Evaluating the Effects of Varying Levels and Patterns of Greentree Retention : Experimental Design of the DEMO Study

In western Oregon and Washington, recent changes in federal forest management policy contained in the Northwest Forest Plan have led to new harvest prescriptions on millions of acres of public lands. For example. on upland sites, standards and guidelines now require that live (green) trees are retained in at least 15% of the area within each harvest unit and recommend that at least 70% of this retention is in patches of moderate to larger size (0.21.0 ha or more). These prescriptions [-'or green-tree retention were based on the professional judgement and collective knowledge of many of the biologists who have studied the organisms and ecological processes that characterize these forests, but they have not been rigorously tested nor implemented on a broad geographic scale. Several prescriptions for green-tree retention are being evaluated experimentally by the Demonstration of Ecosystem Management Options (DEMO) study. In this paper, we briefly review recent changes in forest management policy and existing information gaps that led to the establishment of the DEMO study. We then provide an overview of the criteria for site selection, the experimental design and harvest prescriptions, the scope of scientific inquiry, and the collaboration that has occurred between scientists and land managers. These discussio~is provide the context and experimental framework for the individual research papers that comprise the remainder of this volume. Introduction Bureau of Land Management (Tuchmann 1995). In the 1980s, public concern over the fate of the northern spotted owl (Strix occidentalis cauri~za) and of the old-growth Douglas-fir (Pseudotsuga i17erzziesii) forests on which it depends (Gutikrrez and Carey 1985, Thomas et al. 1990) led to unprecedented local and regional interest in natural resource management in the Pacific Northwest. This interest, and the political activism it generated, elevated these issues to national prominence (Ervin 1989, Norse 1990). Lawsuits initiated by environmental groups resulted in injunctions from three separate federal district courts and brought timber sale programs to a standstill on federal lands managed by the USDA Forest Service and USDI In April 1993. in response to this 'timber crisis', President Clinton commissioned the Forest Ecosystem Management Assessment Team (FEMAT 1993, see also articles in Vol. 92(4) of the Journal of Forestry) to formulate and assess the consequences of an array of options for managing federal forest lands within the range of the northern spotted owl. This assessment was the first attempt to develop a comprehensive plan for ecosystem management on a broad geographic scale. The resulting management plan came to be known as the Northwest Forest Plan (Tuchmann et al. 1996). The Record of Decision (ROD) and associated standards and guidelines (S & Gs) for the Plan were published in April 1994 (USDA and USDI 1994a) and lawsuits against the Plan were 'Current address: USDA Forest Service. Alaska ~ k g i o n , resolved in favor of the government in December Tongass National Forest. Juneau, Alaska 99801 1994. 12 Northwest Science, Vol. 73, Special Issue. 999 Among the changes in forest management policy brought about by the Northwest Forest Plan is a greater emphasis on maintaining the diversity of species, structures, and physical and ecological processes that are important to the functioning of mature, late-successional forest ecosystems. These include microclimates associated with interior-forest conditions, spatial heterogeneity in forest composition and structure, fungi, invertebrates, saprophytic plants, nongame wildlife, snags, down woody debris, and other structural and compositional features generally associated with old-growth forests (Franklin et al. 1981). This is not the first time that forest management objectives have shifted in response to changing public perceptions or professional judgements. From the 1930s until the midto late1940s, selective cutting of the largest and most vigorous trees was widely applied in old-growth Douglasfir stands in the Pacific Northwest. Long-term studies revealed, however, that subsequent windthrow mortality was significant and offset increases in residual stand volume for at least 25 yr after harvest (Isaac 1 956). Clearcu tting replaced selective logging in most areas, and from the 1950s through the late 1980s, regeneration harvests consisted primarily of clearcuts of various sizes staggered in time and space, followed by slash burning and planting. This strategy was designed to meet legal mandates for multiple-use management on public lands while providing high volumes of timber at relatively low cost, dispersion of cumulative watershed effects, access for recreation, and habitat for deer and other game species associated with early successional forests. Several studies are proposed or underway in the Pacific Northwest region to evaluate the effects of silvicultural prescriptions designed to accelerate the development of late-successional forest characteristics in young, managed stands that have regenerated after clearcutting (e.g., Tappeiner 1992, Hanington and Carey 1997, Carey et al. in press). Such experiments are both relevant and necessary. However, because of substantial differences in initial conditions-especially the vegetative and structural legacies typical of mature forests-responses to retention harvest in young, managed forests may be very difYerent from those in mature forests. Mature forests generally have a broader array of structures, species, and functions, whereas managed plantations are often structurally and biologically simpler and the development of late-successional characteristics in these stands may require more intensive silvicultural manipulations. Large-scale harvest studies in mature, late-successional forests are lacking. In the Northwest Forest Plan, these forests are defined as singleand multi-storied stands dominated by conifers > 53 cm dbh (USDA and USDI 1994b; pp. 3&4-26). They comprise 682,300 ha of Matrix lands and Adaptive Management Areas (USDA and USDJ 1994b; Table 3&4-8) and, thus, are available for timber harvest under the Northwest Forest Plan. Furthermore, old-growth forests are dynamic and i t will not be possible to provide cathedral groves of ancient forests for future generations simply by preserving existing old-growth stands (DeBell and Curtis 1993). Today's mature forests will become the old-growth forests of the future; thus, if societal objectives are to maintain wood production while increasing the extent of forest stands with old-growth characteristics, we must. begin to develop methods for managing mature forests for these objectives. In the early 1990s, several private research institutions and public interest groups in Washington and Oregon sought federal funds for research aimed at addressing these information needs. In response to these lobbying efforts, the Pacific Northwest Region of the USDA Forest Service received Congressional direction in 1993 to establish a large-scale silvicultural experiment (see Franklin et al. 1999). The Region, in cooperation with the Pacific Northwest Research Station, subsequently established the Demonstration of Ecosystem Management Options (DEMO) study, a collaborative research effort with the Washington State Department of Natural Resources, University of Washington, Oregon State University, and University of Oregon to evaluate the ecological, physical, and social effects of retaining live (green) trees in harvest units in western Oregon and Washington. The DEMO study is designed to provide information to aid in the development of harvest strategies that will retain or accelerate the recovery of some of the species and key ecological features found in mature and old-growth forests. In this paper, we briefly review recent changes in forest management policy and existing information gaps that led to the establishment of the DEMO study. We then provide an overview of the criteria for site selection, the experimental DEMO: A Study of Green-tree Retention 13 design and harvest prescriptions, the scope of scientific inquiry, and the collaboration that has occurred between scientists and land managers. These discussions provide the context and experimental framework for the individual research papers that comprise the remainder of this volume. Facilitating the integration of research findings among these disciplines was a guiding principle during development of many aspects of the DEMO study.