Effects of Acacia dealbata Invasion and Removal on Soil and Vegetation in Communal Grasslands in (…)
ABSTRACT
Acacia dealbata has invaded South African grasslands, yet few studies have assessed its invasion and clearing effects on grasslands. We assessed the soil (moisture, repellency, penetration resistance, infiltration rate and hydraulic conductivity) and vegetation (diversity, composition and cover) impacts of A. dealbata invasion and clearing in Upper Tsitsana communal grasslands, Eastern Cape Province of South Africa. Soil and vegetation surveys were conducted on replicated 25 m2 plots in invaded, cleared and uninvaded treatments. Soil compaction and hydraulic conductivity showed no significant differences across treatments (p > 0.05), but monthly variations were observed (p < 0.05). Slightly repellent soils were observed in the invaded and cleared treatments compared to wettable soils in the uninvaded treatment. Acacia dealbata significantly (p < 0.05) affected forb and graminoid species richness and cover but not trees and shrubs. Most alien forbs and graminoids assembled more in the A. dealbata cleared treatment than in uninvaded treatments, indicating that secondary invasion is occurring. We conclude that A. dealbata should be removed to enable ecosystem recovery; however, such ecosystem recovery could be hampered by re-invasion and secondary invasion.