Invasive alien tree species have negative environmental and economic impacts throughout the world. For example, black wattle (Acacia mearnsii) threatens native habitats by competing with and so repressing or excluding indigenous vegetation: in this way it replaces grass communities, reduces biodiversity, and increases water loss from riparian zones, thereby fundamentally damaging the ecosystem. The Acacia mearnsii threat requires urgent attention: effective control and management is urgently required if these deleterious impacts are to be reversed or prevented. The present study was conducted in the Elliot and Ugie communities situated in the Sakhisizwe and Elundini Local Municipalities. The objective of this study was to design integrated, efficient and cost-effective methods to help farmers and members of these communities with control and management of alien plant invasions. Further the study aimed to evaluate the implementation and efficacy of Working for Water (WfW) initiatives in poverty alleviation, and skills development: in addition the study attempted to assess WfW inputs as regards relevant legislation aimed at combating major wattle invasions. Mixed methodological approaches were employed, utilizing both qualitative and quantitative techniques. Questionnaire surveys, semi-structured interviews, use of photos, content analyses of local documents and experimental field work were all employed in order to collect and interpret data for the study. The study reveals that mechanical control and rehabilitation in combating should provide efficient and cost-effective methods for proper management of rangelands. Moreover the National Department of Agriculture, Forestry and Fisheries (DAFF) should be urged to devise and enforce legislation that will help to ensure sustainable control and management of black wattle through conservation of the natural environment. Furthermore funds should be made available for wattle eradication programmes so as alleviate poverty by creating more job opportunities for members of poor communities.

Studies conducted to determine life history and starch allocation of common reed (Phragmites australis), and evaluate haplotype susceptibility to aquatic labeled herbicides. Twelve 0.1 m2 samples were taken from four sites in the Mobile River delta from January 2006 to December 2007. Samples separated into above and belowground biomass dried and weighed. Starch determination used the amylase/amyloglucosidase method. Biomass decreased with decreasing temperature. Aboveground biomass was 2200 and 1302 g m2 in October 2006 and December 2007. Belowground biomass was 1602 and 1610 g m-2 in November 2006 and December 2007. Aboveground starch was highest in December of 2006 and November of 2007. Belowground starch peaked in August of 2006 and September of 2007. RFLP methodologies were used to identify populations of I and M used for herbicide sensitivity screening. No difference detected in the susceptibility of haplotypes. Glyphosate, imazapyr, and triclopyr are effective herbicides for common reed control.

Forests provide a number of ecosystem services which sustain and enrich the wildlife, human societies, and the environment. However, many disturbances threaten forest ecosystems, making it necessary to monitor their health for optimal management and conservation. Although there are many indicators of forest health, changes in biogeochemical cycling, loss of species diversity, and invasive plants are particularly useful due to their vulnerability to the effects of climate change and intensive agricultural land use. Thus, this work evaluates the use of imaging spectroscopy to monitor forest nutrient status, species diversity, and plant invasions in the Mid-Atlantic region. The research is divided into four separate studies, each of which evaluated a unique application for imaging spectroscopy data at a different scale within the forest. The first two studies examined loblolly pine nutrient status at the leaf and canopy scales, respectively. The first study determined that loblolly pine foliar macronutrient concentrations can be successfully modeled across the Southeastern US (R2=0.39-0.74). Following on these results, the second study focused on the relationship between physical characteristics, reflectance, and nutrients. Reflectance values and W scattering coefficients produced successful nitrogen models across loblolly pine plots at the canopy scale. Regression models showed similar explanatory power for nitrogen, although W scattering coefficients were significantly correlated with nitrogen at multiple wavelengths and reflectance variables were not. However, the direction of some of the correlations with W and the unusually high directional area scattering factor values indicate a need for further experimentation. The third study found that several imaging spectroscopy algorithms were moderately successful in identifying wavyleaf basketgrass invasions in mixed deciduous forests (overall accuracy=0.35-0.78; kappa=0.41-0.53). Lastly, the fourth study used a novel imaging spectroscopy/lidar fusion to identify canopy gaps and measure species diversity of understory vegetation. The lidar algorithm identified 29 of 34 canopy gaps, and regression models explained 49 percent of the variance in gap species diversity. In conclusion, imaging spectroscopy can be used to evaluate ecosystem health through forest nutrient status, nitrogen models, species diversity estimates, and identification of invasive plant species. / Ph. D.

