These files contain radiocarbon, d13C, NSC concentrations, and CO2 efflux rates measured for aspen (Populus tremula hybrids) roots collected during 2018 growing season in the Großer Hermannsberg Mountain, Germany (50°42’50’’ N, 10°36’13’’ E, 616 m a.s.l). Coarse (> 2 mm) and fine (2 ≤ mm) roots collected from three 'treatments': before stem girdling (Pre-girdling), ~3 months after girdling (Girdling) and ~3 months after girdling but in un-girdled trees (Control). The files with the relevant results: '13C', '14C', 'CO2_efflux', 'NSC'. Few roots from the 'Pre-girdling' treatment were incubated for respiration measurements 7 d after harvest. The files with the relevant results: 'Repeated_incubations_isotopes', 'Repeated_incubations_fluxes'. Results of incubations used for Q10 calculations presented in the file 'CO2_efflux_Q10'. Temperature and rainfall in the site during 2018 growing season are presented in the file 'Field_temperature_rainfall'. Results used to reconstruct local atmospheric D14C-CO2 record are presented in the file 'Local_atmospheric_CO2_D14C'. The file 'Metadata' contains information about the headers in the other files.

Funding: the Max Planck Institute for Biogeochemistry and the European Research Council Horizon 2020 Research and Innovation Programme, grant agreement 695101 (14Constraint).