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Primary minerals that enter soils through bedrock weathering and atmospheric deposition can generate poorly crystalline minerals (PCM) that preferentially associate with soil organic carbon (SOC). These associations hinder microbial decomposition and the release of CO2 from soils to the atmosphere, making them a critical geochemical control on terrestrial carbon abundance and persistence. Studies that explore these relationships are typically derived from soil chronosequences that experience negligible erosion and thus do not readily translate to eroding landscapes. Here, we propose a theoretical framework to estimate steady-state PCM density and stocks for hilly and mountainous settings by coupling geochemical and geomorphic mass balance equations that account for soil production from bedrock and dust, soil erosion, PCM formation from weathering, and the transformation of PCMs into crystalline phases. We calculate an optimal erosion rate for maximum PCM abundance that arises because PCMs are limited by insufficient weathering at faster erosion rates and loss via "ripening" into more crystalline forms at slower erosion rates. The optimal erosion rate for modeled hilltop soil is modulated by reaction rate constants that govern the efficiency of primary mineral weathering and PCM ripening. By comparing our analysis with global compilations of erosion and soil production rates derived from cosmogenic nuclides, we show that landscapes with slow-to-moderate erosion rates may be optimal for harboring abundant PCM stocks that can facilitate SOC sequestration and limit turnover. Given the growing array of erosion-topography metrics and the widespread availability of high-resolution topographic data, our framework demonstrates how weathering and critical zone processes can be coupled to inform landscape prioritization for persistent SOC storage potential across a broad range of spatial and temporal scales. [ABSTRACT FROM AUTHOR]

It is now well established that European earthworms are re-shaping formerly glaciated forests in North America with dramatic ecological consequences. However, few have considered the potential invasiveness of this species assemblage in the European arctic. Here we argue that some earthworm species (Lumbricus rubellus, Lumbricus terrestris and Aporrectodea sp.) with great geomorphological impact (geoengineering species) are non-native and invasive in the Fennoscandian arctic birch forests, where they have been introduced by agrarian settlers and most recently through recreational fishing and gardening. Our exploratory surveys indicate no obvious historical dispersal mechanism that can explain early arrival of these earthworms into the Fennoscandian arctic: that is, these species do not appear to establish naturally along coastlines mimicking conditions following deglaciation in Fennoscandia, nor were they spread by early native (Sami) cultures. The importance of anthropogenic sources and the invasive characteristics of L. rubellus and Aporrectodea sp. in the arctic is evident from their radiation outwards from abandoned farms and modern cabin lawns into adjacent arctic birch forests. They appear to outcompete previously established litter-dwelling earthworm species (i.e. Dendrobaena octaedra) that likely colonized the Fennoscandian landscape rapidly following deglaciation via hydrochory and/or dispersal by early Sami settlements. The high geoengineering earthworm biomasses, their recognized ecological impact in other formerly glaciated environments, and their persistence once established leads us to suggest that geoengineering earthworms may pose a potent threat to some of the most remote and protected arctic environments in northern Europe. [ABSTRACT FROM AUTHOR]