http://hdl.handle.net/10204/932 Thu, 23 May 2013 15:51:22 GMT 2013-05-23T15:51:22Z http://hdl.handle.net/10204/6521 Title: Water relations and the effects of clearing invasive Prosopis trees on groundwater in an arid environment in the Northern Cape, South Africa Authors: Dzikiti, S; Schachtschneider, K; Naiken, V; Gush, M; Moses, G; Le Maitre, DC Abstract: Several Prosopis species have been introduced into South Africa in the last century and many of them have become invasive. This study investigates the water relations, effects of clearing, and the seasonal dynamics of groundwater use by invasive Prosopis trees. The trees were growing on deep sandy soils in the floodplain of an episodic river in the arid Northern Cape Province of South Africa. Data were collected on tree water uptake, evapotranspiration and water table depth over different seasons. Effects of tree clearing on groundwater were quantified by comparing data from a Prosopis invaded and an adjacent cleared area. Transpiration rates were less than 1.0 mm/d throughout the year and the trees showed structural and physiological adaptations to the combined low rainfall and low water holding capacity of the soils by developing very narrow sapwood areas and by closing their stomata. The trees abstracted groundwater as evidenced by the decline in borehole water levels in the Prosopis stand before the rainy season. Groundwater savings of up to 70 m3/month could be achieved in spring for each hectare of Prosopis cleared. The study suggests that clearing of invasive Prosopis would conserve groundwater in the arid parts of South Africa. Description: Copyright: 2013 Elsevier. This is the Pre/post print version of the work. The definitive version is published in Journal of Arid Environments, vol. 90, pp 103-113 Fri, 01 Mar 2013 00:00:00 GMT http://hdl.handle.net/10204/6521 2013-03-01T00:00:00Z http://hdl.handle.net/10204/6373 Title: Quantitative comparison of fire danger index performance using fire activity Authors: Steenkamp, KC; Wessels, KJ; Van den Bergh, F; McFerren, GA; Frost, PE; Lai, CW; Swanepoel, D Abstract: Fire danger indices (FDI) describe the conditions that influence ease of ignition, rate of spread and the impact caused by fires. It is used to assess the safety of prescribed burning activities, to improve real-time fire fighting preparedness and in logistic planning of fire fighting resources. In this study historical fire activity from remotely sensed data are compared with various FDIs to identify which index has the strongest statistical relationship with fire occurrences and therefore the highest forecasting potential for fires in the future. Description: Copyright: 2012 IEEE. This is the accepted version of the paper. Reprinted, with permission, from Steenkamp, KC, Wessels, KJ, Van den Bergh, F, McFerren, GA, Frost, PE, Lai, CW and Swanepoel, D. Quantitative comparison of fire danger index performance using fire activity. IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Munich, Germany, 22-27 July 2012, pp. 3375-3378. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of CSIR Information Services' products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org. By choosing to view this document, you agree to all provisions of the copyright laws protecting it. Sun, 01 Jul 2012 00:00:00 GMT http://hdl.handle.net/10204/6373 2012-07-01T00:00:00Z http://hdl.handle.net/10204/6285 Title: Assessing the impacts of Acacia mearnsii (black wattle) on grazing provision and livestock production in South Africa Authors: Yapi, T; O'Farrell, P; Dziba, LE; Esler, K Abstract: The central aim of this research is to develop a deeper understanding of the ecological impacts of A. mearnsiiinvasions on the functioning and productivity of rangelands in South Africa and their ability to sustain livestock production. Description: 4th CSIR Biennial Conference: Real problems relevant solutions, CSIR, Pretoria, 9-10 October 2012 Mon, 01 Oct 2012 00:00:00 GMT http://hdl.handle.net/10204/6285 2012-10-01T00:00:00Z http://hdl.handle.net/10204/6096 Title: Three centuries of managing introduced conifers in South Africa: benefits, impacts, changing perceptions and conflict resolution Authors: Van Wilgen, BW; Richardson, DM Abstract: Alien conifers, mainly pines, have been planted in South Africa for a range of purposes for over 300 years. Formal plantations cover 660 000 ha of the country, and invasive stands of varying density occur on a further 2.9 million ha. These trees have brought many benefits but have also caused unintended problems. The management of alien conifers has evolved in response to emerging problems such as excessive water use by plantations of conifers, changing values and markets, and the realities of a new ecological order brought about by invasive alien conifers. This paper reviews the history of conifer introductions to South Africa, the benefits and impacts with which they are associated, and the ongoing and evolving research that has been conducted to inform their management. The South African approach has included taking courageous steps to address the problem of highly invasive species that are also an important commercial crop. These interventions have not, however, had the desired effect of both retaining benefits from formal plantations while simultaneously reversing the trend of growing impacts associated with self-sown invasive stands. We suggest that different approaches need to be considered, including the systematic phasing out of commercial forestry in zones where it delivers low returns, and the introduction of more effective, focussed and integrated, region-specific approaches to the management of invasive stands of conifers. These steps would deliver much improved economic outcomes by protecting valuable ecosystem services, but will require political commitment to policies that could be unpopular in certain sectors of society. Description: Copyright: 2012 Elsevier. This is an ABSTRACT ONLY. Tue, 01 May 2012 00:00:00 GMT http://hdl.handle.net/10204/6096 2012-05-01T00:00:00Z