Browsing by Author "Morris, Craig Duncan."

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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.
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.
A comparison of in-field techniques for estimating the feed intake of young boer goats on a Leucaena leucocephala/grass hay diet.
(1997) Letty, Brigid Aileen.; Zacharias, Peter John Kenneth.; Morris, Craig Duncan.
Two methods of estimating the intake of a 25% leucaena : 75% grass hay diet by young male Boer goats were assessed, (a) The purine derivative technique which uses the urinary excretion of purine derivatives (expressed relative to creatinine concentration in the same sample) as an index of feed intake, and (b) the conventional marker method, utilizing chromic oxide (Cr₂O₃) contained in gelatin capsules and dosed twice daily, as the marker. Following a prerun the two techniques were compared in three runs of an indoor experiment. In each run 10 goats were randomly allocated to five feeding levels (500 to 1100 g fodder d ¯¹ on air dried basis). A preliminary and an adaptation period during which goats were dosed with the Cr₂O₃ and fed their daily feed allowance, was followed by a 4 day collection period during which spot samples of urine were collected and analysed for allantoin and creatinine (allantoin being used instead of total PDs) and faecal samples were collected for chromium analysis and percentage dry matter determination. For the first two runs, two grab samples per day for each goat were bulked and analysed for chromium content. For the last run, the total daily faecal collection was subsampled and analysed for chromium. Work was done in metabolic crates to determine the effect of time of collection on the ratio of allantoin : creatinine (A/C) in spot urine samples and it was found to non-significant (P>0.05). Linear regressions of: (a) feed intake expressed per unit metabolic mass (g.d ¯¹.LW ¯°∙⁷⁵ (I_mmass)) against A/C ratio; (b) faecal output (g d ¯¹) against feed intake (g d ¯¹); and (c) faecal chromium concentration (mg kg ¯¹) against faecal output (g d ¯¹) were fitted to the data. During the prerun, only regression (a) was fitted and was non-significant (P>0.05), showing no trend at all. For the first true run, the regression of I_mmass against A/C ratio was significant and the correlation was high (P≤ 0.001, R² [A] 0.715, n = 10) but for the second and third runs, the correlations only became significant when the apparent outliers were discarded from the data. (Run 2: P≤ 0.001, R² [A] 0.824, n = 8; Run 3: P≤ 0.05, R² [A] 0.430, n = 9). It was concluded that the relation between I_mmass and A/C ratio is not well enough defined to be used for predictive purposes. When regression (b) was investigated, all the runs produced significant results (P≤0.001, P≤0.01, P≤ 0.001 for runs 1,2 and 3 respectively) however the correlations were not as high as expected (R² [A] being 0.714, 0.565 and 0.863 respectively). For the regression of faecal Cr concentration against faecal output (regression c), all runs showed significant relations (P< 0.001, P< 0.0001, P:s 0.001 for runs 1,2 and 3 respectively) and the correlations were high (R²[A] being 0.836, 0.837 and 0.912 respectively). The data from the three runs were pooled and single equations established for regressions (b) and (c) to allow for the prediction of intake from faecal chromium concentration. Faecal output = feed intake * 0.448 + 19.341 (P≤ 0.001, r 0.853, R² [A] 0.718, SE 25.664, n - 30) Faecal chromium concentration = faecal output * -241.547 + 1.315E+05 (Ps 0.001, r 0.904, R² [A] 0.811, SE 5603.788, n = 30). In vitro figures were determined for a range of leucaena : hay mixes but no apparent trend was found between percentage leucaena in the mix and the digestibility of the mix. These results compared favourably with in vivo results obtained for a 25% leucaena : 75% hay mix. Neither technique proved entirely satisfactory, but the external marker method was found to be more effective than the purine derivative technique. More work is required especially with respect to the latter method.
Determinants of grass production and composition in the Kruger National Park.
(2003) Zambatis, Nicholas.; Zacharias, Peter John Kenneth.; Morris, Craig Duncan.; Biggs, Harry Cawood.
The dynamics and complexities of climate-soil-vegetation relations in the Kruger National Park are poorly known. Although primary production and composition of the grass layer are very important components of the Park's ecosystem, equally little is known about the determinants of these parameters. A better understanding of these processes and relations will be of value to the management of this Park, as well as providing a better insight into these complex dynamics. A study was consequently undertaken covering a 14-year period to identify the most important determinants of above-ground grass production and composition. At the core of the study is the soil water balance. The use of evapotranspiration data in a study of this nature is however not absolutely essential, provided a variety of rainfall parameters are used, though it has the important advantage of providing a much more detailed and more complete insight into the relations of the grass sward with its environment. Stepwise and tree regression procedures were used to identify the important factors. It is concluded that rainfall in its various forms is the primary determinant of grass production, standing crop, and composition, the latter either as perennials or Decreasers. Secondary determinants, in varying degrees of importance, are the thickness and base status of the A horizon, distance to permanent drinking water, and competition by woody plants. Herbivore utilization is insignificant or at most, plays a relatively minor role. Herbivores appear to exert a negative influence on Decreaser abundance only when soil moisture stress exceeds a threshold level. When this is exceeded, relatively low herbivore densities are apparently sufficient to reduce Decreaser abundance. The definitions of Decreasers and Increasers consequently require revision to take into account the overriding influence of environmental factors, particularly those of soil moisture stress. The calibration of the disc pasture meter was re-evaluated. The relation between mean disc height and standing crop is non-linear. Up to a mean disc pasture meter height of 260 mm, the correlation between this parameter and above-ground standing crop is very strong (r2 = 0.95; P<0.0005). Beyond this height, the correlation is very poor (r2 =0.09; P<0.0005), apparently being strongly influenced by the structure of the grass plant, with tall grasses, or grasses with highly lignified culms resulting in a weaker correlation.
