This thesis explores the effect of Acacia mearnsii on streamflow in the Eastern Cape. There is a need for data on the localised effects of removing alien trees from the riparian zones within the Fynbos Biome. Fynbos catchments throughout the Western and Eastern Cape yield large quantities of good quality water which is an essential resource in the region. To convince local land owners to manage their riparian zones, small scale experimental results will prove invaluable to assure them of the immediate advantages for themselves and for downstream water users. Three permanent weirs were built 500 m apart to monitor the effect of removing A. mearnsii on streamflow in the Sand River, Eastern Cape. Consecutive weirs allowed for the comparison of streamflow between a cleared and uncleared section of the river without significant differences in riparian conditions, channel morphology and vegetation densities. A site survey confirmed comparable densities of A. mearnsii in both sections. A sample of trees was weighed and a relationship was found between diameter at breast height and above ground wet biomass. Between the first two weirs, 2.5 ha of riparian zone was cleared amounting to approximately 160tlha. Streamflow was monitored from the 10th of January 1996 to the 9th of September 1996. The average streamflow reduction for the duration of the experiment was 15.1 m³/ha/day or 551 mm per annum. Initially, after a period of above average rainfall, streamflow was augmented by discharge from the riparian zone but as conditions dried out, there was a net uptake of water with the highest average uptake of 23. 7m³/ha/day in June. A comparison between weather conditions and streamflow reduction indicated there is a complex relationship, with evidence of A. mearnsii exhibiting control of water loss during dry conditions. Acacia mearnsii trees in the riparian zone have been shown to cause significant streamflow reduction. Permanent weirs were found to be appropriate for this type of study. There is a need for further research on the effect of alien trees in riparian zones around South Africa as there is potential for significant increases in streamflow.

Debarking of Acacia mearnsii in South Africa has been conducted using mainly manual systems. Labour shortages and reliability of these systems has caused interest in alternative systems that might be able to debark A. mearnsii. The aim of the research is to compare three mechanised debarking technologies used to debark A. mearnsii. Research trials were conducted on the Demuth, Hyena and Hypro debarkers that would form part of semi-mechanised harvesting systems. The debarking technologies were analysed and compared in terms of productivity per productive machine hour (PMH), debarking quality, system costs and the quality of the bark that was produced. Furthermore, the effect that tree volume, strippability and form have on each of the debarking technologies was determined. The debarking technologies were affected by each of the factors researched. Decreasing tree form had a negative effect on the productivity of each of the technologies. An increase in strippability class (strengthening wood-bark bond strength) caused a decrease in the productivity of each of the machines. An increasing tree volume had a positive effect on the productivity for the three debarking technologies. After the debarking had taken place, samples of bark were analysed at a laboratory to determine if it was acceptable for the processing facilities. Each of the debarking technologies produced bark of varying dimensions, but they were all found to be acceptable. The system costs of the three debarking technologies were compared to a manual system cost at tree volumes of 0.1m³, 0.15m³ and 0.2m³. The Demuth debarker had the best system cost for a tree size of 0.1m³, while the manual system was best for tree volumes 0.15m³ and 0.2m³. The Demuth, Hyena and manual system costs were very similar for each of the tree volumes, with the Hypro being a little higher.

