Primary productivity of forest ecosystems depends on the availability of plant‐essential mineral nutrients. Because nutrient demand of trees often exceeds nutrient supply from rock, tree nutrition is sustained by efficient reutilization of organic‐bound nutrients. These nutrients are continuously returned from trees to the forest floor in litterfall. However, over millennia nutrient limitation may develop in landscapes from which nutrients are permanently lost by drainage and erosion. Such a deficit is prevented if advection of unweathered bedrock toward the surface as driven by erosion continuously supplies fresh nutrients. Yet the mechanisms and the depth range over which this deep nutrient resource is accessed are poorly known. We show that in two montane temperate forest ecosystems in the Black Forest and Bavarian Forest the geogenic source of nutrients was found within a depth zone of several meters. This deep zone contains a large pool of biologically available nutrients. We applied isotope ratios as proxies for nutrient uptake depth, and we tracked the regolith depth at which the isotope ratios of Sr/Sr and Be(meteoric)/ Be match the respective values in plant tissue. We mapped the depth distribution of the biologically available calcium‐bound form of the most plant‐essential mineral nutrient phosphorus and found that the depth of phosphorus availability is as deep or even deeper as the range defined by the isotope ratios. We conclude that nutrient supply from a regolith depth of several meters is critical for forest ecosystem function in landscapes of moderate hillslopes and rainfall that are affected by permanent nutrient loss.

中文翻译：

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源自深层风化层的矿物质养分维持山地温带森林生态系统的长期营养

森林生态系统的初级生产力取决于植物必需矿质营养素的可用性。由于树木的养分需求通常超过岩石的养分供应，因此通过有机结合养分的有效再利用来维持树木营养。这些养分在枯枝落叶中不断从树木返回到森林地面。然而，在由于排水和侵蚀而永久丢失养分的景观中，可能会出现数千年来养分限制。如果由侵蚀驱动的未风化基岩向地表平流不断提供新鲜养分，则可以防止这种不足。然而，人们对这种深层营养资源的获取机制和深度范围知之甚少。我们表明，在黑森林和巴伐利亚森林的两个山地温带森林生态系统中，在几米的深度区域内发现了营养物质的地质来源。这个深区包含大量生物可利用的营养物质。我们应用同位素比率作为养分吸收深度的代理，并跟踪了 Sr/Sr 和 Be（陨石）/Be 的同位素比率与植物组织中的相应值相匹配的风化层深度。我们绘制了植物必需矿物质营养磷的生物可利用钙结合形式的深度分布图，发现磷的可利用深度与同位素比率定义的范围一样深甚至更深。