Dry woodland and savanna vegetation dynamics in the Eastern Okavango Delta, Botswana.
(2012) Tedder, Michelle Jennifer.; Kirkman, Kevin Peter.; Bonyongo, Mpaphi Casper.; Morris, Craig Duncan.; Trollope, Winston Smuts Watts.
The Okavango Delta is an extremely dynamic system with variable vegetation comprised of permanent swamps, seasonal swamps, dry islands, floodplains and dry grassland, savanna and woodland. The system is largely driven by the interaction between fire and the annual flood, which filters down from the Okavango River catchments in Angola. While extensive research has been conducted on the flood-driven vegetation little is known about the dry woodland and savanna regions bordering these flood-driven habitats. A taxonomic classification of woody species composition resulted in eleven vegetation types. These data were then reanalyzed in terms of woody species morphology allowing these eleven vegetation types to be grouped into four functional response groups in order to provide a platform for improving the understanding of how dry woodland and savannas interact with the environment. These four groups were the savanna group mixed thornveld and the three woodland groups; mixed broadleaf woodland, shrub mopane woodland and tall mopane woodland. Burning in mixed thornveld and mixed broadleaf woodland was found to decrease woody species density and grass fuel loads and could be used for grazing management to remove unpalatable growth and improve grass species composition, while burning in shrub mopane woodland and mixed mopane woodland merely decreased the woody understory and is not recommended. Utilization dominated by grazing livestock resulted in overutilization of the grass sward leading to bush encroachment in both mixed thornveld and shrub mopane woodland, while utilization by goats alone resulted in underutilization of the grass sward and a dominance of herbaceous annuals. Livestock utilization had no effect on the occurrence of Pecheul-loeschea leubnitziae, a shrubby pioneer previously thought to be an indicator of overgrazing, however extensive P. leubnitziae cover was associated with a sward dominated by shade-tolerant grasses with low forage quality. Shrub mopane woodland and tall mopane woodland appear to be more stable vegetation states than mixed broadleaf woodland and mixed thornveld being less vulnerable to colonization by pioneer species and alteration as a result of utilization or environmental factors. For this reason management and monitoring of mixed thornveld and mixed broadleaf woodland is essential to prevent vegetation degradation and to ensure optimal forage availability for both livestock and wildlife.
The effects of land use and management practices on soil microbial diversity as determined by PCR-DGGE and CLPP.
(2011) Wallis, Patricia Dawn.; Titshall, Louis William.; Hunter, Charles Haig.; Morris, Craig Duncan.
The environmental impact of anthropogenic disturbances such as agriculture, on the soil ecosystem, and particularly on soil microbial structural and functional diversity, is of great importance to soil health, conservation and remediation. Therefore, this study assessed the effects of various land use and management practices on both the structural (genetic) and functional (catabolic) diversity of the soil bacterial and fungal communities, at two long-term sites in KwaZulu-Natal. The first site is situated at Baynesfield Estate, and the second at Mount Edgecombe Sugarcane Research Institute. At site 1, the land uses investigated included soils under pre-harvest burnt sugarcane (Saccharum officinarum, Linn.) (SC); maize (Zea mays, Linn.) under conventional tillage (M); permanent kikuyu (Pennisetum clandestinum, Chiov) pasture (KIK); pine (Pinus patula, Schiede) plantation (PF); and wattle (Acacia mearnsii, De Wild) plantation (W), all fertilized; and undisturbed native grassland (NAT) that had never been cultivated or fertilized. At site 2, a sugarcane (Saccharum officinarum × S. spontaneum var. N27) pre-harvest burning and crop residue retention trial was investigated. The treatments studied included conventional pre-harvest burning of sugarcane with the tops removed (Bto), and green cane harvesting with retention of crop residues on the soil surface as a trash blanket (T). Each of these treatments was either fertilized (F) or unfertilized (Fo). The polymerase chain reaction (PCR), followed by denaturing gradient gel electrophoresis (DGGE) were used to determine the structural diversity, and community level physiological profiling (CLPP) using BIOLOG plates, the catabolic diversity. In addition, the soils were analysed with respect to selected physicochemical variables, and the effects of these on the soil microbial communities were determined. Replicate soil samples (0–5 cm) were randomly collected from three independent locations within each land use and management, at both sites. Soil suspensions for the CLPP analyses were prepared from fresh soil subsamples (within 24 h of collection) for the bacterial community analyses, and from 8-day-old soil subsamples (incubated at 4°C to allow for spore germination) for the fungal community analyses. BIOLOG EcoPlates™ were used for the bacterial CLPP study and SF-N2 MicroPlates™ for the fungal analysis, the protocols being adapted and optimized for local conditions. This data was log [X+1]-transformed and analysed by principal component analysis (PCA) and redundancy analysis (RDA). For PCRDGGE, total genomic DNA was isolated directly from each soil subsample, and purified using the MO BIO UltraClean™ soil DNA Isolation kit. Protocols were developed and optimized, and fragments of 16S rDNA from soil bacterial communities were PCR-amplified, using the universal bacterial primer pair 341fGC/534r. Different size 18S rDNA sequences were amplified from soil fungal communities, using the universal fungus-specific primer pairs NS1/FR1GC and FF390/FR1GC. Amplicons from both the bacterial and fungal communities were fingerprinted by DGGE, and bands in the fungal DGGE gels were excised and sequenced. The DGGE profiles were analysed by Bio-Rad Quantity One™ Image analysis software, with respect to band number, position, and relative intensity. Statistical analyses of this data then followed. Soil properties [organic C; pH (KCl); exchangeable acidity; total cations (ECEC); exchangeable K, Ca and Mg; and extractable P] were determined by PCA and were shown to have affected the structural and catabolic diversity of the resident microbial