Arizona Cooperative Extension Publication 190043 / Originally published 1990, revised 1995, revised 1997.

Arizona Cooperative Extension Publication 190043 / Originally published 1990, Revised 1995.

To proffer a sustainable solution to ecological degradation in rangeland ecosystems as a consequence of fire, grazing and browsing, an understanding of rangeland ecological processes is vital. Due to the complexity of ecological processes and their interrelationships, it is usually difficult or expensive to directly measure status of ecological processes. Therefore, biological and physical characteristics are often used to indicate the functionality of ecological processes and site integrity. Long-term effects of fire, grazing and browsing on characteristics of the vegetation and organic matter and their subsequent effects on selected rangelands ecosystem ecological processes was conducted at Honeydale section of the University of Fort Hare farm in the Eastern Cape Province of South Africa and Matopos Research Station in Zimbabwe. In this study, attributes of biotic community integrity (species richness, composition and diversity), soil stability (basal cover, standing dead grass biomass, tuft to tuft distance, tufts diameter, canopy distance and stem to stem distance), productivity and plant vigour (grass yield, total canopy volume, plant height, canopy height, canopy diameter, main stem diameter, sprouts diameter and number of sprouts) and hydrologic function and nutrient cycling (grass litter biomass, soil organic carbon and microbial biomass carbon) were used to estimate long-term effects of burning, grazing and browsing by goats on the functionality of ecological processes in the rangeland ecosystem. Burning did not have differential effect on grass species richness (P>0.05), woody species diversity as well as compositional percentage for D.eriatha, C.plurinodis, S.fimbriatus, A.karro and E.rigida. Burning increased decreasers and increaser II species proportions and reduced (P ≤ 0.05) grass yield, total canopy volume, tree height, canopy height main stem diameter and sprouts diameter. Long-term burning, grazing, and goats browsing had differential effects on site stability. The effects on basal cover, tuft to tuft distance, tufts diameter, canopy distance and basal distance as a consequence of long-term burning, grazing, and goats browsing were not significantly different, whereas the effects on standing dead grass biomass as a result of long-term burning frequencies were significantly different. Long-term effects of burning followed by ten-year period of fire exclusion had significantly different effects on tuft-tuft distance but did not have statistically different effects on tufts diameter, canopy distance and basal distance. Long-term burning grazing and browsing had significantly different effects on attributes of hydrologic functions and nutrient cycling in the rangeland ecosystem (grass litter biomass, SOC and BMC). Long-term effects of burning followed by ten-year period of fire exclusion had significantly different effects on grass litter biomass, and SOC. Through their effect on vegetation and organic matter characteristics, burning, grazing and browsing could influence functionality of selected rangeland ecological processes such as biological community integrity, productivity and plant vigour, site stability, hydrologic function and nutrient cycling.

Thesis (MSc. Agriculture (Remote Sensing)) -- University of Limpopo, 2015 / Savannas are the most important ecosystems for raising livestock in Africa. In the past 50 years, evidence has shown that savannas throughout the world are being altered by bush encroachment. This is an ecological succession process where perennial plants such as shrubs and trees replace annual vegetation. This reduces the amount of palatable fodder and directly threatens livestock productivity in many localities. This study evaluated long-term bush encroachment using multi-date Landsat Thematic Mapper (TM) images 1989, 1990, 1993, 1995, 1999, 2004 and 2008 to reconstruct changes in spatial distribution of trees and shrubs at the Towoomba Reseach Station over a period of 19 years, from 1989 to 2008. Grasses and woody species were classified using unsupervised classification and Normalised Difference Vegetation Index was used to assess forage productivity and change in vegetation with years. The study was carried out at Towoomba Research Station in Bela Bela, Limpopo Province, South Africa. The study revealed that bush encroachment is a natural process and is independent of the grazing patterns. The results show that if not monitored encroaching species will make it difficult for grazers to get underneath the trees and also disturb the photosynthetic process of grass thereby replacing the grass. The study further showed that satellite remote sensing has the potential for monitoring rangeland quality. Keywords: Bush encroachment, remote sensing, classification and Normalised Difference Vegetation Index

