Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.A.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed Aug. 17, 2007. Includes bibliographical references (p. 70-77).

Thesis (Ph.D.)--Mississippi State University. Department of Biological Sciences. / Title from title screen. Includes bibliographical references.

2 pp. / Camelthorn is an invasive weed classified as a noxious weed in Arizona. The weed has the potential to cause serious damage for private landowners and their property. This fact sheet provides the means for landowners to identify and take steps to control and eliminate this weed.

Mapping their location and extent is a critical step in noxious weed management. One of the most common methods of mapping noxious weeds is to walk the perimeter of each patch with a handheld GPS receiver. This is the method used at Camp Williams, a National Guard Bureau training facility in Utah where this study was conducted. It was proposed that a low-cost Unmanned Aerial Vehicle (UAV) that made use of a hobbyist remote control airplane equipped with a Global Positioning System (GPS) receiver and digital camera could be used along with automated post-processing techniques to reduce the cost of weed mapping compared to the on foot method. Two noxious weeds were studied: musk thistle (Carduus nutans) and dalmation toadflax (Linaria dalmatica). The musk thistle was visually identifiable in the imagery but the dalmation toadflax was confused with yellow sweet clover (Melilotus officinalis). It was found that after the automated post-processing the photos were not positioned well enough to produce a consistent and accurate weed perimeter. A supervised classification was attempted with imagery of the musk thistle, however, the accuracy of the classification was too low to be able to identify the weed perimeter from the classification. To achieve accurate results the photos had to be registered to a base image and the perimeter of each patch hand digitized. The time it took to do so increased the costs well above the on foot method. A number of improvements to the UAV could make the image registration step unnecessary. There are other applications for which this low cost UAV could be used.

Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: This project consists of two botanical investigations in an agricultural area of the Western Cape Province. A farm known as De Rust, in the Elgin Valley, was used to sample the geographic location, density, height and life stage of six prominent invasive plant species in various land-use categories. In the first investigation, the density, height and age structures of the six invasive species populations were analyzed. The density distribution of the six species was also displayed cartographically. Species were then ranked according to the potential threat that they pose to the conservation of the remaining natural areas on the farm. Results indicated that Acacia mearnsii and Acacia saligna are the major invaders at De Rust and that Hakea sericea can be considered as an emerging invader. The second investigation explores the statistical relationship between the various land-use categories and density, height and age of the six prominent invaders identified in the first investigation. The loglikelihood ratio analysis of observed frequencies resulted in statistically significant (P<0.01; P-values range between 1.35 x 10-3 and 2.7 x 10-224) relationships between certain land-use types and certain invasive species. A conclusion was reached that it could be useful to include land-use categories in simulation models of invasive plant species distribution and spread. / AFRIKAANSE OPSOMMING: Hierdie projek behels twee botaniese ondersoeke in ‘n landbou gebied van die Weskaap. Die plaas bekend as De Rust, in die Elgin Vallei, was gebruik vir die versameling van data te doen met die geografiese ligging, plant digtheid, lengte en lewens stadium van ses prominente indringer plant spesies in verskeie landgebruik kategorieë. Die digtheid, lengte en ouderdomstruktuur van ses indringerspesies was in die eerste ondersoek geanaliseer. Die verspreiding van digtheid was ook in kaarte uitgelê. Spesies was daarna volgens hulle potentiële dreiging teen die bewaring van oorblywende natuurlike dele van die plaas in ‘n rangorde geplaas. Resiltate dui aan dat Acacia mearnsii en Acacia saligna die belangrikste indringer plante op De Rust is en dat Hakea sericea as ‘n opkomende indringer beskou kan word. Die tweede ondersoek kyk na die verhouding tussen verskeie grondgebruik kategorië en die digtheid, lengte en ouderdom van die ses prominente indringer spesies wat in die eerste ondersoek identifiseër is. ‘n Log tipe ratios ontleding van bewaarde frekwensies het ‘n statisties belangrike uitkoms gehad (P<0.01; P-waardes tussen 1.35 x 10-3 en 2.7 x 10-224) vir die verhoudings tussen sekere grondgebruik tipes en sekere indringer spesies. Die gevolgtrekking was dat dit handig mag wees om grondgebruik kategorieë in simulasies van indringer plant verspreiding te gebruik.

MENVM / Department of Ecology and Resource Management