Appropriate management of mid-rotation pine plantations can improve habitat for early successional and pine-grassland adapted avian species. I tested effects of Imazapyr selective herbicide and prescribed fire on plant and avian communities in thinned, mid-rotation pine stands contracted under the Conservation Reserve Program. Within 12 replicate sites, 2 8.1-ha plots were assigned either herbicide and prescribed fire treatment or control. I described components of vegetation structure and composition in 2006. I tested effects of herbicide and prescribed fire treatment on avian relative abundance, species richness, total avian conservation value, and density of select species during 2003 - 2006. Hardwood midstory decreased and abundances of grasses and forbs increased following treatment. A shift occurred in the bird community from closed-canopy forest species to early successional and pine-grassland species. Treatment stands benefited many avian species exhibiting negative population trends.

<p>Biological invasion is a major and growing threat to global biodiversity and human well-being, but research on the impacts of invaders on their recipient environments lags behind that on the mechanisms driving invader establishment and spread. The total impact of an invader is defined by its range size, abundance per unit area, and per-capita effect, with both per-capita effects and abundance varying over time and across the invader’s range. These context-dependencies are determined, in part, by functional differentiation between the invader and its recipient system. In this thesis, I investigate how functional differentiation between invaders and their recipient communities regulates the impact of plant invaders on community diversity and/or biomass production.</p> <p>First, I compare the effects of invasive Callery pear (<em>Pyrus calleryana</em> Decne.) to functionally similar native trees in three early-successional meadow environments in Indiana’s eastern corn belt plains. Despite my prediction that <em>P. calleryana</em> would have greater negative effects on the total biomass and diversity of the understory plant community compared to native trees, I found that <em>P. calleryana</em> had no significant impact on total cover, species richness, or Shannon’s or Simpson’s diversity indices for the understory community, compared to native <em>Liriodendron tulipifera</em> L., <em>Platanus occidentalis</em> L., or non-tree control plots. Likewise, <em>P. calleryana</em> had no significant impact on the native, introduced, woody, or native tree subsets of the understory community. These results indicate that the trait differences between <em>P. calleryana</em> and functionally similar native trees – and thus the per-invader effect of <em>P. calleryana</em> on its recipient community – are not of a great enough magnitude to produce changes in the understory community composition of these highly invaded, low diversity meadow environments with relatively new and sparse <em>P. calleryana</em> invasions. </p> <p>I then investigate the role of functional overlap in moderating invader impacts in California serpentine grassland communities through the lens of classic niche theory, which predicts that functional differentiation minimizes competition and therefore allows functionally distinct invaders to achieve higher establishment success but lower per-capita effects on their recipient communities. I tested this prediction by establishing small-scale experimental communities composed of individual or multiple functional groups differentiated by phenology – early-season annuals, nitrogen-fixing early-season annuals, and late-season annuals – and seeding these communities with early- or late-season invaders. I found that as invader density increased, effects on resident community biomass depended on complex patterns of invader and resident functional overlap. Across all resident community functional groups, the high density of early-season invaders enables them to capture a greater portion of total community biomass than late-season invaders, but early-season invaders reduce the ratio of resident:total invader biomass production by less, per-unit-biomass, than late-season invaders. These results highlight the need to consider both niche and fitness differences in predicting invader impacts and the complex nature of resident-invader interactions, which may not be sufficiently captured by coarse functional groups.</p>

In my thesis, I examined impacts of nesting and floral resources on ground-nesting bee assemblages at nine ranch sites with differing grazing histories. Because ecological disturbances can strongly affect the availability of foraging and nesting resources over time, I also examined the impacts of grazing history on nesting and floral resources for ground-nesting bees. I sampled bee assemblages, a comprehensive array of vegetation and soil measures, and floral abundance and richness. I used these data to determine (1) the importance of different nesting habitat resources and livestock grazing history for ground-nesting bees and (2) how livestock grazing history influenced the availability of nesting and floral resources. I found that sites with sandier soils had greater abundance and richness of ground-nesting bees, and sites with less compacted soils had greater bee abundance. Contrary to many other studies, the availability of bare ground was not important for ground-nesting bee abundance or richness. Grazing history did not affect any measures of nesting or floral habitat, and had negligible effects on ground-nesting bee abundance, richness, and community composition. My results suggest that the availability of sandier or less compacted soils may be limiting for ground-nesting bee abundance or richness, especially in areas with predominately clay soil types. In this context, the availability of such nesting resources may be more limiting than floral resource availability. More research is necessary to tease apart the effects of different nesting and floral resources for bees, and how different grassland management types affect bees through those resources. My findings highlight the importance of considering nesting habitat resources in bee conservation and restoration efforts.