The mountains of Lesotho form the catchments for the Lesotho Highlands Water Project (LHWP), which is presently under construction, and their condition will determine the longevity of the LHWP. The mountain rangelands also support an extensive livestock system. However, there is concern that grazing is negatively affecting the mountain vegetation to the detriment of both livestock production and catchment function. Therefore, the impact of environment and grazing on the vegetation was investigated to aid the development of management policy for the conservation of the grazing, floristic and water resources of the mountains. Vegetation surveys were conducted in the mountains in the east (Study Area 1: 2 625 - 3 350 m a.s.l.) and in the west (Study Area 2: 2 240 - 3 125 m a.s.l.). Indirect gradient analysis (IGA) and classification were used to investigate the influence of environment on vegetation pattern. Results of the IGA indicated that variation in species composition in the mountains is related primarily to topographic variation, in particular elevation and aspect. Five vegetation communities were identified in Study Area 1 and seven in Study Area 2. These communities occurred consistently in specific topographic positions in the landscape and were arranged along a temperate/subtropical grass species continuum which was associated with a gradient in elevation and aspect. In Study Area 1, the elevation boundary between the high-lying temperate grasslands and the lower subtropical grasslands corresponded with the generally recognised boundary between the Alpine and Subalpine vegetation belts (viz. c. 2 950 m a.s.l. on northerly aspects and c. 2 750 m a.s.l. on southerly aspects). This boundary was lower in Study Area 2 (viz. c. 2 800 m a.s.l. on northerly aspects and c. 2 300 m a.s.l. on southerly aspects). Vegetation-insolation relationships were investigated in Study Area 1 using a model for simulating solar radiation, temperature and potential evaporation patterns on sloping terrain (RADSLOPE). The spatial distribution of the identified vegetation communities and the ratio of temperate (C₃) and subtropical (C₄) grasses in the sward were related to solar irradiance patterns, as influenced by topography. Results suggest that exposure, which increases with altitude, is probably also an important determinant of vegetation pattern in the mountains. The influence of grazing on the vegetation was studied by examining changes in species composition and cover that were associated with gradients in grazing intensity that exist around cattleposts in the mountains. There was little evidence of a shift in species composition and cover under grazing in the Alpine Belt but there was an identifiable grazing gradient in the Subalpine belt. There, short dense grasslands, dominated by palatable species, degrade to a dwarf karroid shrubland with sparse cover under prolonged, intense grazing. The optimum position along the grazing gradient of the more abundant species was identified. It was proposed that the relative positions, or scores, of these species along the grazing gradient can be used in a weighted scoring procedure to provide an index for monitoring the response of the mountain vegetation to grazing. However, the species’ scores still require verification. The need for monitoring temporal changes in vegetation composition and cover in order to assess the possible effects of the LHWP and other development initiatives was noted. Such monitoring should be undertaken in conjunction with an overall programme to assess the dynamics of the socio-economy in the mountains. Therefore, interdisciplinary monitoring programmes are required to achieve this. These programmes should be focused in a few key study locations rather than spread over a wide area. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg.

