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中文摘要：
目前有关森林根系分泌物及其诱导的土壤生态学效应研究主要关注根系碳（C）源输入,而极少关注根系分泌物氮（N）源输入及其伴随的C：N化学计量特征对土壤过程和功能的影响,极大地限制了我们对森林根系-土壤-微生物互作机制的深入认识。该研究以川西亚高山天然林和云杉（Picea asperata）人工林土壤为对象,模拟配制不同C：N化学计量特征（只有N、C：N=10、C：N=50、C：N=100和只有C处理）的根系分泌物溶液进行人工添加试验,以探究根系分泌物化学计量特征对两种林分土壤碳动态及其微生物群落结构的影响差异。结果表明：模拟根系分泌物C添加总体促进了两种林分土壤有机质分解激发效应而降低了土壤总碳（TC）含量,而N添加在一定程度上缓和了两种林分土壤TC含量的降低幅度,且C添加导致天然林土壤TC含量的降低幅度明显低于土壤N有效性更低的人工林。几种根系分泌物添加处理对两种林分土壤活性和惰性碳库的影响无明显规律。另外,根系分泌物C添加总体降低了天然林土壤微生物总磷脂脂肪酸（PLFA）含量和细菌、放线菌、真菌PLFA含量,而总体增加人工林土壤微生物PLFA总量和细菌、放线菌、真菌PLFA含量,并诱导两种林分土壤微生物群落结构（细菌：真菌相对丰度）也发生了各自不同的变化。上述结果表明森林根系分泌物N源输入和土壤N有效性共同调控根系C源输入对土壤有机质分解激发效应的方向和幅度。研究结果为深入揭示典型森林根系分泌物化学计量特征对土壤生物化学循环过程的调控机制提供了一定的理论依据。
英文摘要：
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 bio-geochemical 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 treat-ments 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 plan-tation 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 planta-tion than that in the natural forest. The influence of exudate additions produced no significant influence on labile＆amp;nbsp;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 theoretica
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