Date of Award


Degree Name

Doctor of Philosophy


Biological Sciences


Craig E. Tweedie


Land cover change is a significant contributor to environmental change on a global scale. In the arid regions of the southwest US, shrub encroachment is one of the most important forms of land cover change. Many factors contribute to shrub encroachment, which can impact structure and function. In the Chihuahuan Desert, mountain ecosystems are known as biodiversity hotspots and are especially susceptible to environmental change making them useful indicators of global change. The overarching goal of this dissertation is to improve i) understanding of land cover change in a Chihuahuan Desert mountain landscape, and ii) how knowledge of land cover change could be taught to undergraduate students.

Chapter 1 discusses the importance of land cover change (Section 1.1.1) and shrub encroachment (Section 1.1.2), drivers of change (Section 1.1.3), and what affects shrub encroachment has on ecosystem structure and function (Section 1.1.4). Technological advances that aid the detection of land cover change through time (Section 1.1.5), research challenges in land cover change research on shrubification in the US southwest (Section 1.1.6), and the importance of teaching future scientists to live a more sustainable lifestyle, especially in desert ecosystems susceptible to shrub encroachment and desertification. Key research questions and objectives (Section 1.2.1) are outlined, an overview of the methodologies employed (Section 1.2.2), and a review of the biophysical environment of the IMRS are also given (Section 1.3).

Chapter 2 focuses on the development of a land cover classification for IMRS. Following field-based vegetation sampling, the land cover classification for IMRS was generated using a high spatial resolution satellite image (IKONOS) and supervised classification techniques. This resulted in a land cover map that had good overall, and user and producer accuracies. The land cover map, in combination with other geospatial data extracted using a Geographic Information System (GIS), was used to produce a baseline and conceptual state-and transition model for IMRS land cover using correlation and regression tree analysis. The model shows that the vegetation is distributed along an elevational gradient, and that other factors such as slope, and soil and geology type are also influential.

Chapter 3 focuses on the assessment of land cover change, namely changes in shrub cover, at the IMRS spanning 68 years. The land cover map produced in Chapter 2 was used to select five key sites for change assessment. An automated method for detecting shrub cover was created for GIS, and used to assess changes in shrub cover using aerial photographs spanning 1943 to 2011. The incorporation of kite aerial photography was useful for determining optimal sampling resolution and quantifying uncertainty in the change analysis techniques employed. Results of this analysis show an overall increase in the total number of shrub clumps, but a decline in total and percent cover of all shrubs in the transect, suggesting either fragmentation of shrub clumps or a shift in species composition has occurred over time.

Chapter 4 focuses on the development and evaluation of an undergraduate module-based curriculum that was aimed at developing a holistic understanding of environmental problems and the use of technology in ecological studies related to land cover change and desertification, environmental monitoring, and mitigation in desert ecosystems. To evaluate the effectiveness of the modules, changes in student knowledge and attitude toward ecology and technology, and their sense of efficacy regarding those topics was measured using a series of pre- and post-tests and statistical analyses. Significant increases were observed in almost all categories of evaluation, with marked increases and large effect sizes in knowledge acquisition, and technological and environmental efficacy. It is inferred that the modules effectively enhanced student content knowledge and changed their attitudes towards environmental science and technology.

Chapter 5, the general discussion, reviews the objectives and key questions outlined for the dissertation and discusses these based on the studies outlined above and findings in recent literature. This chapter also addresses priorities for future research based on these discussions.




Received from ProQuest

File Size

237 pages

File Format


Rights Holder

Rebecca Anne Escamilla