Masters Degrees (Grassland and Rangeland Science)

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Utilising GIS and remote sensing to assess the impacts of the invasive Rubus cuneifolius on veld grazing capacity.
(2023) Mnikathi, Ayanda Pretty.; Kirkman, Kevin Peter.; Sibanda, Mbulisi.
This study was motivated by the heavily invasion of Rubus cuneifolius (bramble) in the Mistbelt grasslands of KwaZulu-Natal province of South Africa, particularly at Wakefield Farm. When not effectively managed, bramble invasion results in dire consequences, including the reduction of veld grazing capacity. The initial steps in managing invasive alien plants (IAPs) in rangelands involves understanding their distribution and extent. This requires a suitable satellite data with optimal temporal, spectral and spatial resolution, a task that necessitates accurate and feasible mapping of IAPs. In this regard, this study aimed to assess the utility of Sentinel-2 multispectral imager in mapping the spatial distribution of bramble and assessing its impact on veld grazing capacity. This overarching aim was addressed using two specific objectives. The first objective was to test the capabilities Sentinel-2 Multispectral Imager (MSI) in detecting and mapping bramble during the senescence period. To address this objective, four sets of spectral features (all spectral bands, mNDVI, mSR and combined inputs) and the Discriminant Analysis algorithm were used to test the utility of Sentinel-2 MSI’s in detecting bramble during the senescing stage. Inputs were tested when red edge bands were included in the analysis (inclusive bands) compared to when they were excluded from the analysis (exclusive bands). The second objective was to assess the impacts of bramble invasions on grass production, species diversity and dominance. To address this objective, grass biomass and species data we gathered and dry weight rank (DWR) and double sampling techniques were utilised. A relationship between the estimated biomass and the actual biomass was determined in the invaded and the uninvaded patches. Then, Shannon-Wiener diversity index and the Simpson’s Index were used to calculate species diversity and dominance, respectively. Results showed that bramble could be detected using Sentinel-2 MSI to an overall accuracy of 89.33% with red edge derived mNDVI being the most influential discrimination variable. Furthermore, results showed a significant relationship between the estimated and the actual biomass as well as a higher total biomass in the invaded patches. In uninvaded patches, species diversity was higher while dominance was lower and in the invaded patches species diversity was lower while dominance was higher. This study highlights that Sentinel-2 MSI's red edge bands are well-suited for discriminating invasive alien plants, particularly bramble, in rangelands during annual senescence. Additionally, it emphasizes that bramble invasion diminishes the value of rangelands by reducing the productivity of palatable grass species.
The seasonal patterns in plant quality in various ecological zones in Natal.
(1990) Zacharias, Peter John Kenneth.; Tainton, Neil M.
The objectives of this study required that the following investigations be undertaken: 1) to determine if plant quality can be altered by modifying growing conditions; 2) to quantify the seasonal trends in plant quality from different sites; 3) to relate differences between sites to environmental variables; 4) to develop an objective classification of SWEETNESS; and 5) to plan future research. The majority of the commercial and subsistence livestock in southern Africa rely almost entirely on veld (rangeland) for their supply of nutrients. These rangelands are traditionally and conventionally managed according to their classification as 'SWEETVELD' and 'SOURVELD'. An intermediate group 'MIXED-VELD' is also recognised. The subjective classification is based on the quality (nutritive value) of the rangeland when it is mature (winter). Both extremes of 'sweet' and 'sour' rangeland contain many of the same species and this thesis considers the relationship between the soil ( chemical and physical) and the physical environment and plant quality of a single indicator species Themeda triandra (red grass). A glass house experiment was used to determine the effect of manipulating the soil environment on the quality of T. triandra. There were no significant differences ( P> 0. 05) between any of the six treatments (combinations of eutrophic, ameliorated and dystrophic soil together with 'sweet' and 'sour' T. triandra plan ts) . When compared as a group significantly (PsO. 01) higher in disappearance ( CDMD) than the SOUR group. the SWEET group were cellulase dry matter However the difference was only 1 . 5% CDMD uni ts and is believed to be biologically unimportant. It was concluded that the quality of T. triandra can not be altered by manipulating its growing conditions. In a field investigation the seasonal pattern and the relationship between environmental variables and plant CDMD, N, P, K, Mg, Ca, Sand Zn are described for Natal, South Africa. Most models have significant (Ps0.01) R2 values but very few show any strong relationship between soil chemical status and forage j~-l quality. ALTITUDE appears most in the models as a related variable. The models would have little predictive value outside Natal and do not contribute or describe adequately the factors determining seasonal patterns in plant quality at different locations. A multivariate approach is used to provide an objective index of 'SWEETNESS' (based on seasonal variations in plant quality at 31 sites over 23 months), and this is related to environmental variables. This analysis also showed that the soil environment was only weakly related to plant quality. The results are confusing given the wide variations in both plant quality and soil chemistry in the data presented.
Factors affecting the seasonal variation of veld quality in South Africa.
(1988) Kirkman, Kevin Peter.; Tainton, Neil M.
This project was initiated to investigate the factors affecting the seasonal variation of veld quality in South Africa, with specific objectives as follows: (1) to establish what factors might play a role in seasonal variation of plant quality in South African grassveld; {2) to provide a more objective definition of the terms sweetveld and sourveld than already exists; (3) to determine an objective and quantitative method of measuring or indexing the degree of sweetness or sourness of a representative species of both sweetveld and sourveld using Themeda triandra as the reference species and (4) to establish which factors, if any, may be manipulated to improve veld quality. The results indicate that cellulase dry matter digestibility, neutral detergent fibre, nitrogen status and phosphorus levels were the plant factors most important in indicating veld quality. Climate and soil fertility were found to have no consistent relationship with veld quality. Thus any definition of sweetveld and sourveld will have to be based on the winter quality of veld and not on the climate or soil fertility. The winter quality of veld appears to be a function of the seasonal quality patterns of all species present and not only a reflection of the winter quality of '.L_ triandra. As the seasonal quality patterns are likely to vary between species, management will influence the degree of sourness in the long term by influencing species composition and in the short term by affecting the ontogeny of the plants present i.e. the amount of preferred material left on palatable and unpalatable species available for winter grazing. The seasonal quality pattern and inherent winter quality of '.L_ triandra has been shown to vary considerably from area to area. As each species is expected to show unique quality patterns, the sweetveld/sourveld situation becomes extremely complex. There are no obvious factors (except management) that can be manipulated to improve the winter quality of veld.
