This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. Pp. 220-244 in .Marti~,T., and I? M. Finch (eds.), Ecology and management of neotropical mIgratory bIrds. Oxford Univ. Press, New York, NY (1995). 8 EFFECTS OF SilVICUl TURAl TREATMENTS IN THE ROCKY MOUNTAINS SALLIE J. HEJL, RICHARD L. HUnO, CHARLES R. PRESTON, AND DEBORAH M. FINCH INTRODUCTION silvicultural practices on birds in Rocky Mountain forests, to suggest future research Neotropical migrants have been affected by needs, and to suggest how managers can the loss and fragmentation of forests in the make decisions based on what we currently eastern United States (Askins et aI. 1990). know. We offer a description of current Changes in western forests and the effects of forest structure and basic information on these changes on birds may be different from bird distribution across forest habitats in those in the East. While timber harvesting is the Rockies as background knowledge for widespread in the western United States, the understanding the effects of silviculture on purpose of silvicultural systems on public birds in these habitats. We also offer a land is to perpetuate forests, not to convert comparison between the effects of silviculture, forests to agricultural land or residential and the effects of fire and fire suppression on areas. Western logging has resulted in forest birds in an attempt to give a holistic landscapes that are primarily composed of perspective on the health of forest birds' in forests of different ages and treatments, the Rockies. rarely isolated forests. The silvicultural systems used to manage these forests, how­ ever, include timber harvesting, intermediate CURRENT FOREST STRUCTURE treatments, and stand-regeneration practices that usually result in forests different Three major factors contribute to the current from presettlement ones (Thompson et aI., forest structure of the Rocky Mountains. Chapter 7, this volume). Managers interested These three factors are: (1) floristic composi­ in maintaining western birds need not be as tion; (2) natural disturbances, especially fire; concerned with deforestation as with the loss and (3) human-induced disturbances, includ­ of old growth and whether managed forests ing logging, fire exclusion, -and other forest successfully substitute for un manipulated management activities. forests. While baseline studies on birds in most forest types in the Rocky Mountains exist (e.g., Marshall 1957, Salt 1957, Flack Floristic Composition of Rocky Mountain Forests 1976, Winternitz 1976, Balda and Masters 1980, Finch and Reynolds 1987, Raphael Plant composition will be discussed in the 1987a,b, Scott and Crouch 1988, Block et al. context of Southern, Central, and Northern 1992, Morrison et aI. 1993), studies on the Rocky Mountains, as defined by Daubenmire effects of silvicultural practices on songbird (1943). The Southern Rockies extend from populations in the Rocky Mountains are Mexico to the northern borders of Arizona relatively rare. Most studies consider only and New Mexico, and the Central Rockies the effects of timber harvesting. extend from that border to the middle of The purpose of this synthesis is to Wyoming. The Northern Rockies encompass summarize knowledge about the effects of the region from northern Wyoming to central 220 SILVICULTURE AND ROCKY MOUNTAIN FOREST BIRDS 221 Alberta and British Columbia. All three Rockies, the most mesic forests in the provinces share many tree species, but both Rockies, are restricted to the Pacific maritime­ the Southern and Northern Rockies exhibit influenced climate of northern Idaho and some species specific to their region. Many adjacent Montana, Washington, and British distinctive pine and oak species grow in the Columbia. Species typical of the Cascade southern region. Some of the species unique Mountains in the Pacific Northwest comprise to the northern region are typical of forests these forests and include western hemlock on the western slope of the Cascades in the (Tsuga heterophylla), western red cedar Pacific Northwest. (Thuja plicata), grand fir (Abies grandis), The Rocky Mountains are dominated by and Pacific yew (Taxus brevifolia). coniferous forests (Gleason and Cronquist Douglas fir (Pseudotsuga menziesii) is 1964, Peet 1988) with the only widespread characteristic of the Douglas-fir forest and abundant broadleaved tree being quaking throughout the Rocky Mountains. In the aspen (Populus tremuloides). Excluding the Southern and Central Rockies, white fir riparian zone, Peet (1988) recognized nine (Abies concolor), blue spruce (Picea pungens), forest types: (1) madrean pine-oak woodland; ponderosa pine, limber pine (Pinus jlexilis), (2) pygmy conifer woodland; (3) ponderosa and quaking aspen