Landscape dynamics of aspen and conifer forests

Abstract—Quaking aspen (Populus tremuloides Michx.) is widely dispersed across the landscape of North America. Seventy-five percent of the aspen in the western United States occurs in the states of Colorado (50%) and Utah (25%). Reproduction in aspen is primarily by asexual means, e.g., root sprouts that are generally referred to as suckers. An aspen clone consists of numerous stems that are genetically alike that began from a single seed that germinated sometime in the past. Generally, these clones have been perpetuated on site by disturbance that allowed the clones to survive and expand in the area. The importance of aspen in the Interior West is well described and documented in the literature. Besides adding diversity to the landscape, aspen also provides water, forage, wood products, and so on for use by the public. Since European settlement, the natural disturbance regime (usually fire) has been interrupted. This has caused much of the aspen-dominated lands to succeed to conifers. The decline in aspen ranges from 49 % in Colorado to 95 % in Arizona. Numerous techniques are available to aid the manager in restoring aspen to a level approaching its historical occurrence. I have studied quaking aspen (Populus tremuloides Michx.) for the past 28 yearsfor Forest Service Research. Early in my career I studied the vegetative responses of aspen systems to various types of disturbances (burning, cutting, spraying, and so on). More recently, I have been involved primarily in technol-ogy transfer of knowledge about the functioning and restoration of aspen in the Intermountain West. During this time, there has been a marked increase in public awareness and concern regarding aspen lands, resulting in an urgency, in some areas, for restoring aspen on the landscape