The effects of fire and mechanical clearing were investigated for their potential in assisting with the eradication of Chromolaena odorata (previously Eupatorium odoratum). The study was divided into two focus areas, the first focused on mechanical clearing of dense stands of C. odorata on three sites and the second focused on the long term influences of a single burn on C. odorata plants in the different size categories. For mechanical clearing, two key issues were investigated; namely whether this type of clearing procedure was effective in dense C. odorata stands and whether rehabilitation was necessary in these cleared areas. The study was conducted from July 2002 to June 2004. The area was subject to a severe drought throughout the duration of the study. The severe drought had a large influence on the result in both focus areas. A bulldozer was found to be a very effective at clearing dense C. odorata stands. Results from the mechanical clearing study showed that there was still a large viable grass seed population in the areas that had been covered by a dense stand of C. odorata plants for over three years. Thus, indigenous plants were able to re-colonize the area after removal of C. odorata without human intervention, even thought the area was experiencing a severe drought. The density of C. odorata seedlings emerging in the cleared areas was far lower than expected. The C. odorata density in the permanent plots, for seedlings that germinated in the first season after clearing (SeptemberOctober 2002), was only 0.25,0.03 and 0.72 per 5 m2 in the three sites respectively by the end of the study in June 2004. For the C. odorata seedlings that germinated in the second season (September-October 2003) the density was, 0.5, 0.56 and 1.06 per 5 m2 in the three sites respectively by the end of the study in June 2004. It was suspected that the drought influenced seed germination. Unfortunately the number of C. odorata seedlings was so low, that no significant relationship could be found between grass and C. odorata seedling density. By the end of the study the grass fuel mass in all the rehabilitated sites was already over 3000 kg ha-1, even though the area was experiencing a severe drought. This grass fuel load, when burnt, will assist land managers in controlling C. odorata plants, especially seedlings. Very few other alien invasive plant species emerged in the cleared areas. At the Mhlosinga site, Senna pendula made up less than one percent of the herbaceous species composition and only a single Ricinus communis plant was recorded. No alien plant species were recorded on the other two sites. Results from the burning trials revealed that plants in all the size categories were affected by fire. Greater fuel masses and fire intensities were required to kill larger C. odorata plants relative to smaller ones. Fire was found to be very effective at eliminating small and medium size C. odorata plants. Fire applied as a once off treatment had a significant long-term effect on the C. odorata population. The following fuel loads were required to achieve 80% mortality in this 11 study: for small plants a fuel load of over 4000 kg ha-I, for medium plants a fuel load over 4200 kg ha-I and for large plants a fuel load over 4600 kg ha-I. Little difference could be detected between a head or a back burn, as both fire types had their own advantages and disadvantages. Although some of the C. odorata plants in the burnt plots had not perished by the time of the first investigation, following the burn (February 2003), by the time of the second investigation (June 2004), many of these plants had eventually succumbed. These results highlighted the fact that plants which are damaged by fire were more likely to persish during an extended droughts period, than plants which were not subjected to fire. Results from the control plots, in the burning trials, for medium and large plants showed dramatic increases in density over time. Tagged individuals from the control plots did reveal that some of the medium and large plants did die during the drought, although the amount was negligible when compared to the number of new plants growing into the new size categories. A large proportion of the small plants in the control plots also survived the drought with many of them even growing into the medium category. The difference between the control plots and the burnt plots was obvious and significant, especially once the fuel mass exceeded 3783 kg ha-I. Results from this study show that fire can be used as a very effective tool in assisting land managers to control C. odorata in open savanna bushveld. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

