<b>12 年田间氮添加</b><b>通过两种截然不同的微生物酶途径</b>

Soil organic carbon (SOC) decomposition can be significantly influenced by plant C inputs, i.e., the priming effect. However,the current understanding of priming effect under nitrogen (N) addition is overwhelmingly based on short-term incubation studies with simple C addition (e.g., glucose). How long-term N addition in the field affects the priming effect caused by complex C remains unclear, especiallyin boreal forests with severer N limitation.Here, soils were collected from a 12-year in-situN addition field experiment in a boreal forest, and were incubated with 13C-labeled cellulose. Further, a global data synthesis was conducted to compare the effect of N addition on priming between simple and complex C types. The results showed that long-term N addition reduced the priming effectby on average 150%, and meanwhile increased peroxidasebut decreased β-1,4-N-acetylglucosaminidase.The partial least squares path modellingexplained 68.3 % of the variation of the priming effect among all the treatments with two contrasting pathways of hydrolytic enzymes versusoxidases with the extent explainedcomparable. These results suggested that the inhibited effect of long-term N addition on priming could be attributed to changes in microbial utilization of soil C. Based on data synthesis, the N-inhibited effect on priming caused by complex C was higher than by simple C, indicating that the N inhibition might be underestimated by studies with simple C addition. Our results provide insights into accurately assessing SOC decomposition via the priming effect in the context of N deposition in boreal forests.