The vegetation communities of the Save Valley Conservancy in southeastern Zimbabwe

Abstract

Vegetation maps are critical tools for the effective management of savanna ecosystems. To inform conservation planning, we mapped, classified and described the diverse vegetation of the Save Valley Conservancy in southeastern Zimbabwe. We utilised a combination of intensive field surveys across 310 sample plots and supervised object-based image analysis of Sentinel-2 satellite imagery. To assess the environmental drivers of vegetation distribution, we analysed 20 topoedaphic and landscape variables using principal component analysis and linear discriminant analysis. We identified 25 distinct vegetation types, recording a total of 315 plant species (247 woody and 68 herbaceous). The landscape was predominantly characterised by woodland communities, with Colophospermum mopane being the most extensive. In accordance with the Plant Available Moisture and Available Nutrients framework, soil physical and chemical properties, specifically clay content, exchangeable base cations and available phosphorus, were identified as the primary bottom-up environmental determinants sorting the plant communities. However, our findings indicate that edaphic constraints alone are insufficient to explain the present vegetation patterns and structural heterogeneity observed across the conservancy. The current, highly variable structural state of these woodlands reflects an active ecological trajectory driven by intense top-down disturbances, specifically the legacy of historical cattle ranching and fire suppression (driving widespread shrub densification) compounded by a rapidly growing elephant population. Establishing the spatial distribution of the conservancy’s vegetation and understanding this dynamic interplay between bottom-up soil constraints and top-down disturbance regimes provides a critical scientific foundation for informed management decisions, particularly regarding fire planning, wildlife stocking rates and the targeted mitigation of bush encroachment.