communities. At Baynesfield, canonical correspondence analysis (CCA) relating the selected soil variables to bacterial community structural diversity, indicated that ECEC, K, P and acidity were correlated with CCA1, accounting for 33.3% of the variance, whereas Mg and organic C were correlated with CCA2 and accounted for 22.9% of the variance. In the fungal structural diversity study, pH was correlated with CCA1, accounting for 43.8% of the variance, whereas P, ECEC and organic C were correlated with CCA2, and accounted for 30.4% of the variance. The RDA of the catabolic diversity data showed that the same soil variables affecting fungal structural diversity (organic C, P, ECEC and pH) had influenced both the bacterial and fungal catabolic diversity. In both the bacterial and fungal RDAs, organic C, P and ECEC were aligned with RDA1, and pH with RDA2. However in the bacterial analysis, RDA1 accounted for 46.0%, and RDA2 for 27.5% of the variance, whereas in the fungal RDA, RDA1 accounted for only 21.7%, and RDA2 for only 15.0% of the variance. The higher extractable P and exchangeable K concentrations under SC and M, were important in differentiating the structural diversity of these soil bacterial and fungal communities from those under the other land uses. High P concentrations under M were also associated with bacterial catabolic diversity and to a lesser extent with that of the soil fungal communities under M. Similarly, the higher organic C and exchangeable Mg concentrations under KIK and NAT, possibly contributed to the differentiation of these soil bacterial and fungal communities from those under the other land uses, whereas under PF, the high exchangeable acidity and low pH were possibly influencing factors. Under W, low concentrations of P and K were noted. Other factors, such as the presence/absence and frequency of tillage and irrigation, and the diversity of organic inputs due to the diversity of the above-ground plant community, (in NAT, for example) were considered potentially important influences on the nature and diversity of the various land use bacterial and fungal communities. At Mount Edgecombe, CCA showed that organic C and Mg had a significant effect on soil bacterial structural diversity. Organic C was closely correlated with CCA1, accounting for 58.7% of the variance, whereas Mg was associated with CCA2, and accounted for 41.3% of the variance. In the fungal structural diversity study, ECEC and pH were strongly correlated with CCA1 and accounted for 49.1% of the variance, while organic C was associated with CCA2, accounting for 29.6% of the variance. In the functional diversity studies, RDA showed that both bacterial and fungal community catabolic diversity was influenced by soil organic C, pH, and ECEC. In the bacterial analysis, RDA1 was associated with organic C and pH, and accounted for 43.1% of the variance, whereas ECEC was correlated with RDA2, accounting for 36.9% of the variance. In the fungal analysis, RDA1 was correlated with ECEC and accounted for 47.1% of the variance, while RDA2 was associated with pH and organic C, accounting for 35.8% of the variance. The retention of sugarcane harvest residues on the soil surface in the trashed treatments caused an accumulation of organic matter in the surface soil, which did not occur in the pre-harvest burnt sugarcane. This difference in organic C content was a factor in differentiating both bacterial and fungal communities between the trashed and the burnt treatments. Soil acidification under long-term N fertilizer applications caused an increase in exchangeable acidity and a loss of exchangeable Mg and Ca. Thus, as shown by CCA, a considerably lower exchangeable Mg concentration under F compared to Fo plots resulted, which was influential in differentiating the bacterial and fungal communities under these two treatments. In the structural diversity study at Baynesfield, differences were found in bacterial community species richness and diversity but not in evenness, whereas in the fungal analysis, differences in community species richness, evenness and diversity were shown. The soil bacterial and fungal communities associated with each land use were clearly differentiated. Trends for bacterial and fungal diversity followed the same order, namely: M < SC < KIK < NAT < PF < W. At Mount Edgecombe, no significant difference (p > 0.05) in bacterial structural diversity was found with oneway analysis of variance (ANOVA), but two-way ANOVA showed a slight significant difference in bacterial community species richness (p = 0.05), as an effect of fertilizer applications. A significant difference in fungal species richness (p = 0.02) as a result of management effects was detected, with the highest values recorded for the burnt/fertilized plots and the lowest for the burnt/unfertilized treatments. No significant difference was shown in species evenness, or diversity (p > 0.05), in either the bacterial or the fungal communities. In the catabolic diversity study at site 1, the non-parametric Kruskal-Wallis ANOVA showed that land use had not affected bacterial catabolic richness, evenness, or diversity. In contrast, while fungal catabolic richness had not been affected by land use, the soil fungal community catabolic evenness and diversity had. At site 2, the land treatments had a significant effect on soil bacterial community catabolic richness (p = 0.046), but not on evenness (p = 0.74) or diversity (p = 0.135). In the fungal study, land management had no significant effect on the catabolic richness (p = 0.706), evenness (p = 0.536) or diversity (p = 0.826). It was concluded, that the microbial communities under the different land use and trash management regimes had been successfully differentiated, using the optimized protocols for the PCR-DGGE of 16S rDNA (bacteria) and 18S rDNA (fungi). Sequencing bands produced in the 18S rDNA DGGE, enabled some of the soil fungal communities to be identified. CLPP of the soil microbial communities using BIOLOG plates showed that, on the basis of C substrate utilization, the soil bacterial and fungal communities’ catabolic profiles differed markedly. Thus, it was shown that the different land use and management practices had indeed influenced the structural and catabolic diversity of both the bacterial and fungal populations in the soil.
Getting the write message right: review of guidelines for producing readable print agricultural information materials.
(LiASA, 2003) Morris, Craig Duncan.; Stilwell, Christine.
