This set of data comprises substrate utilisation profiles for saprotrophic fungi (using the commercially available BIOLOG plate method) and moisture content data from soils sampled from experimental plots at Sourhope, Scotland. The data were collected in order to determine how the high species richness of decomposer (saprotrophic) fungi and their relative frequencies of occurrence influence the decomposition of organic matter. Data were collected during a project funded under the NERC Soil Biodiversity Programme, established in 1999 and centred upon the intensive study of a large field experiment located at the Macaulay Land Use Research Institute (now the James Hutton Institute) farm at Sourhope in the Scottish Borders (Grid reference: NT8545019630). During the experiment, the site was monitored to assess changes in above-ground biomass production (productivity), species composition and relative abundance (diversity). Full details about this dataset can be found at https://doi.org/10.5285/662b8cb3-afca-43c6-a6e8-e56fcf94626b