Passive restoration of native woody vegetation and soil properties following Lantana camara clearing in the Kavango–Zambezi Transfrontier Conservation Area, Zimbabwe

Résumé fourni par la source

Lantana camara L. is a widespread invasive shrub that suppresses native woody vegetation and alters soil properties in southern African savannas. Passive restoration following invasive species removal is widely promoted as a cost-effective strategy, yet evidence from Transfrontier Conservation Areas is limited. This study assessed vegetation and soil responses eight years after mechanical clearing of L. camara at two sites in the Kavango–Zambezi Transfrontier Conservation Area, Zimbabwe: the Victoria Falls Rainforest protected area and adjacent Ndlovu Communal Land. Using a space-for-time design, 42 plots (25 × 25 m) were surveyed across cleared, invaded, and uninvaded patches. Native woody species composition and structure were assessed, and soil samples (0–15 cm depth) analysed for selected chemical properties. Cleared plots showed numerically higher native woody species richness (10.3–11.9 vs. 4.3–4.9) and stem density (468–493 vs. 180–208 stems ha⁻¹) than invaded plots, approaching uninvaded controls (16.1–18.3 species; 644–752 stems ha⁻¹). Significant treatment effects occurred for Shannon–Wiener diversity (2.0–2.1 vs. 0.9–1.3; p = 0.024), stem height ( p < 0.001), mean stem diameter ( p = 0.012), and canopy cover ( p = 0.042), but not for species richness ( p = 0.089) or stem density ( p = 0.075). Mean stem diameter was lower in cleared plots (≈30 ± 10 cm) than controls (60–70 ± 10 cm). Canopy cover remained substantially below control levels. Soil properties showed weak responses with no significant overall treatment effects, although pH differed in the communal area (one-way ANOVA, p = 0.006). Re-invasion by L. camara occurred in 43% of cleared communal plots. These findings indicate that passive restoration can promote meaningful recovery of native woody vegetation within eight years, particularly diversity and structure, but soil recovery is slower and trajectories remain vulnerable to re-invasion.

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