Black wattle (Acacia mearnsii) is one of South Africa's leading commercial exotic species comprising nearly seven percent of South African forestry plantations. The planting of black wattle has become increasingly popular, initially for its high quality tannin content and in more recent times, for its wood and wood products. The industry also provides jobs for more than 36 000 people. Despite the commercial value of black wattle, if left unmanaged, it is one of South Africa's top invader species that aggressively colonise and rapidly out-competes indigenous vegetation. Thus, both plant breeders and environmentalists alike are faced with an interesting paradox of balancing the commercial significance of black wattle on the one hand with increasing environmental concern on the other. At the Institute for Commercial Forestry Research (ICFR), black wattle breeding programmes are being designed and implemented in order to reduce invasiveness whilst still maintaining product quality. One way of minimising invasiveness is to decrease fertility through the introduction of semi-sterility; while at the same time leaving product yield and quality unaffected. A method of achieving semi-sterility is by the induction of autopolyploidy that results in unviable gametes. Autopolyploidy, tetraploidy, is induced chemically through doubling of the chromosomes of diploids. These induced tetraploids may then be crossed with diploids to produce triploids. Thus, an effective method to identify polyploids at the seedling stage would greatly facilitate the success of the abovementioned breeding programmes in the black wattle industry. Polyploidy in plants is often associated with physiological and biochemical changes that become apparent as gigantism of organs which include fruits, flowers and leaves. Polyploidy is also associated with an increase in the number of organelles such as the number of stomatal chloroplasts and nucleoli, as well as an increased production of some proteins and pigments such as chlorophyll. These ploidy-related manifestations are often utilised in breeding programmes to increase the size and quality of plant products as well as a tool to discriminate between polyploids and diploids. Two putative diagnostic procedures to differentiate between diploid and tetraploid black wattle were developed in this investigation. The study focused on the discriminating power of stomatal chloroplast numbers and arrangements as well as the chlorophyll content in the two different ploids. A number of associated experiments were initially conducted to establish the optimal conditions for chlorophyll content analyses such as the type of leaf material and storage conditions. Stomatal chloroplast frequencies were determined in diploid and tetraploid black wattle and comprised three lines per ploidy level with five plants per line. A thin epidermal layer from the abaxial surface of a pinnule was stripped, stained, mounted and 15 stomatal guard cells per plant were viewed at 40X magnification. The mean number of chloroplasts per cell in diploids (9.89 ± 0.222) was found to be statistically different (p < 0.001) to that of tetraploids (22.43 ± 0.222) with no overlapping of the mean chloroplast values between the two ploidy levels. The ratio of diploid and tetraploid stomatal chloroplast numbers was roughly 1:2. An analysis of the least significant difference (LSD) was performed and indicated significant differences between plants within lines, between lines of different ploids (LSD =0.6266), as well as between the different ploids (LSD =0.2802). Furthermore, stomatal chloroplasts spatial arrangements were distinctly different in diploids and tetraploids. In diploids, chloroplasts were clustered into two regions, each towards the extreme ends of the kidney shaped stomatal cells. In the tetraploids, no clustering of chloroplasts could be identified, with an even distribution around the convex curvature/perimeter of the cells. There are a number of factors that influence chlorophyll content and degradation, which are either environmental or genetic in nature. Environmental factors that were considered are sample age and sample storage conditions. Genetic factors include genetic composition and, specifically, the number of sets of chromosomes, that is, the ploidy. Chlorophyll content was investigated by chemically extracting chlorophyll from leaf material and obtaining absorbance spectra with a PerkinElmer UV/vis spectrometer for wavelengths from 400 nm to 700 nm. Chlorophyll absorbance spectra were generated in terms of leaves stored prior to chlorophyll extraction, leaves of different ages, trees of different ages and ploidy. The effects of storage of leaves on chlorophyll content were determined in five non-identical two year-old nursery diploid black wattle genotypes. Fifteen leaf samples from each genotype were either oven dried and then stored for one week or one month at room temperature, or frozen for one week or one month at -4 °C, before chlorophyll was extracted and absorbance spectra determined. Chlorophyll absorbance values of chlorophyll extracted from leaf material on the day of collection (day-0) was used as the control. An analysis of variance (ANOVA) revealed that the chlorophyll