Grasländer sind wichtige Elemente der zentraleuropäischen Landschaft und stellen essenzielle Ökosystemdienstleistungen bereit. Dürren, welche durch den globalen Klimawandel zunehmen, haben negative Auswirkungen auf die Vitalität und Produktivität von Grasland. Satellitenmissionen wie Sentinel-2 und Landsat liefern große, bisher ungenutzte Möglichkeiten für das Grasland Monitoring. Ansätze auf Basis quantitativer Parameter, z.B. Prozentanteile von photosynthetisch aktiver Vegetation (PV), nicht photosynthetisch aktiver Vegetation (NPV) und Boden sind bisher für die Anwendung in zentraleuropäischen Grasländern nicht erforscht. Das Ziel der Arbeit war es, das Verständnis von Dürreeinflüssen auf zentraleuropäische Grasländer durch die Entwicklung eines fernerkundungsbasierten Monitoring Frameworks zu verbessern. Der erste Teil dieses Frameworks umfasste die Ableitung konsistenter Zeitreihen von PV-, NPV-, und Bodenanteilen. Der zweite Teil umfasste die Quantifizierung von Dürreeffekten anhand dieser Zeitreihen. Die Ergebnisse zeigten einen großflächigen, massiven und langanhaltenden Rückgang von Graslandvitalität in extremen Dürrejahren (z.B. 2003, 2018-2020). Robuste statistische Zusammenhänge bestätigten die starke Kopplung von Graslandvitalität und Dürre, insbesondere bei gleichzeitigen Hitzewellen. Zudem beeinflussten Bodeneigenschaften sowie klimatische und hydrologische Bedingungen die Dürresensitivität. Die Ergebnisse unterstreichen den Wert von generalisierten Entmischungsansätzen basierend auf Sentinel-2/Landsat Zeitreihen für großflächiges, quantitatives Monitoring von Grasland. Die Ergebnisse deuten darauf hin, dass durch den Klimawandel verstärkte Dürreereignisse in Zukunft erheblichen Einfluss auf die Vitalität von Grasländern in Zentraleuropa haben werden. Die hier gewonnenen Informationen liefern wichtige Beiträge zur Verbesserung von Dürremonitoring und können die Maßnahmenentwicklung zur Verringerung von Dürreschäden im Grasland unterstützen. / Grasslands are vital landscape elements in Central Europe providing essential ecosystem services. Drought events, which are increasing with global climate change, negatively affect grassland vitality and productivity. Satellite remote sensing missions such as Sentinel-2/Landsat offer untapped potential for monitoring grassland vitality. However, workflows for grassland monitoring based on fractional cover of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), and soil, remain largely unexplored. The goal of this thesis was to advance the understanding of drought impacts on Central European grasslands by developing a framework for monitoring grassland vitality. The framework included the retrieval of consistent PV, NPV, and soil fractional cover time series from Landsat/Sentinel-2, which was achieved by implementing and generalizing an unmixing workflow. Second, drought impacts were quantified and evaluated based on fractional cover time series. Results showed large-scale, severe, and long-lasting negative impacts on grassland vitality in extreme drought years (e.g., in 2003, and 2018-2020). Robust statistical links confirmed the overall consistent coupling of grassland vitality to drought, specifically to compounding droughts and heatwaves. Spatiotemporal patterns of grassland drought sensitivity revealed that underlying factors such as soil features, and climatic and hydrological conditions modulate drought impacts on local to regional scales. Findings of this thesis emphasize the value of generalized unmixing workflows based on Sentinel-2/Landsat time series for quantitative grassland monitoring across large areas. Furthermore, results suggest that droughts amplified by climate change will pose substantial challenges for grassland vitality across Central European grasslands in the future. The findings provide a steppingstone towards improved drought monitoring and can thus inform adaptation efforts to alleviate drought impacts on grasslands.

