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Black Wattle (Acacia mearnsii, Fabaceae) represents one of the most important invasive alien species that have spread over large catchment areas in South Africa, with well documented effects on reducing water yield and in altering indigenous plant structure. Nationwide measures are being applied to eliminate this species, and different protocols are being evaluated for restoring heavily invaded areas, such as the rehabilitation site at the Lower Witteklip River in the Eastern Cape Province.
As a part of the Kouga River Rehabilitation Pilot Project, this study described four topics: (a) the degradation state of the area which was concluded that it was related to the presence of Black Wattle, (b) revegetation practices which were established as an experiment to evaluate the guilds which could be used to rehabilitate similar areas, defining as a priority from the early state of the experiment, to use a vast mix of species and densities as treatments, (c) effects of different biomass loads on burning and on the temperature to which soil was exposed in which it was observed that values dependent on the biomass load and not on the sampling site and (d) an assessment of the effects of fire and transformation of wood to chips, as methods to remove biomass left from clearing from the site which from the data available, there were not a definitive conclusion on which one of the treatments influenced on the results, mainly because of the lack of time for the soil seedbank to be fully germinated, and due to a mistake in the methodology by not segregating between the indigenous species group. This technical report also includes an assessment and some recommendations for the activities applied to the Lower Witteklip Rehabilitation Site and for the experiments.