Ecological Forestry Integrating Disturbance Ecology Patterns Into Forest Treatments

Home , Forest management, Regeneration (ecology)

forestry

Ecological Forestry Integrating disturbance ecology patterns into forest treatments

By R. Gregory Corace III, Ph.D., and P. Charles Goebel, Ph.D.

orty years ago the Kirtland’s warbler (Dend- can be agents of disturbance simply by mechanically roica kirtlandii)—a neotropical migrant that altering forest structure or attempting to influence the F breeds in young jack pine (Pinus banksiana) severity or magnitude of natural disturbances. forests—was on the brink of extinction. Concerted recovery efforts by federal and state land manag- Fortunately, natural and human-caused disturbance ers in the northern Lower Peninsula of Michigan regimes can be integrated into forest wildlife habitat brought the species back from the brink (Probst et management, thereby addressing the issues of land

Credit: Laurie Tansy al. 2003). However, this success has come at a cost: stewardship (Leopold 1949). Once known as “New

R. Gregory Corace Recovery efforts aimed at producing breeding habi- Forestry” (Franklin 1989), this ecological approach III, Ph.D., is Forester tat have resulted in relatively simplified landscapes to forest management bases actions on the underly- and Ecologist at and forest stands, to the detriment of some ecosys- ing disturbance regime of a given ecosystem, recovery the Seney National Wildlife Refuge tem functions and wildlife species. periods between disturbance events, and resulting and Kirtland’s vegetation patterns, which are of special interest to Warbler Wildlife Unfortunately, this pattern of ecosystem sim- managers of forest wildlife habitat. Ecological forestry Management Area. plification has too often been repeated by forest does not attempt to maximize the productivity of any managers. In the zeal to accomplish highly focused single commodity, amenity, or species. Instead, it population-based or commodity-based objectives, allows for multiple goals—improved wildlife habitat, forest management has at times ignored underly- carbon sequestration, soil stabilization, water filtration, ing ecological principles and disturbance patterns and economic gain—thus enabling forest conserva- (Holling and Meffe 1996). tion and restoration across various ecosystem and ownership types (Sarr et al. 2004). The key is linking Following Nature’s Lead site conditions and natural disturbance regimes with A contrasting approach to wildlife habitat manage- silvicultural treatments that emulate the outcomes Credit: Ken Chamberlain ment is predicated on understanding ecology—the of natural disturbances (Seymour and Hunter 1999, P. Charles Goebel, Ph.D., is an Associate capabilities of land as determined by landscape posi- Franklin et al. 2007). Fortunately, many texts (e.g., Professor of tion, soils, and changes in vegetation due to natural Frehlich 2002) outline the natural disturbance ecology Forest Ecosystem disturbances—and then managing wildlife habitat patterns of various forest ecosystems, providing useful Restoration and Ecology in the School within this context. A “disturbance” is an agent of background for forest managers. of Environment and change that shapes an ecosystem over time in a Natural Resources dynamic manner, such as wild- In pine-dominated landscapes of northern at The Ohio State University. fires, wind events, floods, insects, Michigan and elsewhere in the Upper Mid- and disease. Land managers, too, west, fire suppression or fire intervals that poorly emulate the historical range of variation have degraded the ecological integrity of many forests (Schulte et al. 2007). These changes have led to declines in the distribu- tion and abundance of many fire-dependent pine-dominated ecosystems, from the Credit: Mike McDowell openland-dominated jack pine barrens to

An aerial view of the structural patterns of jack pine stands in the Kirtland’s Warbler WMA reveal markedly different management strategies. The foreground shows a plantation managed intensively for Kirtland’s warblers, with diamond-shaped openings created by the “opposing wave” pattern of planting jack pine seedlings after a clearcut. The area at center shows patterns resulting from a prescribed fire. Warblers (inset) breed in both of these managed areas, but the patterns in the burned stand emulate those of wildfires more closely. Credit: R. Gregory Corace III

