Diversity indices and structural metrics of wild fruit tree communities in Zuru Local Government Area, Kebbi State, Nigeria

This study assessed the ecological diversity and structural characteristics of wild fruit tree species across six districts of Zuru Local Government Area. A systematic line transect design was used, comprising 18 plots (200 m × 200 m) subdivided into four quadrats (100 m × 100 m), covering a total area of 72 ha. All trees with diameter at breast height (DBH) ≥ 5 cm were identified and measured. A total of 3,438 individual trees belonging to 43 species were recorded. Mean DBH ranged from 9.42 ± 2.72 cm in Guiera senegalensis to 74.45 ± 8.60 cm in Parkia biglobosa, while mean height ranged from 3.70 ± 0.65 m to 14.28 ± 0.74 m, indicating substantial structural variability. Significant differences in DBH and height occurred among districts (Kruskal–Wallis, p < 0.001), with Manga recording the highest mean DBH (46.36 cm) and Dabai the lowest (24.15 cm). The Shannon–Wiener diversity index (H′) ranged from 1.22 in Ushe to 2.37 in Manga, indicating generally low to moderate species diversity. Simpson’s diversity index (1 − D) ranged from 0.54 to 0.86, while Pielou’s evenness (J′) ranged from 0.49 to 0.75. Detarium microcarpum recorded the highest Importance Value Index (IVI = 63.59), dominating three districts. Universal flowering and fruiting observed during sampling reflected peak fruiting season conditions, while dormancy varied significantly among species across districts (χ², p < 0.001). The findings provide baseline ecological information for biodiversity conservation, sustainable utilization, and food security planning in semi-arid savannah ecosystems.