Print agricultural information materials (PAIMs), such as leaflets, booklets and fact sheets, are used extensively to provide information to farmers. Such print materials can play a vital supportive role in extension, even to low-literate communities. Principles for repackaging technical and scientific agricultural information in print are reviewed to provide guidelines for producing PAIMs that are 'considerate' of the target audience's information needs, communication and language style, and level of reading and education. Criteria for choice of content include brevity, accuracy, appropriateness and relevance to the end user. An understanding of factors affecting readability, accompanied by readability assessment and pretesting materials on users, will ensure greater clarity of expression and aid comprehension. Important elements of the design and layout of PAIMs include logical organisation of content and arrangement of text on the page, legibility of the text as affected by colour and typography, highlighting, and the use of pictures to complement and reinforce the message. Such design tools should be used to attract and not distract the reader. It is concluded that a collaborative effort of communicators and audience in the development process will aid the production of PAIMs that contribute effectively to the diffusion of agricultural and development information in rural areas.
Impact of land use on water quality and aquatic ecosystem health of stream networks in the upper uMngeni catchment feeding Midmar Dam, KwaZulu-Natal, South Africa.
(2012) Van Deventer, Ross.; Hill, Trevor Raymond.; Morris, Craig Duncan.
Freshwater in adequate supply and quality is vital to life on Earth; however, land-based activities such as development, agriculture, mining and industry, and their associated contaminants, pose a major threat to the quality of freshwater water resources and health of aquatic ecosystems. The upper uMngeni catchment draining into Midmar Dam is a strategically significant water resource, supplying clean drinking water to the eThekwini, uMgungundlovu and Msunduzi municipalities. The quality of this resource is under threat from current land-based activities such as Mpophomeni settlement and agriculture and emerging threats in the form of the Khayalisha social housing project. Monitoring sites were established in varying land use types in three sub-catchments of the upper uMngeni, to assess water quality and ecosystem health impacts of current land uses on Midmar Dam. A suite of physical, chemical and biological water parameters were sampled in conjunction with SASS5 bio-monitoring to assess the associated impacts. Water quality and ecological condition were highest in forested land use and upstream of Mpophomeni where natural land cover and sparse settlement occurred. Marked declines in water quality and ecological condition were observed at areas under commercial agriculture, indicated predominantly by rises in nutrient concentrations and declines in the SASS5 indices. The most notable declines in water quality and ecological condition were observed at sites downstream of Mpophomeni settlement as a result of severe sewage contamination, indicated by high E. coli counts. Nutrient concentrations downstream of Mpophomeni settlement ranged from mesotrophic to hypertrophic, with nitrogen to phosphorus ratios indicative of nitrogen limitation. Ecological condition remained in the ‘seriously/critically modified’ category over the study period. Nutrient loads produced by Mpophomeni are the highest of all the land uses, followed by that of commercial agriculture; both should be viewed as a concern, more so when viewed in terms of their compound effect on Midmar Dam water quality. Current water quality draining the commissioned Khayalisha social housing development area is good and although not natural, is of no contamination concern to Midmar Dam. Results indicate that with current land use activities, urban development and agriculture pose a potential threat to the quality of Midmar Dam resource and that further development in the form of the Khayalisha social housing project may replicate impacts already prevailing in Mpophomeni, whereby a principle water resource may be threatened by eutrophication.
The influence of environment and livestock grazing on the mountain vegetation of Lesotho.
(2011) Morris, Craig Duncan.; Tainton, Neil M.; Kirkman, Kevin Peter.
The mountains of Lesotho form the catchments for the Lesotho Highlands Water Project (LHWP), which is presently under construction, and their condition will determine the longevity of the LHWP. The mountain rangelands also support an extensive livestock system. However, there is concern that grazing is negatively affecting the mountain vegetation to the detriment of both livestock production and catchment function. Therefore, the impact of environment and grazing on the vegetation was investigated to aid the development of management policy for the conservation of the grazing, floristic and water resources of the mountains. Vegetation surveys were conducted in the mountains in the east (Study Area 1: 2 625 - 3 350 m a.s.l.) and in the west (Study Area 2: 2 240 - 3 125 m a.s.l.). Indirect gradient analysis (IGA) and classification were used to investigate the influence of environment on vegetation pattern. Results of the IGA indicated that variation in species composition in the mountains is related primarily to topographic variation, in particular elevation and aspect. Five vegetation communities were identified in Study Area 1 and seven in Study Area 2. These communities occurred consistently in specific topographic positions in the landscape and were arranged along a temperate/subtropical grass species continuum which was associated with a gradient in elevation and aspect. In Study Area 1, the elevation boundary between the high-lying temperate grasslands and the lower subtropical grasslands corresponded with the generally recognised boundary between the Alpine and Subalpine vegetation belts (viz. c. 2 950 m a.s.l. on northerly aspects and c. 2 750 m a.s.l. on southerly aspects). This boundary was lower in Study Area 2 (viz. c. 2 800 m a.s.l. on northerly aspects and c. 2 300 m a.s.l. on southerly aspects). Vegetation-insolation relationships were investigated in Study Area 1 using a model for simulating solar radiation, temperature and potential evaporation patterns on sloping terrain (RADSLOPE). The spatial distribution of the identified vegetation communities and the ratio of temperate (C₃) and subtropical (C₄) grasses in the sward were related to solar irradiance patterns, as influenced by topography. Results suggest that exposure, which increases with altitude, is probably also an important determinant of vegetation pattern in the mountains. The influence of grazing on the vegetation was studied by examining changes in species composition and cover that were associated with gradients in grazing intensity that exist around cattleposts in the mountains. There was little evidence of a shift in species composition and cover under grazing in the Alpine Belt but there was an identifiable grazing gradient in the Subalpine belt. There, short dense grasslands, dominated by palatable species, degrade to a dwarf karroid shrubland with sparse cover under prolonged, intense grazing. The optimum position along the grazing gradient of the more abundant species was identified. It was proposed that the relative positions, or scores, of these species along the grazing gradient can be used in a weighted scoring procedure to provide an index for monitoring the response of the mountain vegetation to grazing. However, the species’ scores still require verification. The need for monitoring temporal changes in vegetation composition and cover in order to assess the possible effects of the LHWP and other development initiatives was noted. Such monitoring should be undertaken in conjunction with an overall programme to assess the dynamics of the socio-economy in the mountains. Therefore, interdisciplinary monitoring programmes are required to achieve this. These programmes should be focused in a few key study locations rather than spread over a wide area.