Savannahs regulate an agro-ecosystem crucial for the production of domestic livestock, one of the main sources of income worldwide as well as in South African rural communities. Nevertheless, globally these ecosystem functions are threatened by intense human exploitation, inappropriate land use and environmental changes. Leaf area index (LAI) defined as one half the total green leaf area per unit ground surface area, is an inventory of the plant green leaves that defines the actual size of the interface between the vegetation and the atmosphere. Thus, LAI spatial data could serve as an indicator of rangeland productivity. Consequently, the accurate and rapid estimation of LAI is a key requirement for farmers and policy makers to devise sustainable management strategies for rangeland resources. In this study, the main focus was to assess the utility and the accuracy of the PROSAILH radiative transfer model (RTM) to estimate LAI in the South African rangeland on the recently launched Landsat 8 sensor data. The Landsat 8 sensor has been a promising sensor for estimating grassland LAI as compared to its predecessors Landsat 5 to 7 sensors because of its increased radiometric resolution. For this purpose, two PROSAIL inversion methods and semi- empirical methods such as Normalized difference vegetation index (NDVI) were utilized to estimate LAI. The results showed that physically based approaches surpassed empirical approach with highest accuracy yielded by artificial neural network (ANN) inversion approach (RMSE=0.138), in contrast to the Look-Up Table (LUT) approach (RMSE=0.265). In conclusion, the results of this study proved that PROSAIL RTM approach on Landsat 8 data could be utilized to accurately estimate LAI at regional scale which could aid in rapid assessment and monitoring of the rangeland resources. / Environmental Sciences / M. Sc. (Environmental Science)

The KwaZulu-Natal Drakensberg, South Africa, is predominantly a grassland ecosystem maintained by fire. The effect of the current burning regime on invertebrate and flowering forb diversity in this ecosystem is poorly understood. The overall aim ofthis study was to contribute towards the development of an effective burning regime for the KwaZulu-Natal Drakensberg that will conserve invertebrates and indigenous forbs, two major components of biodiversity. The objectives were to examine the effect of fire and fire frequency on flowering forb and invertebrate species diversity, to determine whether fire frequency, time since last burn or locality were influencing species composition, and to identify potential biodiversity indicators that reflect overall species richness for use in monitoring of invertebrates and forbs. Sampling took place in March, September and November of 2002 at Giants Castle Game Reserve. Invertebrates were sampled using sweep netting and targeted netting along transects, yellow pan traps and soil quadrats. Invertebrate taxa sampled were ants (Formicidae), butterflies (Lepidoptera), grasshoppers (Orthoptera), leafboppers (Cicadellidae), bees (Apoidea), bee flies (Bombyliidae), hover flies (Syrphidae), robber flies (Asilidae), spiders (Araneae), earthworms (Oligochaeta) and millipedes (Diploda). These were identified to species level with the assistance of taxon experts. Flowering forbs were sampled using five replicates of five by five metre quadrats randomly placed in each site. Overall flowering forb and invertebrate species diversity was higher in grasslands that were burnt for two consecutive years in 2001 and 2002 than in grasslands that were not burnt during those two years. Frequently (annual) and intermediately (biennial) burnt grasslands had significantly higher invertebrate and flowering forb diversity than infrequently (five years without burning) burnt grasslands. This, together with the fact that grasslands burnt during the year of sampling had higher species richness than grasslands burnt two and five years previously suggests that invertebrates and forbs are generally resilient to fire and many forb species appear to be stimulated by fire. However, each burn frequency had its own suite of unique flowering forb and invertebrate species. Invertebrate communities were influenced mostly by locality and the length of time past since the last fire and flowering forb communities were influenced mostly by the length oftime past since the last fire. Fire frequency had the least influence on both invertebrate and forb communities. Ecological succession occurred after each fire in the invertebrate communities but forb communities appear to need more than five years without fire for ecological succession to occur. The findings of this study therefore suggest that using a combination of three fire frequencies would result in patches of grassland in various stages of ecological succession, and would conserve species unique to each burning frequency, and would therefore conserve maximum diversity. Flowering forb species richness and certain invertebrate taxa (ants, leafboppers, spiders and bees) have the potential to act as indicators of overall invertebrate species richness for use in monitoring programmes. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

