Photodegradation accelerates coarse woody debris decomposition in subtropical Chinese forests

Abstract

Abstract Enhanced solar radiation (induced photodegradation) is an important driver of global environmental change. Coarse woody debris (CWD) plays a key role in forest carbon (C) dynamics because it contains a sizeable proportion of total forest C. Therefore, understanding the effects and underlying mechanisms of photodegradation on CWD decomposition is critical for the assessment of C storage in forests. We conducted a field-based experiment to investigate the effects of photodegradation on the respiration of CWD (RCWD) of Cunninghamia lanceolata (CL), Schima superba (SS), and Cinnamomum camphora (CC) over a 24-month period in subtropical China. And we also determined the effects of changes in CWD temperature and moisture content on RCWD of the three tree species. We found that photodegradation significantly accelerated RCWD, with its effect further amplified by increasing temperature. The temperature sensitivities of RCWD to CWD temperature as indicated by Q10 were increased by photodegradation treatments. The CWD temperature can explain over 70% of the variation in RCWD among different tree species and treatments. Our results indicate that the positive effect of photodegradation on CWD decomposition and C cycles could potentially impact C cycling in forest ecosystems. These findings may provide insight on the effects of photodegradation and temperature change on biogeochemical cycling of forest ecosystems under the future global change.