Divergent Decomposition Patterns of Leaf Litter and Fine Roots from an Urban Forest in Mid-Subtropical China

Abstract

Litter decomposition plays a pivotal role in carbon (C) and nutrient cycling in terrestrial ecosystems. However, little is known about the litter decomposition processes and nutrient dynamics in urban green space. In this study, the decomposition and nutrient dynamics of leaf litter and fine roots from Cinnamomum officinarum Nee ex Wall. and Elaeocarpus decipiens Hemsl. were studied in an urban forest in subtropical China. The results showed that the leaf litter mass loss, and nitrogen (N) and phosphorus (P) mineralization of E. decipiens were faster than that of C. officinarum in the first 180 days, but in the whole decomposition period, the leaf litter decomposition constant of C. officinarum was higher than that of E. decipiens. There was no difference in fine root decomposition constant and P mineralization, although the fine root N immobilization was higher relative to C. officinarum during the 90th to 270th days. Additionally, both the leaf litter mass loss, decomposition rate, and nutrient mineralization were faster than fine roots for these two tree species. The soil microbial biomass showed positive effects on leaf litter decomposition and negative effects on fine root decomposition. The correlation analysis indicated that initial litter quality, soil physicochemical properties, and microbial activity mainly affected early-stage litter decomposition and nutrient mineralization. Also, the leaf litter production and N and P storages of E. decipiens were higher than that of C. officinarum, suggesting faster decomposition rate and nutrient return for E. decipiens leaf litter. Consequently, we propose that tree species with fast nutrient return, such as E. decipiens, could be introduced to urban green space with pervious surfaces in respect of the nutrient balance. This work improves the understanding of litter decomposition and nutrient cycling and promotes the management for urban green space.