Selective impacts on the vigour and mortality of Aristida junciformis (subsp. junciformis)
(2019) Scharlach, Anke.; Kirkman, Kevin Peter.; Tedder, Michelle Jennifer.; Morris, Craig Duncan.
The aim of grazing management is to maximise livestock production by maintaining high sward quality. Many southern African grasslands have become degraded allowing grass species unfavourable for livestock production, such as Aristida junciformis subsp. junciformis, to become dominant thereby reducing the available sward quality. Aristida junciformis persists once established and is remarkably understudied. Three studies were conducted to investigate the dynamics of this grass and to find focused management techniques to control and manage A. junciformis. The studies compared the impact of a high density graze (HDG), targeted herbicide application and a control on the survivorship and productivity of A. junciformis tufts, on the species and cover composition and on the post-treatment seedbank. Tufts exposed to herbicide had a lower probability of survival (p = 0.887) than those subjected to a HDG (p = 1.000) or control (p = 1.000). After treatment implementation, grazed tufts were significantly (p = 0.0018) shorter than control tufts. The tufts displayed a linear growth rate under the control (F1,8 = 456.84; P < 0.001), increasing steadily over time, and a quadratic growth rate under the HDG (F2,7 = 125.35; P < 0.001), initially growing rapidly then declining towards the end of the growing season. There was no significant difference in the height (p = 0.9481) and the aboveground net primary productivity (ANPP) (p = 0.7053) between the tufts in the control and HDG paddocks. The plant species composition (p = 0.4169) and cover composition (p = 0.4169) did not differ among treatments, however there were significant shifts in species composition (p = 0.0002) and cover composition (p = 0.0005) over time (p = 0.0002). The directional shift in species and cover composition were similar in all paddocks. Most of the grazing resistant perennial grasses, or ‘mtshiki’ species (Eragrostis curvula, E. plana, Sporobolus pyramidalis and S. africanus) and A. junciformis increased and Themeda triandra decreased over time. Total vegetation cover increased across all paddocks for all grass and forb species such that the bare soil cover was reduced from 53% to 34%. No A. junciformis seedlings emerged from the seedbank study. Most of the seedlings emerging from the seedbank (92%) and field studies (40%) were forbs. In the field study A. junciformis (30%) was second most dominant, followed by T. triandra (13%). The plant species composition of emerged seedlings did not differ among treatments (p = 0.8134). Aristida junciformis is and remains a persistent, indigenous weed that is difficult to eradicate. More research is required to prevent its establishment in areas not yet dominated but prone to its invasion and to eradicate it in veld where it is already dominant.
Effect of elevated temperatures on growth and defence of Vachellia 1 sieberiana seedlings grown with or without grass.
(2020) Ncisana, Lusanda.; Scogings, Peter Frank.; Mkhize, Ntuthuko Raphael.
Warming is suggested to increase globally in the next few decades. Warming, soil nutrients, 2 water, CO2 and sunlight are the most important environmental factors for plant life. Elevated 3 temperatures can highly impact plant metabolism, photosynthesis and consequently woody 4 plant performance and fecundity. An increase in minimum temperatures will possibly result in 5 the transformation of grasslands to savannas. The effects of rising temperatures on growth and 6 defence of woody plant seedlings and trade-offs between growth and physical defence 7 particularly thorn length of woody plants that potentially invade grasslands have been studied 8 utilising open-top warming chambers (OTCs). Furthermore, it is important to study the effect 9 of warming on woody plant growth and defence when competing with grass. Field experiments 10 were conducted in three different seasons to determine the effect of warming on growth and 11 defence of Vachellia sieberiana seedlings growing with or without grass, and the effect of 12 warming on trade-offs between growth and defence of V. sieberiana seedlings growing with or 13 without grass. It was predicted that elevated temperatures would increase growth and thorn 14 length of V. sieberiana seedlings growing (1) with or without grass in the dormant season and 15 early growing season, but (2) in the later part of the growing season only when grass cover is 16 absent. It was also predicted that warming, with or without grass cover increases seedling 17 growth, but elevated temperatures would decrease investment in defences relative to growth of 18 V. sieberiana seedlings when grass cover is absent. To test these predictions, 120 seedlings 19 that were three weeks old were transplanted into 20 field plots. Ten plots were warmed, and the 20 other ten plots were not warmed. In both warmed and unwarmed plots the grass was either 21 cleared or not. OTCs raised air temperature by 1.0 to 2.5 °C. Stem length, plant height, stem 22 diameter, thorn length, and dry mass of shoot, leaf, and root were measured after 6 weeks for 23 the dormant season, and after 6 weeks and 12 weeks in the growing season for the first 24 experiments. For the second experiment, plant height, stem length, stem diameter and thorn 25 length were measured after 6 weeks. To determine effects of warming and grass cover on the 26 relationship between defence and growth, ratios of thorn length (a measure of defence) to plant 27 height, stem length and stem diameter (measures of growth) were calculated. The first 28 experiment revealed that warming increased growth of V. sieberiana seedlings in all seasons. 29 Defence was low in the presence of grass cover in the growing season, but not in the dormant 30 season. The second experiment revealed that warming and grass cover significantly and 31 independently reduced the thorn length: plant height ratio and thorn length: stem length ratio. There was a significant interaction effect between warming and grass cover on the thorn length: 1 stem diameter ratio. Lastly these results suggest that, with an increase of 1 – 2.5 °C regardless 2 of grass cover at the time of seedlings establishment, the rate of woody encroachment will 3 increase as temperature rises. The findings also suggest that there are trade-offs between the 4 growth of V. sieberiana seedlings and physical defence in terms of thorn length.
Local and global controllers of grassland ecosystem stability during global change.
(2019) Demmer, Stuart.; Kirkman, Kevin Peter.; Tedder, Michelle Jennifer.