38 The Wildlife Professional, Spring 2010 © The Wildlife Society cial Fo pe re Educa S s l tio t ia c n S e S e p e

S c

i t

o i

n n the closed canopy, late successional mixed-pine stands not emulating patterns of natural disturbance, man- dominated by long-lived red pine (Pinus resinosa) and agement has produced monotypic plantations with eastern white pine (Pinus strobus). drastically simplified structure compared to stands generated by wildfire. Indeed, the typical biological Although drastically different in terms of structure and legacies of fire-produced stands—such as residual composition, these forest ecosystems share similar live trees, dead standing trees or snags, and downed sandy soils, a reliance on fire, successional states, and coarse woody debris—are nonexistent or significantly many species of wildlife. However, differences in the reduced (Spaulding and Rothstein 2009). Such severity and the return interval of disturbances (the homogenized conditions do not bode well for many latter often a result of management objectives) can ecological processes (LeDuc and Rothstein 2007). yield contrasting forest conditions. More frequent and/ or more significant disturbances (e.g., stand replacing Fortunately, because Kirtland’s warbler population re- fires or clearcuts) yield different vegetation patterns covery objectives have been met for the past nine years, and habitats for different wildlife species compared to a more ecological approach to infrequent surface fires or partial harvests. the species’ habitat management may now be possible. We Cautionary Tale of Warblers suggest that the focus of future The challenge of managing forests altered by changes management should be to in the natural disturbance regime is particularly emulate patterns of wildfire. In acute in Michigan, where the endangered Kirtland’s doing so, the judicious applica- warbler breeds. This species evolved to breed within tion of prescribed fire should be a habitat influenced by wildfire. Fire opens jack pine used, especially in landscapes cones for seed dispersal and prepares the soil surface with large contiguous blocks of for the seeds to germinate. Years of fire suppression public land (Wilson et al. 2009). and other changes in land use have led to a loss in ap- It is also important to note that propriate habitat and a dramatic population decline plantations do not necessar- of Kirtland’s warblers: In 1971, only 201 singing males ily restore habitat, but instead were counted in Michigan (Probst et al. 2005). provide a surrogate condition for breeding birds. Plantations Although prescribed or managed wildfire would yield are therefore not a ‘silver-bullet’ the most “natural” breeding habitat for the birds, for the management of jack pine changes in land use make broad-scale application of forest ecosystem types. fire untenable in Michigan’s northern Lower Peninsu- la, where most of the birds breed. Consequently, most That said, plantation manage- warbler habitat management involves clear-cutting ment for Kirtland’s warbler Credit: R. Gregory Corace III mature jack pine, then trenching and densely planting habitat will still be necessary, With its bark these sites with jack pine seedlings in an “opposing and in this vein we suggest that future habitat man- mechanically stripped wave” pattern (see photo). Akin to the way natural agement take the following approaches: off in a process called wildfire would move across the landscape and produce • Consider the dynamic nature of jack pine forests girdling, this pine will large patches of burned-over land, these plantations and manage for the range of successional states and die and create a snag—a potential future home for are managed as multiple-square-mile patches with a associated structure of jack pine ecosystems. Of woodpeckers and other rotation age that approximates natural return intervals these, perhaps the most imperiled is the openland- wildlife in the Kirtland’s for stand-replacing fire events (Frehlich 2002). This dominated jack pine barrens (Houseman and Warbler WMA. Such type of jack pine plantation management has resulted Anderson 2002). techniques help vary the structure in monotypic in an unprecedented nine-year run in which the global • Set aside large-scale (hundreds of acres) openings jack pine plantations, population of singing male warblers exceeds the for the rotation age (estimated time of harvest) of mimicking historic established recovery objectives of 1,000 singing males. the nearby plantations, with both managed as a disturbance patterns In 2009, nearly 1,800 singing male warblers were shifting mosaic of barrens and plantations across and enhancing species diversity. counted in Michigan alone. Breeding birds are also the landscape. Doing so would help restore pre- now found in neighboring Wisconsin and Ontario (see Euro-American landscape structure that has been photo on page 38). degraded by changes in land use. Such management would also benefit many openland wildlife species, Research has shown a downside to this single-species such as upland sandpiper (Bartramia longicauda) approach, however. By placing such an emphasis on and sharp-tailed grouse (Tympanuchus phasianel- habitat variables important for Kirtland’s warblers and lus) (Corace et al. in press, a).