A l’échelle mondiale, les prairies fournissent une grande variété de services écosystémiques et sont le support économique de nombreux systèmes d’élevage. Dans un contexte global éminemment changeant, une meilleure compréhension de la structure et du fonctionnement des prairies est incontournable pour proposer à la fois des gestions plus durables des ressources et promouvoir la fourniture de services écosystémiques diversifiés par ces écosystèmes. Les prairies étant des écosystèmes dynamiques et hétérogènes, notre capacité à prédire leur fonctionnement et leurs trajectoires de réponse à un facteur environnemental (climat, gestion) reste un défi scientifique important. Ainsi, dans des prairies pâturées, l’activité de grands herbivores va être facteur d’hétérogénéité des nutriments du sol via l'excrétion. Cependant les effets de ces apports nutritifs en « patchs » et de l'hétérogénéité spatiale du sol sur la structure et les propriétés de la prairie restent peu connus. L’objectif de cette thèse est d’examiner les effets de l'hétérogénéité spatiale de l'azote (N) dans le sol sur l’écosystème prairial, en portant une attention particulière sur les réponses des communautés végétales. Notre démarche a combiné des approches expérimentales et de modélisation pour analyser les impacts d'un certain nombre d'attributs de « patch » (différentes formes d’N, taille et contraste du patch), et leurs interactions possibles avec le régime de pluviométrie ou encore la date des apports en N. Nous montrons que des apports hétérogènes en N augmentent la production des plantes et la variabilité de la biomasse intra-parcelle quel que soit la forme d’N, mais qu’ils ne modifient pas, à court terme, la production à l’échelle de la parcelle prise dans son entier. Néanmoins, des apports hétérogènes d’N-organique favorisent l’asynchronie spatiale et temporelle entre les compartiments plante - sol, avec des implications pour le fonctionnement de la prairie à plus long terme. Contrairement à la production, la structure de la communauté végétale répond significativement à l’hétérogénéité en N, avec une dominance accrue de certaines espèces et un changement dans le rang des espèces subalternes. Contre toute attente, dans cette étude, la quantité de pluie ne modifie pas les effets de l'hétérogénéité sur la production et la structure de la communauté végétale. Des simulations réalisées avec un modèle spatialisé montrent que les effets de l'hétérogénéité sur la production à l’échelle de la parcelle varient selon la taille et le niveau de contraste du patch. Pour un même apport total en N, la production répond positivement à la taille de patch, mais elle diminue dans des conditions de fort contraste en comparaison à des conditions de faible contraste. Nous n’avons pas relevé d’interactions entre la taille de patch, le niveau de contraste de patch ou la date des apports en N sur la production de prairie. D’une manière générale, nos résultats soulignent l'importance de l’hétérogénéité en N pour les processus plante-sol à différentes échelles spatiales et montrent que les effets de l'hétérogénéité varient en fonction des attributs des patchs. Les interactions biotiques (ici la compétition) semblent jouer un rôle relativement plus important que les facteurs abiotiques (ici changements chroniques de pluviométrie) pour les effets d'hétérogénéité. Nous concluons que les impacts de l'hétérogénéité en N sur les processus plante-sol peuvent avoir des conséquences sur les rétroactions plante-sol impliquées dans la régulation des cycles biogéochimiques, et sont à même de fournir des informations utiles pour le développement de pratiques de gestion efficientes dans l’utilisation de l’N. / Grasslands provide a variety of important ecological and economic services worldwide. Improved understanding of grassland structure and function is necessary for the development of sustainable