Human impacts on grasslands dramatically affect grassland biodiversity which impacts the ability of ecosystems to sustainably provide ecosystem services. As the extents of these anthropogenic impacts increase (due to agricultural intensification, for instance) solutions to this problem are becoming increasingly important. The ecosystem stability concept provides a framework to investigate how biological systems such as grasslands respond to disturbances. However, there is uncertainty relating to the ecosystem components which influence the various facets of ecosystem stability. Therefore, the aim of this dissertation is to 1) outline the current academic consensus pertaining to the drivers of grassland ecosystem stability, 2) contribute to underrepresented research areas identified in the literature review, and 3) investigate whether there are general environmental conditions which predispose to grassland destabilisations following anthropogenic disturbance. Academic consensus was assessed using a systematic map of review articles discussing grassland ecosystem stability concepts. This review highlighted the many complex interactions that exist in grassland ecosystems. There was also a strong consensus that diversity mediates ecosystem functioning and stability. Other ecosystem processes such as fire, herbivory, woody encroachment, and plant invasions were also well represented and discussed in these review publications, however, climatic impacts on grasslands were identified as an important knowledge gap. To address this, nutrient enriched grassland stability responses to temperature variability were studied using a long-term nutrient addition experiment. Surprisingly, nutrient enriched grassland productivity was more stable than control grasslands in response to temperature variability. Finally, environmental drivers of grassland stability changes following nutrient addition were assessed using a globally replicated experiment. This investigation showed that grasslands with a history of intensive anthropogenic management are positively affected by nutrient addition whilst stability in more naturally assembled grasslands is greatly reduced following nutrient addition. Stability changes were also associated with changes in nutrient availability and soil macronutrient (specifically Ca and K, but not micronutrient) status. Sward structure changes (such as increased compositional dissimilarity, greater dominance, and reduced asynchrony) were associated with stability reductions following nutrient addition. The findings of these three investigations highlight the serious impacts that human activities which result in increased nutrient deposition in grasslands are having on grassland ecosystems. In relation to the prevailing consensus identified in the review literature concerning the positive effects of grassland diversity on ecosystem stability and functioning, this dissertation advocates for the increased preservation of intact grasslands.
Ecological effects of Festuca costata on the Drakensberg grasslands.
(2018) Mwambilwa, Kabemba.; Tsvuura, Zivanai.; Kirkman, Kevin Peter.
Fire and herbivory are important in determining the vegetation structure in savannas and grasslands. In addition, anthropogenic activities have significantly contributed to alterations in the relative abundance and distribution of plant species in many grasslands through increased nitrogen deposition and elevated concentration of carbon dioxide in the atmosphere. Using a field experiment, the study explored the effect of neighbouring plants, defoliation, and fire on the ecological performance of a major C3 grass, Festuca costata, whose range is expanding in Afro-temperate grasslands of the Drakensberg Mountains in South Africa. The experiment had three factors: fire at two levels (burned, unburned), defoliation by clipping 50mm above-ground surface, at four levels (no defoliation, defoliation of focal plant, defoliation of neighbouring plant within a 300 mm radius, and defoliation of both the focal and the nearest neighbouring grass within a 300 mm radius from the focal plant). The third factor was plant neighbourhood types at three levels (the focal plant growing alone, focal plant growing with other F. costata plants, focal plant growing with any other grass species) for a total of 24 treatment combinations with five replicates. Using a pot experiment under garden conditions, the study evaluated the influence of soil nutrient amendment with 140 KgHaˉ¹ limestone ammonium nitrate in the performance of F. costata. The variables of interest in both experiments were; above-ground biomass production, tuft circumference, number of tillers and specific leaf area of the focal plant. Generalised Linear Models in SPSS were used to analyse the data from both experiments. The results showed that burning had a significant negative effect on above-ground biomass production, number of tillers and tuft circumference of the focal plant (P < 0.001), with the unburned grassland showing greater mean values for all parameters than the burned grassland. Defoliation had significant negative effects on above-ground biomass production, number of tillers, tuft circumference while it showed strong positive influence on specific leaf area of the focal plant. Neighbourhood types were significantly negative for above-ground biomass production, number of tillers and tuft size of the focal plants (P< 0.001 in all cases). Nutrient addition reduced the number of tillers of F. costata and tuft size and showed no significant effects on above-ground biomass production and specific leaf area. Defoliation significantly increased SLA, above-ground biomass production, number of tillers and tuft circumference were not affected.. Plant neighbourhood types showed significant negative influences on tuft circumference. Defoliation accounted for the most variations in reduced tuft size, above-ground biomass and number of tillers, however, it resulted in increased specific leaf area. These results suggest that defoliation by herbivores and use of fire may be complementary tools for managing high altitude grasslands under climate change. The findings of both the field and pot experiment suggest that F. costata may not be tolerant to selective herbivory. In addition, the study shows that the increase in nitrogen availability due to anthropogenic activity may have a negative influence on the performance of F. costata.
Optimal spatial and temporal utilization of grassland resources for extensive livestock production.
(2018) Mamayo, Ntomboxolo.; Kirkman, Kevin Peter.
South Africa naturally experiences variation in rainfall patterns with distinct seasonal distribution. The anticipated disruptive effects of climate change, in this region, on vegetation dynamics is likely to accentuate the impact of seasonal forage nutrient fluctuations on livestock production. Although there are several grazing philosophies that have been adopted to mitigate these constraints (continuous and variations of rotational grazing systems), debates on superiority between these systems continue to be of interest to researchers and livestock producers. Nonetheless, continuous grazing systems have largely been condemned due to the detrimental effects of extensive selective grazing on vegetation composition and soil conservation. Poor implementation of these systems has resulted in extensive veld degradation, significantly reducing sustainability of livestock production. This is more pronounced in communal rangelands where production capital is limited. Moreover, erratic rainfall and extreme temperatures have resulted in the abandonment of large areas of croplands, and thus further impacting negatively on livestock production dynamics. Therefore, it is necessary to quantify utilization regimes of the abandoned crop lands, continuously and rotationally grazed veld and examine their effects on ecosystem health and livestock production. To examine these effects, a study was conducted in Mzongwana, Matatiele (old lands and continuously grazed veld) and in Wakefield Research Farm, Fort Nottingham (rotationally grazed veld). In each site, six 100m line-transects were laid and a 0.5 by 0.5m quadrat were placed in 2m intervals along each transect. In each quadrat, sampling for species composition, biomass accumulation, and bulk forage quality were sampled. Along each transect, soil samples were collected at 0-15cm depth at 25m intervals and analysed for soil fertility. To examine the influence of forage utilisation intensities, as affected by the previous management, seasonal nutrient dynamics, data were collected during summer (November, January, and April) and during winter (June and August). The results revealed that species composition and biomass accumulation had a direct influence on forage quality, while grazing systems mostly affected soil fertility. Additionally, the results confirmed that previous cultivation has a negative effect on soil organic carbon (C) and nitrogen (N) concentrations, and revealed a significantly high mineral variation between seasons. These variations were also evident in the nutrient accumulation in the forage, with distinctively high crude protein (CP) and low acid detergent fibre (ADF) and neutral detergent fibre (NDF) in early summer. Therefore, to effectively utilize the old lands towards improved livestock production, grazing should be during early to mid-summer. On the other hand, despite soil nitrogen in the continuously grazed site being lower than the rotationally grazed site, CP was significantly higher and steadily declined over the season. Therefore, suggesting that biomass accumulation has a negative influence on forage quality. Moreover, lower forage quality in the rotationally grazed veld was largely attributed to extended rest periods which allowed grass to mature, thus reducing the overall quality. Based on these findings, it can therefore, be recommended that the old lands be grazed during the early to mid-summer and rested during late-summer. This will improve nutrient availability for livestock and will allow for seeding rest to improve succession rate. Moreover, the continuously grazed veld is recommended to be grazed interchangeably with the old land, that is, in winter. As a result of slow crude protein decline in the continuously grazed veld, grazing in winter will improve livestock morbidity and mortality resulting from low forage availability. Finally, in the rotationally grazed veld high intensity grazing should be incorporated in the grazing systems employed to reduce biomass carryover and keep forage low and nutritious, as this veld in a high rainfall area.
