摘要：The relationship between stable carbon isotope composition (δ 13 C -CO 2 ) of soil CO 2 flux, vegetation cover and weather conditions was investigated in a short-term campaign at a temperate re-established grassland in Germany. During August-September 2016, we measured surface CO 2 flux with a closed-chamber method at high and low soil moisture content (‘wet’, ‘dry’), with and without above ground vegetation (‘planted’, ‘clear-cut’) and estimated the effects of treatments on respective δ 13 C -CO 2 values. The concentration and stable carbon isotope composition of CO 2 were determined using the gas chromatography and mass spectrometry analyses. The δ 13 C -CO 2 of the soil fluxes decreased over sampling time for the ‘dry-warm’ conditions and canopy manipulation. The ecosystem-derived δ 13 C -CO 2 values (corrected for the atmospheric δ 13 C -CO 2 ) which included predominately soil-and rhizosphere respiration were –26.2 ± 0.8‰ for the ‘dry-warm’ conditions and decreased down to –28.1 ± 1.4‰ over a period of 28 days from late August to the end of September. The decrease coincided with the lowering of CO 2 flux and could be attributed to changes in plant physiological processes at the end of the vegetation season. Though the removal of shoots did not significantly affect the δ 13 C -CO 2 values as compared with the control, the pattern of further δ 13 C -CO 2 decrease (down to –28.8 ± 0.8‰) supported the role of living vegetation in a contribution of 13 C-enriched CO 2 to the ecosystem respiration.
