The role of photo- and thermal degradation for CO₂ and CO fluxes in an arid ecosystem

Recent studies have suggested the potential importance of abiotic degradation in arid ecosystems. In this study, the role of photo- and thermal degradation in ecosystem CO2 and CO exchange is assessed. A field experiment was performed in Italy using a FTIR-spectrometer coupled to a flux gradient system and to flux chambers. In a laboratory experiment, field samples were exposed to different temperatures and radiation intensities. No photodegradation-induced CO2 and CO fluxes were found in the field and in the laboratory study. In the laboratory, thermal degradation fluxes for CO2 and CO have been observed. In the field, CO uptake and emission have been observed and are proposed to be a result of biological uptake and abiotic thermal degradation-production. We suggest that previous studies, studying direct photodegradation, have overestimated the role of photodegradation and observed fluxes might be due to thermal degradation, which is an indirect effect of radiation. The potential importance of abiotic decompostion in the form of thermal degradation, especially for arid regions, should be considered in future studies.