Seeing the wood for the trees : an evaluation of the Buffelsdraai Landfill Community Reforestation Project.
(2016) Roy, Kathryn Elizabeth.; Kirkman, Kevin Peter.; Adie, Hylton Ralph.; Douwes, Errol.; Roberts, Debra Cynthia.
Cities, and African cities in particular, will need a suite of relevant tools and approaches to deal with the varied climate change-related threats that these cities will likely endure in the future. African cities will be most affected due to the challenges of underdevelopment and resource shortages and, therefore, must address the climate change challenge in a way that ensures meaningful developmental co-benefits and overall cost-effectiveness. Local level actions, such as ecosystem-based adaptation (EBA), and community-based adaptation (CBA), are both effective forms of adaptation for African cities. The City of Durban (eThekwini Municipality, South Africa), has embarked on a novel approach that combines both these tools, the community ecosystem-based adaptation (CEBA) concept, of which the Buffelsdraai Landfill Community Reforestation Project (BLCRP) is a powerful example. The BLCRP is restoring indigenous forest in the buffer zone surrounding the Buffelsdraai Regional Landfill Site. The project aims to sequester a proportion of CO2 emissions generated locally during the 2010 FIFA World Cup™, whilst also uplifting local impoverished communities and building functional ecological infrastructure. The need to build the resilience of the city to climate change, in the face of increased uncertainty and risk, is considered urgent by planners. Building functional ecological infrastructure, which includes indigenous forest ecosystems, can help bolster this resilience. Early detection in restoration projects, such as the BLCRP, can allow problems to be identified and rectified through adaptive management in the early stages of restoration. This approach will affect the success and cost effectiveness of the restoration project. The BLCRP is currently in the establishment phase, a time when enrichment planting is best evaluated. This study examines the extent to which the composition, measures of diversity, and functional traits of planted species at restoration sites, are comparable with a local forest reference site. After three to five years, restored sites show low similarity with the reference forest due to different species composition and low species diversity and richness. Functional richness is significantly lower in two of the Buffelsdraai sites. Additionally, few bird-dispersed species were planted at Buffelsdraai and the restoration sites are infested with invasive alien plants compared with the reference ecosystem site. Furthermore, planted tree densities at the restoration site were considerably lower than figures recommended for restoration projects. Given these findings, the BLCRP is unlikely to meet long-term goals. To address these project shortfalls, I propose a higher planting density and a rigorous process to select tree species for planting. This includes implementing the framework species method at Buffelsdraai, which has proven successful in various countries. The framework species method encompasses the planting of mixtures of early and late successional species to capture the site, establish a multi-layered canopy, modify the microclimate and diminish weed growth in the years immediately after plantings. Species planted will also attract animals that will further disperse seeds into the planted area. A desktop assessment of forty-eight tree species helped determine which species would be suitable for field-testing and for eventual planting as framework species at Buffelsdraai. These included tree species common to the vegetation type found at the reference ecosystem site. A total of 18 species were considered unacceptable and removed, leaving 30 species as candidates for future testing. Best performing species were Celtis africana, Ekebergia capensis, Ficus natalensis, Bridelia micrantha and Croton sylvaticus due to their ability to attract wildlife, grow fast and tall and remain resilient to climate change. Worst performing species were Eugenia natalitia, Dalbergia obovata, Millettia grandis, Allophylus natalensis and Baphia racemosa, all of which were rejected from further testing. Future steps, such as nursery- and field-testing of candidate species, are recommended. The framework species method can be integrated with the current restoration method at Buffelsdraai. These recommendations will enhance biodiversity, increase canopy closure and reduce site management costs. Critically, appropriate and continuous monitoring is required to initiate appropriate management responses.
Burning wetlands: the influence of fire on wetland vegetation structure and composition.
(2013) Luvuno, Linda.; Kirkman, Kevin Peter.; Kotze, Donovan Charles.; Morris, Craig Duncan.
Water is a very important component of the natural world and human survival but water sources (river systems and wetlands) are becoming increasingly degraded and less functional. In particular the increase of woody C3 species into wetlands is a cause for concern, as they invade wetlands which are predominantly herbaceous. Woody species use more water than herbaceous species and this impacts wetland function. In moister savannahs and grasslands woody species are influenced significantly by fire, and fire is consequently used widely as a means of reducing woody plant density. However, in wetlands there is uncertainty about the effectiveness of fire in combating woody plant encroachment and the general impact of fire. The Kwambonambi wetlands of South Africa have been recently experiencing an invasion by woody species which are both indigenous and alien. This area was historically herbaceous and experienced frequent natural fire but is now largely under timber plantation and thus fire has been mainly excluded. This has led to a continual increase of woody species into the wetland and has seen a change from mainly herbaceous to a matrix of fern, herbaceous grasses and sedges and an invasion of swamp forest species such as Macaranga capensis. This has now affected ecosystem functions and changed fire behaviour in these wetlands. A search through the literature has revealed a lack of studies which investigate the influence of fire on wetland structure and composition. This ambiguity highlights the need for more focused research that will influence management decisions. In order to develop meaningful management strategies, there needs to be a good understanding of the problem and the underlying processes contributing to the degradation and loss of the system you are trying to manage, in this case it is wetlands. This study investigates wetland changes and losses at a small spatial and temporal scale for informing management on the best use of fire on wetlands. A temporal study (a change detection analysis) reveals that the main drivers of the vegetation structure in this landscape are the land use/land cover change in the form of large scale plantation forestry coupled with fire suppression. 92.4% of the landscape has been altered with the greatest degree of change in this landscape accounted for through the change from grassland and herbaceous wetland (1519ha and 524ha loss respectively) to timber plantation and the spread of indigenous forest indicated by an increase of 70% and 11% increase respectively. The large scale plantation forestry in the landscape has led to the drying of the landscape (which affects the hydrology of the wetlands) and therefore reduces the levels of soil saturation. Simultaneously, plantation forests are fire suppression areas to avoid tree loss. These factors, together with the disturbance of converting wetlands into plantation forest and clear felling (which occurred to 7%/155ha of the wetlands in the study site), have allowed forest species such as the fern Staenoclina tenuifolia and Macaranga capensis to invade the wetland areas. Over time, the combination of fire suppression, disturbance and drying encourages the establishment of woody seedlings, turning wetlands into swamp forests/woodlands. This regime shift is more evident in wetlands which were once converted into plantation forest with insufficient woody plant species control to accompany the withdrawal of plantation. The few wetlands which have maintained their herbaceous structure and function are those maintained with fire as a management strategy. A burn experiment shows that fire does have a significant negative effect on tree density in these wetlands-especially previous disturbed wetlands. The recommendation from this study is to remove the forest species out of the wetlands and reintroduce fire (biennial burns) into the management of these wetlands. A better relationship between the forest managers and researchers is recommended to continually co-adapt to any changes occurring in these wetlands.