Information seeking behaviour of students with visual impairments : a case study of the University of KwaZulu-Natal, Pietermaritzburg.
(2009) Seyama, Lungile Goodness.; Stilwell, Christine.; Morris, Craig Duncan.
The aim of the study was to establish the visually impaired students' information seeking behaviours, which comprises information needs, seeking and use. Identifying the students' information seeking behaviour helped to determine whether the services that are provided by the University of KwaZulu-Natal on the Pietermaritzburg (UKZN-PMB) campus met their information needs or not. The population of the study comprised three units of analysis which were nine students with visual impairments, seven Subject Librarians of the UKZN-PMB Cecil Renaud main library and the Disability Unit Coordinator. The students were surveyed by means of a semi-structured interview where they were asked what their information needs were, how they met those needs and whether the information they found from the institution's information system met their needs or not. The student' information seeking behaviour was plotted using Wilson's (1999) Information Behaviour model and the model was assessed for use with this group. The Subject Librarians and the DUC were surveyed by means of self-administered questionnaires where they were asked to specify their length of services, the frequency with which they assisted students with visual impairments and the students with visual impairments' preferences in information sources and formats, which the researcher consequently collected. The response rate was 100% from all the units of analysis. The results of the study indicated that most of the students preferred electronic compared to print information formats, depending on their level of sightedness for those who were partially sighted. Results from the three units of analysis were integrated into an overall consideration of the dynamics of information seeking behaviour exhibited by the students and modifications were suggested on Wilson's (1999) Information Behaviour model which suited the group under study.
Printed information access, preferences and use by farmers with potential for small-scale organic production, KwaZulu-Natal.
(2004) Stefano, Lynn.; Hendriks, Sheryl Lee.; Stilwell, Christine.; Morris, Craig Duncan.
Printed information access, preferences and use by small-scale farmers in KwaZulu-Natal, who are experimenting with or converting to organic farming, were investigated to establish the need for information on organic production, certification, and marketing. Forty-six resource-poor farmers from four groups at Umbumbulu, Tugela Ferry, KwaMashu and Muden participated in semi-structured group interviews. Guiding questions, information tabulation, ranking and sorting, and voting were used to gather data. Five printed agricultural information materials were evaluated. The findings indicated that the participants trusted and relied on intermediaries for access to innovative, research-based information, and preferred interpersonal communication over other information channels. Printed materials were valued for their permanence, while participants preferred materials in isiZulu as 75% of participants were able to read and write isiZulu or were able to ask family members to read materials in isiZulu. At least one functionally literate farmer was a member of each of the participating farmer groups. Appropriate printed information on organic production, certification and marketing had not reached the participants. Characteristics of printed information materials preferred by participating farmers included: large typeface, photographs, drawings, step-by-step instructions, stories about people and events, context-specific content, the use of plain language in English or preferably isiZulu.
Productivity of South African indigenous Nguni goats possessing Synergistes jonesii bacteria on Leucaena Leucocephala-grass and natural pastures.
(2002) Akingbade, Adebayo Abel.; Nsahlai, Ignatius Verla.; Morris, Craig Duncan.
The main objectives of the study reported in this thesis were to investigate the cause of poor conception and high pre-weaning kid mortality rates among South African indigenous Nguni goats (SAING) maintained on Leucaena leucocephala-grass pasture (LGP), and the potential of natural pasture (NP) and improved pasture (LGP) for the productivity of the mimosine-susceptible SAING breed after receiving dihydroxypyridone (DHP)-degrading rumen bacteria (Synergistes jonesii) via animal-to-animal transfer. Seasonal variation in forage quality and mimosine contents of two Leucaena leucocephala varieties, detection of S. jonesii from rumen digesta, effects of feeding Leucaena foliage on semen quality, grazing activities and blood metabolite profiles during gestation and reproductive performance prior and post kidding were evaluated. Aspects relating to reproductive performance prior and post kidding, colostrum and milk constituents, growth performance and blood profiles of weaned and unweaned kids, dams-to-kid transfer of S. jonesii, protein and energy requirements of the SAING kids were also examined. Cultivar Cunningham was better suited for the location ofthe study than cv. Spectra because it was available during ten months of the year compared to the six months of cv. Spectra availability. Growth performance, reproductive performance and overall productivity of SAING maintained on LGP were better than those of their counterparts on NP. Benefits of LGP during gestation include higher body weight gain of does, higher incidence of twin multiple births and higher birth weight of kids compared to values on NP. Higher milk yield, earlier return to first postpartum oestrus and better pre-weaning growth of kids relative to values obtained on NP, were the benefits of maintaining SAING on LGP during lactation. Over the entire study, conception on LGP treatment compared favourably to that on NP. Feeding Leucaena foliage did not have any detrimental effect on semen quality and fertility of the SAING bucks. Feeding LGP as gestation or/and lactation feed had no detrimental carry-over effect on the post kidding reproductive performance of SAING does and kids. The kids were also able to acquire S. jonesii from dams via animal-to-animal transfer.
