Interactions between soil nitrogen (N) availability, fungal community composition, and soil organic matter (SOM) regulate soil carbon (C) dynamics in many forest ecosystems, but context dependency in these relationships has precluded general predictive theory. We found that ectomycorrhizal (ECM) fungi with peroxidases decreased with increasing inorganic N availability across a natural inorganic N gradient in northern temperate forests, whereas ligninolytic fungal saprotrophs exhibited no response. Lignin-derived SOM and soil C were negatively correlated with ECM fungi with peroxidases and were positively correlated with inorganic N availability, suggesting decay of lignin-derived SOM by these ECM fungi reduced soil C storage. The correlations we observed link SOM decay in temperate forests to tradeoffs in tree N nutrition and ECM composition, and we propose SOM varies along a single continuum across temperate and boreal ecosystems depending upon how tree allocation to functionally distinct ECM taxa and environmental stress covary with soil N availability.

中文翻译：

---

外生菌根真菌的腐烂将土壤有机质与氮的有效性结合起来

土壤氮 (N) 可用性、真菌群落组成和土壤有机质 (SOM) 之间的相互作用调节了许多森林生态系统中的土壤碳 (C) 动态，但这些关系中的环境依赖性排除了一般预测理论。我们发现，在北部温带森林中，具有过氧化物酶的外生菌根 (ECM) 真菌随着天然无机 N 梯度中无机 N 可用性的增加而减少，而木质素分解真菌腐生菌没有表现出响应。木质素衍生的 SOM 和土壤 C 与具有过氧化物酶的 ECM 真菌呈负相关，并与无机 N 的有效性呈正相关，这表明这些 ECM 真菌对木质素衍生的 SOM 的衰变减少了土壤 C 的储存。我们观察到的相关性将温带森林中的 SOM 衰减与树木 N 营养和 ECM 组成的权衡联系起来，