absorbance values of the different storage treatments were all significantly lower than the chlorophyll absorbance values of the control (p < 0.001). Assessment of the mean chlorophyll absorbance (TĀ), sum of the three peak absorbance values at three wavelengths, namely, 433 nm, 456 nm and 663 nm, revealed significant differences (p < 0.001) from the control (TĀ = 1.275) for all treatments. Dried leaves that were stored for seven days (TĀ = 1.132) resulted in the least amount of chlorophyll degradation followed by 28 day ice storage (TĀ = 1.114), seven day ice storage (TĀ = 1.103) and lastly 28 day dried storage (TĀ = 1.093). An analysis of least significant differences (LSD) revealed that chlorophyll absorbance values within lines and between wavelengths were significantly different (LSD = 0.005). Furthermore, LSD analysis revealed significant differences between all treatments (LSD =0.003) which also supported the ANOVA findings. Chlorophyll absorbance values within dried and frozen treatments were compared with respect to storage time periods of one week and one month. It was noted that whilst all treatments decreased from the control (day-0), dried samples responded differently to storage periods as compared to frozen samples. Chlorophyll absorbance values of dried material decreased steadily over time from control to seven-day storage to one-month storage, whereas, in the case of frozen material, a similar trend could not be identified. A greater decrease from the control to seven day ice storage was recorded than for the decrease from the control to 28 day ice storage. The effects of tree and leaf ages of diploid black wattle on chlorophyll content were determined. Two types of leaf flushes namely, old and new flush, were examined in relation to different tree ages; two, four, six, eight and nine year-old; in order to assess whether the choice of material impacts on chlorophyll absorbance values. Five leaf samples from each tree were collected, bagged and chlorophyll extracted within two hours of collection. These chlorophyll absorbance values were compared to young diploid seedling material as a base-value and as a control value. An analysis of variance (ANOVA), revealed significant differences between tree ages and between leaf ages (p < 0.001). An analysis of least significant differences (LSD) revealed that new flush of all tree age groups were significantly different from the control (LSD = 0.006). This was mostly true for old flush, except that of six year-old old flush which was not significantly different from the control (LSD =0.006). The chlorophyll absorbance values of both old and new flush of different age groups produced spectral graphs for which no specific trends could be ascertained. Therefore, the data from the two flush types were pooled and revealed a marked increase in chlorophyll absorbance as trees became older. Moreover, this increase was more apparent in new flush than in old flush. Interestingly, juvenile characteristics were identified in two year-old black wattle trees, where a marked increase in chlorophyll content was noted. The effects of the number of chromosome sets on chlorophyll content were assessed for diploid and tetraploid black wattle. Seedlings, bagged juveniles as well as two year-old field trees were analysed. Three genetic lines per ploidy level comprising of ten plants per line were used in the analysis. An analysis of variance (ANOVA) revealed significant increases of chlorophyll absorbance values (p < 0.001) for diploid seedlings (TĀ = 1.1086) to bagged trees (TĀ = 1.149) to field trees (TĀ = 1.224). Similar significant increases were recorded for the tetraploid seedlings (TĀ = 1.886) to bagged trees (TĀ = 1.931) to field trees (TĀ = 2.059). There were distinct differences in chlorophyll absorbance between the two levels of ploidy (LSD =0.002). Furthermore, chlorophyll absorbance within lines, between wavelengths were found not to be significant (p = 0.984), which was supported by an analysis of least significant differences (LSD = 0.004). Moreover, the ratio of diploid to tetraploid chlorophyll absorbance was roughly 2:3. Additionally, the increase of chlorophyll content from seedlings to bagged juveniles to field material of both diploid and tetraploid black wattle further supported the findings in the previous age study that there was an increase in chlorophyll content as the tree matures. Stomatal chloroplast frequencies and chlorophyll content have been identified as two methods that are able to effectively, and with ease, discern between diploid and tetraploid black wattle. