Four species of acacia of Auatralian origin are associated with the wattle industry in South Africa. Black wattle, Acacia mollissima willd., is the most important of these and is today almost exclusively cultivated. The tree grows successfully only in a limited area of rich soil and high rainfall and is easily affected by adverse conditions caused by insect pests, frost damage and drought. Expansion of the area under cultivation is therefore, not feasible, although the world demand for vegetable extracts far exceeds the available supply. The remaining species such as green (Acacia decurrrens willd.) and silver wattles (Acacia dealbata Link.) possess many desirable characteristics which resist such adverse factors. Their barks, however, give reddish extracts, which are considered unsuitable for tannery usage because of the red colour they impart to the leather. Hybridisation studies, involving the crossing of green and silver wattle with the black, and aimed at produc1ng progenies containing many of the desirable characterlstics of the parent plants, are thus a natural result and have been in progress for a considerable period. Summary, p. i.

The distribution of flavonoid constituents in the barks of Acacia mearnsii De Wild.(black wattle) , A· decurens Willd. (green wattle), A. dealbata Link.(silver wattle) and A. pycnantha Benth.(golden wattle) has been studied. Bark extracts of the four wattle species have been fractionated into low molecular weight fractions containing mainly catechins and other low molecular weight constituents, and high molecular weight fractions containing the bulk of the polymerized tannins. The low molecular weight fractions have been further fractionated by "preparative paper chromatography". (-)-Robinetinidol, (-)-7:3': 4': 5'-tetrahydroxy flavan- 3-ol, a new naturally occurring catechin, (+)-catechin and (+)-gallocatechin have been isolated from the barks of A. mearnsii, A. dealbata and A. pycnantha. (-)-Epicatechin and (-)-epigallocatechin have been identified in the bark extracts of A. dealbata and A. pycnantha, but appeared to be absent in the barks of A. mearnsii and A. decurrens. (-)-Epicatechin has been isolated fron A. dealbata, and both (-}-epicatechin and (-)-epigallocatechin were isolated from A. pycnantha. (-)-Epicatechin gallate, (-)-epigallocatechin gallate and gallic acid were isolated from A. pycnantha only. These three constituents appeared to be absent in the barks of the three other wattle species. (-)-Epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate which were not available for direct comparison, were subsequently isolated from green tea where they are present as major phenolic constituents. A method for the quantitative estimation of polyphenolic substances on two dimensional paper chromatograms has been developed, and a photoelectric densitometer constructed. Two spray reagents, ammoniacal silver nitrate and bisdiazotised benzidine, were found to give straight line relationships of instrument deflection against log concentration for flavonoid substances. This estimation method for the first time supplied means for a detailed study of the concentration of catechin constituents in the bark extracts of A. mearnsii, A. decurrens, A. dealbata, A. pycnantha and of A. mearnsii x A. decurrens hybrids. The concentration of catechin constituents has been shown to vary considerably between species whereas variation within species was small. In the latter respect silver wattle is an exception. Taxonomic significance may possibly be attached to the distribution of catechin constituents in the bark of the four Acacia species. The concentration of (-)-robinetinidol, which appears to be the characteristic compound of these Acacias, progressively decreases in the sequence black-, black x green hybrid, green-, silver- and golden wattle, while the number of catechin constituents of the "phloroglucinol series" increases in the same sequence. It thus appears, that by the examination of their bark components, a differentiation between species of a subgenera may be possible. Two tannins, constituents D and B, which are related to the leuco-anthocyanidins (flavan-3:4-diols) have been found in the barks of the four wattle species. One of the two, constituent D, was isolated in a pure form from the barks of A. mearnsii and A. pycnantha. Constituent D was found to generate robinetinidin and an orange pigment, the structure of which has not yet been fully identified. Compound D and its acetyl- and methoxyl derivatives did not crystallize. From the results of alkaline-, acidic- and enzymatic degradations, colour reactions and light-absorption studies, combustion analysis of the compound and its derivatives and molecular weight estimations, constituent D is surmised to be a dimer of 7:3': 4': 5'-tetrahydroxyflavan-3:4-diol (leuco-robinetinidin), The isolation of this complex leuco-anthocyanidin tannin represents the first isolation of a flavonoid tannin from commercial vegetable tannin sources. The second tannin obtained from the bark of A.mearnsii, "constituent B" appears to consist of two overlapping substances, which have not yet been separated. The tannin (B) was found to have an average molecular weight of 676 and it is considered likely that both substances may be dimolecular. On heating with mineral acid robinetinidin, fisetinidin and an orange pigment are generated, the pigment being identical with the pigment generated from constituent D. It may therefore be assumed that "Constituent B" consists of a mixture of complex leuco-robinetinidins and leucofisetinidins. The distribution of complex leuco-anthocyanidins in the bark extracts of Acacia mearnsii, A. decurrens, A. dealbata and A. pycnantha has been examined. A correlation between the distribution of leuco-anthocyanidins in the bark of the four wattle species, and accepted systematics, does not, apparently, exist.

