http://hdl.handle.net/10204/932 2013-06-20T12:30:00Z 2013-06-20T12:30:00Z Hughes, DA Gush, M Tanner, J Dye, P http://hdl.handle.net/10204/6803 2013-06-18T21:55:14Z 2013-02-01T00:00:00Z

Title: Using targeted short-term field investigations to calibrate and evaluate the structure of a hydrological model Authors: Hughes, DA; Gush, M; Tanner, J; Dye, P Abstract: This study combines the application of a hydrological model with the use of field data derived from short period measurement campaigns at two sites, one a low topography forested area and the other a steep grassland catchment. The main objective was to determine if the structure of the widely used Pitman model could be considered appropriate for simulating the field data. The model is typically applied at coarse spatial and temporal (1 month) scales, while the tests reported here use data from small catchments and are applied in a daily version of the model. The results demonstrate the importance of ensuring that field observations are measuring the same hydrological variables as the model simulations. At one study site, there was a mismatch in the soil moisture data that was corrected by incorporating a two-layer soil algorithm into the model. The model results from both field sites identified the sensitivity of the model to assumptions about evaporative demands and indicate that the model structure is very sensitive to the potential evaporation inputs. The overall conclusion is that the model structure is generally appropriate for simulating the hydrological responses at the two sites, but that there remain some unresolved uncertainties about specific model components and the use of certain types of input data. The study lends support for the future development of a more complete daily version of this widely used model. Description: Copyright: 2013 Wiley Online Library. This is an ABSTRACT ONLY. The definitive version is published in Hydrological Processes, vol. 27(10)

2013-02-01T00:00:00Z Sithole, B Lapierre, L Watanabe, C http://hdl.handle.net/10204/6785 2013-06-12T21:55:31Z 2013-03-01T00:00:00Z

Title: A study of polymerization of aspen (Populus) wood lipophilic extractives by SEC and Py-GC/MS Authors: Sithole, B; Lapierre, L; Watanabe, C Abstract: Studies have been conducted on the formation of polymerised wood resin in model compounds and in lipophilic extracts of aspen. Our studies indicate that polymerization of wood resin components occurs during seasoning of aspen wood. The polymerization probably occurs via oxidation of fatty acids, especially the unsaturated ones, and glyceride components. It results in formation of products that are difficult to dissolve in normal solvents, depending on the extent of the polymerization. Also, the polymerization seems to result in the formation of sterols, compounds that are typically associated with “aspen wax”. This implies that the seasoning practices used in aspen mills can result in the formation of polymerized wood resin that will be difficult to remove if present in pulp and paper products. On the other hand, these problems may be minor compared to using unseasoned wood. Description: Copyright: 2013. Appita. This is the definitive version of the work.

2013-03-01T00:00:00Z Dzikiti, S Schachtschneider, K Naiken, V Gush, M Moses, G Le Maitre, DC http://hdl.handle.net/10204/6521 2013-02-04T21:55:16Z 2013-03-01T00:00:00Z

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

2013-03-01T00:00:00Z Steenkamp, KC Wessels, KJ Van den Bergh, F McFerren, GA Frost, PE Lai, CW Swanepoel, D http://hdl.handle.net/10204/6373 2012-11-26T21:55:35Z 2012-07-01T00:00:00Z

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.

2012-07-01T00:00:00Z