[Field decomposition and dissolved organic matter release dynamics in leaf litter of typical trees in South China.]

Leaf litters of Pinus elliottii (needle-leaved) and Schima superba (broad-leaved), which are commonly found in subtropical regions of South China, were decomposed in a field for 0, 30, 60, 90, 150, 210, 240 and 365 d to evaluate changes in concentrations, compositions and properties, and amount of dissolved organic matter (DOM) released and dissolved organic carbon (DOC) in soil. Although the concentrations of DOM derived from S. superba were higher than those from P. elliottii, similar variation patterns of DOM characteristics (e.g., concentrations, composition and properties) were observed between the two types of litter during decomposition. The concentrations of DOM showed a downward trend. Upward trends were obtained for the aromatization and molecular mass of DOM, as well as fulvic acid and humic acid levels in DOM, while a downward trend was found for levels of simple aromatic proteins, such as tyrosine, in DOM. During the initial phase of decomposition, DOM was generally composed of hydrophilic neutral and acidic components, which were easily decomposed and transferred, and their effects on surface soil DOC were not significant. At later stages, DOM was mainly composed of humic and fulvic acid and other aromatic, complex structure substances, which could easily adsorb on soil, and decreased the DOC concentration of surface soil.