Management of Western Forests and Grasslands

This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. BIRD COMMUNITIES IN MIXED CONIFER FORESTS OF THE INTERIOR NORTHWEST H. Reed Sanderson Range Scientist Pacific Northwest Forest and Range Experiment Station, USDA Forest Service, La Grande, Oregon Evelyn L. Bull Wildlife Biologist Pacific Northwest Forest and Range Experiment Station, USDA Forest Service, La Grande, Oregon Paul J. Edgerton Wildlife Biologist Pacific Northwest Forest and Range Experiment Station, USDA Forest Service, La Grande, Oregon ABSTRACT Forest management practices adjust the direction and pace of plant succession. The species composition and st~ucture are altered, and, in turn, the avian species. Forest management must include wildlife as an integral part of the management decision. A wildlife biologist must provide sound biological alternatives for the land manager's consideration. We present a discussion of ecological concepts that ~ildlife biologists can use to predict the response of bird alterations in the interior Northwest mixed conifer forest type. KEYWORDS: mixed conifer forest, silviculture, birds, nongame habitat. Society's demand for products is the primary driving force for the management of our natural resources. Whatever that management is, it also affects wildlife populations whenever habitat is altered. As the human population increases in number and affluence, the demand for products will also increase (Maser 1979). Although timber harvest, livestock grazing, and wildlife harvest provide products, they also " ••• stir man's economic interest and, in the longer term, protective interest" (Maser and Thomas 1978:2). Economic demands must now be balanced by ecological consequences because of such laws as the Environmental 224 Policy Act, Federal Land Policy and Management Act, and the Forest Policy Act. Specifically, a land manager is to be held responsible for the consequences of his decisions and their resulting impact on the resource, land, and environment. A wildlife biologist's role is to provide a land manager with a set of management alternatives and their respective consequences to habitats and attendant wildlife species. The responsibility of wildlife biologists is to provide biologically sound data. We can no longer shirk our responsibility with the too often heard wildlife biologists' rationalization that, "We do not have enough information." Our objective is to provide wildlife biologists with some ecological concepts to assist in predicting the generalized responses of both plant communities and birds to habitat alterations in the interior Northwest mixed conifer forests. VEGETATION The interior Northwest is characterized by a wide range of physical features that create a variety of habitats for different kinds of biotic communities. Diversity in these communities results not only from physiography, soils, and climate, but also from fire, insects, disease, and management activities such as timber harvesting and livestock grazing. Foresters and ecologists have studied the vegetation of the mixed conifer forests that occupy about 10.5 million hectares of the interior Northwest. Kuchler (1964) broadly mapped this area as Douglas-fir (Pseudotsuga menziesii)11 in the northern Rocky Mountains and Washington, cedar-hemlock-pine (Thuja-Tsuga Pinus) forests in the northern Rocky Mountains, and grand fir (Abies grandis) - Douglas-fir forests in central Idaho, eastern Oregon, and southeastern Washington. Regional ecologists have refined these forest descripti_ons to provide an ecologically based system of land stratification for use by local resource planners and land managers. They include Franklin and Dyrness (1973), Oregon and Washington; Hall (1973), the Blue Mountains of eastern Oregon and southeastern Washingon; Daubenmire and Daubenmire (1968), northern Idaho and adjacent Washington; Steele et al. (Being prepared), central Idaho; and Pfister et al. (1977) for Montana. Interior Northwest coniferous forests occur along a predictable environmental gradient. Climax Douglas-fir associations are usually found at mid-elevations where they intergrade with the upper limits of more xeric ponderosa pine (Pinus ponderosa) forests. In some areas, such as north-central Washington and the east slopes of the northern Rocky Mountains, however, climax ponderosa pine may be absent and Douglas-fir forests may border grasslands or shrub-steppe vegetation. In Idaho and the Blue Mountains of Oregon and Washington, climax Douglas-fir forest is less common. Instead, it is an important component of mixed conifer communities transitional from ponderosa pine to grand fir. Douglas-fir and grand fir generally dominate climax stands, but Engelmann spruce (Picea engelmannii) may be locally abundant on moist sites, and subalpine fir (Abies lasiocarpa) becomes an important component at higher elevations. Fire has played a major role in determining the composition and stucture of mixed conifer forests. Ponderosa pine, lodgepole pine (Pinus contorta), western white pine (Pinus monticola), or western larch (Larix occidentalis) dominate seral stands because they are better adapted to severe disturbance, especially fire, than are the climax species. Ponderosa pine or lodgepole pine 1/ Nomenclature follows that of Garrison et al. (1976). 