The Ngorongoro Crater is a volcanic caldera located within the Ngorongoro Conservation Area in Tanzania. The Crater comprises a flat grassland plain surrounded by steep, bushy walls. It contains extremely high densities of animals and is ecologically the central feature of Ngorongoro Conservation Area. The management of the Ngorongoro Crater has changed significantly in recent times, with cattle being removed and fire excluded about 30 years ago. A detailed vegetation assessment was carried out in the Crater floor by Herlocker & Dirschl in 1972. Since then noticeable changes in vegetation structure and composition, with associated changes in wild herbivore numbers have occurred. The original vegetation survey was repeated in this study as accurately as possible using similar point-based techniques in order to quartify changes and form a baseline for management decision-making and future monitoring. In addition to repeating the vegetation survey, the standing biomass was estimated using a Pasture Disc Meter with associated calibration equations. Data were summarised using multivariate classification and ordination techniques in order to delineate six Homogenous Vegetation Units (HVUs) which can be used for management and management planning purposes, define transects and HVUs in terms of dominant species, describe the main species in relation to their occurrence in different associations and determine the fuel load of the standing crop. A key grass species technique was developed for rapid assessment of the Crater rangeland by the Ngorongoro Conservation Area staff who only need to be familiar with the dominant species. Bush surveys using a point centred quarter technique were conducted along transects in two distinct vegetation types, namely the Lerai Forest and Ngoitokitok Acacia xanthophloea forests and the lower caldera scrub vegetation. The data collected from these transacts were analysed to determine density and composition of the vegetation in the various height classes and the overall structure of the vegetation communities, A range monitoring system in conjunction with a controlled burning programme has been developed to provide an objective means of managing the- rangeland of the Ngorongoro Crater. Data revealed that changes have taken place in the vegetation, with a trend towards dominance by taller grasses and dominance by fewer species. Lack of fire has probably contributed to these changes. Reincorporating fire in the crater is recommended. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

A grazing trial investigating the effect of season of grazing and stocking rate initiated at the Nortier Experimental Farm in 1988 provided an opportunity to assess the response of the veld to both grazing and environmental influences in an arid environment. The trial allowed an assessment of the relative influence of internal (equilibrium) and external (non-equilibrium) forces on the dynamics of an arid rangeland. This study involved the analysis of a nine year data set stretching from 1988 to 1996 and served to provide evidence supporting the existence of an equilibrium/non-equilibrium continuum in rangeland dynamics. The most significant implication of this result is that rangeland systems should not be classified as either equilibrial or non-equilibrial, but rather according to a continuum extending between equilibrium and non-equilibrium poles. The exact position of any system on this continuum is a function of the relative influence of internal and external forces on its species dynamics. The dynamics of the veld at the Nortier Experimental Farm showed significant response to both grazing and environmental variables suggesting conformity to both equilibrial and non-equilibrial paradigms. Both ordination and analysis of variance highlighted the importance of rainfall particularly in the fluctuations of the predominant grass species, Ehrharta calycina, which increased in abundance with rainfall. Partial ordination enabled the assessment of species variation following the removal of variation associated with rainfalL Partial ordinations revealed the gradual, directional movement of samples through multivariate space in response to grazing treatments. Individual plant species were also shown to be responding to grazing, the extent of which was influenced by season of grazing and stocking rate. Both the partial ordinations and the ANOVA showed Melothria sp., Tetragonia fruiticosa and Hermannia scordifolia as increasing and Ruschia caroli as decreasing in absolute abundance in response to grazing. Season of grazing was shown to significantly influence the abundance of H. scordifolia over time. The 'shrublherb complex', which constitutes the 'key resource' at the Nortier Experimental Farm displayed an increase in absolute abundance over the duration of the trial. This increase in absolute abundance was accompanied by an increase in the relative abundance of the palatable component of this resource. The application of medium to heavy stocking rates during spring, summer and autumn and low stocking rates during winter resulted in elevated absolute abundances of palatable plants. Furthermore, low stocking rates, when averaged across all season of grazing treatments, resulted in a significantly higher absolute abundance of unpalatable plants. These findings provide the basis for the development of management principles for the Strandveld Vegetation Type. The application of medium to heavy stocking rates within a rotational grazing system, as recommended by the literature dealing with grazing systems in the Karoo, is supported by the results of the Nortier grazing trial. Medium to heavy stocking rates should be applied during spring, summer and autumn and low stocking rates during the winter months. Furthermore, it is recommended that rests of between 12 and 14 months should be afforded to portions of the veld periodically due to the variability in growth, flowering and fruiting times ofdifferent plants in the Karoo. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Long-term trends in rangeland sward dynamics (species composition, structure, productivity) were examined on three trials established between 1989 and 1996 at Kokstad Research Station in the Highland Sourveld, while animal performance (average daily gain and gain per hectare) was examined on two of the trials. The region enjoys moderate rainfall of 782mm per annum, with hilly topography, and soil depths ranging from >1m to <20cm. The first trial was labelled the simulation trial, as it simulated a four-paddock rotational grazing system, in which animals spent two weeks in each of three paddocks while the fourth was rested for the entire season. The rested paddock was rotated each year. The trial tested two stocking rates (0.5 and 1.0 AU.ha-1) at five ratios of cattle to sheep, ranging from cattle only to sheep only. The trial was unreplicated, and was established in 1989 on flat topography with deep soils. The second trial (labelled the flat two-paddock trial) was established in 1992 adjacent to the simulation trial. The trial examined two stocking rates of sheep weaners (0.5 and 1.0 AU.ha-1 seasonally) in a continuous grazing two-paddock system, in which one paddock of each treatment was burned and grazed continuously while the second paddock was rested, to be burned and grazed in the following season. The trial was replicated twice. The third trial (labelled the steep two-paddock trial) mimicked the grazing system of the flat trial, but was located on a steep (c. 20%) West-facing slope with shallow soils. The trial incorporated two additional treatments: an intermediate stocking rate of 0.7 AU.ha-1 and an ungrazed treatment. Species composition of the sward was recorded biennially on all trials using the nearest plant-point technique with between 200 and 800 points per paddock. Sward standing crop was measured in the rested seasons of the simulation trial and at the beginning, middle and end of each season in one paddock of each two-paddock treatment of the two-paddock trials. In the two-paddock trials, sward standing crop was measured within and outside permanently placed exclosure cages. Animals were weighed fortnightly. The response of species to grazing pressure or animal type was mediated by soil depth and slope, as well as the grazing system. Tristachya leucothrix declined on all grazed treatments. The ungrazed treatments remained relatively stable over ten years. On the low stocking rate treatments of the steep trial, unpalatable species increased, but so did Themeda triandra. The heavily grazed treatment of the steep trial was surprisingly stable, with little significant change in relative abundance of key species other than an increase in the unpalatable Alloteropsis semialata and decline in T. leucothrix. The medium stocking rate treatment on the steep trial showed significant shifts in relative abundance of key species, with declines in T. triandra and T. leucothrix and increases in A. semialata and the unpalatable wiregrass D. filifolius. These trends were not repeated on the flat trial, however, with T. triandra and A. semialata increasing and all other key species declining or remaining stable. On the simulation trial, species responded largely unpredictably with species abundances often fluctuating considerably over time. Microchloa caffra and A. semialata increased substantially in both the low and high stocking rate sheep-only treatments, with a concurrent decline in T. triandra in the high stocking rate but not the low. Changes in composition over time, as measured by Euclidean distance, showed that shallow soils, high stocking rates and a high proportion of sheep caused greater shifts in species composition over time than deep soils, low stocking rates or more cattle. Three treatments, the sheep-only treatments on the simulation trial and the high stocking rate on the steep trial, showed an initial rapid shift in composition over about 6 years, before stabilising in subsequent seasons. The flat trial showed no substantial shift in composition over time. This general pattern of change was confirmed by Non-Metric Multidimensional Scaling. On the simulation trial, total standing crop was influenced by stocking rate and by the proportion of sheep in most seasons. On the two-paddock trials, increasing stocking rate significantly reduced sward vigour, and vigour declined over time. Stocking rate reduced total standing crop on both trials at the end of the 2004/05 seasons and the crop of unpalatable species on the steep trial. Total palatable plants were unaffected by stocking rate on both trials. The classic Jones-Sandland model of animal performance as influenced solely by stocking rate was not supported. Sheep performance was influenced by stocking rate and the interaction of stocking rate and seasonal rainfall. There was no difference in average daily gain between treatments over time, and hence cumulative animal production per hectare increased with increasing stocking rate. Animal performance was possibly influenced by many factors beyond the scope of this study, including the effect of predator attacks on surviving animals, and resource availability such as shade and shelter and high-production patches in some paddocks and not others. Scale effects on ecology are being increasingly investigated and a meta-analysis of this type shows that, even in one research farm, slight differences in management and environment can have significant effects on plant and animal responses to grazing. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