From Summary: The structural elucidation of condensed tannins, which are considered to consist of C₁₅-flavan units, presents certain difficulties. These tannins occur in extremely complex mixtures, and their isolation is complicated by their susceptibility to oxidative denaturation. Limitations in the formation of significant degradation products add to these problems. Since condensed tannins of black wattle bark yield anthocyanidins on treatment with mineral acids, they are considered to be proanthocyanidin in character. For this reason the initial approach to the investigation of the structures of condensed tannins was by way of the synthesis of novel 7-hydroxyflavan-3,4-diols having a low degree of hydroxyl substitution. Submission of these to modern physical techniques such as nuclear magnetic resonance (n.m.r.) spectroscopy would yield valuable data regarding the chemical shifts and coupling constants of heterocyclic and benzenoid protons which may be used for subsequent work on more highly hydroxylated diols, biflavanols and finally the condensed tannins themselves.

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.

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.

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.

Multiple shoots were produced from nodal explants of thirty-day-old in vitro grown seedlings and from pretreated three, five- and nine-month-old greenhouse grown Acacia mearnsii plants, respectively. Explants were sterilized for 15 minutes using 0.1 % HgCl₂ for the three-month-old explants and 0.2 % for the five and nine-month-old explants. Nodal explants were induced to form multiple shoots when placed on Murashige and Skoog (MS) medium supplemented with 2.0 mg l ¯¹ benzyladenine (BA). Rooting of these shoots was achieved on MS medium supplemented with 1.0 mg l ¯¹ indole-3-butyric acid (IBA). Plantlets were acclimatized in transparent plastic containers under greenhouse conditions with a 90 % success rate. These plantlets were successfully acclimatised under greenhouse conditions and planted in the field together with plants regenerated by cuttings. In an attempt to overcome maturation effects and loss of juvenile characteristics, when using adult plant material in vitro, investigations were undertaken into the use of coppice material, as an alternative explant source. A. mearnsii trees from five ages (two, four, six, eight and ten-years old, respectively) were decapitated to a height of 1.5 m. After three weeks, coppice was noted on the stumps of trees from all ages. A linear response to coppice production was noted, with the greatest coppice production being on the two-year-old tree stumps and the least on the ten-year old tree stumps. Decontamination of the coppice was successful and multiple shoot production was obtained from coppice taken from all age groups on MS medium supplemented with 2.0 mg l ¯¹ BA. The effect of various sucrose concentrations were investigated. Greater shoot production occurred with increased sucrose concentrations (20 and 30 g l ¯¹). It was evident that rejuvenation of mature tissue could be achieved through the use of coppice material. A second approach to rejuvenate adult material and to overcome the deleterious effects of maturation, was in the use of apical meristems. Meristems were taken from 30-day-old in vitro grown plants, from coppice (rejuvenated tissue) and adult material of five various tree ages (two, four, six, eight and ten-years-old, respectively). Plant material were taken over two seasons (1997 to 1999) and the use of agar and liquid support media were tested under both light and dark conditions. The coppice and adult material was successfully decontaminated in both seasons. In the first season (1997/1998), shoot production was obtained from meristems of in vitro grown plants, coppice and adult material from all trees on MS medium alone or MS medium supplemented with 2.0 mg l ¯¹ BA. In the following season (1998/1999), the use of a solidified agar medium was superior to the use of a liquid culture. There appeared to be no significant difference (p<0.05) between the use of light or dark culture conditions. Various media were tested and maximum shooting occurred on half-strength MS medium and Woody Plant Medium (WPM). However, once multiple shoot primordia were initiated, shoot elongation posed a problem. It was for this reason that the size of the meristems excised from the coppice material was increased from 0.5 mm to 1.0 mm in the 1997/1998 season, to 1.0 to 2.0 mm in the 1998/1999 season. The use of gibberellic acid and 100 ml jars were also investigated to see if this might enhance shoot elongation. Sufficient plant material was not available for a thorough investigation. Environmental conditions under which the