Data from: Moderately thinning encroaching shrub species is key to balancing rangeland restoration and arthropod biodiversity conservation in Namibia

Abstract

Bush encroachment poses a critical threat to rangeland productivity and ecosystem functioning worldwide, with particularly severe impacts in southern Africa. Although bush thinning (“debushing”) is widely employed as a control measure, its ecological consequences for arthropod communities remain poorly understood. We assess how bush thinning methods (manual vs. chemical) and intensities (50% vs. 100% removal) affect arthropod community composition, abundance, and diversity in bush-encroached rangeland savannah ecosystems dominated by three common encroaching shrub species: Dichrostachys cinerea, Senegalia mellifera, and Terminalia sericea in Namibia. Arthropods were sampled from ground, canopy, and aerial strata across 135 plots representing five treatment combinations during wet and dry seasons. Complete shrub removal (100% thinning through felling) induced the strongest ecological changes, reducing overall arthropod abundance by up to 30%, double the effect observed under moderate felling (50%). Solifugae were highly abundant in fully cleared plots. Functionally significant groups, including pollinators (Thysanoptera), herbivores (Curculionidae), decomposers (Psocodea), and predators (Araneae), responded positively to moderate compared to complete manual thinning. Complete chemical treatments significantly suppressed common herbivorous (Auchenorrhyncha) and sensitive taxa including Coccinellidae and Opiliones. The soil properties further mediated the responses of arthropods among shrub species. The abundance of arthropods increased with near-neutral soil pH, reaching peak in the S. mellifera plots, but declined under elevated phosphorus and organic matter. Synthesis and Applications: Moderate manual thinning (50F) maintained arthropod diversity comparable to untreated controls while reducing shrub dominance, demonstrating that structural heterogeneity buffers biodiversity loss during rangeland restoration in Namibian bush encroached systems. These findings advocate mosaic debushing strategies that preserve vegetation complexity and edaphic mosaics, reconciling bush control with arthropod conservation to ensure long-term savannah ecosystem resilience.