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Leaf area index (LAI) is an important variable in models that attempt to simulate carbon, nutrient, water and energy fluxes for forest ecosystems. LAI can be measured either directly (destructive sampling) or by using indirect techniques that involve estimation of LAI from light penetration through canopies. Destructive sampling techniques are laborious, expensive and can only be carried out for small plots. Although indirect techniques are non-destructive and less time consuming, they assume a random foliage distribution that rarely occurs in nature. Thus a technique is required that would allow for rapid estimation of LAI at the stand level. A means of getting this information is via remotely sensed measurements of reflected energy with an airborne or satellite-based sensor. Such information on an important plant species such as Acacia mearnsii (Black Wattle) is vital as it provides an insight into its water use. Landsat ETM+ images covering four study sites In KwaZulu-Natal midlands encompassing pure stands of Acacia mearnsii were processed to obtain four types of vegetation indices (VIs). The indices included: normalized difference vegetation index (NDVI), ratio vegetation index (RVI), transformed vegetation index (TVI) and vegetation index 3 (VB). Ground based measurements of LAI were made using destructive sampling (actual LAI) and LAI-2000 optical instrument, (plant area index, PAl). Specific leafarea (SLA) and leaf area (LA) were measured in the field for the entire sample stands to estimate their LAI values. The relationships between the various VIs and SLA, actual LAI and PAl values measured by LAI-2000 were evaluated using correlation and regression statistical analyses. Results showed that the overall mean SLA value of Acacia mearnsii was 8.28 m2kg-1 SLA showed strong correlations with NDVI (r=0.71, p<O.Ol) and RVI (r=0.76, p<O.Ol) and a moderate correlation with TVI (r=0.66, p<0.05). Regression analysis revealed that SLA had significant relationship with RVI (R2=0.59) and NDVI (R2=0.51). Actual LAI values showed strong correlation with PAl values (r=0.86) and the analysis revealed that 74 % of the variation in the relationship between actual LAI and PAl values could be explained by regression. PAl values were strongly correlated with NDVI (r=0.75,p<O.Ol) and moderately correlated with RVI (r=O.63, p<O.05) and TVI (r=O.58, p<O.05). Actual LAI was strongly correlated with NDVI (r=O.79, p<O.Ol) and moderately correlated with RVI (r=O.61, p<O.05). Out of the various VIs examined in this study, NDVI was found to have a better relationship with actual LAI values (R2=O.62) and with PAI values (R2=O.56); while VB didn't show any significant relationship with SLA, PAl or actual LAl. In conclusion, preliminary estimate of SLA of Acacia mearnsii could be obtained from RVI or NDVl. The relationship obtained between PAl and actual LAI values was satisfactory, thus the regression equation can be used to calibrate the LAI-2000 plant canopy analyzer. Because NDVI was observed to have a good relationship with actual LAI and PAl, LAI of Acacia mearnsii can be estimated from Landsat ETM+ satellite imagery with a reasonable degree of accuracy. These results can satisfactorily be used as inputs into models that attempt to estimate water use by Acacia mearnsii. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

Acacia mearnsii (black wattle) is an important South African commercial forestry species, providing a source of high quality raw material (fibre) for both the domestic and international pulp and paper industries. Compared with many Pinus and Eucalyptus species, there has been very little research into the wood and pulping properties of black wattle. The ability to assess pulp yield in a non-destructive manner, using near infrared (NIR) spectroscopy, is vital from a tree improvement perspective. Destructive sampling and analysis, results in the loss of the genotype, while also being very expensive and time consuming. In order to assess some of the important characteristics that make the species desirable from a fibre perspective, this study investigates growth characteristics, wood density and pulp yield of ten trees grown on each of three different sites namely, Bloemendal, Glen Echo and Phoenix, and from each of three different age classes being 7- , 9- and 11-years-old. In total, 90 trees were sampled for this stage of the study. In general, physical characteristics such as utilisable height and diameter at breast height of the trees differed between sites and increased with age, this age effect trend was not reflected in the pulp yield or wood density results. Pulp yield measurements ranged from 52.61 to 59.91% across all sites and age classes, which, when compared to the pulp yield from many other forestry species, is relatively high. Laboratory pulp yield data was used in conjunction with NIR spectra obtained from the same wood samples to calibrate a NIR spectrophotometer to predict pulp yield. Thirty 11- year-old trees were then chosen from the Bloemendal site and sampled extensively to investigate the within-tree variation in pulp yield. The NIR model developed was used to measure the pulp yield from the numerous samples taken from within the trees. In general, pulp yield decreased from pith to bark and from the base of the tree to about 20% of the tree height and then decreased towards the top of the tree. The within-tree variation data for pulp yield was analysed to identify the best position for non-destructive sampling, and a model was then developed to predict whole tree pulp yield based on this sample, which was taken at 1.4 m up the tree. The analyses of small samples of wood meal, using near infrared spectroscopy, enabled the prediction of whole tree pulp yield. / Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2009.

No description available.

