Abstract: Litter-derived dissolved organic matter (DOM) is an important source of soil DOM, and the response of which to climate warming may change forest soil carbon and nitrogen dynamics, such as soil carbon and nitrogen mineralization. In this study, we conducted a field manipulative warming experiment in natural Castanopsis kawakamii forests. Combined with litter leaching solution collected in the field and ultraviolet-visible and three-dimensional fluorescence spectroscopy analyses, we explored the effects of warming on the content and structure of litter-derived DOM in subtropical evergreen broad-leaved forests. The results showed that litter-derived dissolved organic carbon and nitrogen content exhibited monthly dynamics, with the peak (in April) and the mean monthly content being 1.02 and 0.15 g·m^-2, respectively. Litter-derived DOM had higher fluorescence index and lower biological index, indicating the microbial-origin of DOM from litter. The litter DOM mainly included humic-like fractions and tryptophan-like substances. Warming did not affect the content, aromaticity, hydrophobicity, molecular weight, fluorescence index, biological index and humification index of DOM, suggesting neutral effect of warming on the quantity and structure of litter DOM. Warming also did not affect the relative contribution of main components in DOM, indicating that the temperature variation exerted no effects on microbial degradation. In summary, warming did not change the quantity and quality of litter-derived DOM in subtropical evergreen broadleaved forests, indicating warming had little effect on litter-derived DOM input to soil.

Key words: warming, subtropical forest, litter, dissolved organic matter, ultraviolet-visible spectrum, three-dimensional fluorescence spectrum