Tree susceptibility and suitability for herbivorous insects depends upon a wide array of chemical compounds including potential toxins such as monoterpenes. Silvicultural techniques such as thinning and fertilization may change the concentration of these compounds within tree tissue foliage. The relative toxicities to Douglas-fir tussock moth larvae of five monoterpenes commonly present in host foliage were determined in laboratory assays. Of the five monoterpenes tested, limonene and γ-terpinene were significantly more toxic to the larvae then β-pinene, 3-carene or α-pinene. We also examined the effect of three fertilization treatments applied to previously thinned stands on the concentration of foliar monoterpenes one year following stand thinning. No significant differences were detected among treatments in the concentration of individual or total monoterpenes present in foliage. The effect of stand thinning may have overwhelmed any short-term fertilization impacts.

As ecosystem engineers, beavers (Castor canadensis) influence biogeomorphology and riparian vegetation. Streams with historic beaver removal and grazing often become incised, thereby altering stream and riparian processes. Anthropogenic structures that mimic beaver dams called beaver dam analogs (BDAs) may reverse incision by reintroducing historic processes. To understand BDAs as a process-based restoration tool, monitoring is needed across a range of watershed and stream conditions, but monitoring lags behind implementation. We constructed five BDAs in Central Oregon, on a low-gradient stream to test whether it may transport sufficient sediment to favor streambed aggradation behind BDAs. The stream also lacks woody riparian vegetation, and we examined how water temperatures and restoration plantings respond to BDAs where woody riparian vegetation is absent. We monitored structure integrity, aggradation, water temperature, groundwater, and vegetation for 1–2 yr after structures were installed. BDAs retained flows equally whether they were constructed from on-site juniper or off-site willow. During high flows, three structures failed and were rebuilt using improved design. After one year, aggradation of sediment above the two structures that survived flooding was negligible at one structure and high (33.7 m³) at the other. Groundwater levels rose 18–30 cm up to 135 m upstream of BDAs and 12 m into the floodplain. We found no evidence that BDAs raised stream temperatures. Within six months, willow cuttings planted near BDAs exhibited 1.3 times more growth than those on unimpounded locations. Overall, BDAs promoted a restoration trajectory on a low-gradient stream lacking woody riparian vegetation.

Weasels can be important components of grassland and meadow communities where they influence the dynamics of small mammal populations which, in turn, can be keystone species in these communities. We evaluate a method for detecting and identifying two species of North American mustelines (i.e., Mustela frenata and M. erminea) in mountain meadow systems. It is based on previous knowledge that weasels often co-opt the winter nests of their vole (or lemming) prey and frequently deposit scats there. We exploit this aspect of the predator-prey relationship and describe how, when paired with genetic identification of species from scat, searching after spring melt for weasel scats in winter-constructed vole nests may be an alternative survey method for detecting weasels in meadows. Our work was conducted at the Sagehen Experimental Forest in the Sierra Nevada Mountains. We discovered and examined 90 winter vole nests over four spring seasons, resulting in an average (SD) of 3.31 (1.81) nests found per survey hour per year. From these nests we collected an average of 0.57 (0.37) putative weasel scats per survey hour. Of the seven scats that were verified to be from a weasel, five were from M. frenata and two from M. erminea. This was a proof of concept effort, to which we conclude that searches of vole nests for scat that can be genetically verified as weasel should have a place in the biologist's toolkit. The method is likely to be the most efficient for obtaining a genetic sample for weasels in mountain meadow systems.

We used molar measurements from 136 known-age red tree voles (Arborimus longicaudus) to develop regression models that could estimate tree vole age from skeletonized remains. The best regression included a quadratic structure of the ratio between two measurements, crown height and anterior height, and natural log-transformed age in days. The regression predicted that molar roots begin to develop at 40 days of age and that molar crowns are worn completely away at 1,177 days of age. We used the regression to estimate the age distribution of 1,703 red tree voles found in northern spotted owl (Strix occidentalis caurina) pellets collected in western Oregon during 1970–2009. The age distribution of red tree voles in pellets was dominated by young individuals, with 81% younger than one year and only 0.5% older than two years. The proportion of individuals 61–120 days old was particularly high relative to other age classes. The proportion of subadult (52–120 days old) individuals exhibited regional variation between the Oregon Cascades and the Coast Range. Localized annual variation in age distribution was low, exhibited no evidence of cyclic variation, and was positively associated with local precipitation rates during the spotted owl nesting season (March–June). We hypothesize that the age distribution of tree voles in owl pellets may be similar to the age structure of tree vole populations in the wild, but acknowledge that this is virtually impossible to test because tree voles cannot be adequately sampled using conventional small mammal capture methods.