The invasion of Acacia mearnsii in the Kouga catchment, Eastern Cape, South Africa, has various negative impacts on the ecosystem. These impacts include: reduced species richness, increased water use, increased nutrients and increased N cycling rates. The native shrubby fynbos vegetation has adapted to the acidic nutrient poor soils and Mediterranean climate of the Kouga Mountains. Fynbos, however, is currently being out competed by the much taller Acacia mearnsii trees, due to their competitive nature and ability to fix nitrogen, thereby enriching the soil. The invaded sections of the valley bottoms and lower hill slopes are characterised by an almost complete monoculture of Acacia mearnsii, with very few fynbos species still present. The Department of Water and Environmental Affairs sponsored Working for Water programme started clearing Acacia mearnsii in 1996 in the Kouga Mountains. Cleared sites have remained bare for long periods, indicating that soil properties are not favourable for indigenous propagule re-establishment. The aim of this research was to assess how A. mearnsii invasion and clearing affect fynbos recovery through its impact on soils. This was done by characterising vegetation and soil properties on fynbos, infested and cleared slopes. Vegetation cover for various growth forms was determined and a species list was compiled for each plot. The slope angle, surface hardness, litter cover, bare ground cover and soil depth were measured in the field, whereas water repellency, particle size and the chemical composition were measured in the laboratory. Furthermore, the plant establishment capacity of soils from fynbos, infested and cleared slopes was calculated. This was done by germinating fynbos seeds and growing fynbos plants in soils from the various slopes. The effect that invasion and clearing has on soil erosion was quantified using erosion plots on fynbos, infested and cleared slopes. The invasion and clearing of Acacia mearnsii led to an increase in soil nutrients, especially nitrogen, phosphorus, potassium, carbon and manganese. Furthermore, soils became more acidic, with increased water repellency and reduced surface hardness. The vegetation changed to a tree-dominated structure, replacing the native species. Native plant germination was relatively unaffected by invasion and clearing, with an increase in germination just after clearing. Plant growth of a native grass, Themeda triandra, and herb, Helichrysum umbraculigerum, has increased on soils from cleared slopes. This study showed that soil movement increased on slopes which are invaded and cleared of Acacia mearnsii, with erosion rates doubling on invaded slopes

The Kouga Riparian Rehabilitation Project (KRRP) is seen as a pilot rehabilitation project in the Kouga region that is heavily invaded with Acacia mearnsii along the riparian zones of many mountain streams. Clearing of these black wattles and re-planting of indigenous vegetation are imperative to rehabilitation efforts. In this context, two invaded catchments were identified - the Baviaans and the Heuningnes. The aim of this research is to characterise the effects that the woody alien invasive Acacia mearnsii has had on the river channel morphology of the Baviaans and Heuningnes Rivers. A desktop and initial field analysis of the relevant study area catchments was completed. This was followed by a comparison of the channel morphology of the various study channel reaches using fixed channel transects. Ecological resource quality objectives (RQOs) for river rehabilitation from a fluvial geomorphological viewpoint were then established. A long-term monitoring protocol to assess whether or not these RQOs will be achieved was recommended. Follow-up channel transects were measured post wattle clearance in the Baviaans and short-term (<2yrs) changes in channel form were described. Differences in terms of the effect of Acacia mearnsii on channel form were then interpreted by direct comparison and through statistical analysis. Results indicate a number of significant differences between those channels impacted by black wattle infestation and those channels seen as unimpacted and natural. Short-term changes (<2yrs) that occurred within the study period post Baviaans wattle clearance were shown to be minimal for channel form as well as for bed material. The lack of any clear relationship or explanation between channel form and other channel controls suggests vegetation as the primary control. Vegetation, specifically the invasive alien vegetation, is the key controlling variable acting on channel form in the two study catchments.

In their article ―Naturing the Nation: Aliens, the Apocalypse and the Post Colonial State (2001) Jean and John Comaroff look at ―the contemporary predicament of South Africa through the prism of environmental catastrophe. Through it they reveal the context in which alien plants have become an urgent affair of the state. Following their lead, I show how alien plants (particularly Australian wattle) continue to provide grounds for new social and political aspirations in South Africa, though in a different setting. With reference to a group of private landowners on the fringe of a World Heritage Site -- the Baviaanskloof Mega-Reserve, Eastern Cape, South Africa -- I show how an increasingly apocalyptic and xenophobic environmental agenda has influenced local activists seeking to address social and ecological issues in tandem with alien-eradication. These local activists adhere to a particular brand of environmentalism which Milton (1993) argues can be considered a social, cultural and religious phenomenon. The subjects of my main empirical investigation offer practical ways of achieving a transformational end through a new ritual activity in relation to a spread and exchange of environmental ideas and practices on a world-wide scale. On the ground this group practices ecosocietal restoration through which they aspire to mend the bond between people and the land in a spiritual and moral sense, bolstering intrinsic incentives for environmental stewardship and achieving ―cultural reconciliation in an attempt to reimagine what South Africa could be.