Recovery, resilience and stability of piospere systems in the Kruger National Park.
(2010) Matchett, Katherine Jean.; Kirkman, Kevin Peter.; Ward, David Mercer.; Peel, Michael John Stephen.; Morris, Craig Duncan.
Water provision is an important tool in the management of savanna ecosystems. Artificial water sources are a potential focus for degradation (biodiversity and loss of ecosystem resilience at a range of spatio-temporal scales), because they alter plant-animal interactions and soil function and stability, through the creation of piospheres. This study was undertaken as part of a drive by the Kruger National Park (KNP) to enable managers to integrate artificial waterhole management (e.g. waterhole closure or rotation) when setting goals for heterogeneity and biodiversity conservation in the park. The over-arching goal was to quantify the relationship between water provision and different attributes of heterogeneity, as part of a broader initiative to place water provision and piospheres within an ecosystem threshold framework. Herbivore utilisation gradients (piospheres) around artificial waterholes in the KNP, described in 1990, were resurveyed in 2006-2007, against a backdrop of waterhole closure in the KNP, to contribute to an understanding of the factors governing recovery and resilience in grazing systems. The responses of the plant community and soil parameters to a relaxation of herbivore utilisation pressure around closed waterholes (recovering piospheres) were examined, as were changes in the same parameters at sites that have remained open (active piospheres). These ecosystem properties were considered in relation to structural and functional ecosystem thresholds, and the piospheres surveyed incorporated a range of rainfall and edaphic gradients in the KNP. Herbaceous basal cover and soil infiltration capacity both increased significantly between 1990 and 2006/7, regardless of waterhole status. This was linked to higher rainfall in 2006/7, compared to 1990. The only vegetation variables to respond consistently to distance from water were the remote-sensed Normalized Difference Vegetation Index (NDVI) and herbaceous species composition. NDVI increased with distance from water, and annual grasses and forbs were most abundant close to water. Perennial, disturbance-sensitive climax species increased in abundance further from water. Soil analyses (N, P, pH, organic matter, and texture) and field measurements (infiltration, compaction) revealed no systematic piosphere patterns. Waterhole closure did not result in soil or vegetation recovery, but piosphere intermittency and the increases of basal cover and infiltration rate indicated that ecosystem resilience has not been compromised vii by long-term artificial water provision in the KNP. This study has shown that the traditional piosphere model is of limited use in sub-humid savanna ecosystems like the KNP during above-average rainfall periods.
The relative tolerance of mesic grassland species to defoliation and competition.
(2018) Zama, Naledi Zola.; Tedder, Michelle Jennifer.; Morris, Craig Duncan.; Mkhize, Ntuthuko Raphael.
Effective grazing management is dependent on understanding grass species responses to herbivory. These responses to herbivory can be broadly grouped into 3 categories, namely decreaser (plants that decline in abundance) and increasers (plants that increase in abundance). Tolerance is defined as the capacity of a plant to withstand herbivory, while suffering little loss in growth or its ability to reproduce and it can be equated to the ability of the plant to compensate. The relevance of this strategy to rangeland management has become increasingly apparent and has allowed researchers to investigate more questions and test long-standing ideas within the Grassland Science discipline. Therefore, the general aim of this research was to determine how Increaser and Decreaser grass species common in mesic grasslands tolerate defoliation and competition. Two experiments were conducted as controlled pot trial experiments under shade cloth at the NM Tainton Arboretum. Simulated herbivory in the form of clipping was used for both experiments. Categorising species into four grazing response groups (Increaser I, II,III and Decreaser) has led to generalisations made across and between species in terms of responses to herbivory. To determine if these generalisations are appropriate, the growth response of two Decreaser (Themeda triandra and Tristachya leucothrix) and two Increaser (Eragrostis curvula and Eragrostis plana) grass species was investigated. Results indicate that defoliation tolerance is not necessarily explained by response groups and differences can be observed between species, within response groups. Grouping species into response groups may be an over simplification. This implies that species identity may be more important in understanding species composition changes within natural communities than originally thought. Plant traits, such as shoot biomass, roots biomass , tuft height and root to shoot biomass ratios also responded differently across species highlighting the importance of further research on specific species as generalisations may not be entirely useful. To provide more insight into this, the response of T. triandra to defoliation and competition with E. curvula was investigated. Results show that veld dominated by T. triandra and few E. curvula tufts should be leniently grazed every other year with rest applied following a growing season, to allow T. triandra tufts to regrow. A non-selective grazing system should be adopted by veld managers during the growing season to lower the competitive pressure exerted on T. triandra tufts by other species and to enhance growth. These results need to be considered as a basis to understand how T. triandra swards respond on a small scale and further investigations are necessary to validate impact on natural communities. Overall, defoliation tolerance is species specific and depends on the combined effects of defoliation and competition as these affect the cumulative and morphological 2 responses of important mesic grassland species.
"The road is made by walking ..." : a case study of learning, knowledge creation and knowledge sharing at The Valley Trust, a South African NGO.
(2010) Bruzas, Clive Anthony.; Lawrence, Ralph Bruce.; Stilwell, Christine.; Morris, Craig Duncan.
