Email:
wshepperd@fs.fed.us

Email: jguyon@fs.fed.us

Wayne D. Shepperd is a Research Silviculturist at the U.S. Forest Service Rocky Mountain Research Station in Fort Collins, Colorado. He holds a BS in Outdoor Recreation, and MS and Ph.D. degrees in Silviculture from Colorado State University. A Colorado native, Dr. Shepperd has been with the Forest Service since 1969 and will retire in January. He has conducted research on aspen since the 1970’s and has outlasted most (but not all) of his contemporaries to become a recognized “aspen geezer."

John Guyon is a Plant Pathologist at the U.S. Forest Service Forest Health Protection Field Office in Ogden Utah. He holds a BS in Botany from the University of Illinois, and a master's in Forest Pathology from Colorado State University. A migratory native of the midwest, John has been with the Forest Service since 1989, starting out with Rocky Mountain Research Station, and has been stationed in Ogden for the last 15 years. He conducted research on aspen diseases and environmental stress back in graduate school and recently set up a system of 75 monitoring plots in Utah, Nevada and western Wyoming to examine the insects and diseases present in aspen stands.

Abstract:
Massive aspen die-off in the western U.S.: What is going on?

Wayne D. Shepperd, USDA-FS Rocky Mountain Research Station, Fort Collins, CO, and John Guyon, USDA-FS State and Private Forestry, Ogden, UT

Aspen die-off differs from normal aspen vegetative succession or decline in that mature trees die quickly within a year or two and no new sprouting occurs as a result. Lack of sprouting may indicate that lateral roots are also dead, preventing aspen from re-occupying the site. Die-off seems to begin in epicenters and spread radially through an affected aspen stand. Stands on all topographic positions, moisture regimes, and soil types are affected, and the phenomenon has been reported throughout the west from Arizona into Alberta. Die-off can affect one clone and leave other nearby clones untouched. Younger age classes and advanced regeneration are often not affected to the same extent as mature overstory trees in the same clone. Cytospora cankers, poplar borers, and other damage or stress agents are often associated with die-off epicenters.

Our presentation will discuss factors that may be associated with aspen die-off and present potential hypotheses to be investigated in multidisciplinary research to identify causal agents or environmental factors contributing to aspen die-off and determine whether possible management options exist to reduce the risk of die-off, or loss of parent roots.