Photodegradation is a dominant control of aboveground carbon turnover in terrestrial ecosystems

BERENSTECHER, P; AUSTIN AT; VIVANCO, L; MÉNDEZ, MS; BALLARE, CL

Ghent

Congreso; British Ecological Society Annual Meeting; 2017

British Ecological Society

Plant litter decomposition is an essential process in the first stages of carbon turnover in terrestrial ecosystems, and together with soil microbial biomass, provide the principal inputs of carbon for the formationof soil organic matter. Photodegradation, the photochemical mineralization of organic matter due to exposure to solar radiation, has been identified as a mechanism for previously unexplained high rates of litter mass loss in arid and semiarid ecosystems. Nevertheless, the indirect effects of photodegradation and wavelength dependence on biotic stimulation or inhibition of carbon turnover have been debated in recent studies. In controlled conditions of a two phase experiment, we demonstrated that in a wide range of plant species, previous exposure to solar radiation, and visible light in particular, enhanced subsequent biotic degradation of leaf litter. Field studies in Patagonian woodland ecosystems confirm the importance of biotic facilitation on litter decomposition, which appears to have larger stimulatory effects than those observed in controlled conditions. Litter decomposition of previously exposed grass litter decomposed more than two times faster than unexposed litter in a one year field experiment, while strong seasonal effects of direct photodegradation and biotic facilitation of solar radiation were observed with changes in solar irradiance using attenuation filters. The generalized positive effect of solar radiation exposure on subsequent microbial activity appears to be mediated by increased accessibility to cell wall polysaccharides,which is consistent in both field and controlled condition experiments. These results suggests that photodegradation is quantitatively important in determining rates of mass loss and nutrient release through itsimpacts on biotic decomposition, which has implications for the potential alterations in carbon turnover in terrestrial ecosystems to predicted climate or land use change.