Most suggestions for adapting forest management in times of rapid global change have focused on tree regeneration, mortality, and productivity under predicted future climates. Adaptation to other aspects of global change, such as invasive species or changes in social settings, has received much less attention, which may be partially due to the high unpredictability of such events. Based on a review of recent silvicultural practices and ecological theory with a special emphasis on complex adaptive systems, we propose three guidelines for increasing the likelihood that forests will provide desired levels of a variety of ecosystem services in an increasingly variable and uncertain future. Basically, the guidelines promote a system level instead of the traditional command and control approach (sensu Holling and Meffe 1996) to silviculture. They are based on the well-supported ecological notions that having a high diversity and redundancy of key elements that are well connected across spatial, temporal, and organizational scales will allow forests to adapt on their own in response to predictable and unpredictable perturbations without the need for major management interventions. The guidelines encourage the maintenance of stand structural and compositional diversity at multiple spatial and temporal scales, thus reinforcing cross-hierarchical interactions in ecosystems, with an emphasis on encouraging self-organization. We provide examples of silvicultural practices as they relate to these guidelines.

The purpose of this study was to assess potential effects of nutrient addition in the previously unassessed lower Kootenai River (Meander Reach), 44–155 km downstream from the nutrient dosing site. We hypothesized that downstream periphyton and plankton densities would increase due to nutrient spiraling and organismal drift following seasonal upstream nutrient addition. Liquid inorganic ammonium polyphosphate fertilizer (10:34:0, N:P:K) was added to the Kootenai River in Idaho immediately downstream from the Idaho-Montana border with an in-river target concentration of 3.0 µg L^-1 total dissolved phosphorus for 16 weeks (01 June–01 October) from 2006 through 2012. As predicted, mean periphyton, phytoplankton, and zooplankton densities increased significantly (P < 0.05) post-nutrient addition. Periphyton density increased 5.1 times (pre: 685.1 mm^-2, post: 3501.0 mm^-2), phytoplankton densities increased 1.7 times (pre: 1775.9 L^-1, post: 3005.4 L^-1), and zooplankton densities increased by 49% (pre: 67.0 L^-1, post: 99.7 L^-1). While nutrient uptake, water chemistry, algal and chlorophyll accrual, periphyton, macroinvertebrate, and native fish community responses to nutrient addition have been previously published, including results from upstream reaches of the Kootenai River, this study provides the first published account of lower trophic level responses at considerable distances downstream from the dosing site in altered, low velocity habitats which are very different from the upstream gravel-bed reaches reported in other studies. Results of this study add to the growing body of empirical knowledge regarding the use of nutrient addition for restoring large culturally denutrified rivers in the Pacific Northwest and provide valuable new insights regarding the longitudinal patterns of response magnitude.

Biological nitrogen fixation is one of the most critical processes contributing to ecosystem productivity and stability on a global scale. In temperate climates of the northern hemisphere, plant-root associated bacteria of the genus Frankia are the major nitrogen fixers in forest environments. Trees belonging to the genus Alnus are the most widespread hosts of Frankia in the Pacific Northwest, and a myriad of biotic and abiotic factors can influence the robustness of this symbiosis. Host identity and bacterial strain are important features that can impact Alnus-Frankia association, but little is known about the interplay of intrageneric hosts that co-occur in natural settings. In this study we investigated the genetic diversity and host specificity of Frankia bacteria associated with sympatrically occurring populations of Alnus rubra (red alder) and Alnus rhombifolia (white alder) in Oregon. Based on sequence analysis of the nifH gene recovered from root nodules we found low overall bacterial diversity. One dominant Frankia genotype was associated with both host species, indicating a lack of strong host specificity in this system. Our results suggest that certain intrageneric plant hosts with overlapping distributions show cross-compatibility with symbiotic actinorhizal bacteria, and that low strain diversity of these bacteria can persist across mixed host populations.