A long-term grazing trial was started in 1977 at Armoedsvlakte Research Station, about 10km west of Vryburg, in Tarchonanthus veld of the Ghaap’s Plateau, which is a variation of the Kalahari Thornveld veld type. The main aim of this study was to use the extensive veld condition and animal production data set to investigate the effects and interactions of stocking rate, grazing system applied and seasonal rainfall on veld condition and cattle production. The grazing trial has changed three times since its inception resulting in three different phases. The main changes in veld condition during phase one (1977-1991) was due to density independent effects (e.g. seasonal rainfall) and not density dependent effects (e.g. stocking rate). A major change occurred in 1985 following a multiple year drought. The drought resulted in adverse changes in species composition, basal cover and residual biomass of all treatments. The system did not recover from the drought during phase one, despite well above mean seasonal rainfall for a number of years after the drought. During phase two (1992-1999) and phase three (2000 to present) completely different vegetation dynamics occurred than what was experienced during phase one. Density dependent effects (e.g. stocking rate) were more important in explaining variation in veld condition during these two phases. High stocking rates resulted in adverse changes in species composition, poor basal cover and a low residual biomass production. It is however important to note that seasonal rainfall did explain a significant additional amount of variation in veld condition. This suggests that a continuum of non-equilibrium and equilibrium vegetation dynamics occurred in these two phases. The residual biomass and seasonal rainfall model for phase one indicate completely different results for the gain per animal data. In the seasonal rainfall model, stocking rate does not have a significant effect on gain per animal, but seasonal rainfall and the interaction of stocking rate with seasonal rainfall explains most of the variation in gain per animal. This suggest a continuum of non-equilibrium and equilibrium dynamics and that animal production is more sensitive to seasonal rainfall than to stocking rate, although the significant interaction of stocking rate with seasonal rainfall suggest that the seasonal rainfall effect on animal production is dependant on stocking rate. The residual biomass model however indicates that stocking rate is more important than rainfall in explaining variation in the mass gains per animal. The stocking rate effect on gain per animal was significant and indicated that as stocking rate increased, that gain per animal decreases. Seasonal rainfall and the interaction of stocking rate with seasonal rainfall had no significant effect on gain per animal. The amount of variation explained by the seasonal rainfall model was larger than the residual biomass model and this indicates that rainfall explains more variation in gain per animal, than residual biomass does. This possibly indicates that non-equilibrium effects are stronger than the equilibrium effects, but it is important to notice that stocking rate had a significant effect in some cases. The gain per hectare models (seasonal rainfall and residual biomass) for phase one indicates that stocking rate has a significant effect on gain per hectare. Increasing stocking rates resulted in higher gain per hectare, which suggests that the turning point of the typical “Jones and Sandland model” has not been reached and this might be due to light stocking rates applied during the duration of phase one. The seasonal rainfall model however has significant effects of seasonal rainfall and interactions of stocking rate with seasonal rainfall on gain per hectare. This suggests that the effect of stocking rate is dependent on seasonal rainfall and that seasonal rainfall explain an additional amount of variation in gain per hectare. In general, it appreared that the optimal stocking rate for animal production was higher than those applied during the duration of the trial, but this is due to lower than planned actual stocking rates applied during all three phases of the trial. It is very difficult to determine a generic optimal stocking rate for different rainfall volumes and it is recommended that the actual stocking rate for different ecological zones be determined based on rainfall, biomass, species compos[i]tion, basal cover and available browse and not just on the provisional recommendations. The type of grazing system applied did not show any statistically significant effects on both gain per animal and gain per hectare for the animal production data during phase one. This result is interesting and contradictive to most of the scientific literature where some authors concluded from their studies that rotational grazing systems produce higher animal production than continuous grazing systems, whereas others researchers state that continuous grazing systems produce higher animal production than rotational grazing systems. In phase two both the residual biomass and seasonal rainfall models for phase two did not show any significant effects and interactions of stocking rate, seasonal rainfall level and/or residual biomass on both gain per animal and gain per hectare. Both the residual biomass and seasonal rainfall models for phase three did not show any significant effects and interactions of stocking rate, seasonal rainfall level and/or residual biomass on animal gains per animal. The seasonal rainfall model did not show any any significant effects and interactions of stocking rate, seasonal rainfall level and/or residual biomass on animal gains per hectare. However, the residual biomass model indicated that stocking rate had a significant effect on gain per hectare and the production closely followed the Jones and Sandland (1974) model as at low stocking rates, gain per hectare increases at a rapid rate, but as stocking rates increases to high stocking rates, the rate of increase in gain per hectare declines, until it eventually reaches a turning point, where after gain per hectare declines with increasing stocking rates. Stocking rate only had a significant effect on the condition score of cows during phase two and phase three, as high stocking rates resulted in poor animal condition in both phases. No significant effects and interactions of stocking rate and seasonal rainfall were indicated on calving percentage, weaning percentage, conception rates and percentage of desirable meat produced during phase two. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, [2011].

