The decomposition rates of leaf litter and fine root and their temperature sensitivities are influenced differently by biotic factors

Abstract

Determining the temperature sensitivities of the decomposition rates of leaf litter and fine root is important for predicting the impact of climate warming on above- and belowground carbon (C) cycles in forest ecosystems. However, the responses of leaf and root decomposition rates to temperature have rarely been examined together. Here, we present the results of paired leaf litter and fine root decomposition experiments at four forest sites spanning 32° latitude in eastern China. The mean annual soil temperature explained the variances of the decomposition rates of the leaf litter (kLeaf, R2 = 0.95) and fine root (kFine root, R2 = 0.86) across the different biomes well and exerted a positive effect on the kLeaf: kFine root ratio. As a result, the sensitivity of the decomposition rate to temperature was significantly higher in the leaf litter (Q10 = 2.17 ± 0.07) than in the fine root (Q10 = 1.40 ± 0.06). The results of structural equation models indicated that the initial C:nitrogen (C:N) ratio exhibited negative effects, and phosphorus (P) cycling related enzymes activity exhibited positive effects on the kFine root when the effects of temperature were controlled. Even when the variables of these biotic factors were added, the soil temperature still exerted a dominant effect on the kLeaf. Our results suggest that temperature directly influences the kLeaf but indirectly affects the kFine root through litter quality and soil decomposers.