Spatial Structuring of Soil Fungal Diversity Associated with Ziziphus lotus (Rhamnaceae) in Arid Agricultural Soils.

Ziziphus lotus (L.) Lam., (Rhamnaceae) a resilient shrub native to Moroccan's arid regions, functions as a keystone species by creating microhabitats that buffer temperature extremes, retain soil moisture, and accumulate organic matter. However, its role in structuring soil fungal diversity and community composition in these environments remains largely unexplored. This study investigated the spatial distribution of fungal communities associated with Z. lotus in barley-planted and non-planted fields. Soil samples were collected at 0, 3, and 6 m from shrub clusters during the barley harvest. The fungal community was dominated by Ascomycota (93.5%). Alpha diversity indices (Shannon-Wiener and Simpson) were significantly higher near shrub bases (0 and 3 m) compared to more distant soils (6 m), indicating a clear decline in diversity with distance (0 m vs. 6 m: p = 0.0012; 3 m vs. 6 m: p = 0.0007). Soil physicochemical parameters, including calcium carbonate content, nitrate, and salinity, significantly influenced fungal diversity (p ≤ 0.05). Beta diversity analysis revealed significant spatial differentiation in fungal community composition (PERMANOVA: p = 0.001). Overall, fungal richness and diversity were highest near shrub. Genera such as Cladosporium, Fusarium, and Alternaria were more abundant near shrub bases, while taxa like Didymellaceae and Alfaria were specially restricted. Functional predictions indicated dominance of fungi with mixed trophic modes (pathotroph-saprotroph-symbiotroph), suggesting ecological plasticity. Despite barley cultivation, the fungal community structure remained largely similar between the planted and non-planted fields. Overall, our findings underscore the ecological importance of Z. lotus as a reservoir of stress-tolerant fungi and as a potential keystone species for restoring degraded arid ecosystems.