This thesis explores, from a very personal perspective, the engagement of one South African non-government organization, The Valley Trust, with knowledge work as an integral dimension of its practice. The thesis is written as an autoethnographic case study, drawing on the complementary methodologies of writing inquiry and arts-based inquiry, including the use of metaphor as an aid to understanding learning and knowledge creation as ongoing flow and movement. It is also strongly influenced by narrative theory, and it incorporates participatory action research, with a cooperative inquiry group made up of 12 colleagues playing a key role. Although the inquiry set out to address the question: How can The Valley Trust integrate its learning processes and its knowledge creation and sharing so as to improve its effectiveness and contribute to the broader discourse around health and development?, what emerged during the inquiry process was that there are no simple answers to this question, and confirmed that within the context of the organization‟s work and the author‟s lived experience, knowledge is indeed a “…process, a temporary state…scary to many” (Eisner, 1997:7). For this reason, and to honour the importance of the co-creation of meaning which was a key theme in the inquiry, the thesis avoids conclusions and relies rather on the reader‟s engagement with the process as represented in the text and the images to allow meaning to emerge. The thesis also creates spaces for multiple voices to be heard, although not to the extent originally intended. The thesis foregrounds those dimensions of knowledge work which are neglected in many other writings on the subject: the practical difficulties of finding organizational time for conversation, reflection, and the co-creation of meaning; the challenges introduced by organizational change processes; the tensions which inevitably occur between colleagues; and the challenges of promoting a shared understanding of knowledge work and its significance in an organization where multiple paradigms help to determine priorities. Other key themes which emerged during the inquiry were the importance of seeing knowledge work within the context of the whole organizational landscape rather than as an isolated component of the organization‟s practice, and the critical importance of locating knowledge creation and sharing in relationship. The thesis closes with a reflection on the process of writing, emphasizing the primacy of process in knowledge work, and recognizes the challenges confronting the representation and sharing of knowledge work as process in the complex context of an organization working in the fields of health and development.
The roles of competition, disturbance and nutrients on species composition, light interception and biomass production in a South African semi-arid savanna.
(2012) Mopipi, Keletso.; Kirkman, Kevin Peter.; Trollope, Winston Smuts Watts.; Morris, Craig Duncan.
Plants are the major source of food or energy required to sustain life on the planet, but humans are grappling with the deteriorating conditions of natural ecosystems such as compositional change, desertification, invasive plants and soil erosion. In the face of global climate change and growing demands for agricultural productivity, future pressures on grassland ecosystems will intensify, therefore sustainable utilization of all plant resources is of vital importance to enhance food security within the limits of good conservation. The semi-arid grasslands of southern Africa represent major grassland resources for grazing. Herbage production in these areas is determined not only by water and nutrient availability, but also by controlled and uncontrolled fires. Since fire is regarded as a natural factor in savannas, it is essential to develop a deeper understanding of the role of fire in community structure and function for the development of appropriate burning regimes. A study was conducted in the Eastern Cape of South Africa where the rural communities are faced with the challenges of rangeland degradation in the form of encroachment by unacceptable bush, karroid, macchia and less desirable grass species, as well as soil erosion. The main objective of this thesis was to investigate the roles of competition and disturbance regimes (fire and simulated non-selective grazing) on species composition, habitat productivity and the performances of selected species from this semi-arid savanna. Long-term effects of burning frequency on herbaceous species composition, Leaf Area Index (LAI), Photosynthetically Active Radiation (PAR) within the herbaceous canopy, biomass production and soil chemical properties were investigated. These studies were conducted on a fire trial set up in 1980 at the University of Fort Hare research farm in the Eastern Cape, South Africa. The treatments comprise an annual, biennial, triennial, quadrennial, sexennial and no burn control, all replicated twice in a Complete Randomized Design. The data from the trial collected between 1980 and 2008 were used to determine compositional variation for herbaceous species using the Non-metric Multidimensional Scaling and Bray-Curtis Dissimilarity tests. The PAR ceptometer was used to determine LAI and intercepted PAR, while random samples were harvested from 1m² quadrats from each plot. Soil samples were taken at four depths (0-2 cm; 2-4 cm; 4-6 cm and 6-8 cm) from each plot and analyzed for pH, Ca, K, P, total C and total N. The Resin-Bag technique was used to determine nitrogen mineralization. Burning frequency caused significant variation in herbaceous species composition over time. The species were distributed along gradients of increasing burning frequency, and these responses were in three categories: Those that increased with burning frequency such as Themeda triandra; those that decreased with burning frequency such as Melica decumbens, and those that showed little response such as Panicum maximum. The three-year burn resulted in the highest compositional variation, light interception, Leaf Area Index, aboveground biomass production, while the annual, biennial and no burn treatments resulted in the lowest. The fact that infrequent burning resulted in higher species variation, improved habitat productivity due to increased leaf area for light interception shows that appropriate use of fire can maintain a more diverse and productive savanna system. Burning frequency had significant effects on the soil properties, while soil depth did not show any significance. Frequent burning increased soil pH, K, Ca, and Na, but reduced C, N, P and N mineralization. There was a negative correlation between burning frequency and N mineralization, but no correlation existed between N mineralization and total N, total C or the C:N ratio. These results imply that frequent burning can cause nutrient losses and a greater nutrient limitation to plants in the long-term, especially soil C and N loss from combustion of organic material in the soil top layer. The ability of shade-tolerant plants to persist under shade and regular defoliation such as in burnt and grazed systems may be of greater importance for long-term productivity and sustainability of forage crops. It is therefore imperative to explore the mechanisms by which some species were favoured by frequent burning which created low shade conditions, while others were favoured by high shade conditions where burning is infrequent or absent. A pot experiment was conducted to investigate the shade tolerances of seven grass species that were abundant in the long-term fire trial. The test species were