Effects of climate factors and vegetation on the CO₂fluxes and δ¹³C from re-established grassland

Abstract

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

Assessment of GHG Interactions in the Vicinity of the Municipal Waste Landfill Site—Case Study

“…The relationship between the CO 2 mole fraction and δ 13 C(CO 2 ) values (Figure 5B) clearly indicated a biogenic input of the surrounding landfill agriculture fields and grassland. An assimilation process of CO 2 by vegetation or by soil microorganisms [67][68][69] caused a lower CO 2 mole fraction of residue carbon dioxide in ambient air, as well as the enrichment of 13 C due to preferential 12 C consumption.…”