Eutrophic soils and weathering levels influence the distribution of seasonally dry forests in Brazil

Abstract

Seasonally Dry Forests, or ‘Dry Forests,’ are characterized by deciduous vegetation that sheds leaf during the dry season due to strong soil moisture stress. Despite their ecological significance, as part of the Atlantic Forest realm, research on the diversity, genesis, and soil-vegetation interactions in these ecosystems remains limited. This study investigated the soil attributes of Dry Forests of an ecotonal zone, comparing with the neighboring biomes, the Caatinga (Steppe Savanna) and Cerrado (Brazilian Savanna). We analyzed 16 soil profiles, evaluating their physical, chemical, and mineralogical properties using Principal Component Analysis (PCA). Dry Forest soils (DFS) showed higher amounts of exchangeable cations such as Ca²⁺, Mg²⁺, and K⁺ (Sum of Bases: 2.84–14.79 cmol_c dm⁻³ in the surface horizons) and no detectable Al³⁺. The clay fraction of DFS is mainly illite and kaolinite. The PCA results (PC1: 29.4 %) revealed that Dry Forest soils, particularly on limestone, are more fertile than adjacent Caatinga and Cerrado soils. In contrast, according to the interpretation of PC2 (19.5 %) Cerrado soils are much more weathered and nutrient-depleted (Sum of Bases: 0.37–1.29 cmol_c dm⁻³ in the surface horizons), while Caatinga soils exhibit an intermediate fertility (Sum of Bases: 1.48–21.81 cmol_c dm⁻³ in the surface horizons), and less weathered. The lithologies under DFS at northern Minas Gerais are limestones of the Bambuí Group, resistant sedimentary rocks of the Macaúbas Group, and Granite/gneisses of the Crystalline Basement, which strongly influence soil fertility, mineralogy, and weathering degree. The higher nutrient levels and organic matter contents (2.05–12.03 % in the surface horizons) in DFS support greater productivity and biomass accumulation. These findings highlight the ecological significance of DFS on diverse geological substrates, offering insights for conservation, sustainable management, and ecological restoration in the face of increasing deforestation and land degradation threats.