It is becoming increasingly important to monitor biodiversity in the extensive Australian rangelands; currently however, there is no method capable of achieving this goal. There are two potential sources of relevant data that cover the Australian rangelands, and from which measures of biodiversity might be extracted: traditional field-based methods such as quadrat surveys have collected flora and fauna species data throughout the rangelands, but at fine scale; satellite remote sensing collects biologically relevant, spatially comprehensive data. The goal of this thesis was to provide the spatially comprehensive measure of biodiversity required for informed management of the Australian rangelands. The study specifically focused on the Stony Plains in the South Australian rangelands. To that end the thesis aimed to develop indices capable of measuring and/or monitoring biodiversity from vegetation quadrat survey data and remotely sensed data. The term biodiversity is so all-encompassing that direct measurement is not possible; therefore it is necessary to measure surrogates instead. Total perennial vegetation species richness (y-diversity) is a sound surrogate of biodiversity: the category of species is well defined, species richness is measurable, and there is evidence that vegetation species richness co-varies with the species richness of other taxonomic groups in relation to the same environmental variables. At least two broad scale conventional vegetation surveys are conducted in the study region; the Biological Survey of South Australia; and the South Australian Pastoral Lease Assessment. Prior to the extraction of biodiversity data the quality of the BSSA, the best biodiversity survey, was evaluated. Analysis revealed that false-negative errors were common, and that even highly detectable vegetation species had detection probabilities significantly less than one. Without some form of correction for detectability, the species diversity recorded by either vegetation survey must be treated with caution. Informed by the identification of false-negative errors, a method was developed to extract y-diversity of woody perennials from the survey data, and to remove the influence of sampling effort. Data were aggregated by biogeographic region, rarefaction was used to remove most of the influence of sampling effort, and additional correction removed the residual influence of sampling effort. Finally, additive partitioning of species diversity allowed extraction of indices of a-, β- and y-diversity free from the influence of sampling effort. However, this woody perennial vegetation y-diversity did not address the need for a spatially extensive, fine scale measure of biodiversity at the extent of the study region. The aggregation of point data to large regions, a necessary part of this index, produces spatially coarse results. To formulate and test remotely sensed surrogates of biodiversity, it is necessary to understand the determinants of and pressures on biodiversity in the Australian rangelands. The most compelling explanation for the distribution of biodiversity at the extensive scales of the Australian rangelands is the Productivity Theory, which reasons that the greater the amount and duration of primary productivity the greater the capacity to generate and support high biodiversity. The most significant pressure on biodiversity in the study area is grazing-induced degradation, or overgrazing. Two potential spatially comprehensive surrogates of pressure on biodiversity were identified. The first surrogate was based on the differential effect of overgrazing on waterenergy balance and net primary productivity: water-energy balance is a function of climatic variables, and therefore a measure of potential or expected primary productivity; net primary productivity is reduced by high grazing pressure. The second surrogate was based on the effect of grazing-induced degradation on the temporal variability of net primary productivity: overgrazing reduces mean net primary productivity and rainfall use efficiency, and increases variation in net primary productivity and rainfall use efficiency. The two surrogates of biodiversity stress were derived from the best available remotely sensed and climate data for the study area: actual evapotranspiration recorded by climate stations was considered an index of water-energy balance; net primary productivity was measured from NOAA AVHRR integrated NDVI; rainfall use efficiency (biomass per unit rainfall) was calculated from rainfall data collected at climate stations and the net primary productivity measure. Finally, the surrogates were evaluated against the index of woody perennial a-, β- and y-diversity, on the assumption that prolonged biodiversity stress would reduce vegetation species diversity. No link was found between Surrogate 1 and woody perennial a-, β- or y-diversity. The relationship of Surrogate 2 to woody perennial diversity was more complex. Only some of the results supported the hypothesis that overgrazing decreases y-diversity and average NPP and RUE. Importantly, none of the results supported the most important part of the hypothesis that the proposed indices of biodiversity pressure would co-vary with woody perennial a-diversity. Thus, the analysis did not reveal a convincing link between either surrogate and vegetation species diversity. However, the analysis was hampered to a large degree by the climate data, which is interpolated from a very sparse network of climate stations. This thesis has contributed significantly to the measurement and monitoring of biodiversity in the Australian rangelands. The identification of false-negative errors as a cause for concern will allow future analyses of the vegetation survey data to adopt methods to counteract these errors, and hence extract more robust information. The method for extracting sampling effort corrected indices of a-, β- and y-diversity allow for the examination and comparison of species diversity across regions, regardless of differences in sampling effort. These indices are not limited to rangelands, and can be extracted from any vegetation quadrat survey data obtained within a prescribed methodology. Therefore, these tools contribute to global biodiversity measurement and monitoring. Finally, the remotely sensed surrogates of biodiversity are theoretically sound and applicable in any rangeland where over-grazing is a significant source of degradation. However, because the evaluation of these surrogates in this thesis was hampered by available data, further testing is necessary. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1346544 / Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2008

