Interactive effects of landscape position and soil diversity drive the spatial variability of soil organic carbon concentration in subalpine soils of Switzerland

Subalpine soils store a significant amount of soil organic carbon (SOC), yet the factors driving its landscape-scale variability remain poorly constrained. Although topography, soil type, soil texture, and moisture are recognised as key drivers of SOC concentration, their interactive effects in subalpine environments remain largely unexplored. In particular, the extent to which soil type shapes landscape-scale SOC patterns remains unclear. In this study, we assessed SOC concentration, soil type, soil moisture conditions and texture, elemental composition across 100 plots in two subalpine catchments in the Swiss Alps. Using factor analysis, we generated three standardised continuous predictors from our dataset, namely, mineral content, sedimentary rock influence and texture index. We investigated the joint influence of these continuous predictors on SOC variability at the landscape scale in a linear mixed-effects model with topography (plain vs. slope areas), soil depth and soil type as additional categorical predictors. We found that soil type diversity was greater on the plain than on the slope, reflecting a greater hydrological heterogeneity. Plains supported a broad spectrum of soils, ranging from organic-rich Histosols to mineral-rich Fluvisols, while slopes were dominated by Cambisols. Although plains exhibited higher moisture and SOC concentration, and slopes were characterised by higher clay fractions and lithogenous elements, topographic position alone was insufficient to explain the