The data consist of soil carbon in kilogrammes (kg) of carbon per metre squared. Soil cores were taken to a depth of 1 metre and divided into 15 cm depth increments. Soil carbon (kg carbon per metre squared) was determined for all soil depth increments. The soil samples were taken in the Conwy catchment in North West Wales. Samples were collected in the spring of 2014 across a land use intensification gradient ranging from semi-natural peatlands, acid grasslands to improved grasslands and arable fields. Soil parameters were tested across a land use intensification gradient to detect parameters that can predict aboveground biomass production across different land management types. Data were used to enhance the predictions of biomass production in the Joint UK Land Environment Simulator model (JULES). Measurements informed the improvement of the nitrogen cycle component in the model. This dataset is part of a data series where plant and soil measurements were collected together to increase our understanding of coupled aboveground and belowground processes. Measurements were undertaken by trained members of staff from Bangor University, the Centre for Ecology and Hydrology and Exeter University. 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 ; Intact soil cores were collected in spring 2014 using a Van Walt percussion (Cobra TT) core. Soil cores were taken to a depth of 1 metre and divided into 15 centimetre (cm) depth increments. Total carbon (in percent ) was analysed using thermal oxidation measured by an Elementar Vario Cube Select. Soil water content (SWC) and bulk density (BD) were measured using standard techniques. SWC and BD were used to calculate the soil carbon in kg per metre squared. All results were entered into Excel spreadsheets. Results from all the analyses were combined into one Excel spreadsheet. Data were then exported from this combined Excel spreadsheet as .csv files for ingestion into the EIDC.