Habitone analysis of quaking aspen in the Utah Book Cliffs: Effects of site water demand and conifer cover

Abstract Quaking aspen (Populus tremuloides Michx.) is the most widely distributed tree species in North America, but its presence is declining across much of the Western United States. Aspen decline is complex, but results largely from two factors widely divergent in temporal scale: (1) Holocene climatic drying of the region has led to water limitation of aspen seedling recruitment, and (2) anthropogenic fire suppression during the 20th century has allowed shading of aspen clones by fire-intolerant conifers. These processes interact variously and often diffusely, but traditional, binary habitat mapping approaches can only resolve their net effect after complete loss of aspen patches. To provide information for preemptive land management in the Book Cliffs – a biogeographic link between the Utah and Colorado Rocky Mountains and a location experiencing aspen decline typical of the region – we developed a regression-based generalization of niche/habitat analyses that is usable in GIS, is capable of detecting anomalies in cover before complete patch conversion, and can be incorporated smoothly into the decision-making process. We estimated the realized Hutchinsonian niche of quaking aspen to potential evapotranspiration (PET) by nonparametric, likelihood-based regression techniques, projected (continuous) values of aspen's niche expectation and uncertainty geographically, and correlated differences between observed and expected aspen cover to remotely sensed conifer cover. Results confirm the strong constraint of site water demand on aspen cover and suggest that conifer cover decreases aspen cover beneath its expectation given the PET environment. Compared to sites without quaking aspen, our aspen sites have lower PET in every month of the growing season, but the difference increases over the growing season as drought effects become more extreme. Superimposed on this broader environmental constraint, conifer cover displaces aspen cover and shows a positive correlation with model deviance (r = 0.344). Ultimately, the thematic information conserved by our approach allowed us to resolve detailed rasters of management potential and map a modest potential increase of aspen cover – 14.63 ha (0.14%) of the study area, or +2.46% of current aspen cover – within one management cycle.

[1]  C. Kay.  Evaluation of Burned Aspen Communities in Jackson Hole, Wyoming , 2001 .

[2]  William Silvert,et al.  Fuzzy indices of environmental conditions , 2000 .

[3]  C. Daly,et al.  A Statistical-Topographic Model for Mapping Climatological Precipitation over Mountainous Terrain , 1994 .

[4]  P. McCullagh,et al.  Generalized Linear Models , 1992 .

[5]  G. E. Hutchinson,et al.  A Treatise on Limnology Vol. II: Introduction to Lake Biology and the Limnoplankton , 1967 .

[6]  E. L. Little.  Conifers and important hardwoods , 1971 .

[7]  R. Tibshirani,et al.  Generalized additive models for medical research , 1986, Statistical methods in medical research.

[8]  Trevor Hastie,et al.  Generalized linear and generalized additive models in studies of species distributions: setting the scene , 2002 .

[9]  C. Kay.  Is Aspen Doomed? , 1997, Journal of Forestry.

[10]  J. Cayford,et al.  Growth and utilization of Poplars in Canada , 1968 .

[11]  F. S. Baker.  A Revised Tolerance Table , 1949 .

[12]  D. Binkley,et al.  Sustaining aspen in western landscapes: Symposium proceedings; 13-15 June 2000; Grand Junction, CO , 2001 .

[13]  W. Humphries,et al.  A preliminary quantification of the impacts of aspen to conifer succession on water yield. II. Modeling results , 1984 .

[14]  John R. Jones.  Aspen site index in the Rocky Mountains , 1967 .

[15]  T. Brown,et al.  Esthetics and landscaping , 1985 .

[16]  Leo Breiman,et al.  Classification and Regression Trees , 1984 .

[17]  David W. Roberts,et al.  Ordination on the basis of fuzzy set theory , 1986, Vegetatio.

[18]  Fangju Wang,et al.  Fuzzy supervised classification of remote sensing images , 1990 .

[19]  D. Deering.  Measuring forage production of grazing units from Landsat MSS data , 1975 .

[20]  W. P. Cottam.  Prevernal Leafing of Aspen in Utah Mountains , 1954, Journal of the Arnold Arboretum..

[21]  Robert H. Whittaker,et al.  Vegetation of the Great Smoky Mountains , 1956 .

[22]  E. L. Little.  Atlas of United States trees. , 1971 .

[23]  Trevor Hastie,et al.  Statistical Models in S , 1991 .

[24]  Nicholas L. Crookston,et al.  Percent canopy cover and stand structure statistics from the Forest Vegetation Simulator , 1999 .

[25]  John R. Jensen,et al.  Introductory Digital Image Processing: A Remote Sensing Perspective , 1986 .

[26]  E. P. Meinecke.  Quaking Aspen: A Study in Applied Forest Pathology , 1929 .

[27]  J. Rolf.  Aspen Fencing in Northern Arizona: A 15-Year Perspective , 2001 .

[28]  Gretchen G. Moisen,et al.  Comparing five modelling techniques for predicting forest characteristics , 2002 .

[29]  M. Austin.  Spatial prediction of species distribution: an interface between ecological theory and statistical modelling , 2002 .

[30]  J. Sexton.  Models for the distribution of quaking aspen in geographic and potential evapotranspiration spaces relevant to the Book Cliffs (Utah), 2000-2002 , 2003 .

[31]  C. White,et al.  Long-Term Ecosystem States and Processes in Banff National Park and the Central Canadian Rockies , 1999 .

[32]  B. V. Barnes.  The clonal growth habit of American Aspens. , 1966 .

[33]  Robert G. Bailey,et al.  Ecoregions: The Ecosystem Geography of the Oceans and Continents , 1998 .

[34]  N. Debyle,et al.  Aspen : Ecology and Management in the Western United States , 1985 .

[35]  Sašo Džeroski,et al.  Using regression trees to identify the habitat preference of the sea cucumber (Holothuria leucospilota) on Rarotonga, Cook Islands , 2003 .

[36]  Antoine Guisan,et al.  Predictive habitat distribution models in ecology , 2000 .

[37]  J. S. Maini.  Silvics and ecology of Populus in Canada , 1968 .

[38]  C. Kay.  Aspen seedlings in recently burned areas of Grand Teton and Yellowstone National Parks , 1993 .

[39]  B. V. Barnes,et al.  Clone size in American aspens , 1976 .

[40]  J. Hart,et al.  Interaction Among Cervids, Fungi, and Aspen in Northwest Wyoming , 2001 .

[41]  H. R. Haise,et al.  Estimating evapotranspiration from solar radiation , 1963 .

[42]  Lotfi A. Zadeh,et al.  Fuzzy Sets , 1996, Inf. Control..

[43]  N. Stephenson.  Climatic Control of Vegetation Distribution: The Role of the Water Balance , 1990, The American Naturalist.

[44]  C. Kay.  Long-term aspen exclosures in the Yellowstone ecosystem , 2001 .