management and maintaining the provision of multiple ecosystem services in a changing environment. However, predicting grassland structure and function is a challenge because grasslands are dynamic, heterogeneous systems. In grazed grasslands, large herbivore activities promote heterogeneity in soil nutrients via excretion, but the effects of patchy nutrient inputs and soil spatial heterogeneity on grassland structure and function remain unclear. This thesis addresses effects of spatial heterogeneity in soil nitrogen (N) for grassland ecosystem structure and function, with particular emphasis on community responses. A combination of experimental and modelling approaches are used to study impacts of a number of different patch attributes (N form, patch size, patch contrast), as well as possible interactions with rainfall regime and timing of N inputs. We find that patchy N inputs enhance within plot-plant production and biomass variability irrespective of N form, but do not modify whole-plot plant production in the short term. Nevertheless, patchy organic N promotes spatial and temporal asynchrony in plant-soil responses, with implications for longer-term grassland function. Unlike plant production, community structure responds significantly to patchy N inputs, with increased community dominance and a shift in the rank of subordinate species. Contrary to expectations, rainfall quantity does not modify heterogeneity effects on either plant production or community structure. Modelling work shows that heterogeneity effects on field-scale production vary depending on patch size and patch contrast. For a fixed total N input, field-scale grassland production responds positively to patch size, but decreases in high- versus low-patch contrast conditions. Patch size does not interact with patch contrast or timing of N inputs on grassland production. Overall, our results highlight the importance of N heterogeneity for plant and soil processes at different spatial scales, and demonstrate that heterogeneity effects vary depending on patch attributes. Biotic interactions (competition) appear to play a relatively greater role than abiotic factors (chronic rainfall changes) for heterogeneity effects. Impacts of N heterogeneity on plant and soil processes may have significant implications on plant-soil feedbacks involved with the regulation of biogeochemical cycling, and provide useful information for the development of efficient N management strategies.

La modélisation dynamique des systèmes écologiques constitue une méthode incontournable pour comprendre,prédire et contrôler la dynamique des écosystèmes semi-naturels, qui fait intervenir des processuscomplexes. Le principal objectif de cette thèse est de développer un modèle permettant de simuler la dynamiqueà moyen terme de la végétation herbacée dans les prairies permanentes, en tenant compte à lafois de la productivité et de la biodiversité. Les prairies sont des réservoirs présentant une forte biodiversitévégétale, qui soutiennent de nombreux services écosystémiques. Sur le plan agricole, cette importantediversité contribue à la qualité de la production fourragère, et de plus, elle permet une plus grande résistancede la végétation face à des changements climatiques (réchauffement moyen, vagues de chaleur etde sécheresse).Pourtant, cette notion clé de biodiversité n’est que faiblement prise en considération dans la modélisationde l’écosystème prairial : elle est souvent absente ou alors présente sous une forme très simplifiée. Enréponse à ces considérations, ces travaux de thèse présentent la construction d’un modèle de successionbasé sur des processus, décrit par un système d’équations différentielles ordinaires, qui représente ladynamique de la végétation aérienne des prairies tempérées. Ce modèle intègre les principaux facteursécologiques impactant la croissance et la compétition des espèces herbacées, et peut s’ajuster à n’importequel niveau de diversité, par le choix du nombre et de l’identité des espèces initialement présentes dansl’assemblage. Ce formalisme mécaniste de modélisation nous permet alors d’analyser les relations qui lientdiversité, productivité et stabilité, en réponse à différentes conditions climatiques et différents modes degestion agricole.