Desertification of high latitude ecosystems: conceptual models, time-series analyses and experiments

Desertification of High Latitude Ecosystems: Conceptual Models, Time-Series Analyses and Experiments. (December 2008) Johann Thorsson, B.S., University of Iceland Chair of Advisory Committee: Dr. Steven R. Archer Ecosystem degradation in Iceland has been severe since man arrived 1100 years ago. Birch woodlands cover has declined from 25% of the land area, to only 1%. The deforestation is considered to be the initial stage in the land degradation process, followed by surface destabilization, and later erosion. The objective of this study was to quantify and evaluate factors that contribute to the early stages of land degradation in Icelandic ecosystems. Specific objectives were to improve our understanding of how livestock grazing might initiate early degradation stages, elucidate field-based landscape metrics useful for characterizing degradation stages, and to determine if landscape metrics obtained from remote sensing data can be used to detect landscape structure changes and identify degraded and at risk rangelands in real time over extensive and remote areas. A State-and-Transition conceptual model was constructed for the experimental area to identify potential key processes in the degradation sequence, and to formalize research questions. Experimental plots were established in five plant community types representing a space-for-time degradation sequence. Birch seedling (Betula pubescens Ehrh.) growth and survival was reduced with repeated clipping treatment applied to simulate browsing, but the amount of decline