Effects of agroforestry practices on insect abundance, richness, and diversity, in transformed ecosystems of the semi-arid area, Dodoma, Tanzania

Abstract

This study investigated surface-active insect abundance, diversity, and community composition to evaluate the conservation potential of agroforestry in transformed semi-arid ecosystems. Insects were sampled using pitfall traps across four land-use types: afforested sites, agroforestry plots, shrubland, and bushland. A total of 2,889 insects representing 53 species from 14 orders were collected. Afforested habitats supported the highest insect abundance (30%, n=863), while shrubland exhibited the greatest species richness (36 species) and diversity (Shannon = 1.86; Simpson = 0.75). Agroforestry ranked second in abundance (28%, n=810) but had the lowest diversity and richness, with high species dominance driven by Pachycondyla tarsata . Bushland showed relatively low abundance but moderate diversity and evenness. Community composition analyses revealed a clear visual separation, but statistically insignificant differences in insect assemblages across habitats (NMDS stress = 0.068, F = 0.96, p = 0.546). By contrast, PERMDISP detected highly significant differences in dispersion (p < 0.001), demonstrating that within-habitat variability rather than habitat type per se was the primary driver of community structure. Regression models confirmed that afforested habitats significantly influenced higher insect abundance and diversity, whereas other habitats showed no meaningful differences. The findings suggest that agroforestry enhances insect abundance but supports fewer species and lower diversity than shrubland and afforested habitats. Conservation strategies in semi-arid landscapes should therefore emphasize maintaining habitat heterogeneity and structural complexity to stabilize insect communities and sustain ecosystem services.