Root exudates induce microbial nitrogen (N) mineralization and hence increase soil N availability to plants. To elucidate why the flux rates of root exudates explain microbial N mineralization quantitatively in woody plants, we assessed how the flux rates of root exudates affect the microbial C/N ratio and fungi-to-bacteria (F:B) ratio and therefore the N-degrading enzymes and net N mineralization. We investigated four co-existing canopy species in a warm temperate forest. The flux rates of root exudates were measured in situ using syringe-based cultivation. Microbial biomass carbon (C) and N, fungal and bacterial biomarkers, the activities of N-degrading enzymes, and net N-mineralization rate were measured in both rhizosphere and bulk soils. Microbial biomass C (N) and fungal and bacterial biomarkers were positively related to root exudation rates. Microbial C/N ratio remained unchanged, while the F:B ratio was positively correlated with exudation rates. Mediator analysis suggested that a ‘microbial biomass to N-degrading enzyme’ pathway mediated the microbial N mineralization induced by root exudation, probably because both the fungal and bacterial group contributed to the N-degrading enzyme NAG. In this forest, root exudation stimulated microbial N mineralization linearly due to a growing N demand to sustain a constant microbial C/N ratio. Therefore, the C investment of root exudation can be an efficient N-acquisition strategy for co-existing woody species.

根系分泌物诱导微生物氮（N）矿化，因此增加了土壤对植物的氮利用率。为了阐明为什么根系分泌物的通量率定量地解释了木本植物中微生物氮的矿化作用，我们评估了根系分泌物的通量率如何影响微生物的C / N比和真菌-细菌（F：B）比，从而影响N降解酶和净氮矿化。我们在温暖的温带森林中调查了四种并存的树冠物种。根系分泌物的通量率是就地测量的使用基于注射器的种植。在根际土壤和块状土壤中都测量了微生物生物量碳和氮，真菌和细菌生物标记，氮降解酶的活性以及净氮矿化率。微生物生物量碳（N）以及真菌和细菌生物标志物与根系分泌率呈正相关。微生物的C / N比保持不变，而F：B比与渗出率呈正相关。介体分析表明，“微生物量转化为N的微生物”途径介导了根系分泌物诱导的微生物N矿化，这可能是因为真菌和细菌基团都对N降解酶NAG起作用。在这个森林中，由于对氮的需求不断增长，以维持恒定的微生物碳氮比，根系分泌物线性地刺激了微生物的氮矿化作用。因此，