Evaluation of number of restoration technologies in two degraded areas in the Mpumalanga Province, South Africa

Abstract

This study was conducted to evaluate different scientific techniques to restore degraded rangelands. It involves field-descriptive, fieldanalytical and laboratory-analytical assessments. The work took place in a degraded savanna (lowveld) ecosystem, at two sites characterised by duplex soils . The two sites are Mthethomusha Game Reserve (MGR) of Mpumalanga Parks Board and Sabi Sand Game Reserve, a private game reserve (SSPGR). The site at Mthethomusha game reserve is a fenced denuded area around a buffalo boma (in South Africa, a protective enclosure for domestic and game animals for research purposes is referred to as a boma) . The Sabi Sand private game reserve site represents an open , heavily degraded, flat rangeland . This site was water logged during the month of February, three months after the trials. Both study sites fall within the duplex ecological unit. Duplex soils refer to soils with relatively permeable topsoil that abruptly overlay a very slowly permeable diagnostic horizon that is not a hardpan. The duplex soils at the SSPGR and MGR study sites are classified under the Estcourt form. Soil samples were taken from both sites to analyse their physical and chemical properties . The effects of different restoration techniques at these two degraded areas were examined and compared . The aim was to establish the appropriate restoration techniques suitable for the two sites and to recommend the techniques to land owners with similar ecological problems. Different restoration treatments , which included the combination of organic matter treatments, brush packing , ripping, over-sowing, and lime application, were implemented. At both restoration sites, all the sub-plots, with the exception of the control plots, were ripped by rip-plough . The same mixture of Chloris gayana, Cenchrus ciliaris, Digitaria eriantha and Panicum maximum was used in the over-sowing treatment at both sites . The establishment of the seedlings, vegetative and reproductive growth forms from the grass mixture of all the treatments were compared to each other. Sites restored at MGR were compared to sites at SSPGR. The restoration sites were monitored for a period of two seasons between the years 1999/2000 and 2000/ 2001. The surveys that were carried out in this study are: frequency (through the use of a wheel point) , density, population dynamics, importance value (through the use of a quadrat) and soil analysis. Frequency and density tables and graphs were

constructed from data collected at both sites through the use of the Microsoft Excel program and statistical analysis. Principal Component analysis (PCA), Canonical Correspondence analysis (CCA) and Redundancy analysis (RDA) ordinations with the CANOCO program were used to identify positive and negative correlation and to quantify data and deductions made from tables and graphs. They were also used to compare species and environmental by habitat data as well as species and experimental treatment data. Results from the field analytical assessments of soil samples from both sites and the different experimental treatments are discussed. The results from the soil analysis indicated that the soil at MGR is highly sandy with a high calcium concentration . It has a lower sodium content than at SSPGR, but is deficient in phosphorus . The analysis results also indicated a high sandy soil with high calcium concentration at SSPGR. However, the analytical values of calcium, sodium and magnesium at this site were relatively high especially the concentration of sodium and magnesium which gave the soil the characteristics of a saline soil. During the first survey in 1999/2000 the frequency and density of C. gayana, P. maximum and C. ciliaris were higher at Mthethomusha game reserve, the fenced site than at Sabi Sand private game reserve, the open site, where the game animals roam freely. Rip plough cultivation at both sites stimulated the germination and establishment of most species in the soil seed bank as compared to the control plots . For a quicker establishment of seedlings from the soil seed bank as well as sown-in species, ripping is recommended as a treatment in restoration of degraded duplex soil types . It was also observed that C. gayana and C. ciliaris responded rapidly in sub-plots with the rip-organic-seed application and controlled grazing as compared to rip-seed application, with or without grazing . This is due to the good influence of organic material in the soil which include : improvement of soil structure, reduction of soil erosion, regulating effect on soil temperature, reduction of plasticity, cohesion, and stickiness of clay soils and helping the soil to store more moisture . It therefore seems that if degraded sites are restored with the addition of organic materials after rip plough application, rapid results could be achieved in improving the state of the area . Among the sown-in species in the seed mixture, C. gayana was outstanding in its rapid response to both rip plough cultivation and organic treatment by spreading with its stoloniferous growth form to cover the soil surface. Through this growth pattern, its stems

(stolons) and leaves interact with water flow at the ground surface, resulting in higher interception storage and higher volume of water for infiltration. It also provides greater soil surface roughness and obstacles for the flow of air and water, reducing their velocity. This stoloniferous nature makes C. gayana a suitable pioneer species, which is therefore highly recommended for inclusion in restoration projects. From this study it was also noted that all the other sown-in species established well at MGR (the fenced site). The seedlings of C. ciliaris, however, do not withstand grazing and water logged areas. At the SSPGR study site, which is also sandy, C. ciliaris seldom developed to the vegetative growth stage . At MGR, C. ciliaris was a co-dominant species with C. gayana in most of the sown-in treatment plots. At the SSPGR, where the game animals grazed freely at the study site , C. ciliaris was absent in most of the treated plots. The few seedlings recorded during the second survey were in the plots treated with brush . This absence could be attributed to the fact that it is a palatable species that is heavily grazed by game animals when not protected . Rainfall could have been another contributing factor to the absence of C. ciliaris at SSPGR. During the first season there was a higher rainfall at both sites, which caused SSPGR to be waterlogged. Cenchrus ci/iaris, which is adapted to dry, well-drained sandy soils could not establish in the waterlogged situation at SSPGR. It is recommended that C. ciliaris should not be used in restoration projects in waterlogged areas . The numbers of seedlings recorded for the rest of the sown-in species at SSPGR were lower compared to the numbers at MGR. It is therefore recommended that, for a better species establishment, species richness and sustainability, restoration sites in game reserves and communally managed rangelands with over-sowing treatments should either be fenced or protected with brush packing . It was further observed from the results of the current study that the rip plough cultivation stimulated the establishment of the seedlings of the sown-in species as well as seedlings from the soil seed - bank. Rip plough cultivation is therefore a suitable technique that can be included in restoration projects on degraded duplex soil types. From the results of these assessments, rangelands with a duplex soil type of the above soil conditions can be restored through the application of appropriate techniques as tested in this study.