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ABSTRACTThe degree to which invasive Acaciaspecies affect South Africa’s livestock production has received little attention. We investigated the ecological impacts of Acacia mearnsiiinvasion on forage quality and quantity and on soil resources, along A. mearnsiiinvasion gradients, on South African rangelands and the subsequent conditions following clearing. Grazing capacity was reduced by 72% in densely invaded sites, whereas clearing improved grazing capacity by 66% relative to densely invaded sites within 5 years. In densely invaded sites total grass species basal cover was reduced by up to 42%. As a result, A. mearnsiireduced grazing capacity, from 2 to 8 ha required to support one large stock unit (ha/LSU) in uninvaded and densely invaded sites, respectively. Soil moisture content was lower in densely invaded sites compared with lightly invaded and cleared sites. Plant litter increased from 1.3% to 4.2%, carbon content of the soil increased from 2.0% to 4.0% and nitrogen concentrations increased from 0.1% to 0.2% in response to invasion by A. mearnsii. Clearing resulted in improved grazing capacity within 5 years. These results also showed that, if left uncontrolled, wattle species can reduce livestock carrying capacity within montane grasslands in South Africa.EDITED BYJames Aronson

The roles of edaphic factors and competition in explaining species distribution of Pteronia(family Asteraceae) dominated plant communities, were investigated. Soil characteristics, species plant covers and competitive interactions were determined at three sites (one on a colluvial plain and two on tillite slopes) on the farm Tierberg in the semi-arid Karoo, South Africa. These sites represented areas where Pteroniaspecies replace each other in apparently distinct habitats. Direct (Canonical Correspondence Analysis, CCA) and indirect (Detrended Correspondence Analysis, DCA) gradient analyses gave similar eigen values, indicating that edaphic variables accounted for much of the variation in species data. The first axis of the CCA-biplot separated species on the colluvial plain from those on tillite slopes along a soil texture gradient. The separation of species in the second CCA axis indicated that soil phosphorous, pH, magnesium and calcium levels were also important in determining species distribution patterns. Together, these axes accounted for 50.1% of the variation in the species data. Nearest-neighbour analyses indicated that there were strong inter- and intraspecific competitive interactions at Pteroniacommunity boundaries. If edaphic specialization alone was responsible for Pteroniadistribution patterns, one would expect there to be reduced competition at the boundaries of species overlap. It is concluded that Pteroniaspecies distribution patterns in the Karoo result from the combined effects of soil physico-chemical factors and competition.

The article discusses how investing in wetland restoration is beneficial to the area surrounding the Kromme River in South Africa. According to the author, the Kromme River has been damaged by poor road design and construction, channelization and dredging, as well as illegal farming on the riverbanks. The author stresses that there is an urgent need for research on the potential of Palmiet revegetation as a means of wetland restoration.

The article discusses the ecological management of habitat corridors used for public service. Due to increasing population and a growing economy, landscapes are converted into concrete-laden corridors for production and transportation causing fragmentation of habitats. But the author believes that these corridors can also be utilized to link habitat fragments through road reserves best practices.