In March 2014 soil (0-10cm) was collected in Dennenkamp (the Netherlands), a former arable site that has developed into a natural grassland. In the laboratory, fresh soil was sieved (4 mm), homogenized and stored at 4 ºC until further use. We report the following data:

• CO2 evolution after addition of 13C labelled substrates (glucose, cellobiose and vanillic acid) to the soil.
• Abundance of microbial groups (fungi and/or bacteria) that used labeled and non-labeled carbon, measured as increase in 16S rRNA gene copy numbers and 18SrDNA copy numbers, for bacteria and fungi respectively, per g of soil.
• Biomass yield (for fungi and bacteria separately) for three substrates (glucose, cellobiose and vanillic acid), used that as a proxy for microbial usable energy