[...]Ces résultats soulignent alors le besoin de prendre en compte le rôle clé joué par la biodiversité dansles modèles de l’écosystème prairial, de par son impact sur le comportement des dynamiques simulées.De plus, pour rendre correctement compte des interactions au sein de la végétation, le nombre d’espècesconsidéré dans le modèle doit être suffisamment important. Enfin, nous comparons les simulations devégétation de ce modèle à des mesures issues de deux sites expérimentaux, la prairie de fauche d’Oensingen,et le pâturage de Laqueuille. Les résultats de ces comparaisons sont encourageants et soulignentla pertinence du choix et de la représentation des processus écologiques clés qui composent ce modèlemécaniste.Ce travail de thèse propose donc un modèle, en total adéquation avec les besoins actuels en terme demodélisation de l’écosystème prairial, qui permet de mieux comprendre la dynamique de la végétationherbacée et les interactions entre productivité, diversité et stabilité. / Dynamic modelling of ecological systems is an essential method to understand, predict and control thedynamics of semi-natural ecosystems, which involves complex processes. The main objective of this PhDthesis is to develop a simulation model of the medium- and long-term dynamics of the herbaceous vegetationin permanent grasslands, taking into account both biodiversity and productivity. Grasslandecosystems are often hot spots of biodiversity, which contributes to the temporal stability of their services.On an agricultural perspective, this important biodiversity contributes to the forage quality, andbesides, it induces a higher ability of the vegetation cover to resist to different climatic scenarios (globalwarming, heat and drought waves).However, this key aspect of biodiversity is only poorly included in grassland models : often absent ofmodelling or included in a very simple form. Building on those considerations, this PhD work exposes thewriting of a process-based succession model, described by a system of Ordinary Differential Equationsthat simulates the aboveground vegetation dynamics of a temperate grassland. This model implementedthe main ecological factors involved in growth and competition processes of herbaceous species, and couldbe adjust to any level of diversity, by varying the number and the identity of species in the initial plantcommunity. This formalism of mechanistic models allows us to analyse relationships that link diversity,productivity and stability, in response to different climatic conditions and agricultural management.In mathematical grassland models, plant communities may be represented by a various number of statevariables, describing biomass compartments of some dominant species or plant functional types. The sizeof the initial species pool could have consequences on the outcome of the simulated ecosystem dynamicsin terms of grassland productivity, diversity, and stability. This choice could also influence the modelsensitivity to forcing parameters. To address these issues, we developed a method, based on sensitivityanalysis tools, to compare behaviour of alternative versions of the model that only differ by the identityand number of state variables describing the green biomass, here plant species. This method shows aninnovative aspect, by performing this model sensitivity analysis by using multivariate regression trees. Weassessed and compared the sensitivity of each instance of the model to key forcing parameters for climate,soil fertility, and defoliation disturbances. We established that the sensitivity to forcing parameters ofcommunity structure and species evenness differed markedly among alternative models, according tothe diversity level. We show a progressive shift from high importance of soil fertility (fertilisation level,mineralization rate) to high importance of defoliation (mowing frequency, grazing intensity) as the sizeof the species pool increased.These results highlight the need to take into account the role of species diversity to explain the behaviourof grassland models. Besides, to properly take into account those interactions in the grassland cover, theconsidered species pool size considered in the model needs to be high enough. Finally, we compare modelsimulations of the aboveground vegetation to measures from two experimental sites, the mowing grasslandof Oensingen, and the grazing grassland of Laqueuille. Results of these comparison are promising andhighlight the relevance of the choice and the representation of the different ecological processes includedin this mechanistic model.Thus, this PhD work offers a model, perfectly fitting with current needs on grassland modelling, whichcontribute to a better understanding of the herbaceous vegetation dynamics and interactions betweenproductivity, diversity and stability.

No description available.

