Plant litter inputs can influence soil organic carbon (SOC) decomposition via the priming effect. However, our understanding of the priming effect and underlying mechanisms is primarily from studies with leaf litter addition, while little is known about root litter effects, particularly of woody plants. Here, using a ¹³C natural tracer approach, we conducted a 12-week incubation experiment to investigate litter decomposition and priming effect of mature-tree root orders (1^st to 5^th) of Cunninghamia lanceolata (Lamb.) Hook. We explored how litter decomposition and the priming effect were related to microbial biomass of main groups, enzyme activities, and root tissue chemistry. Root litter decomposition rates increased with increasing root order, especially during the first 4 weeks, which was likely due to higher non-structural C and lower tannin concentrations for higher order roots. A negative priming effect occurred at this initial intensive stage when microbes may have preferred utilizing litter-derived labile C. Subsequently, the priming effect switched to positive, and showed larger priming effects for the higher order roots than the lower order ones. Higher order roots also showed higher fungi to bacteria ratios and enzyme activities than the lower order roots. These patterns of fungi to bacteria ratios and enzyme activities and thus the priming effect could be attributed to the difference in carbon:nitrogen ratio among root orders. Overall, we for the first time provide strong evidence for the effect of root order on the priming effect, and thus highlight that separating root litter based on root order is necessary for accurately evaluating its influence on SOC decomposition.

植物凋落物输入可以通过启动效应影响土壤有机碳 (SOC) 分解。然而，我们对启动效应和潜在机制的理解主要来自对凋落物添加的研究，而对根凋落物的影响知之甚少，尤其是木本植物。在此，使用¹³ C NATURAL示踪剂的方法，我们进行了12周的培养试验以调查垃圾分解和成熟树根的订单（1启动效应^ST〜5^个的）杉木（羔羊。）钩。我们探讨了凋落物分解和引发效应如何与主要群体的微生物生物量、酶活性和根组织化学相关。根凋落物分解率随着根序的增加而增加，尤其是在前 4 周，这可能是由于较高序根的非结构 C 和单宁浓度较低。当微生物可能更喜欢利用枯枝落叶衍生的不稳定 C 时，在这个初始密集阶段发生了负面启动效应。随后，启动效应转为正，并且对高阶根显示出比低阶根更大的启动效应。高级根也比低级根表现出更高的真菌与细菌比率和酶活性。真菌与细菌比例和酶活性的这些模式以及引发效应可归因于根级之间碳氮比的差异。总体而言，我们首次为根序对启动效应的影响提供了强有力的证据，因此强调根据根序分离根凋落物对于准确评估其对 SOC 分解的影响是必要的。