Condensed tannin effects on decomposition of very fine roots among temperate tree species

Below-ground litter is the dominant soil carbon and nutrient input in many ecosystems, yet the general functional traits underlying below-ground decomposition remain elusive. As defensive compounds, condensed tannin (CT) might be expected to be abundant in very fine roots (<0.5 mm) and are associated with decomposition dynamics. Here, we quantified the interspecific variation in fine root CT concentrations and examined the functional significance of CT for fine root decomposition over four years among 15 Chinese temperate tree species. Concentrations of CT varied between 5.82% and 16.02% among species. After four years of decomposition, initial litter nutrients explained no interspecific variation in fine root decomposition rates in this relatively nutrient-rich temperate forest. In contrast, substrate carbon compounds strongly control the process of fine root decomposition and CT was important for predicating fine root decomposition rates. Our results imply that the strong negative effects of CT on fine root decomposition can have great impacts on soil biological processes.