The flood of 2000 caused extensive changes within the riparian landscape of the Sabie River, Kruger National Park (KNP). Changes within the riparian landscape and the removal of vegetation resulted in considerable changes in riparian vegetation characteristics. Open patches created by the flood served as a template for the establishment of new species and the regeneration of existing species, which consequently resulted in a patch mosaic. This memorable event encouraged an investigation into the response of the Sabie River ecosystem to the memorable Large Infrequent Disturbance (LID). Riparian ecosystems are driven by varying combinations of environmental factors, such as water availability, disturbance, herbivory, fire and river morphology. This complexity depicts unique vegetation structure and assemblages of associated plant species. The lack of sufficient knowledge on the role of riparian vegetation in the health assessment of surrounding ecosystems along semi-arid rivers prompted the establishment of the Kruger Rivers Post Flood Research Program (KRPFRP). Research conducted through this monitoring program four years after the 2000 flood, revealed no significant changes in the species composition, although the location and density of many common riparian species have been changed. There was a decrease in species density across the macro channel floor (MCF) and an increase in species density across the macro channel bank (MCB). Furthermore, it was reported that the flood altered the distribution of height classes across the macro channel. In general the riparian vegetation was shorter and bushier four years post-flood. These studies furthermore illustrated that the tree to shrub ratio did not change drastically from pre-flood conditions, although a decrease in the number of shrub individuals was reported. The research presented in this dissertation was designed to further explore changes in woody species composition and structure along the Sabie River, KNP at a post flood temporal interval, i.e. between the last survey in 2004 (by the KRPFRP) and 2010. For data compatibility, the sampling and analytical approach of this study conforms to the approach followed by the KRPFRP. Data were sampled within four preselected belt-transects that form part of the larger KRPFRP. All established woody individuals were counted and measured within each contiguous 10 m x 30 m plot within each of the four belt-transects. Log transformed species composition data were analysed through the application of the Bray Curtis dissimilarity index in combination with Ward’s method of clustering. Statistical significant differences between clusters were tested through the application of the Fisher’s exact relationship test. The MIXED Procedure or PROC MIXED model was used to investigate change within the vegetation structural data. Results obtained through the various analytical methods broadly support the findings of the KRPFRP. No significant change in woody species composition could be detected between 2004 and 2010. However, a change in the density (increase and decrease) of certain species across the MCB and MCF was revealed. Species richness and density increased significantly on the MCF oppose to small changes on the MCB. A significant increase in the total number of shrubs on the MCF contributed to an overall increase in woody density for the entire study area between 2004 and 2010. Shrubs therefore remained the most dominant growth form in both sampling years. Trees decreased across the MCB although the total number of established trees remained unchanged between 2004 and 2010. Riparian vegetation structure is directly linked to species assemblages, hence the continued dominance of shrub species along the Sabie River in the KNP The Sabie River riparian landscape is therefore still characterised by short and multi-stemmed woody individuals ten years after the LID. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

The flood of 2000 caused extensive changes within the riparian landscape of the Sabie River, Kruger National Park (KNP). Changes within the riparian landscape and the removal of vegetation resulted in considerable changes in riparian vegetation characteristics. Open patches created by the flood served as a template for the establishment of new species and the regeneration of existing species, which consequently resulted in a patch mosaic. This memorable event encouraged an investigation into the response of the Sabie River ecosystem to the memorable Large Infrequent Disturbance (LID). Riparian ecosystems are driven by varying combinations of environmental factors, such as water availability, disturbance, herbivory, fire and river morphology. This complexity depicts unique vegetation structure and assemblages of associated plant species. The lack of sufficient knowledge on the role of riparian vegetation in the health assessment of surrounding ecosystems along semi-arid rivers prompted the establishment of