Thesis (MScConsEcol (Conservation Ecology and Entomology))--University of Stellenbosch, 2005. / The veld condition in the Little Karoo is in various states of degradation and grazing by domestic livestock is considered as the major anthropogenic force that changed the landscape. This region with its extremely rich plant species diversity and endemics, has supported small livestock for at least 2 000 years, and since colonization (250 years ago) been intensively used for the production of a variety of livestock. Ostrich production developed as the major source of income for this region. The first part of this study investigates the current veld management practices employed by livestock farmers in the Little Karoo region. Recommended veld management practices considered in this study are grazing rotation, moderate stocking rate control, moderate veld utilisation, separation of ecotopes, veld rehabilitation, controlling declared weeds and alien vegetation and regular assessment of veld condition. One hundred randomly selected farmers were personally interviewed by means of a structured questionnaire. Questions were grouped into the following categories: (a) demography of farmers, (b) ostrich farming, (c) perceptions and knowledge of farmers on farming practices, (d) grazing rotation, (e) stocking rate, (f) veld utilisation and veld assessment, (g) separation of ecotopes, (h) veld rehabilitation, (i) control of alien vegetation and (j) farmers’ knowledge on legislation. This was used to obtain information on the Little Karoo farming community, sizes of farms and camps, types of farming enterprises and on adoption of recommended veld management practices in the region. The main findings from this section are that relatively small farming units with few camps, poor separation of ecotopes and a low estimated grazing capacity, limit extensive livestock farming within the region. Perceptions of farmers on veld condition, grazing rotation, stocking rate, separation of ecotopes are fairly optimistic. As a result grazing capacities are overestimated and overstocking occurs within this region. The current stocking rate in ostrich camps (67.7% overstocked) and mammalian livestock camps (55.1% overstocked) is evidence that farmers overstock to compensate for these limiting factors in order to make a living from the land. The majority of farmers are well aware of the Articles in the Conservation of Agricultural Resources Act of 1983, which are applicable to veld management. Only more that 50% comply with this legislation by rehabilitating veld and 80% of them control invasive alien species on their farm. In the second part, veld assessments were done in randomly selected veld camps, using the multi-criterion, semi-subjective Quick Rangeland Health Assessment (QRHA) Method. Veld condition was significantly poorer closer to water or feeding points due to the piosphere effect caused by livestock. Veld condition in the Little Karoo can be related to altitude, vegetation types and land use. Therefore, the lowlying Little Succulent Karoo vegetation type is in a poorer condition compared to Spekboom Succulent Thicket and South and South-west Coast Renosterveld. Ostrich production on plains in the Little Succulent Karoo vegetation type is the main cause for the degradation of this vegetation type. It would seem as if historically high stocking rates cannot be ignored in explaining the current veld condition. A positive correlation between veld condition and the diversity of plant species (species density) were found, which highlights the importance of good veld management practices in sustainable agriculture. The third part tested whether all indicators in the QRHA method are equally sensitive and whether there is a positive correlation between the QRHA method and the Grazing Index Method. A significant positive linear correlation was found between the two methods. Cover was the least sensitive indicator of rangeland condition, and livestock induced disturbances (which include the indicators grazing intensity, disturbance indicators, soil health and species richness) were the most sensitive for Karoo veld assessment. A major benefit of the QRHA method is heuristic; therefore this method may have value in agricultural extension work.

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.

The Okavango Delta is an extremely dynamic system with variable vegetation comprised of permanent swamps, seasonal swamps, dry islands, floodplains and dry grassland, savanna and woodland. The system is largely driven by the interaction between fire and the annual flood, which filters down from the Okavango River catchments in Angola. While extensive research has been conducted on the flood-driven vegetation little is known about the dry woodland and savanna regions bordering these flood-driven habitats. A taxonomic classification of woody species composition resulted in eleven vegetation types. These data were then reanalyzed in terms of woody species morphology allowing these eleven vegetation types to be grouped into four functional response groups in order to provide a platform for improving the understanding of how dry woodland and savannas interact with the environment. These four groups were the savanna group mixed thornveld and the three woodland groups; mixed broadleaf woodland, shrub mopane woodland and tall mopane woodland. Burning in mixed thornveld and mixed broadleaf woodland was found to decrease woody species density and grass fuel loads and could be used for grazing management to remove unpalatable growth and improve grass species composition, while burning in shrub mopane woodland and mixed mopane woodland merely decreased the woody understory and is not recommended. Utilization dominated by grazing livestock resulted in overutilization of the grass sward leading to bush encroachment in both mixed thornveld and shrub mopane woodland, while utilization by goats alone resulted in underutilization of the grass sward and a dominance of herbaceous annuals. Livestock utilization had no effect on the occurrence of Pecheul-loeschea leubnitziae, a shrubby pioneer previously thought to be an indicator of overgrazing, however extensive P. leubnitziae cover was associated with a sward dominated by shade-tolerant grasses with low forage quality. Shrub mopane woodland and tall mopane woodland appear to be more stable vegetation states than mixed broadleaf woodland and mixed thornveld being less vulnerable to colonization by pioneer species and alteration as a result of utilization or environmental factors. For this reason management and monitoring of mixed thornveld and mixed broadleaf woodland is essential to prevent vegetation degradation and to ensure optimal forage availability for both livestock and wildlife. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.