Cymbopogon plurinodis, Digitaria eriantha, Eragrostis curvula, Melica decumbens, Panicum maximum, Sporobolus fimbriatus and Themeda triandra. Individual grass tillers of each species were collected from the natural vegetation, propagated in separate seedling trays and transplanted into individual pots, and were grown under five shading treatments: full sun (0 % shading), 55 %; 70 %; 85 % and 93 % shading respectively. Shading significantly reduced the dry matter production of all the species. Biomass production of all the species decreased linearly to varying degrees with an increase in shade intensity. Digitaria eriantha and Eragrostis curvula were most adversely affected by shading, hence are classified as shade intolerant, while Melica decumbens was the least affected by shading, and is hence classified as shade tolerant. Cymbopogon plurinodis, Panicum maximum, Sporobolus fimbriatus and Themeda triandra are classified as moderately shade-tolerant. From the results it was apparent that some species could perform optimally in partial shade than in full sunlight, and these results lead to a conclusion that for satisfactory natural regeneration and seedling growth of this savanna vegetation would require a gap large enough to provide at least 30 % of ambient light. Investigating patterns in competitive effects and responses of species in these communities may not only explain the abundance of each species, but may also provide insight into the nature of forces that affect the structure and function of that community. Since fire, herbivory and soil nutrients are natural drivers of savanna community structure and function, their influence on competitive interactions of selected species were investigated. Two experiments were conducted to investigate the competitive effects and responses of eight selected common species in the area. The test species (phytometers) included one woody shrub, Acacia karroo and seven grass species namely: Cymbopogon plurinodis, Digitaria eriantha, Eragrostis curvula, Melica decumbens, Panicum maximum, Sporobolus fimbriatus and Themeda triandra. In an outdoor plot experiment the responses of the phytometers to competition from neighbours (0; 2 and eight neighbours respectively), fertility (fertilized, unfertilized) and clipping (clipping, no clipping) were investigated. The second comprised a pot experiment where the competitive effects of the species were investigated. Each species was grown under 3 levels of fertility (0 %; 50 % and 100 % Hoagland‘s solution) and clipping (clipping, no clipping) in pots filled with fine river sand and 4 neighbours. Competition intensity, soil fertility and clipping had significant effects on the biomass production of the phytometer species. Acacia karroo and Melica decumbens, exhibited the weakest competitive effects and responses, and incurred the highest mortalities after clipping and with 8 neighbours. Digitaria eriantha and Panicum maximum exhibited the strongest competitive effects and responses, especially in high fertility, and experienced the lowest mortalities. T.triandra exhibited stronger competitive effect after clipping in low fertility, while A. karroo and C. plurinodis exhibited stronger competitive effects in moderate (50 %) fertility. Cymbopogon plurinodis, Eragrostis curvula and Sporobolus fimbriatus ranked between these two extreme groups in terms of competitive effects and responses. Relative Competitive Interaction increased with soil fertility and number of neighbours in the absence of clipping. These results indicate that in general, taller or broad-leaved grass species outgrow the shorter ones, and this gives them a competitive advantage over light and soil resources. One of the range management objectives in the False Thornveld of the Eastern Cape is to promote the abundance of Themeda triandra, which is of high forage value and an indicator of rangeland that is in good condition. The general situation under livestock farming conditions in this area is that if the grass sward is optimally grazed and rested then there is a great potential for Themeda triandra to dominate.The results of the competition experiments indicated that the species exhibits strong competitive interaction, and also exhibited stronger competitive effect after clipping in low fertility. These results imply that it has a low response and a high effect, an attribute that would enhance its performance if it is moderately grazed or the area is burnt. The species is also moderately shade tolerant, and this may explain why it thrives in burnt and moderately grazed areas. These studies have demonstrated the important role that competition and disturbance in the form of fire and herbivory play in the maintenance of this savanna grassland. Through natural selection species are able to occupy different niches in the same area and coexist in a heterogeneous environment and minimize their chances of extinction.
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.
Vegetation change over fifty years in humid grasslands of KwaZulu-Natal (Acocks's sites)
(1997) Marriott, David John.; Morris, Craig Duncan.; O'Connor, Timothy Gordon.
Eighty three of Acocks's sites, originally surveyed about 50 years ago, were resurveyed in 1996 to determine the extent of grassland change in the humid grasslands of KwaZulu-Natal. Sites were relocated using 1:10 000 scale ortho-photos and present land cover was determined for each site. Forty six of the sites that were still under original grassland were further examined to determine present species composition. A survey method was designed that would emulate Acocks's data and comparisons were drawn between original and present species composition. These differences were then analysed together with some environmental variables to try to determine the factors which had the most influence on the change and which environment and management factors are related to the present variation in composition among sites. Of the 83 sites, 26 had changed from natural vegetation to some other form of agriculture such as forestry or cultivation. Most of this change had occurred in the Natal Mistbelt Ngongoni Veld where large areas are forested. Cultivation is found predominantly in the communal areas where subsistence, cultivation practices are employed. The remainder of the sites had changed significantly in terms of their species composition. The most pronounced change had occurred in areas under communal tenure although significant changes had occurred in the commercially farmed areas. The direction of change was also more consistent towards species that commonly predominate in heavily grazed areas in the communal areas compared to the commercial areas. The exact reasons for this were unclear but this could possibly be attributed to heavier stocking rates in the communal areas. Change in floristic composition was also more pronounced at lower altitudes where the mean annual rainfall is lower and the mean annual temperature higher. This could possibly be a result of the vegetation at lower altitudes being less stable and thus less resistant to change. Basal cover differed significantly between commercial and communally grazed sites. Lower basal cover was found in the communal sites where intensive grazing limits the growth of individual tufts. Number of species found at each site did not differ significantly between communal and commercially grazed sites. This study was also a practical implementation of the resurveying of Acocks's sites and the original data set was found to be a useful baseline data set to determine coarse long-term changes in the vegetation.