This dataset contains forest floor thickness, forest floor dry mass, pH, soil Bulk density, C and N concentrations and stocks data from the Exploratory plots.

Whenever possible, nine forest floor and nine core samples of mineral soil per plot were taken. Forest floors were sampled from 25 x 25 cm plots using a wooden frame. All living plant parts within the frame were clipped off and then the forest floor was then removed by hand and/or knife. After removal of the forest floor, one core sample was taken down to 10, 20 or 40 cm in mineral soil given the stoniness of the site (i.e. in Spain coring was made only to 10 cm depth; in Romania, Italy, Germany and Finland, coring was made to 20 cm depth but in Poland it was made to 40cm depth). Cores were sampled with a long corer (inner diam. 3.56 cm, length 50 cm). Mineral soil core samples were divided by fixed depth into: forest floor, 0‐10 cm, 10‐20 cm, 20‐30 cm and 30‐40 cm. The nine replicate samples serve to represent the soil conditions across the core plot. Analyses of soil C was done on these composite samples.

Poland, Germany, Finland,Spain, Romania and Italy