Anthropogenic nitrogen (N) and sulfur (S) deposition can change above- and belowground biodiversity, including root-associated fungi that are tightly linked to plant fitness. We investigated the effect of eleven years of N and S addition on the diversity of root-associated fungal pathogens and mutualists, including ectomycorrhizal fungi (EMF), dark septate endophytes (DSEs), and ericoid mycorrhizal fungi (ERM), in a broadleaf tree-dominated boreal forest using HiSeq sequencing of ITS2 amplicons of root fungal DNA. Long-term N and S addition increased the diversity of root-associated pathogens, notably the abundance of Venturia macularis, which causes aspen leaf and shoot blight, in the forest floor. Nitrogen addition increased the abundance of several N-sensitive EMF taxa and of EMF related to organic-N uptake from the soil, but had little effect on the overall abundance and diversity of EMF. Nitrogen and S addition did not affect the abundance and diversity of DSEs, but N addition decreased the Shannon diversity and evenness of ERM communities in the mineral soil. The changed diversity of root-associated fungal pathogens and mutualists suggests that long-term N and S addition will impact the host plant's capacity for nutrient acquisition and defense against pathogens in the broadleaf-dominated boreal forest.

人为氮（N）和硫（S）的沉积可以改变地上和地下的生物多样性，包括与植物适应性紧密相关的与根相关的真菌。我们调查了阔叶树中添加氮和硫11年对根相关真菌病原体和互惠生（包括外生菌根真菌（EMF），深色隔膜内生菌（DSE）和类固醇菌根真菌（ERM））多样性的影响。根真菌DNA的ITS2扩增子的HiSeq测序确定的北方森林。长期添加氮和硫增加了与根相关的病原体的多样性，尤其是黄斑云母丰富，导致白杨树叶在森林地上枯萎。氮的添加增加了几种对氮敏感的EMF分类单元的丰度以及与从土壤中吸收有机N相关的EMF，但对整体EMF的丰度和多样性影响很小。氮和硫的添加不会影响DSE的含量和多样性，但氮的添加会降低矿质土壤中ERM群落的香农多样性和均匀性。根系相关真菌病原体和互助生物多样性的变化表明，长期添加N和S将影响宿主植物在阔叶为主的北方森林中获取养分和防御病原体的能力。