Mycorrhizal fungi associated with boreal trees and ericaceous shrubs are central actors in organic matter (OM) accumulation through their belowground carbon allocation, their potential capacity to mine organic matter for nitrogen (N) and their ability to suppress saprotrophs. Yet, interactions between co-occurring ectomycorrhizal fungi (EMF), ericoid mycorrhizal fungi (ERI), and saprotrophs are poorly understood. We used a long-term (19 yr) plant functional group manipulation experiment with removals of tree roots, ericaceous shrubs and mosses and analysed the responses of different fungal guilds (assessed by metabarcoding) and their interactions in relation to OM quality (assessed by mid-infrared spectroscopy and nuclear magnetic resonance) and decomposition (litter mesh-bags) across a 5000-yr post-fire boreal forest chronosequence. We found that the removal of ericaceous shrubs and associated ERI changed the composition of EMF communities, with larger effects occurring at earlier stages of the chronosequence. Removal of shrubs was associated with enhanced N availability, litter decomposition and enrichment of the recalcitrant OM fraction. We conclude that increasing abundance of slow-growing ericaceous shrubs and the associated fungi contributes to increasing nutrient limitation, impaired decomposition and progressive OM accumulation in boreal forests, particularly towards later successional stages. These results are indicative of the contrasting roles of EMF and ERI in regulating belowground OM storage.

中文翻译：

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Ericoid 灌木塑造真菌群落并抑制北方森林中的有机物质分解。

与北方树木和杜鹃花灌木相关的菌根真菌是通过其地下碳分配、它们挖掘有机物获取氮 (N) 的潜在能力以及它们抑制腐生菌的能力而在有机物 (OM) 积累中的核心参与者。然而，对同时发生的外生菌根真菌 (EMF)、石蜡菌根真菌 (ERI) 和腐生菌之间的相互作用知之甚少。我们使用了一项长期（19 年）的植物功能组操作实验，去除了树根、杜鹃花灌木和苔藓，并分析了不同真菌行会的反应（通过元条形码评估）及其与 OM 质量相关的相互作用（通过中期评估红外光谱和核磁共振）和分解（垃圾网袋）跨越 5000 年的火灾后北方森林时间序列。我们发现，杜鹃花灌木和相关 ERI 的去除改变了 EMF 群落的组成，在时间序列的早期阶段发生了更大的影响。去除灌木与提高 N 可用性、凋落物分解和顽固 OM 部分的富集有关。我们得出的结论是，增加缓慢生长的杜鹃花灌木和相关真菌的丰度有助于增加北方森林的养分限制、分解受损和渐进性 OM 积累，特别是在演替后期。这些结果表明 EMF 和 ERI 在调节地下 OM 储存中的对比作用。去除灌木与提高 N 可用性、凋落物分解和顽固 OM 部分的富集有关。我们得出的结论是，增加缓慢生长的杜鹃花灌木和相关真菌的丰度有助于增加北方森林的养分限制、分解受损和渐进性 OM 积累，特别是在演替后期。这些结果表明 EMF 和 ERI 在调节地下 OM 储存中的对比作用。去除灌木与提高 N 可用性、凋落物分解和顽固 OM 部分的富集有关。我们得出的结论是，增加缓慢生长的杜鹃花灌木和相关真菌的丰度有助于增加北方森林的养分限制、分解受损和渐进性 OM 积累，特别是在演替后期。这些结果表明 EMF 和 ERI 在调节地下 OM 储存中的对比作用。特别是在后来的演替阶段。这些结果表明 EMF 和 ERI 在调节地下 OM 储存中的对比作用。特别是在后来的演替阶段。这些结果表明 EMF 和 ERI 在调节地下 OM 储存中的对比作用。