Effects of climate factors and vegetation on the CO₂ fluxes and δ¹³C from re-established grassland

¹ Unit of Ecologistics and Environmental Risk Management, Faculty of Environmental Engineering, Wroclaw University of Science and Technology, Poland
² Dept. of Soil Science of Temperate Ecosystems, Georg August University of Gottingen, Gottingen, Germany

^* Corresponding author: jaroslaw.bezyk@pwr.edu.pl

Abstract

The relationship between stable carbon isotope composition (δ¹³C -CO₂) of soil CO₂ 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 CO₂ 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 δ¹³C -CO₂ values. The concentration and stable carbon isotope composition of CO₂ were determined using the gas chromatography and mass spectrometry analyses. The δ¹³C -CO₂ of the soil fluxes decreased over sampling time for the ‘dry-warm’ conditions and canopy manipulation. The ecosystem-derived δ¹³C -CO₂ values (corrected for the atmospheric δ¹³C -CO₂) 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 CO₂ 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 δ¹³C -CO₂ values as compared with the control, the pattern of further δ¹³C -CO₂ decrease (down to –28.8 ± 0.8‰) supported the role of living vegetation in a contribution of ¹³C-enriched CO₂ to the ecosystem respiration.