Evaluation of improved Brachiaria grasses in low rainfall and aluminium toxicity prone areas of Rwanda.
(2010) Mutimura, Mupenzi.; Everson, Theresa Mary.
Abstract available in the print copy.
The effect of application of nitrogen, phosphorus, potassium and sulphur fertilisers to a perennial ryegrass sward on yield, quality and apparent intake by dairy cows.
(2010) Findlay, Nicola Jean.; Du Toit, Justin Christopher Okes.; Kirkman, Kevin Peter.
Perennial ryegrass is an intensive, temperate pasture grass that responds well to applied fertiliser. The purpose of this project was to study the effects of fertiliser on the productivity and quality of perennial ryegrass in KwaZulu-Natal and how this impacts on animal intake. It was hypothesised that over-application of fertiliser to a perennial ryegrass pasture would negatively affect the quality of the herbage for grazing by dairy cattle and that intake would be affected. Thus the project aimed to assess the effects of applied fertiliser on yield, quality and intake of an established perennial ryegrass pasture. The trial consisted of a set of six separate experiments. Each experiment focused on the interaction between two of the major nutrient elements nitrogen (N), phosphorus (P), potassium (K) and sulphur (S). The experiments (NxP, NxK, NxS, PxK, PxS and KxS) were managed separately to avoid possible transfer of nutrients during grazing, which would result in the contamination of treatments. Each factor had three levels (low, medium and high), giving a total of nine treatments per experiment. Each of the experiments was replicated three times in a randomised block design. Increased fertiliser N application rates increased perennial ryegrass yield with a pattern of diminishing return, where split applications above 40 kg N ha-1 produced smaller increases in yield when compared with the response at lower applications of N. Applied P, K and S did not affect yield, suggesting that even the lowest application levels were sufficient to not limit production. Nitrogen application affected apparent intake, but it is suggested that this is due to the yield effect rather than a direct effect of N on apparent intake. The application of P, K and S did not affect apparent intake. Results from this study showed that the quality of perennial ryegrass herbage, especially in terms of feed value to dairy cows, can be significantly affected by applied fertiliser. The extent of the response was affected by sampling date (i.e. time of year) and this must be taken into account when planning a fertiliser management strategy. This is particularly so with respect to N fertiliser recommendations. Crude protein (CP) content of herbage increased with increasing levels of applied N and the extent of the response was influenced by season. P, K and S did not affect CP concentration in herbage, except in the PxK experiment where increased levels of K lowered herbage CP. Applied N considerably increased the concentration of non-protein nitrogen (NPN) in perennial ryegrass herbage. P and S did not affect NPN levels, whereas applied K decreased NPN content in the iv NxK and PxK experiments. Non-structural carbohydrate (NSC) content of herbage was decreased by applied N but was unaffected by applications of P, K and S. Neither neutral detergent fibre (NDF) nor acid detergent fibre (ADF) was affected by applied fertiliser. In this study herbage P declined and herbage Ca increased with increasing levels of applied N. The addition of fertiliser K resulted in lower herbage Ca values. There was no herbage S response to applied fertiliser in this study. Classification and regression tree (CART) analysis identified the primary determinant of apparent intake in experiments containing N as a factor as the amount of material available to be grazed and that NSC, NPN and ADF are also determinants of apparent intake. Cows do not regulate diet choice within the short-term time frame of a meal. Thus intake is determined by short-term needs rather than by meeting long-term nutrient requirements. Fibre creates physical fill within the rumen, thus restricting intake. High NPN content is associated with high nitrate values. The reduction in intake of herbage with high nitrate content may be due to reduced palatability or to a negative feedback system limiting the intake of nitrate and ammonium. Increased NSC content is associated with increased intake, possibly through the effect of sugar on herbage palatability.
Aspects of the ecology of grass seedlings used for revegetation of degraded land.
(2010) Ellis, Meghan Jane.; Kirkman, Kevin Peter.; Morris, Craig Duncan.
As restoration ecology has matured as a science there has been increased interest in the relationship between species diversity and landscape health. Degraded landscapes tend to be resource poor, which limits species diversity as only species which are capable of growing and reproducing in these resource limiting environments can inhabit the area. Additionally, the established species are strong competitors for resources and will exclude, by way of inter-specific competition, weaker competitor species attempting to invade the degraded area. Several studies have demonstrated that with increased species diversity the overall productivity and functionality of the grassland increases. Seedling development and competitive interactions between grass seedlings has a significant impact on the final community structure and species diversity. It is for this reason that aspects of the ecology of grass seedlings were investigated. The growth and competitiveness of Chloris gayana, Cynodon dactylon, Digitaria eriantha, Eragrostis curvula and E. tef seedlings were determined under three environmental stimuli, namely nitrogen availability, light availability and exposure to plant-derived smoke (in the form of smoke-infused water). The primary conclusion from the competition experiments was that the species can be split into superior and inferior competitors at the seedling stage. Chloris gayana, E. curvula and E. tef were the most competitive seedlings as they had the largest negative effect on the growth of other species (high nitrogen Relative Interactive Index (RII) = -0.449, -0.203 and -0.379 respectively) and they were least affected by competition (high nitrogen RII = -0.251, -0.168 and -0.248 respectively). The calculated RII indicates the strength of the competitive interactions, the more negative the RII the stronger the competitive interaction. Nutrient availability had limited effect on the competitive hierarchy of the tested species. Chloris gayana seedlings, however, increased in competitiveness with an increase in available nutrients. In other words, there was a decreased negative response to competition in a high nutrient environment (high nitrogen RII -0.251, no nitrogen RII -0.605). When D. eriantha was grown under varying shade, nutrient and competition levels it was evident that the primary stress factor was light deficiency (p<0.001), and nutrient availability had no affect on seedling growth (p=0.069). Smoke-infused water had no consistent affect on the germination success or the seedling’s root and shoot vigour for the five grasses. These results indicate that the introduction of a “2-phase” or “multi-phase” restoration plan may be beneficial for the development of species diverse rehabilitated grasslands. Manipulating the time and space that the different species are planted, or the distribution of nutrient concentration over the area, may increase the survivorship of all the species that are introduced to a restoration site.
