Decomposing coarse woody debris (CWD) is a conspicuous and important component of forest ecosystems. Seasonal temperature and precipitation patterns influence heterotroph activity, which determines the rate of CWD decomposition. We tested the hypothesis that moisture content and heterotroph community composition influence carbon flux in freshly-cut Douglas fir (Pseudotsuga menziesii) logs. To evaluate the effects of physical penetration of bark and wood and transmission of basidiomycete compared with ascomycete fungi by insects, 360 experimental logs were assigned to five replicate sites, each with 12 heterotroph×moisture treatment combinations in 1995. Half of the logs in each heterotroph treatment received normal rainfall and half were placed individually under elevated clear plastic tents to reduce water inputs. Respiration was measured every 1-3 months. In 1996 and 1997 a different log representing each treatment combination was harvested from each replicate and analyzed for the presence of inoculated and colonizing fungi. Logs inoculated with decay fungi had higher respiration than uninoculated logs but this effect only approached significance (P=0.08) during the first season. Respiration was significantly higher in sheltered than in exposed logs. Our results indicate that respiration and wood decomposition rates may be depressed by high moisture content in the wet forests of the coastal Pacific Northwest.

We summarize the status of semiochemical-based management of the major bark beetle species in western North America. The conifer forests of this region have a long history of profound impacts by phloem-feeding bark beetles, and species such as the mountain pine beetle (Dendroctonus ponderosae) and the spruce beetle (D. rufipennis) have recently undergone epic outbreaks linked to changing climate. At the same time, great strides are being made in the application of semiochemicals to the integrated pest management of bark beetles. In this review, we synthesize and interpret these recent advances in applied chemical ecology of bark beetles for scientists and land managers.

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Insects are particularly sensitive to environmental conditions and can serve as responsive indicators of changing climatic patterns and habitat conditions. However, changes in patterns of abundance over environmental gradients in forest ecosystems are poorly known. To examine landscape patterns of invertebrate assemblages, arboreal arthropods were collected during two seasons (spring and summer) by bagging branches from the lower, middle and upper canopy levels from six stands in nine second‐growth (100–150 yr old) forests and old‐growth (500 yr old) forests in Washington and Oregon. Detrended correspondence analysis and multi‐response permutation procedure showed that the composition of the canopy assemblages varied significantly with latitude, precipitation and tree age. Indicator analysis was used to assess each taxon's importance in response to the environmental variables. Individual taxa showed associations with latitudinal and precipitation gradients, and between old‐growth and mature Douglas‐fir. These effects may be used to anticipate the impacts of climate change or land use scenarios on the spatial patterns of forest invertebrate assemblages.

We measured canopy arthropod responses to six contrasting green‐tree retention treatments at six locations (blocks) in western Oregon and Washington as part of the Demonstration of Ecosystem Management Options (DEMO) study. Treatments were 100% retention (uncut), 75% retention with three 1‐ha harvested gaps, 40% dispersed retention, 40% aggregated retention with five 1‐ha uncut aggregates, 15% dispersed retention, and 15% aggregated retention with two 1‐ha uncut aggregates. Arthropods were sampled from upper, mid‐, and lower crown levels of one overstory Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) and from three understory vine maple (Acer circinatum Pursh) in each treatment unit during June and August each year to assess seasonal variation in abundances. Pretreatment data were collected in 1996 and posttreatment data in 1999– 2000. Arthropods showed little evidence of response to treatments, but the abundance of arthropods on both plant species showed significant variation among blocks, reflecting responses to environmental gradients at a regional scale. Arthropod abundance also varied significantly over time in unmanipulated (control) treatments, suggesting sensitivity to annual changes in weather. Our results suggest that disturbance at this intensity or scale has little influence on canopy arthropods in the short term. Future sampling will be necessary to evaluate the extent to which arthropods respond to changes in environmental conditions created by these treatments over longer time periods.