Guide to Quaking Aspen Ecology and Management with Emphasis on Bureau of Land Management Lands in the Western United States Paul C. Rogers, Western Aspen Alliance, Wildland Resources Department, and Ecology Center, Utah State University, Logan, Utah Guide to Quaking Aspen Ecology and Management with Emphasis on Bureau of Land Management Lands in the Western United States 2017 BLM-UT-G1017-001-8000. 98 p. Paul C. Rogers Western Aspen Alliance, Wildland Resources Department, and Ecology Center, Utah State University Produced in cooperation with U.S.Department of the Interior Bureau of Land Management Cooperative Agreement Number: L10AC20552 Guide to Quaking Aspen Ecology and Management Contents Chapter 1 – Introduction ...............................................................................................................................................1 How We Got Here ......................................................................................................................................................1 Why Is Aspen Important? ........................................................................................................................................3 Chapter 2 - Aspen: An Evolving Picture .....................................................................................................................7 Issues Affecting Aspen Ecosystems........................................................................................................................7 Science-Management Synergy ..............................................................................................................................12 Chapter 3 - Landscape Interactions And Other Considerations .........................................................................19 Disturbances .............................................................................................................................................................19 Past Management ....................................................................................................................................................21 Ungulate Herbivory.................................................................................................................................................22 Chapter 4 - Aspen Types By Ecological Function ...................................................................................................27 Overview of Functional Types ..............................................................................................................................27 Seral and Stable Functional Types ........................................................................................................................29 Seral Aspen ...............................................................................................................................................................32 Boreal .................................................................................................................................................................32 Montane ............................................................................................................................................................36 Stable Aspen..............................................................................................................................................................40 Parklands ..........................................................................................................................................................40 Colorado Plateau Highlands And Mesas ....................................................................................................43 Elevation/Aspect Limited ..............................................................................................................................47 Riparian ............................................................................................................................................................54 Chapter 5 - Developing An Action Plan ...................................................................................................................57 Setting Objectives ....................................................................................................................................................57 Monitoring: Assess Before Action ........................................................................................................................58 Chapter 6 - Aspen ‘Monitor And Manage’ Toolbox ...............................................................................................65 Selecting from Restoration Actions .....................................................................................................................65 Adapting Management to Monitoring Results ..................................................................................................75 Where to Find More Aspen Information ............................................................................................................77 References .......................................................................................................................................................................81 Appendix 1: Key Terms ...............................................................................................................................................86 Appendix 2: Aspen Stand Condition Rating System .............................................................................................91 Appendix 4: Sample Monitoring Form ....................................................................................................................96 Guide to Quaking Aspen Ecology and Management Page left intentionally blank. Chapter 1 – Introduction How We Got Here Quaking aspen (Populus tremuloides Michx.) have a rich history of both research and management. Particularly in the American West, aspen trees stand out as vibrant icons in forest communities dominated by evergreen-shaded mountainsides (Fig. 1.1). This individuality in the species piqued the interest of early forest scientists working in the region, and the fervor has not abated. Early on, though aspen were not as highly valued as they are today, foresters marveled at the expanses of this species on desert plateaus and its ability to grow profusely following fire. Foresters of the early 20th century, however, felt that the C h aspen species inhibited development of more valued timber species. a p In much of the West, this was also a time of new aspen growth and t e r expansion in