Recovery Plan for the Northern Spotted Owl - DRAFT

I. Summary of Literature Reviewand ExperienceThis report discusses management of forest stands for northern spotted owlhabitat. We present examples of silvicultural systems and treatments whichresemble natural forest disturbances. These systems can be used to acceleratethe development of stand structures used by owls and to grow habitat instands where it is not likely to occur through natural stand development. Weuse stand structure (density, stocking by tree species and size class, snags,logs on the forest floor) of stands that contain owl nest sites as goals (or desiredfuture conditions) for these silvicultural systems. We use data from actualstands to develop examples of silvicultural systems which will produce owlhabitat.A silvicultural system is a series of treatments to trees, shrubs, and otherplants designed to produce a desired stand through time-in this case, astructure that provides habitat for northern spotted owls. The treatments andtechniques employed necessarily will vary throughout the range of northernspotted owls. For example, in some forests in northern California and easternWashington Cascades where there has been a history of harvesting individualtrees or small groups of trees, there are mixed-species stands composed oftrees of various sizes or ages. In these forests, silvicultural systems shouldmaintain this diverse structure, while ensuring that there will be large trees inthe future and protecting stands against fire, insects, and disease. In theseforests, mimicking natural disturbance (i.e., fire) too closely may reduce owlhabitat. In other forests of California, Oregon, and Washington, stands arecomposed of trees of relatively uniform sizes and ages. Here, silviculturalsystems that attempt to mimic natural, small-scale disturbances and increaseunderstory tree regeneration to develop multilayered stands seem appropriate.In many of these forests, windthrow and the regeneration of trees in denseunderstories of shrubs are probably of more concern than fire.Not all these stands "need" to be treated to develop into suitable habitat. Somestands already provide habitat or will provide it in a short time without intervention.However, many other stands have been managed for wood production,not for owl habitat, and they will not readily produce multistoried standswithout treatment. Thus, there are many stands in which treatment mayhasten development of habitat, and many stands in which maintenance ofhabitat and wood production may occur simultaneously. The potential for astand to produce owl habitat varies from stand to stand and depends onvariables such as tree and shrub species composition; site productivity: andthe age, size, number, and spatial distribution of trees. For example, standswith a high stocking of conifers will not quickly produce large trees with deepcrowns or develop a multistoried structure. Stands with a dense understory ofshrubs may not produce additional layers of trees because regeneration oftrees cannot occur under the shrubs. Stands must be evaluated individuallyto determine their potential for producing habitat and which silviculturesystem to apply, if any. The possibilities for managing stands for owls areconsiderable. For example, we estimate that within the habitat conservationareas (HCAs) proposed by the Interagency Scientific Committee (ISC) there aremore than 2 million acres in stands on federal lands in Oregon and Washingtonthat are not suitable owl habitat.Planning for silviculture systems to provide owl habitat must be done at thelandscape and stand levels. Landscape variables to evaluate include locationof owls: habitat for owl prey: types of stands not providing habitat including485