The coastal grasslands of Maputaland, South Africa : effects of fire and grazing on vegetation structure, diversity, and composition.
(2007) Dalton, Brian Patrick Alexander.; Kirkman, Kevin Peter.
A series of trials and investigations were implemented to address concerns surrounding the dynamics of the fire-climax wooded/edaphic grasslands within the iSimangaliso Wetland Park, northern KwaZulu-Natal, South Africa. The research problem surrounded inadequate historical evaluations of changes in vegetation structure, grasslands progressing to a woody dominated composition, and increases in Helichrysum kraussii (Curry bush). These were addressed as follows: Firstly, the recovery of vegetation in response to different periods of fire exclusion in different communities along a topographical gradient of a coastal dune area, was assessed over a two year period. Secondly, the regeneration after wildfire of the persistent, stress tolerant shrub H. kraussii, was studied on different catenal positions with differing fire exclusion periods and with and without defoliation of surrounding plant biomass in the coastal edaphic grasslands north of Manzengwenya, South Africa. Thirdly, aerial photography from 1937, 1975, and 2000 was georectified, digitised and analysed using a Geographic Information System to examine broad vegetation changes in response to different management regimes for a site on the Eastern Shores of Lake St Lucia and a site within the Tewate Wilderness Area. In the absence of fire, the coastal edaphic grasslands progressed to a closed canopied scrub forest within six years. An increase in fire exclusion period resulted in a decrease in species abundance, an increase in woody height, and a decrease in plant density. Richness increased initially but declined marginally with increased fire exclusion period. Higher lying east and west facing sites had a better veld condition index compared with bottom sites and had an increased response (vigour) to defoliation but were far more likely to succeed through to woody scrub forest. Woody plant biomass vigour was greater for west facing sites. Ordination of species composition across sites in response to fire exclusion and catenal position revealed greater similarities within exclusion periods than between. Bottom sites were more similar with similarity decreasing for east and west facing sites. Fire exclusion resulted in an initial increase in woody species and a subsequent increase in herbaceous species. iii Growth response of H. kraussii was unaffected by catenal position and fire exclusion period, whereas defoliation of surrounding grass tended to increase in size (P<0.05). Density and height for this species however increased with increasing fire exclusion. An increase in soil moisture negatively affected H. kraussii growth indicating susceptibility to high water tables. The number of other woody species establishing beneath H. kraussii may be due to changes in the transmission of light through the canopy where an increase in canopy diameter resulted in an increase of photosynthetically active radiation at the soil surface. The effects of fire on landscape change were investigated for the Eastern Shores and Tewate Wilderness Area, iSimangaliso Wetland Park, South Africa using aerial photography. Changes to historical disturbance regimes largely through active exclusion of fire resulted in the majority of the higher lying coastal grasslands changing to savanna scrub or closed canopied forest within 63 years on the Eastern Shores. The degree of fragmentation of these grasslands was greatly reduced within the Tewate Wilderness Area where disturbance regimes included greater frequencies of fire. Hygrophilous grasslands remained largely unaffected by woody encroachment but did not preclude woody species establishment indicating possible susceptibility during long drier periods. Frequent fires result in the maintained distribution of the higher grasslands. This vegetation type is a system which becomes resilient in response to fire, whereas in the absence of fire readily progresses to Dune Forest. The coastal grasslands above the high water table are therefore highly unstable and transformed easily in the absence of regular disturbance. It would appear that a threshold of approximately six years exists, after which substantial management intervention may be required to reverse the succession back to grassland. The growth of H. kraussii was unaffected by fire and remained persistent irrespective of fire exclusion period. An ability to attain size (height and canopy diameter) was limited with increased soil moisture but density was reduced through regular burning. Frequent fires are necessary to reduce density of H. kraussii and reduce the competitive advantage gained with age.
Above- and belowground competition in Savanna systems.
(2008) Payne, Michelle Jennifer.; Kirkman, Kevin Peter.
The structure and composition of savanna vegetation is influenced by resource availability and disturbance. Grasses, a major component of savannas, influence this resource availability by competing directly with trees for light, water and soil nutrient resources. The direct causes of bush encroachment are not always apparent, but are commonly ascribed to overgrazing and consequent decreased grass competition. The interaction, both above and belowground, between tree and grass seedlings and the surrounding grass sward is dependant on many factors, such as soil depth, seedling species and sward composition. These factors, as well as the presence or absence of defoliation, in the form of grazing or fire dictate whether the system will remain in a transition state as savanna or move towards a stable woodland state. The major competitive effects experienced by the tree seedlings were dependant on grass species and nutrient level. A. nilotica was affected by aboveground competition while A. karroo was affected by belowground competition. E. capensis caused the greatest decrease in A. karroo plant biomass. Both E. capensis and H. hirta had large competitive effects on the aboveground biomass of A. nilotica, while S. africanus had the greatest effect on belowground biomass. Increasing nutrient availability resulted in an increase in the competitive effect exerted on A. karroo, while little to no change was seen in the competitive effect exerted on A. nilotica. Soil depth constrained plant size in both tree species. The intensity of belowground interactions on tree biomass was unaffected by soil depth, while aboveground competition had a significant effect on shallow soils. Belowground competition was also of greater importance than aboveground competition in dictating tree seedling height. Grass seedlings growing on all three soil depths differed in mean mass, with E. racemosa having the least mass and T. triandra having the greatest. Simulated grazing by cutting the surrounding sward resulted in biomass increases in all three grass species. Changes in savanna composition and structure are thus likely to be influenced by initial species composition and soil depth and soil nutrient composition. While grazing creates niches for grass seedling establishment, heavy grazing has been observed to increase grass seedling mortality. Encroachment is thus more likely to occur on intensively grazed shallow and deep soils than on medium depth soils. This highlights the importance of ensuring the grass sward remains vigorous by resting and monitoring stocking rates to ensure veld is not over-utilized. It is then possible to maintain some form of tree-grass coexistence at a level where available grazing is not compromised.
