Abstract: Aims Dissolved organic carbon (DOC) and hot-water extractable carbon (HWEC) are important components of active carbon pools, which can be released quickly from decomposing litter and assimilated by soil microorganisms at short term. This fundamental biogeochemical process has been found to facilitate soil organic matter formation and biogeochemical processes. Traditional knowledge assumed that physical leaching is the primary driver of DOC and HWEC release during litter decomposition, but whether and how this process is controlled by litter substrate quality and morphological traits remains largely unknown. This study primarily focuses on how substrate quality and morphological traits of foliar litter control the release rates of DOC and HWEC during decomposition. Methods Here, we conducted an in situ microcosm decomposition experiment to evaluate the release rates of DOC and HWEC from decomposing litter of 21 tree species over 214 days of decomposition in a subtropical forest. Important findings We found that both DOC and HWEC released quickly at early periods but slowly at later periods, but their release rates varied strongly between litters species with different substrate quality and morphological traits. Litter DOC and HWEC release rates were significantly correlated with cellulose and phosphorus contents, and was negatively correlated with accumulated precipitation and monthly average temperature. Conclusion These results suggest that DOC and HWEC release from decomposing litter are not only controlled by local precipitation and temperature, but also interpreted by litter substrate quality but not morphological traits. The new mechanisms underlying labile carbon release during litter decomposition is of great significance for understanding soil biogeochemistry in subtropical forests.

Key words: Litter decomposition, dissolved organic carbon, hot-water extractable carbon, plant traits, subtropical forests