Aims In the Swedish sub-Arctic, mountain birch ( Betula pubescens ssp. czerepanovii ) forests mediate rapid soil C cycling relative to adjacent tundra heaths, but little is known about the role of individual trees within forests. Here we investigate the spatial extent over which trees influence soil processes. Methods We measured respiration, soil C stocks, root and mycorrhizal productivity and fungi:bacteria ratios at fine spatial scales along 3 m transects extending radially from mountain birch trees in a sub-Arctic ecotone forest. Root and mycorrhizal productivity was quantified using in-growth techniques and fungi:bacteria ratios were determined by qPCR. Results Neither respiration, nor root and mycorrhizal production, varied along transects. Fungi:bacteria ratios, soil organic C stocks and standing litter declined with increasing distance from trees. Conclusions As 3 m is half the average size of forest gaps, these findings suggest that forest soil environments are efficiently explored by roots and associated mycorrhizal networks of B. pubescens . Individual trees exert influence substantially away from their base, creating more uniform distributions of root, mycorrhizal and bacterial activity than expected. However, overall rates of soil C accumulation do vary with distance from trees, with potential implications for spatio-temporal soil organic matter dynamics and net ecosystem C sequestration.

中文翻译：

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林线林中菌根圈相互作用塑造土壤有机质动态的空间格局

目标 在瑞典亚北极地区，山桦 ( Betula pubescens ssp. czerepanovii ) 森林介导了相对于相邻苔原荒地的快速土壤碳循环，但人们对森林中个别树木的作用知之甚少。在这里，我们调查了树木影响土壤过程的空间范围。方法 我们测量了呼吸、土壤碳储量、根和菌根生产力以及真菌：细菌比率，沿着从亚北极交错林中山桦树径向延伸的 3 m 横断面的精细空间尺度。根和菌根生产力使用内生技术量化，真菌：细菌比例通过 qPCR 确定。结果呼吸、根和菌根的产生都没有沿着横断面变化。真菌：细菌比例，土壤有机碳储量和立枯物随着与树木距离的增加而减少。结论 由于 3 m 是森林间隙平均大小的一半，这些发现表明 B. pubescens 的根和相关的菌根网络有效地探索了森林土壤环境。个别树木在远离其基部的地方施加影响，产生比预期更均匀的根、菌根和细菌活性分布。然而，土壤碳积累的总体速率确实随着与树木的距离而变化，对时空土壤有机质动态和净生态系统碳固存具有潜在影响。个别树木在远离其基部的地方施加影响，产生比预期更均匀的根、菌根和细菌活性分布。然而，土壤碳积累的总体速率确实随着与树木的距离而变化，对时空土壤有机质动态和净生态系统碳固存具有潜在影响。个别树木在远离其基部的地方施加影响，产生比预期更均匀的根、菌根和细菌活性分布。然而，土壤碳积累的总体速率确实随着与树木的距离而变化，对时空土壤有机质动态和净生态系统碳固存具有潜在影响。