No abstract

Many wildlife species required standing dead trees (i.e., snags) as part of their habitat. Therefore, the ability to predict future density, distribution, and condition of snags can assist resource managers in making land-use decisions. Here we present methods for modeling the dynamics of snags using data from a 10-yr study on the rates of decay, falling, and recruitment of snags on burned and unburned plots in the Sierra Nevada, California. Snags (all species) in advanced stages of decay usually fell within 5 yr, and snags created by fire decayed rapidly and fell quicker (within 10 yr) than those on unburned plots. Pine (Pinus spp.) snags decayed more rapidly than fir (Abies spp.). Although there was an overall net increase in snag density on unburned plots, most of this increase was in the smaller (>13-38 cm diameter at breast height [dbh]) size classes; there was a net decrease in the larger (>38 cm dbh) snags preferred by many birds for nesting and feeding. Overall, snags remained standing the longest that were larger in diameter, shorter in height, less decayed, fir rather than pine, and lacking tops. A Leslie matrix model of snag dynamics predicted changes in snag decay and density only when adjusted for the specific environmental factors(s) causing initial tree mortality. Many snags are created by episodic events, such as fire, disease, drought, and insects. Models of snag dynamics must include the species and condition of trees becoming snags, as well as the factor(s) causing the tree to die. Forest managers must consider this episodic creation of snags when developing snag-management guidelines, and when planning tree-salvage programs based on short-term inventories.

Ecologists have advocated retaining various densities of canopy trees in harvest units in Pacific Northwest forests. In contrast to clear‐cutting, this practice may better emulate the patterns of disturbance and structural complexity typical of natural forests in the region. Several ecological attributes, including vertebrate habitat diversity, are thought to be associated with stands of complex structure. The goal of this study was to determine bird abundance in canopy retention sites relative to other common stand types in the Pacific Northwest and to develop habitat functions for extrapolating bird abundance across current and future landscapes. We used data from five previous studies in the west central Cascades of Oregon to compare bird abundance and to develop habitat functions for forest birds across a wide range of natural and managed stand structures and ages. The 67 stands included clearcuts, retention sites, young closed‐canopy plantations, mature stands, and old‐growth stands. ANOVA revealed that 18 of the 23 species included in the analysis differed significantly in abundance among the stand types, with some species being primarily associated with each of the stand types. The habitat variables used to build habitat functions included tree density by size class, mean tree diameter, and variation in tree diameter. Linear, polynomial, and various nonlinear regression models were evaluated for each bird species. Significant habitat functions were generated for 17 of the 23 bird species. The analyses identified four habitat‐use guilds among the 17 bird species: open‐canopy; open‐canopy with dispersed large trees; structurally complex closed‐canopy; and structurally simple closed‐canopy guilds. This study is the first in the Pacific Northwest to compare bird abundances across natural stands, traditionally managed plantations, and stands managed under ecological forestry approaches. The results suggested that canopy tree retention benefits many, but not all, of the bird species we studied, Moreover, the nonlinear responses of bird abundance revealed thresholds in tree density at which bird abundance changed dramatically. Knowledge of these thresholds allow managers to design stands for specific biodiversity objectives. The habitat functions presented here can be used to predict bird abundance based on habitat measurements derived from field data, remotely sensed data, or output from computer models of forest dynamics.

This report describes options for effectiveness monitoring of long-term status and trends of the northern spotted owl to evaluate the success of the Northwest Forest Plan in arresting downward population trends, and in maintaining and restoring the habitat conditions necessary to support viable owl populations on Federal lands. It describes options to address monitoring questions, profiles population and habitat status, and points out areas of progress and concern. How population and habitat data from demographic studies would be integrated in the development of predictive models is described. A process to report status and trend results is presented that could provide a reference document for decisionmakers during periodic land use plan reviews.Keywords: Northwest Forest Plan, effectiveness monitoring, northern spotted owl, suitable habitat, demographic study, remote sensing, GIS, landscape, stand scale, predictive model. PrefaceThis report is part of a series describing the approach for monitoring effectiveness of the Forest Plan that have been approved by the Intergovernmental Advisory Committee. Other reports present the plans for monitoring late-successional and old-growth forests, marbled murrelet, and aquatic and riparian ecosystems. Future reports may address survey-and-manage species, biodiversity of late-successional and aquatic ecosystems, socioeconomics, and tribal resources. These reports follow the framework for effectiveness monitoring described in "The Strategy and Design of the Effectiveness Monitoring Program for the Northwest Forest Plan." The purpose of this report is to present a range of options for monitoring the northern spotted owl from which the Federal agencies responsible for the Forest Plan can select an approach meeting their respective information needs given current and expected resource availability. This report responds to the assignment from the Federal resource agencies through the Intergovernmental Advisory Committee and incorporates responses to all comments and peer reviews, as requested. The options, recommended by the authors and the interagency Effectiveness Monitoring Team, have been selected for implementation in fiscal year 1998. Manuals, protocols, specific tasks, and annual funding allocations will be provided in individual agency work plans. All these documents, including manuals and work plans, will comprise the full set of guidance for conducting the effectiveness monitoring program for the Forest Plan. Executive SummaryThe purpose of the northern spotted owl effectiveness monitoring plan is to assess trends in spotted owl populations and habitat. Monitoring data will be used to evaluate the success of the Forest Plan in arresting the downward trends in spotted owl populations and in maintaining and restoring the habitat conditions necessary to support viable owl populations on federally administered lands throughout the range of the owl. Data from population and habitat monitoring in selected demographic study areas would be integrated in the development of pred...