plant material (adult or coppice) was harvested was similar in both seasons, with respect to temperature, but differed in rainfall. Rainfall was high (105.1 mm) in 1997/1998 season and low (ranging from 59.8 to 71.45 mm) in the 1998/1999 season. Shoot production from meristems taken from coppice material in the 1998/1999 season was significantly greater (p>0.05) than that in the 1997/1998 season, whereas shooting from the adult plant material remained unchanged. The disadvantage with using coppice material is that its production on decapitated tree stumps is dependant on rainfall, which is unpredictable. The differences in results from coppice material could be attributed to the fact that the trees felled in the two seasons were not related to each other in any way. In both seasons meristems, tree age was not a limiting factor, for meristems from adult and from coppice material. Meristems from the ten-year-old trees were as productive as those taken from the two-year-old trees. In the 1997/1998 season the results from the meristems from the adult material was equal if not greater than those obtained from the coppice material. In the 1998/1999 season, there was no significant difference (p<0.05) in percentage shoot production between the meristems from the adult and coppice material throughout the age groups. This suggests that the use of rejuvenated tissue in the form of coppice is not essential. This re-emphasized the advantage of using meristems taken from adult plant material. This study provided suitable protocols for the micropropagation of both in vitro and ex vitro grown nodal explants of A. mearnsii. However, as the plant material obtained from the field matures so the ease of obtaining sterile material decreased, thus reducing the chances of in vitro micropropagation. For this reason suitable pretreatments and rejuvenation methods are necessary if explants from mature field tissue are to be introduced into culture and successfully micropropagated. This study has shown that through the use of nodal material (taken from coppice produced on adult tree stumps) and apical meristems taken from both coppice and mature plant material, adult material can be successfully decontaminated, introduced into culture and stimulated to produce shoots. Analysis of tannin production was conducted to see if there was any indication that the presence of tannins in the plant material effected in vitro culture of nodal explants. However, no trends were obtained suggesting any influence of tannins on in vitro performance. In future years after further optimisation, these techniques could be incorporated in an A. mearnsii clonal programme, with the advantage of possibly eliminating maturation effects, commonly noted in vegetative practices. This will allow for easy manipulation and amplification of superior quality adult material. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1999.

In South Africa, invasive black wattle trees (Acacia mearnsii D. Wild) are a major threat to ecosystem functionality causing widespread social, economic and environmental degradation. It is important that environmental managers are provided with rapid, regular and accurate information on the location of invasive black wattle trees to coordinate removal efforts. This study investigated the potential of an automated image classification algorithm to accurately identify black wattle (A. mearnsii De Wild.) trees using imaging spectroscopy. Hyperspectral data acquired by the EO-1 Hyperion sensor was used to identify black wattle trees in two study areas near Greytown, KwaZulu-Natal, South Africa. Image classifications were performed by the classification algorithm to identify black wattle trees using general and age specific spectral signatures (three to five years, seven to nine years, eleven to thirteen years). Results showed that using the general spectral signature an overall accuracy of 86.25% (user’s accuracy: 72.50%) and 84.50% (user’s accuracy: 69%) was achieved for study area one and study area two respectively. Using age specific spectral signatures, black wattle trees between three to five years of age were mapped with an overall accuracy of 62% (user’s accuracy: 24%) and 74.50% (user’s accuracy: 49%) for study area one and study area two respectively. The low user’s accuracies for the age specific classifications could be attributed to the use of relatively low resolution satellite imagery and not the efficacy of the classification algorithm. It was concluded that the classification algorithm could be used to identify black wattle trees using imaging spectroscopy with a high degree of accuracy. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2012.

No abstract available. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.