Abstract: Dissolved organic matter (DOM) leached from plant litter plays an essential role in carbon (C) and nutrient cycling in forest soils. However, the characteristics of leaf litter leachates (i.e., amounts, chemical composition and structure) from different plant growth forms are still unclear, especially lacking of empirical evidence of multiple tree species. In this study, we collected leaf litters of 11 broadleaf tree species, 3 coniferous tree species, and 4 fern species from subtropical plantations in Jiangxi Province. A laboratory leaching experiment was conducted to compare the difference in leaf litterleached DOM parameters among plant growth forms. Furthermore, the correlation between DOM parameters and initial leaf litter properties was analyzed. The results showed that amounts and chemical composition of litter-leached DOM exhibited substantial variations among plant growth forms. Specifically, amounts of dissolved organic carbon (DOC) and total nitrogen (DTN) leached from leaf litter were greatest in broad-leaf trees, but ferns had highest amounts of dissolved total phosphorus (DTP). Compared with coniferous trees, broadleaf trees and ferns had higher SUVA₂₅₄ and SUVA₂₈₀ values but lower S_275-295 and S_R values in litter leachates, indicating higher DOM aromaticity and molecular weight in litter leachates from broadleaf trees. Leaf carbon content, nutrient content, stoichiometric ratios, and physical traits (i.e., specific leaf area, tissue density and water-holding capacity) would well explain the variations in production and aromatic degree of DOM of leaf litter from different plant growth forms. Our results suggest that replanting broadleaf tree under low-efficiency and coniferous plantations would be an effective strategy to improve ecological services, such as soil carbon pool and forest productivity by promoting the amounts and diversity of DOM input to soils.

Key words: forest litter floor, understory vegetation, aromatic degree, leaching, ultraviolet spectrum, soil carbon pool.