225 may persist on harsher sites as a fire climax. On the other hand, grand fir and Douglas~fir regenerate abundantly in either mature, undisturbed stands, or seral stands. In the latter situation, they gradually assume dominance as the stand develops. Composition and structure of the associated understory vegetation is diverse and depends on interactions of site, plant community, fire, and forest management activities. On drier sites dominated by Douglas-fir or mixed Douglas-fir and ponderosa pine, grasses mixed with scattered low shrubs and forbs characterize the understory. Dense, multilayered understories of grasses, sedges, forbs, and tall shrubs occur on moist sites where Douglas-fir dominates the overstory. Some characteristic species are pinegrass (Calamagrostis rubescens), elk sedge (Carex geyeri), arnica (Arnica spp.), ninebark (Physocarpus malvaceus), and snowberry (Symphoricarpos albus). The understory of mature or old-growth mixed conifer forest dominated by grand fir is often characterized by low growing plants such as American twinflower (Linnaea borealis), queencup beadlily (Clintonia uniflora), and princespine (Chimaphila spp.). Wild rose (Rosa spp.), huckleberries (Vaccinium spp.), yew (Taxus sp.), and other shrubs are abundant in some communities. Fire can be an important influence in understory development. Intense heat generated by either wildfire or prescribed burns can destroy understory vegetation and favor the germination and establishment of seral shrubs. Dense fields of shrubs, such as snowbrush ceanothus (Ceanothus velutinus) and ninebark may dominate disturbed Douglas-fir sites for 25 years or longer while the seral forest develops. On the other hand, periodic, light underburning once maintained open stands of Douglas-fir mixed with ponderosa pine (Hall 1977). BIRDS OF THE _MIXED CONIFER FOREST More than 90 species of birds use the mixed conifer forests in the interior Northwest (Thomas 1979, Sundstrom 1978). None of these birds, however, restrict their feeding and reproductive activities to a single forest type or to a particular tree species. Because interior Northwest forests tend to be a mosaic of forest types instead of large continuous blocks, management objectives generally are not restricted to a particular forest type. Also, birds apparently respond more to vegetative structure than they do to plant species composition per se (Verner 1975). Consequently, management of bird communities should not be considered by forest type, but rather by the overall impact of management on forest structure. Vegetative structure can be broadly equated to forest succession. As succession progresses, plant species diversity and biomass increase; vegetative structure becomes more complex, which in turn, creates more available niches that result in increased bird species diversity (Meslow 1978) (Fig. 1). We have characterized the mixed conifer forest type with six successional stages, and have listed the birds that feed or reproduce in each successional stage (Appendix 1). Although we may not have all the specific information about habitat requirements for all birds, we can fairly well predict the impact of various management schemes on vegetative structure and plant succession and, consequently, on bird species. Forest managers may wish to maintain as many naturally occurring habitats as possible so future generations can have the same management options we have today (Balda 1976). "Wildlife Habitats in Managed Forests" 226 (Thomas 1979) and "A Holistic Approach to Wildlife and Fish Habitat Management" (Sundstrom 1978) are two publications that can be used to predict impacts of forest management decisions on birds. 80 (/} w u- /"""" ,........,..... w / £L (/} 60 / Feeding 0 0::: / £1) Reproduction LL 40 0 0::: w co 2 :::> 20 z Grass- Shrub- Pole Young Mature Old Forb Seed I i ng Sapling Growth FOREST SUCCESSIONAL STAGES Figure 1.--Enumeration of bird species orientation to forest successional stages in the mixed conifer forest type of the interior Northwest. FOREST MANAGEMENT Forest management is the dominant land management activity in the interior Northwest forests. Forest management is bird habitat management and

Load more