Alpine treeline ecotones in the western United States: A multi-scale comparative analysis of environmental factors influencing pattern-process relations.

摘要

Alpine Treeline Ecotones (ATE) are produced and maintained by a delicate balance of biotic and abiotic controls that function across a range of space-time scales. At regional to global scales climatic conditions are the primary controls acting upon alpine treeline. Conversely, at fine spatial scales ATE characteristics respond to localized topographic conditions that effectively mediate climatic gradients. The net result is a set of scale-dependent and geographically variable pattern-process relationships that ultimately affect morphological, ecological, and geographical characteristics of the ecotone. Previous ATE research has rarely examined the role that scale and space play in the complex relationships between environmental conditions and the ATE. The research presented in this dissertation furthers the understanding of ATE dynamics by examining how relationships between ATE features and abiotic controls vary across space and with scale through an analysis that includes multiple ATE study sites distributed throughout the US American West. Furthermore, this research develops innovative methods for measurement, characterization, statistical analysis, and modeling of the ATE using geo-spatial data sources including satellite imagery and digital elevation models.