Forest soil organic matter (SOM) is derived from both above- and belowground plant inputs, with a significant portion of this plant-derived organic carbon being processed by fungal communities prior to becoming SOM. Despite the central role of fungi in the processing of litter and root inputs, little is known about the relationship between fungal community composition and the relative conversion of aboveground litter versus root inputs into SOM. The Detrital Input and Removal Treatment (DIRT) experiments offer a system in which to test such questions, wherein aboveground litter and root inputs to forest soils are chronically excluded independently and in combination. In this study, we characterized fungal biomass (ergosterol), community composition (ITS2 metabarcoding), and community assembly (via null modeling) under root and litter exclusion treatments in a northern temperate forest DIRT experiment, and we related fungal community parameters to soil carbon. Root, but not litter, presence significantly differentiated fungal community composition and drove a more stochastic community assembly. Roots were associated with higher fungal biomass, particularly that of ectomycorrhizal and saprotrophic fungi, and with higher soil carbon stocks. The resulting strong positive correlation between fungal biomass and soil carbon appeared to be driven by saprotroph biomass in particular. We suggest that fungal communities are important mediators of the conversion of above- and belowground plant inputs into SOM, and that characterizing their composition may aid in understanding the relative importance of these plant input sources to SOM.

森林土壤有机质 (SOM) 来自地上和地下植物输入，这种植物来源的有机碳的很大一部分在成为 SOM 之前由真菌群落处理。尽管真菌在处理凋落物和根输入中的核心作用，但对真菌群落组成与地上凋落物与根输入到 SOM 的相对转化之间的关系知之甚少。碎屑输入和清除处理 (DIRT) 实验提供了一个测试此类问题的系统，其中森林土壤的地上凋落物和根输入被长期独立和组合排除。在这项研究中，我们表征了真菌生物量（麦角甾醇）、群落组成（ITS2 元条形码）、在北温带森林 DIRT 实验中根和凋落物排除处理下的群落组装（通过无效模型），我们将真菌群落参数与土壤碳相关联。根而不是垃圾的存在显着区分了真菌群落组成，并推动了更随机的群落组装。根与较高的真菌生物量有关，特别是外生菌根和腐生真菌的生物量，以及较高的土壤碳储量。由此产生的真菌生物量和土壤碳之间的强正相关似乎特别是由腐生生物量驱动的。我们认为真菌群落是将地上和地下植物输入转化为 SOM 的重要媒介，