The grazing management project in the Okhombe ward of the Amazizi Tribal Authority formed part of the National Department of Agriculture's LandCare program to address communal natural resource management issues. Okhombe land is communal whereby every member of the community is the legal owner of the rangeland with individual ownership of stock with the chieftaincy playing a major role in land allocation. In order to avoid critics of the past and address the top-down approach of the past interventions, a participatory approach was conducted in the planning and implementation of the grazing system. The service providers held a series of visioning workshops with the community in an effort to better understand community resource use patterns, needs, constraints and opportunities as part of the participatory approach. Issues identified by the community were the need for fencing grazing camps, animal health improvement, subdivision of rangeland and crop fields and the development of a rotational grazing system. The main aims of this study were to develop a participatory grazing plan with the community, develop and support institutional structures governing range management, and build capacity of the community in range management. The effect of the current grazing system on species composition was determined. In addition to these, the project investigated the potential different fodder trees has on alleviating feed and nutritional deficit, particularly during the dry winter months of the Upper Thukela. Among the main achievements of this study was the development and strengthening of local institutional structures and effective liaison by all structures with the Inkosi and the tribal council. The community developed a rotational grazing plan, marked the camp boundaries, produced digital maps and successfully built fence boundaries (approximately 20 kms of fencing) to divide their land. The fence boundaries separated the crop fields and rangeland, closed ward boundaries in the upland to prevent access by cattle from neighbouring wards, and divided the land into three camps. Six crush pens were constructed in each subward of the Okhombe ward. A communal herders fund opened and fence construction improved crop yields due to a decrease in crop damage by cattle. Okhombe ward, located in the Highland Sourveld region of KwaZulu-Natal, experiences feed and nutrition deficits to ruminants during winter. The prevailing species composition in Okhombe was investigated as part of the grazing plan. The veld condition of the sites ranged from poor (40.7%) in the bottomland to an averaged of 47.0% in upland sites. The most distinctive feature of the rangeland in this area was the loss of highly palatable Decreaser grass species (P <0.05), such as Themeda triandra in the bottom slopes « 1300 m) when compared to the upland (> 1800 m). The proportional abundance of Decreaser species accounted for an averaged of 1.02% of the bottomland and an averaged of 11.5% of the upland compared to the values of 49% in the benchmark (grassland in optimal condition). The composition of the less palatable Increaser Il species was very high at all elevations (1200 m -80.7%, 1400 m - 75.8% and 1700 m - 55.7%) when compared to the low benchmark composition of 19%. The dominant grasses of the bottom slopes were Increaser Il species, such as Eragrostis curvula, Eragrostis plana and Sporobolus africanus and unpalatable Increaser III species such as Aristida junciformis. A significant difference (P < 0.05) in the composition of Decreaser, Increaser I and Increaser Il species was found between the bottom and slopes compared to the upland region. However, the grass cover formed by these tufted species was generally high, making it more resistant to physical degradation. The bottom slope ranged from reasonable to excellent cover (16.9%), the middle slope ranged from reasonable (15.9%) to a good cover of 18.1%, averaging 16.7% and a range of 16.1% to 17.9% for the upland plateau. In the agroforestry trial the potential of different fodder species for supplementing fodder was examined. Leucaena leucocephala had the potential of being a suitable fodder tree species for use in alley cropping (P < 0.05) compared to Morus alba and Acacia karroo. Results from the partially intercropped treatments showed that L. leucocephala yield (665 kg ha-I) varied significantly (P < 0.05) from the A. karroo (378 kg ha-I) and M alba yield (345 kg ha-I). Treatments that were fully intercropped varied, but no significant difference (P > 0.05) were recorded. Morus alba produced the least yield of 345 kg ha-I, A. karroo yielded 378 kg ha-1 and 1. leucocephala recorded the high of 664 kg ha-I. Results from the second season showed similar trend in that 1. leucocephala yielded a significant (P < 0.05) fodder production of 1715 kg ha-I in comparison to M. alba (1101 kg ha-I) and A karroo (1140 kg ha-I). M alba yielded the least dry matter production (P < 0.05) but had high potential (P < 0.05) for addressing lack of firewood in rural areas. Morus alba yielded high fuel wood production from both two seasons. There were no significant differences in fuel