• As Arctic soils warm, thawed permafrost releases nitrogen (N) that could stimulate plant productivity and thus offset soil carbon losses from tundra ecosystems. Although mycorrhizal fungi could facilitate plant access to permafrost‐derived N, their exploration capacity beyond host plant root systems into deep, cold active layer soils adjacent to the permafrost table is unknown.
• We characterized root‐associated fungi (RAF) that colonized ericoid (ERM) and ectomycorrhizal (ECM) shrub roots and occurred below the maximum rooting depth in permafrost thaw‐front soil in tussock and shrub tundra communities. We explored the relationships between root and thaw front fungal composition and plant uptake of a ¹⁵N tracer applied at the permafrost boundary.
• We show that ERM and ECM shrubs associate with RAF at the thaw front providing evidence for potential mycelial connectivity between roots and the permafrost boundary. Among shrubs and tundra communities, RAF connectivity to the thaw boundary was ubiquitous. The occurrence of particular RAF in both roots and thaw front soil was positively correlated with ¹⁵N recovered in shrub biomass
• Taxon‐specific RAF associations could be a mechanism for the vertical redistribution of deep, permafrost‐derived nutrients, which may alleviate N limitation and stimulate productivity in warming tundra.

中文翻译：

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真菌生物素对冻土来源永久冻土的苔原植物的吸收

• 随着北极土壤变暖，融化的永冻土释放出的氮（N）可以刺激植物的生产力，从而抵消苔原生态系统造成的土壤碳损失。尽管菌根真菌可以促进植物获取永冻土来源的氮，但是它们对宿主植物根系以外的探索能力超出了永冻土表层深，冷的活性层土壤，这一点尚不清楚。
• 我们对根相关真菌（RAF）进行了表征，该真菌定植于类胡萝卜素（ERM）和根外生灌木（ECM）灌木根中，并发生在草丛和灌木冻原社区的多年冻土融化前土壤最大生根深度以下。我们探讨了在冻土边界处施用的¹⁵ N示踪剂的根和融化锋面真菌成分与植物吸收之间的关系。
• 我们显示，ERM和ECM灌木在解冻前沿与RAF相关联，为根与多年冻土边界之间的潜在菌丝体连通性提供了证据。在灌木和苔原社区中，RAF与融化边界的连接无处不在。根和解冻前土壤中特定RAF的发生与灌木生物量中回收的¹⁵ N呈正相关
• 分类单元特有的RAF关联可能是深层，多年冻土源性养分垂直重新分配的一种机制，这可能减轻氮素的限制并刺激苔原变暖。