biomass in woodlands was measured in two 200 square metre areas by means of stem cores and litter collections. Belowground total root biomass (grams of dry mass per square metre) was assessed for the topsoil 0-15 centimetres in three plots per site. Measurements were undertaken by trained members of staff from Bangor University and the Centre for Ecology and Hydrology. This data was collected for the NERC project ‘The Multi-Scale Response of Water quality, Biodiversity and Carbon Sequestration to Coupled Macronutrient Cycling from Source to Sea’ (NE/J011991/1). The project is also referred to as Turf2Surf. ; Methods ; Measurements were made in plots ranging in size from 200 metres square to 0.5 metres square located using a stratified random sampling design. Standing aboveground plant biomass and root biomass were assessed independently at the sites. Standing aboveground plant biomass (grams of dry mass per square metre) was measured at 7 sites (blanket bog, bog (Calluna), soligenous mire and flush, acid grassland, broadleaved woodland (n=3), coniferous woodland, improved grassland, semi-improved grassland), with between 3 and 9 replicates per habitat. For the grassy/bog habitats, all herbaceous biomass was cut to 1cm height in 1 x 1 m quadrats, for 4 plots per habitat. The vegetation was dried then weighed in the lab. For woodland habitats, 2 x 200 metre plots were chosen at random for each site and tree cores collected for each tree and shrub >1.3m in height. Then the following formula was used to calculate above-ground biomass (where DBH = Diameter at Breast Height): Total root biomass (grams of dry mass per metre square) was measured at 8 sites (blanket bog, soligenous mire and flush, acid grassland, broadleaved woodland, improved grassland and semi-improved grassland). Topsoil (0-15 cm) soil cores were taken in three locations at each site. Aboveground vegetation was removed. Samples separated into 5 cm intervals and then washed with water to remove any soil or stones. Roots were collected in sieves and placed into an 80 degree oven to remove any water content and enable a calculation of the dry weight of the roots. Total root biomass was calculated as the sum of roots from the three soil intervals. The full details are available in the supporting documentation. (Turf2Surf_WP2_Supporting_documentation.rtf) All results were entered into Excel spreadsheets. Data were then exported from this combined Excel spreadsheet as .csv files for ingestion into the EIDC.