wood yield (P > 0.05) from the partially intercropped M alba (507.9 kg ha-I) and 1. leucocephala (455.0 kg ha-I) but the yield from both species varied significantly from the A. karroo yield (103.kg ha-I). With regard to fully intercropped plots, fuel wood yield from all tree species varied significantly, A karroo resulting in low yield (63 kg ha-I), 1. leucocephala recorded 243 kg ha-l and M alba the highest yield of 444 kg ha-I. In the second season, M. alba yielded an averaged fuel wood production of 728 kg ha-l and a low of 439 kg ha-I from 1. leucocephala. Acacia karroo, a slow growing indigenous tree, might be preferred by farmers due to its less branches resulting in minimal light competition with crops. Leucaena leucocephala tend to grow slowly in its initial establishment stage, but once roots become well established, it grows fast and produces high quantity of fodder. The effect all fodder trees had on crop yield was not negative during the trial period and further research on long term effects of alley cropping is recommended. The conclusions drawn here were based on tree growth and their likely impact in alley cropping. Leucaena leucocephala was also recommended as a preferred species for rural ruminants based on the forage quality study. The results showed high content of crude protein (19.27%), low NDF content (50.38%) and very low tannin content (1.19%) from 1. leucocephala compared to A. karroo with a high tannin content of 5.69%. Acacia karroo had a crude protein content of 13.60%, NDF percentages of 44.16 and 34.64% of ADF content. Morus alba also had a recommended chemical composition of 11.71% of CP, 42.86% of NDF, 36.96% of ADF and a low tannin content of 0.65%. L. leucocephala foliage proven is readily degradable under different diet ranging within 24 hrs of intake (P < 0.001) compared to other feeds. L. leucocephala had high dry matter loss degraded from the rumen under Eragrostis hay diet with poor nutrients to high protein concentrates diet. Under the Eragrostis hay diet for instance, L. leucocephala tend to degrade rapidly with values of dry matter loss ranging from 32.2% to 39% at 4 hrs to 16 hrs, when compared to low dry mater loss of 26% at 4 hrs to 31.33% at 16 hrs. Feeds such as M alba tend to degrade slowly within 24 hrs of intake and rapidly degrades after the stated period. The ep content of maize stover was very low ranging from 1.60% in maize stalks to 2.63% in maize leaves. The fibre content in maize stover was very high when compared to lower values in fodder samples. The NDF content ranged from 77.92% in maize leaves to 81.60% in maize stalks. Maize leaves when compared to a combination of maize leaves and maize stalks sole tend to degrade better within 24 hrs of intake. This was due to low (P < 0.05) degradability rate of maize stalks compared to a combination of maize stalks and leave and leaves sole and least NDF content in maize leaves might have attributed to these results. Due to poor chemical compositions of these roughage samples, the study recommended the establishment of fodder banks and agroforestry systems to curb the nutrients deficit during winter. In conclusion therefore, this study highlight that the sustainability of rural systems to manage communal grazing land should be further explored. Most of the challenging issues in communal range management are social in nature rather than technical concepts. These include ways of improving social contributions from cattle to the community while maintaining cultural values of the use of cattle. The interventions in communal range management by service providers should understand the institutional arrangements within a community and an attempt to strengthen such existing structures is recommended. Further interventions by service providers in Okhombe ward should bring in the planning discussions, experts from social sciences, to deal with understanding of community dynamics. Complexities in communal range management involve dealing with non-stock owners within project boundaries. Communities from neighbouring wards should not be ignored and ways of improving communications and updating project details to them should be formulated. Shortage of land and closing of ward boundaries to prevent access to land by neighbouring wards is among community complexities to be explored. Communities in rural lands do share land and in most cases boundaries are known but invisible by an outsider to identify. It is important to strengthen and maintain every success in communal lands as that may form core of the project. Successes on grazing management by locals is far from being the improvement in veld but there are rather various factors to the successes of grazing projects in rural areas. Examples of successes based on Okhombe project are reduction in stock theft, improved in relationship between community and locals institutions, a reduction in stock mortalities during winter and improved animal health. Veld improvement is among successes but there are accomplishments phases to fulfil before focusing on improvement of species composition. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.