Does Eucalyptus grandis invasion and removal affect soils and vegetation in the Eastern Cape Province, South Africa?

Many invasive alien plants drive changes in native community composition, structure and diversity. They alter soil nutrient regimes of native communities and affect native plant recovery outcomes following their removal. We assessed whether Eucalyptus grandis invasion and removal alters the soil physico-chemical properties and native vegetation recovery in the Eastern Cape Province, South Africa. We collected samples from topsoil in E.grandis invaded sites (canopy cover>75%), cleared sites (eight years ago) and native sites (canopy cover>80%) and quantified soil moisture, concentrations of soil macro elements (N, C and P), pH and exchangeable cations (K, Ca, Mg, Na) as well as measured soil water repellency using the Water Droplet Penetration Time and infiltration. We conducted vegetation surveys in plots measuring 10x10m. Invasion by E.grandis had varying effects on soil physico-chemical properties, causing increase in soil pH and P, while decreasing total N and C. The removal of E.grandis also showed varying effects on soil physico-chemical properties, but seems to have further triggered the loss of some soil nutrients (especially soil P). Soil water repellency (a measure of soil compaction) has improved in cleared sites to non-repellent soils compared to repellent soils in invaded site. Eucalyptus grandis reduced species richness of the invaded sites. The presence of native species on cleared sites indicates a positive trajectory towards vegetation recovery. We conclude that E.grandis invasion and removal trigger varying effects on soil properties (both increases and decreases). For soil and vegetation restoration of cleared sites to be effective, active restoration techniques such as soil transfer, nutrient manipulation and native plant seeding should be considered.