Status: COMPLETE

Hosts:

• RS/GIS Laboratories (page)
• College of Natural Resources (page)
• Utah State University (page)

Collaborators:

• Joseph O. Sexton (page)
• R. Douglas Ramsey (page), thesis committee co-chair
• Terry L. Sharik (page), thesis comittee co-chair
• Dale L. Bartos (page), thesis committee member
• Fred Baker (page), thesis committee member
• Michelle Colvin, field technician

Clients:

• Bureau of Land Management Vernal Field Office (page)
• USDA Forest Service Rocky Mountain Research Station, Logan, UT.

Abstract:

Quaking aspen is the most widely distributed tree species in North America and an asset to sociological, ecological, and hydrological land values in the western United States. In recognition of these values, land managers seek means to oppose a regional decline of aspen in the Intermountain West—a decline apparently in progress since the close of the Pleistocene and driven by climate change, fire suppression, and increasing ungulate density. One location of special relevance to this decline is the Book Cliffs of Colorado and Utah, which is both a discrete boundary of quaking aspen’s geographic range as well as a potential biogeographic corridor between the sub-alpine communities of the Utah and Colorado Rocky Mountains.

To inform land management plans for the Book Cliffs and develop methods applicable on public lands across the region, a spatial database of aspen cover, potential, and threat was created for a 10,450-ha pilot section of the area. Raster GIS data layers of current aspen cover, current Douglas-fir cover, and monthly potential evapotranspiration (pET) were created from field measurements and satellite remotely sensed imagery. The Hutchinsonian niche concept was generalized with fuzzy-set and likelihood theories to accommodate measurements of continuous vegetation cover, and values of aspen’s fuzzy Hutchinsonian niche were regressed over a 10% sample of the aspen-pET cells using regression trees. Applying the niche model over the cell population created an aspen pET habitat map, and subtracting measured from expected covers created a map of potential aspen cover change.

Validation of aspen’s model pET niche showed that aspen cover is strongly constrained by unmanageable water relations, but aspen’s high spatial aggregation suggests that net-positive local feedbacks maintain aspen cover above expectation at many locations. Also, under-occupation of aspen habitat is strongly correlated with Douglas-fir cover, and by manipulating the latter two factors within the limits imposed by water balance, aspen physiology, and management logistics, the landscape may be coarsely managed to increase aspen cover.

These results will be used in the Book Cliffs as spatially explicit hypotheses for adaptive ecosystem management, and these methods are under consideration for application in similar ecoregions.

keywords: quaking aspen, GIS, potential evapotranspiration, adaptive ecosystem management, niche, fuzzy sets, regression trees, habitat, constraint, likelihood, spatial analysis

Publications:

Sexton, J.O.; R.D. Ramsey; D.L. Bartos. 2006. Habitone analysis of quaking aspen in the Utah Book Cliffs: effects of site water demand and conifer cover. Ecological Modelling 198 (3-4): 301-311 [PDF].

Sexton, J.O. 2003. Models for the distribution of quaking aspen in geographic and potential evapotranspiration spaces relevant to the Book Cliffs (Utah), 2000-2002. Master’s thesis, Dept. of Forest Resources, College of Natural Resources, Utah State University. Logan, UT. [thesis]

Sexton, J.; M. Jenkins; T.L. Sharik; W. Wagner. 2000. A remotely sensed aspen deterioration classification for the study and management of quaking aspen in the Intermountain West. abstract in Shepperd, W. D.; Binkley, D.; Bartos, D. L.; Stohlgren, T. J.; Eskew, L.. G., compilers. 2001. Sustaining Aspen in Western Landscapes, Symposium Proceedings; 13-15 June 2000; Grand Junction, CO. Proceedings RMRS-P-18. Fort Collins, CO: USDA Forest Service, Rocky Mountain Research Station. 460 pp.

Presentations:

Sexton, J.O., 2005. Habitone analysis of quaking aspen in the Book Cliffs (Utah, USA): effects of site water demand and conifer cover. 20th Annual Symposium of the United States Regional Chapter of the International Association for Landscape Ecology. Syracuse, NY, March 12-16, 2005. [abstract]. Also presented as an invited lecture at Restoring the West Conference 2006 - Aspen Restoration. September 12-13, Utah State University, Logan, UT.

Sexton, J.O. 2003. The distribution of quaking aspen in geographic and potential evapotranspiration spaces relevant to the Book Cliffs (Utah), 2000-2002. Master’s thesis seminar. College of Natural Resources, Utah State University. July 2, 2003.

Sexton, J.O., R.D. Ramsey, J. Lowry, T.L. Sharik. 2002. A multiple-scale GIS framework for monitoring quaking aspen in the Intermountain West. Pecora 15/Land Satellite Information IV/ International Society for Photogrammetry and Remote Sensing (ISPRS) Commission I Symposium, Integrating remote sensing at the global, regional, and local scale. Denver, CO (USA), November 10-15, 2002. [abstract]

Sexton, J.O. 2002. Heuristics for interpreting empirically modeled raster data: fuzzy vs. probabilistic uncertainty and potential vs. actual landcover (poster). Utah Geographic Information Council 2002 Conference. September 18-20, 2002. Bryce Canyon National Park, Utah.

Sexton, J.O. 2002. Quaking aspen biogeography: issues of fuzzy vs. probabilistic classification and multispectral vs. environmental raster data (poster). The Ecological Society of America/ Society for Ecological Restoration 2002 Joint Annual Conference. August 7, 2002. Tucson, AZ.

Sexton, J.O.; M. Jenkins; T.L. Sharik; W. Wagner. 2000. A remotely sensed aspen deterioration classification for the study and management of quaking aspen in the Intermountain West (poster). Sustaining Aspen in Western Landscapes Symposium, Grand Junction, CO, June 13-15, 2000.

Sexton, J.O. 2000. A remotely-sensed cover classification to ‘scale up’ aspen monitoring and management. Utah State University Department of Forest Resources seminar, April 19, 2000. Logan, UT.