Seedlings were grown in soil collected from an experiment at Hambleton Forest, North Yorkshire. Soils originated from plots containing either Scots pine or birch monocultures, or a mixture of both species. In the lab, pairs of seedlings of birch and Scots pine were grown as monocultures and mixtures from each of the three plot treatments. The data represent the biomass, leaf C:N ratio and mycorrhizal status determined after 20 weeks. Full details about this dataset can be found at https://doi.org/10.5285/7991871e-382f-422f-b5b2-91b4f6d8598f