o n

• Enhance biological legacies in plantations. Patches With these findings as a framework for restoration, of live trees, especially larger-diameter red pine managers have moved forward with silvicultural that would likely survive many wildfires, should treatments to help restore mixed-pine forests to more be retained, and more patches of snags and coarse natural development trajectories. Because altered fire woody debris, the biological legacies of wild- regimes have modified the successional progression fire, should be created (Corace et al. in press, b). of these forests and increased fuel loads (including Girdling trees using the mechanized logging equip- dominance of jack pine), low-severity prescribed fire ment commonly employed in warbler management treatments are nearly impossible. Managers therefore is one cost-effective option. oversee commercial timber harvests in most stands to clear the way for effective fire management. Restoring Mixed-Pine Forests On the opposite side of the dynamic pine ecosys- Furthermore, unlike in jack pine forests, the historic tem are the late successional, mixed-pine forests fire regimes of mixed-pine forests were not typically dominated by long-lived red and eastern white pine. stand-replacing events, so the type and amount of re- Although turn-of-the-century sidual structure important for biodiversity and wildlife events degraded many (such as snags and coarse woody debris) must be man- sites that were formerly aged differently. Instead of using clearcuts to produce mixed-pine, numerous op- conditions of stand-replacing wildfire, partial harvests portunities exist to restore can promote natural regeneration of red and eastern this forest ecosystem type, white pine and increase the radial growth of residual even without a clear flagship trees. During these harvests, management actions are wildlife species. Fortunately, also creating larger snags to mimic patterns in bench- where most restoration mark stands. Such actions should bode well for many potential exists (especially wildlife species, including crossbills (Loxia spp.) and in Michigan’s Upper Pen- black-backed woodpeckers (Picoides arcticus). insula) the landscape has

Credit: R. Gregory Corace III many features making it Prescribed fire or wildfire may be the best tools for A history of extensive conducive to a more holistic restoring the structure and function of fire-dependent logging led to approach to forest management. Large swaths of ecosystems, but efforts need to be made to better monotypic jack pine public land make the use of prescribed fire easier, and educate the public to this fact, citing research that groves like this one in Michigan’s Seney because the plant community is relatively represen- provides guidance. To this end, we are trying to reach National Wildlife tative of the past, natural seed sources are readily both professionals and the public by working to estab- Refuge, where a rotting available. Consequently, restoration of mixed-pine lish a Fire Consortium for the Upper Midwest, funded stump of white pine forests need not be driven by the need of any one spe- by the federal government’s Joint Fire Science Pro- hints at the potential for restoration. When cies, but by broad-based ecosystem goals predicated gram. The Consortium hopes to work with groups and managed for a mix of on disturbance regimes. individuals responsible for managing and restoring white, red, and jack fire-dependent forest ecosystems including policy- pines, area forests In any restoration attempt, baseline information on makers, federal and state agencies, forest managers, can sustain greater diversity of mammals disturbance patterns and forest composition and and interested citizens and NGOs. and bird communities. structure provide useful benchmarks. For mixed-pine restoration in the Upper Peninsula, this information To provide wildlife habitat, maintain biodiversity, and exists in the virgin red and white pine stands of the meet multiple ownership objectives, contemporary for- 25,150-acre Seney Wilderness Area of Seney National est management should incorporate ecological principles Wildlife Refuge. Research from these areas shows that that are based on landscape position, soils, natural dis- large (12,000 to 25,000 acres), low-severity surface fires turbance regimes, and resulting patterns in composition This article with a return interval of 50 to 60 years characterized the and structure. Doing so will create forest ecosystems that reflects the pre-Euro-American landscape, and that past manage- are more resilient to natural and anthropogenic stressors views of the ment actions over the last 100 years have altered these in a quickly changing world. authors and fire regimes (Drobyshev et al. 2008a). In addition, past not necessarily those of the logging activities and the use of prescribed fire outside U.S. Fish and the historical range of variation resulted in shifts in suc- For a complete bibliography go to Wildlife Service. cessional trajectories, with jack pine displacing red and www.wildlife.org. eastern white pine (Drobyshev et al. 2008b).