Cattle and veld interactions at the Armoedsvlakte Research Station.
(2011) Le Roux, Gustav Nic.; Du Toit, Justin Christopher Okes.; Kirkman, Kevin Peter.
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.
Studies of the management of grazing resources on the Makatini Flats and Pongolo River Floodplain.
(1988) Buchan, Alastair James Charles.; Breen, Charles Mackie.
Subsequent to the impounding of the Pongolo river in the 1970's, development of irrigated agriculture on the Makatini flats has been reducing the area of vegetation available for grazing, and flooding patterns on the seasonally inundated Pongolo River Floodplain have been determined by the controlled release of water from the Pongolapoort dam. About 50 000 people live along the 10 000 ha floodplain within the 63 000 ha northern region of the flats which was studied. This population includes 2 970 registered cattle owners who own a total of 19 300 cattle. The objectives of this study were: to gain an understanding of the Makatini pastoral system which would facilitate prediction of the effects of potential developments, including agricultural expansion, modification of floodplain hydrology and changed cattle management practices on the utility value of cattle; and to provide guidelines for the management of pastoral resources on the Makatini and other traditional African pastoral systems. It was established that the value of cattle cannot be determined without understanding the importance of the subsistence utilities provided and that the value of utilities relative to each other influences the way in which the system is stocked and managed by the local people. The value of all marketed and non-marketed utilities was determined and the implications of the economic evaluation for the identification of management options in African pastoral systems assessed. Despite the "low productivity" of the Makatini system compared to western style ranches, cattle owners receive annual returns worth approximately 100 % of the asset value of their stock. This explains low market offtake rate in this and other subsistence systems. Non-marketed utilities, particularly milk production provide most of the returns to cattle owners. The mean stocking density on the floodplain vegetation was estimated to be three times that of dry-land areas, but only 23 % of all grazing time is spent on the floodplain. Although floodplain forage provides an important supplement to winter grazing, its use is not vital to maintenance of animal condition. The coincident occurrence of an annual "stress period"; greater acceptability of Echinochloa pyramidalis vegetation as forage; the absence of floods; and the reduced use of floodplain fields, results in increased floodplain use in winter to a stocking density approximately ten times that of dry-land areas. How the floodplain hydrology, rainfall and grazing interact with the crop growth rate and quality of E. pyramidalis stands was examined. The forage production potential of E. pyramidalis was found to be higher than that of other floodplain vegetation types and stocking densities of up to 4.5 AU/ha in summer and 2.5 AU/ha in winter are considered possible on the Pongolo floodplain. Echinochloa pastures may become wet and cause scouring if grazed exclusively, but grazing reduces plant moisture content and makes the forage more acceptable. Local pastoral management was found to depend on the collective activities of cattle owners in pursuit of personal needs in a dynamic socio-economic context. Motivation for the manipulation of cattle numbers and herd composition is dictated by a cattle owner's perception of his needs for utilities and his ability to access those benefits. Because of this, the pastoral practices were found to be closely linked to other socio-economic activities such as agriculture and migrant labour. stock owners have a narrow perspective of pastoral resource management and use strategies developed on small spatial and temporal scales. In contrast development planners tend to identify objectives on a regional scale and on long-term (10 - 50 year) time scales and to orient management towards maximising the value of marketable utilities and preventing long-term overstocking. Management of pastoral resources in traditional African systems requires that the needs of local people be met, that the resource base be maintained; that pastoral policy be developed as a component of regional development planning and that close liaison between interest groups be maintained. Failure to establish or maintain this liaison is considered the main reason for the failure of many African pastoral development programmes. It was recommended that local pasture management committees be established on the Makatini and that extension officers, trained specifically to understand management problems of Third World pastoral systems, be used to maintain liaison between stock owners and development planners. It was also suggested that formal cattle camps be established and managed by local people and that at least one flood (river flow> 200 cumecs) be released from the Pongolapoort darn each summer.
Nutrient cycling in grazing systems.
(2004) Kahsay, Anwar Brhanu.; Kirkman, Kevin Peter.
This research was conducted at the University of KwaZulu-Natal, Pietermaritzburg, South Africa. The research encompasses five different studies to assess nutrient cycling in intensive and extensive grazing systems with a view to optimising livestock production. The first study was designed to assess the effect of teff-lucerne mixtures on teff, lucerne and teff-lucerne mixture yields. Lucerne and teff-lucerne mixtures benefited from the association. The overall soil N content of the teff-lucerne mixture plots was greater than the teff alone plots. The second study focused on teff-leucaena association evaluation. It had two leucaena plant row spacings as treatments, 180cm and 120cm, respectively. Teff grown in mixture with leucaena produced a total teff dry matter (DM) of 7931.57 kg ha¯¹ for the 180cm row spacing and 8329.57 for the 120cm row spacing compared to the 3548.93 kg ha¯¹ of DM obtained from the teff alone treatment. The teff-Ieucaena stand also had a greater DM yield response to leucaena row spacing compared to the teff alone. In terms of nutritive quality, all stands from the teff-leucaena plots were better than the quality obtained from the teff alone plots. Total N content of teff from the l80cm row spacing was 21.83 g kg¯¹ and that from the 120cm 16.07 g kg¯¹ compared to the total nitrogen (N) content of 19.77 g kg¯¹ of the teff alone treatment. The total phosphorus (P) content was 2.73, 1.96 and 2.07 g kg¯¹ for the 180cm, 120cm and teff alone treatments respectively. However, the total soil N content was higher for the teff alone plot than for the teff-leucaena plots, which are 1.91, 1.48 and 100 g kg¯¹ for the teff alone, 180cm and 120cm treatments respectively. The third study was designed to assess the effects of different N fertilizer application rates on teff yield response. The rates applied were 0, 50, 100 and 150 kg N ha¯¹. There was significant difference in teff response of the three N fertilizer application rates compared to the control and teff DM yield response was lower for the 150 kg N ha¯¹ (838 kg ha¯¹) treatment compared to the control (553 kg ha¯¹). Both teff DM and nutritive value were higher in the plots treated with N fertilizer than in the plot which received no N fertilizer (control). The soil N content was also higher in those plots treated with N fertilizer. Study four was conducted on the Department of Grassland Science's grassland management techniques trial field at Ukulinga. The effects of nutrient cycling under different management techniques such as burning, mowing and grazing on grass yield response, plant quality and soil nutrients were assessed. However, the response of grass DM yield and P content was not significant but the three treatments had a significant effect on grass N content. Their effect on soil N content was also significant and the grazing plot had the greatest soil N levels. The last study was conducted in the rural areas of Okhombe and Zwelitsha to assess the effects of grazing intensity on grass yield response, plant quality and soil nutrient status at different distances from homesteads. Grass DM yield and nutritive value declined when distance from the homestead increased. The soil N content also was higher nearer to the homestead than further away. Most farmers, particularly in developing countries including those in Eritrea, often experience that their animals prefer forages from some plants such as lucerne, leucaena, and other indigenous leguminous plants. They also observe that they get greater yield from crops grown near leguminous plants or in rotation with legumes. They are also still using manure from their animals to fertilize their croplands. Therefore, it is still the duty of the researchers to demonstrate to farmers on farm studies to convince farmers that it is because leguminous plants have the ability to add quality and quantity to the feed of the animals and soil nutrients to the croplands. Hopefully, this study will convey to farmers the use of growing integrated grassllegume pastures and crops, and illustrate that livestock have their own role in transporting nutrients and hence use them as good means of distributors of soil nutrients.