the Kruger Rivers Post Flood Research Program (KRPFRP). Research conducted through this monitoring program four years after the 2000 flood, revealed no significant changes in the species composition, although the location and density of many common riparian species have been changed. There was a decrease in species density across the macro channel floor (MCF) and an increase in species density across the macro channel bank (MCB). Furthermore, it was reported that the flood altered the distribution of height classes across the macro channel. In general the riparian vegetation was shorter and bushier four years post-flood. These studies furthermore illustrated that the tree to shrub ratio did not change drastically from pre-flood conditions, although a decrease in the number of shrub individuals was reported. The research presented in this dissertation was designed to further explore changes in woody species composition and structure along the Sabie River, KNP at a post flood temporal interval, i.e. between the last survey in 2004 (by the KRPFRP) and 2010. For data compatibility, the sampling and analytical approach of this study conforms to the approach followed by the KRPFRP. Data were sampled within four preselected belt-transects that form part of the larger KRPFRP. All established woody individuals were counted and measured within each contiguous 10 m x 30 m plot within each of the four belt-transects. Log transformed species composition data were analysed through the application of the Bray Curtis dissimilarity index in combination with Ward’s method of clustering. Statistical significant differences between clusters were tested through the application of the Fisher’s exact relationship test. The MIXED Procedure or PROC MIXED model was used to investigate change within the vegetation structural data. Results obtained through the various analytical methods broadly support the findings of the KRPFRP. No significant change in woody species composition could be detected between 2004 and 2010. However, a change in the density (increase and decrease) of certain species across the MCB and MCF was revealed. Species richness and density increased significantly on the MCF oppose to small changes on the MCB. A significant increase in the total number of shrubs on the MCF contributed to an overall increase in woody density for the entire study area between 2004 and 2010. Shrubs therefore remained the most dominant growth form in both sampling years. Trees decreased across the MCB although the total number of established trees remained unchanged between 2004 and 2010. Riparian vegetation structure is directly linked to species assemblages, hence the continued dominance of shrub species along the Sabie River in the KNP The Sabie River riparian landscape is therefore still characterised by short and multi-stemmed woody individuals ten years after the LID. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

This thesis examines landscape change from 1889 to the present within the foothills-parkland ecoregion of Waterton Lakes National Park (WLNP) in southwestern Alberta, Canada. Land cover dynamics are explored qualitatively and quantitatively using Geographical Information Systems and a combination of historical and contemporary data sources including: (1) Dominion Land Survey (DLS) transect records (1889), (2) repeat oblique photographs (1914 and 2004) and repeat aerial photography (1939 and 1999). Results indicate a consistent increase in woody vegetation cover, particularly aspen forest cover, within the foothills-parkland since 1889, largely at the expense of native grasslands. The primary drivers of these changes likely include: climatic influences, changes to the historical grazing regime, the suppression of natural fire cycles and the cessation of First Nations’ land management practices. This research illustrates the value of integrating multiple historical data sources for studying landscape change in the Canadian Rockies, and explores the implications of this change for ecological restoration in the foothills-parkland of WLNP.

This thesis examines landscape change from 1889 to the present within the foothills-parkland ecoregion of Waterton Lakes National Park (WLNP) in southwestern Alberta, Canada. Land cover dynamics are explored qualitatively and quantitatively using Geographical Information Systems and a combination of historical and contemporary data sources including: (1) Dominion Land Survey (DLS) transect records (1889), (2) repeat oblique photographs (1914 and 2004) and repeat aerial photography (1939 and 1999). Results indicate a consistent increase in woody vegetation cover, particularly aspen forest cover, within the foothills-parkland since 1889, largely at the expense of native grasslands. The primary drivers of these changes likely include: climatic influences, changes to the historical grazing regime, the suppression of natural fire cycles and the cessation of First Nations’ land management practices. This research illustrates the value of integrating multiple historical data sources for studying landscape change in the Canadian Rockies, and explores the implications of this change for ecological restoration in the foothills-parkland of WLNP.

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No description available.