Carbon input manipulations affecting microbial carbon metabolism in temperate forest soils - A comparative study between broadleaf and coniferous plantations

Large uncertainties exist about the relative importance of aboveground litter and root carbon input on soil organic carbon decomposition in different forest types. Here, we report on our detritus input and removal treatments conducted to investigate how changes in aboveground and belowground carbon inputs affect soil organic carbon content and various microbial carbon metabolic functions in different plantation types (oak vs. pine, broadleaf vs. coniferous). The results of our study showed that doubling aboveground litter significantly increased SOC content and labile carbon metabolism in the oak plantation but not the pine plantation. Root trenching and aboveground litter removal decreased SOC content and carbon metabolisms. The effect of root trenching on carbon metabolisms was weaker than litter removal in the oak plantation but not the pine plantation. Detritus input and removal treatments changed the diversity and function of labile carbon (starch, carbohydrates, and amines/amides) and the metabolic activity of soil microorganisms in oak plantation, but mainly influenced recalcitrant carbon (polymers) metabolism in the pine plantation. Detritus input and removal treatments influenced the composition of microbial carbon metabolic genes and functions mainly by modifying the soil environment and nutrient availability including moisture, pH, nitrate content, and available phosphorus content in the oak plantation, while it influenced carbon metabolism by altering soil moisture, and the ammonium, nitrate, and organic carbon content in the pine plantation. These findings indicate that different forest ecosystems could respond differently to different disturbances, and forest management should be adjusted accordingly.