response to settlement-era cutting, grazing, and burning 1 – I n t r o d u c t i o n Figure 1.1 Aspen leaf. Guide to Quaking Aspen Ecology and Management 1 (Rogers et al. 2007a; 2011). Later, aspen’s value to humans increased, particularly as rich understory livestock forage. Managers and researchers alike became interested in methods of promoting aspen growth and sustainability. Currently, professionals and the public are attracted to the benefits of aspen for biodiversity, fire resistance, recreation, aesthetics, wood products, forage, water conservation, and wildlife habitat. Realization of aspen’s usefulness has paralleled a number of threats to these forest communities. Indeed, some threats may be attributable to past management actions, such as fire suppression, overgrazing, water diversion, wildlife management, and inappropriate timber harvesting methods. In Utah, for example, an estimated 60% of aspen cover was lost during the 20th century due to past practices (Bartos n o and Campbell 1998). However, such projections warrant caution, as i ct they assume that each location with significant signs of live or dead u d aspen today was once an “aspen forest” where this species comprised o r the dominant cover. Nonetheless, the 20th century did witness both t n increases (Kulakowski et al. 2004) and decreases in aspen cover (Di I – Orio et al. 2005), some attributed to humans and some to the relatively 1 r moist climate (Rogers et al. 2011). More recently, reports of “sudden e pt aspen decline” indicate rapid die-off of both overstory and root systems a h in some parts of the West (Worrall et al. 2008). Subsequent work has C linked regional mortality in aspen and recent climate trends (Worrall et al. 2013). These and other works suggest future climates will acutely affect aspen on southern aspects and at low elevations, conditions commonly found on BLM lands across the West. Land managers, then, face the dilemma of applying the collective knowledge of a large body of aspen science to specific areas of interest, areas that they cannot treat as uniform representations of a single species behaving predictably across its wide range. In this field guide, I use a “systems approach” to aspen ecology and management. We have learned much, though perhaps not adequately communicated, about varying aspen types around our region (Rogers et al. 2014). For example, what new information is available about fire behavior in aspen, and how might we best apply that knowledge best Guide to Quaking Aspen Ecology and Management 2 be applied to forest management practices? Or why do aspen forests vary in their contribution to wildlife management and landscape biodiversity? Are we as land managers making informed decisions about stewardship with processes in mind or working against ecosystem function, which controls such processes? Our driving paradigm in contemporary land management is to first understand, then emulate (to the degree possible), ecosystem function. In terms of western aspen, this means using the best available science and pairing it with local experience. Where there are knowledge gaps, often field monitoring and experimentation are required to move forward. These ideas are not necessarily new, though their application in widely varying quaking aspen communities provides novel opportunities for effective management. One key tactic is agency investment in “learning by doing,” which will be required to adapt to the dynamic institutional C and ecological conditions expected. h a p t Why Is Aspen Important? e r 1 Biodiversity—Among western forests, quaking aspen communities are – I often the most biodiverse (Kuhn et al. 2011; Chong et al. 2001). Due to n t r the presence of relatively moist conditions and abundant flora, a wide o d range of wildlife species—both transitory and resident—is drawn to u c aspen forests (Manley et al. 2000). Thus, it is important to understand t i o that we seek to sustain the range of aspen systems, not just the tree. n As wildlife habitat, aspen types are often among the most critical concerns for state and federal agencies charged with managing viable populations in diverse landscapes (Fig. 1.2). Water Conservation—Relatively high understory biomass, deep snowpack, and rich soils allow aspen systems to retain higherlevels of water in the spring and early summer (Gifford et al. 1983; LaMalfa and Ryle [sic] 2008). While further work is needed on Figure 1.2 Biodiversity in aspen. Guide to Quaking Aspen Ecology and Management 3 this topic, these preliminary investigations suggest that retention of aspen dominance in seral conditions allows deeper infiltration rates, thereby prolonging water availability later into the season. We expect similar water benefits in stable aspen systems where conversion to sage or other dry nonforest types is a possibility. More water in streams benefits fish as well as downstream human uses. Aesthetics—People often underestimate the benefit of landscape beauty to our well-being. Aspen landscapes are iconic in western North America, especially as their brightly colored autumn leaves appear. Regardless of activity, white trunks crowned with fluttering green or gold leaves often lie at the center of our outdoor experience. In addition to potential spiritual, healing, or calming values found among the quaking aspen, nature lovers gravitate to this tree for its n o photogenic qualities. i t c u Recreation—Skiing, hunting, biking, hiking, motor touring, camping, d o fishing, photography, and sightseeing are commonly centered on aspen r nt scenes. Many western resorts that focus on recreational activities use I – aspen backdrops in their advertising. Large aspen die-offs, though 1 perhaps endemic to forest ecosystems, are generally unappealing to r te recreational visitors. p a h Forage—Historically, livestock growers have depended on the diversity, C biomass, and nutrition of understory aspen communities to feed their animals. Often found at high elevations, aspen forests provide cooler and moister conditions for livestock during parched summer months. Use of forage in these locations, provides direct economic benefit to western ranchers, as well as indirect benefits to the municipalities where they reside. Fire Protection—Forests dominated by aspen are less prone to high- intensity burning compared to surrounding conifer types (Shinneman et al. 2013). In wildland urban interface (WUI) situations, aspen may be used as a firebreak around developed areas (Fechner and Barrows 1976). Thus, management that favors aspen (i.e., thinning conifers, light underburning) may be used as a prudent means of protecting homesites. Guide to Quaking Aspen Ecology and Management 4