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Effects of simulated exudate C:N stoichiometry on dynamics of carbon and microbial community composition in a subalpine coniferous forest of western Sichuan,China |
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| Authors: | LIANG Ru-Biao LIANG Jin QIAO Ming-Feng XU Zhen-Feng LIU Qing YIN Hua-Jun |
| Affiliation: | Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China University of Chinese Academy of Sciences, Beijing 100049, China and Key Laboratory of Ecological Forestry Engineering in Sichuan, Institute of Ecology & Forestry, Sichuan Agricultural University, Chengdu 611130, China |
| Abstract: | Aims Exudation measurements focus exclusively on total exudate carbon (C) fluxes without considering how root-derived nitrogen (N) inputs and variable exudate stoichiometries may influence microbial activity and biogeochemical cycles. As a result, the biogeochemical consequences of exudate stoichiometry for soil C-nutrient couplings and feedbacks to environmental changes remain largely unknown. Our objective is to explore to what extent N availability modifies soil microbial processes and the dynamics of soil carbon pool induced by labile C. Methods We conducted a 50-day laboratory incubation experiment by addition of simulated exudates varying in C:N to two coniferous forest soils: a natural forest and Picea asperata plantation. The five exudate addition treatments are C alone, N alone, and combinations of C and three N levels (C:N ratio of 10, 50 and 100). Important findings The addition of labile C exudates decreased soil total C for both natural forest and the plantation by stimulating soil organic matter (SOM) mineralization (i.e. greater priming effect), while the addition of N decreased total C. The decreased soil total C induced by exogenous labile C addition was greater in the plantation than that in the natural forest. The influence of exudate additions produced no significant influence on labile and recalcitrant carbon pools at either soil. The addition of labile C exudate decreased the total phospholipid fatty acid (PLFA), actinomycetic, bacterial and fungal PLFA for the natural forest, but increased them in the plantation. Moreover, the microbial community composition (i.e. the value of bacterial PLFA:fungi PLFA) varied greatly among the treatments. These results indicate that both root-derived N inputs and soil N availability co-regulate the direction and magnitude of priming effects on SOM decomposition by controlling the activity and the relative abundance of bacterial and fungal. Our results provide additional evidences toward a robust theoretical foundation for better understanding the ecological consequences of exudate stoichiometry on soil C cycling in forests. |
| Keywords: | exudate stoichiometry microbial community root exudation soil carbon subalpine coniferous forest |
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