Glomalin-related soil proteins enhance soil health in the rhizospheres of Caatinga trees

Abstract

Glomalin-related soil proteins (GRSP) are linked to soil aggregation, nutrient cycling, and soil carbon dynamics. However, their relationship with native plant species and soil health remains poorly understood in the Caatinga. We quantified total GRSP (T-GRSP), easily extractable GRSP (EE-GRSP), and soil physical and chemical attributes in rhizosphere soils of three Caatinga tree species (Aspidosperma pyrifolium, Cenostigma pyramidale, and Bauhinia cheilantha) at 0–10 and 10–20 cm depths. Soil function scores and a Soil Health Index (SHI) were calculated to evaluate relationships between GRSP fractions and soil functioning. A. pyrifolium showed T-GRSP values 2.81 g kg⁻¹ higher than C. pyramidale and EE-GRSP:T-GRSP ratios 10–15% higher than the other species in the topsoil. Correlation analyses showed positive associations between T-GRSP and Ca²⁺, Mg²⁺, Zn²⁺, Mn²⁺, and soil water content (r > 0.4). Linear regressions revealed significant relationships between T-GRSP and soil carbon, nitrogen, and cation exchange capacity (R² = 0.60, 0.65, and 0.36, respectively). SHI also showed positive relationships with EE-GRSP (R² = 0.56) and T-GRSP (R² = 0.85). These findings suggest species-specific GRSP accumulation patterns and support GRSP fractions as complementary indicators of soil health under semiarid conditions.