Dissolved organic matter and inorganic nutrients released from forest leaf litter through leaching are the important energy and nutrient sources that support the production of aquatic food webs. Leaf litter-derived dissolved organic carbon (DOC) is a critical energy source for aquatic heterotrophic microbes, and inorganic nitrogen and phosphorus can enhance primary production. In this study, we experimentally measured the release efficiencies and amounts of DOC, total dissolved nitrogen (TDN), and total dissolved phosphorus (TDP) of the leaf litter from 11 temperate tree species by soaking the leaf litter in water for 28 days. We found that the maximal release efficiency (% of element released per estimated mass of the element) was the highest for P and lowest for N. These efficiencies were species-specific. Additionally, the DOC:TDP, DOC:TDN, and TDN:TDP ratios varied among the leachate of different leaf litter species. DOC:TDP increased with the C:P ratio in leaf litter biomass but is considerably lower; TDN:TDP was lower than the N:P ratio in leaf litter biomass as well; DOC:TDN ratio was higher than the C:N ratio in leaf litter biomass. These results suggest that the ratios of DOC to dissolved N and P nutrients released into water are related to, but not the same as, the stoichiometry of leaf litter biomass. Based on these findings, we concluded that changes in the vegetations with different leaf litter stoichiometry can alter the relative importance of detrital and grazing food chains in aquatic ecosystems.
Keywords: aquatic food web; ecological stoichiometry; leaf litter; terrestrial subsidy.
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