The role of pedodiversity in shaping biodiversity: a quantitative analysis of an alpine pasture

Soil diversity, or pedodiversity, is crucial for understanding ecological processes and biodiversity patterns, as it underpins the structural and functional complexity of ecosystems. In this study, conducted in a 350-hectare alpine pasture in the Central Italian Alps, we analysed and quantified the relationships between soil and vegetation diversity. Using Random Forest models informed by geomorphometric, geological, and vegetation indices, we mapped eight main soil types and six vegetation types. Diversity was quantified with the Gini-Simpson index (for typological heterogeneity) and relative edge density (for spatial fragmentation), which were then combined into a global diversity index. Analysis with Piecewise Structural Equation Modelling (PSEM) and linear mixed model (LMM) revealed a strong positive relationship between pedodiversity, particularly soil fragmentation, and vegetation diversity (PSEM: β = 0.42, 95 % CI = 0.29–0.55, p < 0.001; LMM: β = 1.15, 95 % CI = 0.03–2.27, p = 0.045). Geomorphometric diversity had a significant direct effect on vegetation (β = 0.28, 95 % CI = 0.16–0.40, p < 0.001) and an indirect effect via soil diversity (β = 0.17, 95 % CI = 0.05–0.29, p = 0.005), while the influence of geological diversity was marginal. Overall, the results indicate a bidirectional interaction between biotic and abiotic components: soil complexity supports the coexistence of multiple plant communities, and vegetation can, in turn, contribute to soil differentiation over time through organic inputs and microenvironmental modifications. This study provides both methodological and conceptual insights into the role of pedodiversity in structuring alpine ecosystems, offering practical quantitative tools for spatial planning and the sustainable management of mountain landscapes.