are associated species in pine woodland; (4) Cascadian forests; (5) the Douglas-fir forests. Associated species in Douglas-fir forest; (6) spruce-fir forest; (7) the Northern Rockies include grand fir, subalpine white pine forests; (8) treeline ponderosa pine, and western larch (Larix vegetation; and (9) montane seral forests. occidentalis). Technically, "mixed coniferous" A diverse assemblage of pines and oaks forests are found in several of these forest characterize the madrean pine-oak wood­ types and, where the types abut, but we use lands of the Southern Rocky Mountains. the term in reference to mixed Douglas-fir Prominent woodland species include Arizona forests. pine (Pinus ponderosa var. arizonica), The subalpine spruce-fir forest, dominated Chihuahua pine (P. leiophylla), Mexican by subalpine fir (Abies lasiocarpa) and pinyon (P. cembroides), Gambel oak (Quercus Engelmann spruce (Picea engelmannii), occurs gambelii), Arizona white oak (Q. arizonica), throughout the Rocky Mountains. In the and Emory oak (Q. emoryi). northernmost Rockies, white spruce (P. The pygmy conifer woodland of the Central glauca) replaces Engelmann spruce. Spruce­ and Southern Rockies often forms the fir forests are poorly developed in the transition between grasslands of the plains mountains of Mexico. and montane forests. Dominant trees in this Subalpine white pine forests are found on zone on the eastern slope of the Rockies are dry ridges and exposed southern slopes of pinyon pine (P. edulis) and one-seed juniper the subalpine zone. Whitebark pine (Pinus (Juniperus monosperma). On the western albicaulis) is the dominant white pine in the slope, pinyon pine or singleleaf pinyon (P. Northern Rockies, bristlecone pine (P. monophylla) and Utah juniper (J. osteo­ aristata) in the Central Rockies, and inter­ sperma) characterize much of this zone. mountain bristlecone pine (P. longaeva) Ponderosa pine woodland is widespread in on peaks in the Great Basin. Limber pine the Rocky Mountains. West of the con­ ranges across much of the Northern and tinental divide in the northern region, the Central Rockies. Mexican white pine (P. primary tree is Pacific ponderosa pine (P. strobiformis) replaces limber pine in the ponderosa var. ponderosa). East of the divide Southern Rockies. and south through the Rockies, Rocky Treeline vegetation typically is subalpine fir Mountain ponderosa pine (P. Ponderosa var. and Engelmann spruce throughout much of scopulorum) is generally dominant. Rocky the Rockies. White bark pine, bristlecone Mountain ponderosa pine, Arizona pine, pine, and limber pine are also important Chihuahua pine, or Apache pine (P. engel­ treeline species, especially on dry or exposed mannii) are characteristic trees in the . ridges. Other pines dominate at treeline in Southern Rockies. the high mountains of Mexico. Subalpine The Cascadian forests of the Northern larch (Larix lyallii) and mountain hemlock 222 FOREST MANAGEMENT (Tsuga mertensiana) are characteristic of individual personalities have also affected treeline habitats in the northern Rockies. how the land has been managed, often Montane seral forests dominate a large irrespective of silvicultural requirements, portion of the landscape in the Rocky site conditions, and conflicting objectives Mountains, since disturbances are common, (Mustian 1977). Therefore, a great diversity especially fire. Quaking aspen and lodgepole of logging practices has occurred in the pine (P. contorta) are two species that are Rockies (S. Arno, personal communication), important postfire seral tree species. Aspen including overstory removal, selection, seed­ and lodgepole are often replaced by stands tree, shelterwood, and clearcut logging (Hejl of more shade-tolerant species, such as 1992). Douglas fir or subalpine fir in the Douglas fir A general rule of historic logging was and spruce-fir zones, respectively. In the that the most accessible and commercially absence of other conifer species, aspen can valuable trees were logged before less form stable, self-maintained stands (Johnston accessible and less valuable trees. The result 1984, Mueggler 1985). Western larch and was that, in general, low elevations and western white pine (P. monticola) are both preferred species such as western white seral species of the Northern Rockies. Other pine, ponderosa pine, and western larch were species (e.g., Douglas fir, ponderosa pine, and logged before high elevations and Douglas limber pine) all act as successional species on fir, western red cedar, western hemlock, sites more mesic than those on which they lodgepole pine, subalpine fir, and Engel­ are typically climax. mann spruce. Some upper-elevation forests were logged early on, because they were accessible.