Date of Award:

5-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Eugene W. Schupp

Committee

Eugene W. Schupp

Committee

Barry B. Baker

Committee

Kari E. Veblen

Abstract

Changes in land-use and climate can trigger changes in ecosystem conditions and may be driving ecosystems toward undesired “states” that provide inadequate ecosystem services. If these changes are drastic enough, energy intensive restoration programs are necessary to restore ecosystems to previous states. Landscape classification systems based on “ecological potential” offer a robust framework to evaluate and manage ecosystems. The ecological site concept is one such landscape classification system that has been developed by the USDA Natural Resources Conservation Service (NRCS) and describes ecosystems and ecosystem dynamics relative to “reference conditions” and response to disturbance. Ecological sites have gained popularity with land managers throughout the western U.S., and have been extensively described for DOI Bureau of Land Management agricultural lands and rangelands; however, they have yet to be described on USDA Forest Service (USFS) lands. In this thesis, I describe a statistical approach for developing ecological sites and state-and-transition models. In Chapter 2, I used a large dataset and multivariate statistics to classify plots based on life zone, soils, and potential vegetation, effectively describing statistical ecological site-like groups. Most of the statistical ecological sites matched ecological sites already described by the NRCS. Additionally, I described one new ecological site that has not been described by the NRCS in the Colorado Plateau region. In Chapter 3, I examined evidence for alternative states in mountain ponderosa pine (Pinus ponderosa Lawson & C. Lawson) and upland piñon-juniper ecosystems. Using multivariate statistics, I found that plots cluster into groups consistent with generalized alternative states described in a priori conceptual state-and-transition models. Additionally, I showed that ponderosa pine clusters were true alternative states and piñon-juniper clusters were not true alternative states because they were confounded by similarities in climate. These results illustrate the range of ecosystem variability that is present throughout the study area and present evidence for alternatives states caused by historical land-use. This project is the first to propose ecological sites and state-and-transition models on USFS lands in the region of our study area. These techniques could be applied to areas that do not have formally described ecological sites and state-and-transition models and could help identify ecological sites that may have been overlooked using other means of delineation. Additionally, these methods can be used to evaluate the range of ecological variability throughout an area of interest and to improved understanding of ecosystem dynamics.

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