Patch grazing in the humid grasslands of KwaZulu-Natal.
(1995) Lütge, Bernd Uwe.; Hatch, Grant Peter.; Hardy, Mark Benedict.
Patch grazing may be an important factor providing the focus from which wide-scale veld degradation has occurred in the humid grasslands of KwaZulu-Natal. A number of discrete studies were therefore initiated to examine the patch grazing patterns and selected factors which may influence patch grazing at two sites in the humid grasslands of KwaZulu-Natal. The sites were located at Ukulinga Research Farm, situated in the Southern Tall Grassveld, and Kokstad Research Station in the Highland Sourveld. An investigation into the frequency and intensity of gazing patches and non-patches at Ukulinga Research Farm indicated that patch grazing was most evident and most extensive during summer and autumn. As forage in the patches became limiting during winter animals were forced to forage in areas not frequently grazed during the season. The patch grazing pattern was further modified by the time of grazing commencement after a burn in early spring. Early grazing significantly reduced the extent of patch grazing. With early stocking animals were forced to graze less selectively while with increased delay in the commencement of grazing, animals became increasingly patch-selective. Early grazing in conjunction with an autumn rest and heavy grazing during winter could significantly reduce patch grazing. Urine and dung significantly influenced the patch grazing pattern. The sward surrounding a urine deposit was preferentially grazed by both cattle and sheep for a period of at least six months after deposition. Cattle rejected the sward surrounding cattle and sheep dung immediately after deposition and for a period of up to six months. Sheep also rejected cattle and sheep dung patches immediately after deposition. As dung deposits aged, sheep tended to increase their grazing around both cattle and sheep dung pats, and after six months dung did not seem to influence sheep grazing. Urine may be an important factor influencing patch initiation and consequent patch development. A study to examine the characteristics of patches and non-patches in the Highland Sourveld revealed that patches were characterised by lower soil moisture, soil depth and hydraulic conductivity, but by a higher soil nutrient status. Patches and non-patches could also be distinguished in terms of species composition and basal cover. Patches were characterised by Increaser II species, especially Microchloa caffra and, non-patches by Increaser I species such as Trachypogon spicatus, Alioteropsis semialata and Eulalia villosa. Three seasons of patch grazing at Kokstad Research Station negatively influenced the vigour of Themeda triandra in patches relative to the non-patches. The vigour of T. triandra in patches was consistently low throughout a full season's rest. The vigour of T. triandra in non-patches was initially significantly higher than the vigour in the patches and remained so for c. 24 weeks. Vigour measurements at the start of the following season showed that photosynthate accumulation had taken place and a full seasons rest proved to be sufficient in restoring the vigour of T. triandra in patches to the same level as that in non-patches. A full seasons rest did, however, not prevent animals from regrazing the same previously grazed patches the following season. Growth in patches also started c. six weeks later than in nonpatches and above-ground herbage production in patches was significantly lower than nonpatches for at least 20 weeks after a bum. At the end of a full season's rest above-ground herbage production in patches was still slightly lower than that in non-patches possibly due to a difference in species composition between patches and non-patches. Some implications of patch grazing are discussed together with an evaluation of some management recommendations for the humid grasslands with the aim of reducing the potential for patch degradation.
Grasslands of Umtamvuna Nature Reserve, KwaZulu-Natal : a description and recommendations for monitoring.
(1995) Le Roux, Noel Peter.; Zacharias, Peter John Kenneth.
The main aim of this study was to classify and map the threatened coastal grassland communities of the 3 257 ha Umtamvuna Nature Reserve (UNR) in KwaZulu-Natal (30°07'30" to 300 11'05"E; 30°55'00" to 31°04'30"S). Secondary aims were to relate past management and selected environmental variables to community composition and to develop guidelines for monitoring. Alpha diversity was measured using a Whittaker plot and revealed 119 species. A pilot study to test the efficiency of botanical techniques showed that a point based technique (nearest plant method in a 20 X 20 m plot) was efficient (52 minutes for recording 200 points), but recorded only 23% of the species. By increasing the number of points to six hundred, 34% of the species were recorded in 178 minutes; the same time was required to randomly place 30 quadrats (50 X 50 cm), which revealed 80% of the species. Tests for replicate similarity showed a high retrieval of internal association (PS = 86%), using abundant species only and 100 points per plot. The point based technique was thus efficient in detecting abundant species and was acceptable for producing a classification, especially in this case where a comprehensive species list already existed. Indirect gradient analysis (TWINSPAN) identified six grassland communities. An ordination using detrended correspondence analysis (DCA) contributed towards the community classification and grazing and fire frequency gradients were inferred from this ordination. Protea roupelliae communities were common but did not influence grass species composition . Canonical ordination revealed that, of the eight environmental variables measured, 'distance from the sea' strongly affected species distribution (r= 0.83). Cost effectiveness was considered in the development of a monitoring programme. Point based monitoring techniques favoured by sourveld researchers in KwaZulu-Natal were found to be inefficient, particularly for studies requiring the measurement of both species richness and community composition. Randomly located 100 X 100 cm quadrats, located in selected sites which represent previously identified communities, was more efficient. This study contributed towards a refinement of information on the grassland communities of KwaZulu-Natal and supported the use of point data for the classification of grasslands not previously studied. It also demonstrated that point based techniques were not suitable for meeting all grassland monitoring requirements.

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