MSc., Faculty of Science, University of the Witwatersrand, 2011 / This research investigated the susceptibility of South African indigenous aquatic plants to competition from invasive species, using the competitive interactions of two sets of aquatic plants as a potential indicator. These interactions were studied in two separate experiments: the submersed weeds, Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae) and an indigenous species, Lagarosiphon major (Ridley) Moss (Hydrocharitaceae) and; the floating weeds, Azolla filiculoides Lamarck (Azollaceae) and the indigenous Spirodela polyrhiza (L.) Schleid (Lemnaceae). Plants were grown under differing nutrient levels, and in an addition series of eight different densities, using the reciprocal yield model to estimate competitive ability. The invasive Hydrilla outcompeted Lagarosiphon in terms of mean length, dry mass, and survival. Major algal infestation in the high nutrient level of the Hydrilla/Lagarosiphon experiment altered light and nutrient conditions, which may have played a significant role in the lack of establishment of Lagarosiphon and the poor growth performance of Hydrilla. The invasive Azolla and indigenous Spirodela both performed well in terms of plant mass and increase in number. While Azolla was affected by intraspecific competition, it showed a steady increase in growth and multiplication with an increase in nutrients. The individual mass of Spirodela plants was highest in the low nutrient level, and multiplication rates were greatest in the high nutrient level. Results indicate that the susceptibility of indigenous plants may be increased in highnutrient systems, and that a continuous monitoring programme of aquatic alien species is vital in protecting our indigenous plants from extinction. This research recommends that the method of investigating competitive interactions between alien and indigenous plants be repeated with a variety of aquatic plants, as a means of anticipating susceptibility to invasions.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 160-166).

Bracken fern (Pteridium aquilinum [L.] Kuhn) is an indigenous invasive plant and it is known to have a negative impact on biodiversity. This research focuses on infestations of bracken fern in two areas within the uKhahlamba Drakensberg Park World Heritage Site; the Royal Natal National Park and the Rugged Glen Nature Reserve. Prior change detection research on bracken fern were constrained due to the low resolution satellite imagery and the inability of hard classification techniques to account for the mixtures of land cover types that occur within pixels of low resolution imagery. To overcome these constraints this research applied the fuzzy image classification technique to multispectral digital aerial imagery of 0.5 m spatial resolution. Multi date imagery used for image classification was captured in the mid-winter of 2009 and mid-spring of 2011. Thereafter post-classification change detection analysis was conducted using the fuzzy classified images. The classified images were verified using ground truth surveys. The 2009 and 2011 fuzzy classified images produced overall accuracies of 81.4% and 94.4% with Kappa coefficients of 0.63 and 0.89 respectively. This research found that the distinct seasonal development pattern of bracken fern and the time of year imagery were captured were significant factors in its detection. As bracken fern was found to be more spectrally distinct in spring as compared to winter, due to the plant growth of bracken fern, grass and other shrubbery. These classified images were used in post-classification change detection analysis which revealed that the bracken fern infestation in the Royal Natal National Park and Rugged Glen Nature Reserve had increased at a rate of 24 % and 27 % per annum respectively. This showed that bracken fern is spreading in the Royal Natal National Park and Rugged Glen Nature Reserve, as expected. Fire regimes, slope and aspect were found as factors that could be promoting the spread of bracken fern, 67.5 % and 75 % of the bracken fern infestation in the Park and Reserve respectively, occurred in areas that were burnt by fire regimes and have gentle to moderately gentle slopes facing east, south east and south. / Thesis (M.Sc.Sur.)-University of KwaZulu-Natal, Durban, 2013.

Thesis (M.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 72-79). Also available in electronic format on the Internet.

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 95-100). Also available on the World Wide Web.

Thesis (M.A.)--Humboldt State University, 2006. / Includes bibliographical references (leaves 36-38). Also available via Humboldt Digital Scholar.

Invasive tree species pose a huge problem in the Garden Route and are particularly damaging to aquatic ecosystems, including wetlands, riparian zones, lakes and estuaries. Therefore, this study aimed to determine priority areas for invasive tree species management, with a focus on aquatic ecosystems. This was achieved by using existing literature to identify priority species, based on their impact on aquatic ecosystems and their associated ecosystem services, and then testing the suitability of SPOT-6 and WorldView-3 multispectral data at detecting these focal species. The priority species identified were: Acacia cyclops (rooikrans), Acacia longifolia (long-leaved wattle), Acacia mearnsii (black wattle), Acacia melanoxylon (blackwood), Acacia saligna (Port Jackson willow), Eucalyptus camaldulensis (red river gum), Pinus pinaster (cluster pine) and Pinus radiata (radiata pine). The Random Forest classifier on SPOT-6 data achieved an overall accuracy of 62.5% and this method was consequently deemed ineffective at separating invasive tree species from other tree species in the Garden Route. The overall accuracy of the WorldView-3 classifier was higher (78.9%) but the cost of the data limited the use of more images for the detection of the focal species throughout the Garden Route. Therefore, to identify priority areas for invasive tree management, criteria derived from existing literature were input into spatial conservation planning software. The analysis identified the: Saasveld section of the Garden Route National Park, the Wilderness Lakes, Knysna Forest, Knysna Estuary, Tsitsikamma Forest around Stormsriver and a disturbed area of fynbos southeast of Kareedouw as management priorities. Currently spatial conservation planning software proved to be cost-affordable and useful tool and is recommended for invasive tree management in the Garden Route.