Degradation and temperature sensitivity of litter-derived dissolved organic matter (DOM) in a temperate freshwater wetland

BackgroundLitter-derived dissolved organic matter (DOM) plays an important role in biogeochemical cycling for wetlands. However, there are few studies to clarify how plant community alteration affects litter-derived DOM degradation. Moreover, little is known about the specific influence of temperature on the degradation, even though it is particularly important when the warming climate is taken into account. Therefore, it is urgently needed to determine interspecific differences in the DOM degradation rates and the responses to temperature increase.MethodsBased on a 42-day incubation experiment regarding nine species from a temperate wetland, we determined litter-derived DOM degradation at 10(o)C, 20(o)C and 30(o)C, and compared their temperature sensitivity coefficient Q(10).ResultsThese species exhibited interspecific variations in degradation at all temperatures, which related closely to initial chemical characteristics, including stoichiometry, aromaticity and molecular weight. Increased temperature generally promoted DOM degradation, especially at 10-20(o)C range, with Q(10) ranging from 1.42 to 3.82 and the mean up to 2.57. Specifically, the temperature sensitivity usually correlated negatively with aromaticity, but positively with carbon:nutrient ratios. The aromaticity, by contrast with other chemical characteristics, explained more interspecific variations in DOM degradation and the temperature sensitivity.ConclusionDegradation rates of litter-derived DOM and the responses to temperature increase vary greatly among species, where the aromaticity could be considered as a decisive indicator for such interspecific differences. This study highlights considerable promotion of climate warming on litter-derived DOM degradation, and sheds new light on influences of plant community on biogeochemical processes in wetlands.