Southwestern Oregon Research Articles

Reproductive Biology of the Del Norte Salamander (Plethodon elongatus)

We examined seasonal reproductive patterns of the Del Norte Salamander, Plethodon elongatus, in mixed conifer and hardwood forests of northwestern California and southwestern Oregon. Seasonal size differences in reproductive structures suggested that maximum spermatogenic activity occurred during the late summer, with spermatozoa transfer to the vasa deferentia occurring in the fall through spring. Maximum development of mature follicles occurred during the winter; however, follicular growth occurred year-round and was asynchronous among individuals. Courtship and mating probably occurred in late fall through early spring, with egg deposition from spring into early summer. Reproduction for females was not annual, and patterns suggested that the reproductive cycle was biennial or less frequent. In contrast, evidence indicated annual reproduction in males. Gravid females contained an average of 10 mature follicles.

Stand development, fire and growth of old-growth and young forests in southwestern Oregon, USA

We studied stand development in three distinct forest types in southwestern Oregon using six stands each in uncut and clear-felled old-growth stands and nearby young stands (18 total). Old-growth stands showed a wide range of tree ages (>300years) and low tree densities for several centuries; rapid early growth produced trees with large crowns and diameters, as well as low height-to-diameter ratios. In contrast, young stands established much quicker and at higher tree densities; beyond their initial 20years, trees had smaller diameters at equivalent ages, slower growth rates, smaller crowns and higher H:D than trees in old-growth stands. Low-intensity disturbance, likely dominated by fire, was common in old-growth stands during their early development. Fire scars showed these stands burned frequently from 1700 to 1900, and low levels of tree recruitment occurred in a complex relationship with fire during this 200years. There was no evidence of fire, however, in either old-growth or young stands after 1909, and their densities were well above that of 1900; in old-growth stands, 15–25% of the basal growth occurred from 1950 to 1990, and it appears that they are on a development pathway different from what they experienced from 1700 to 1900. Furthermore, tree recruitment has been limited in both old-growth and young stands since 1950 while biomass and fuels continue to accumulate rapidly. Past stand dynamics can be emulated by prescribed fire and light thinning to reduce risk of loss from severe fire or insects, as well as to partially restore stand conditions that existed prior to fire exclusion. Our results suggest that young stands can be grown to produce high levels of biomass/wood, or their development can be altered to more closely follow that of old-growth stands depending on management objectives.

Survival and Home-range Size of Northern Spotted Owls in Southwestern Oregon

In the Klamath province of southwestern Oregon, Northern Spotted Owls (Strix occidentalis caurina) occur in complex, productive forests that historically supported frequent fires of variable severity. However, little is known about the relationships between Spotted Owl survival and home-range size and the characteristics of fire-prone, mixed-conifer forests of the Klamath province. Thus, the objectives of this study were to estimate monthly survival rates and home-range size in relation to habitat characteristics for Northern Spotted Owls in southwestern Oregon. Home-range size and survival of 15 Northern Spotted Owls was monitored using radiotelemetry in the Ashland Ranger District of the Rogue River–Siskiyou National Forest from September 2006 to October 2008. Habitat classes within Spotted Owl home ranges were characterized using a remote-sensed vegetation map of the study area. Estimates of monthly survival ranged from 0.89 to 1.0 and were positively correlated with the number of late-seral habitat patches and the amount of edge, and negatively correlated with the mean nearest neighbor distance between late-seral habitats. Annual home-range size varied from to 189 to 894 ha ( = 576; SE = 75), with little difference between breeding and nonbreeding home ranges. Breeding-season home-range size increased with the amount of hard edge, and the amount of old and mature forest combined. Core area, annual and nonbreeding season home-range sizes all increased with increased amounts of hard edge, suggesting that increased fragmentation is associated with larger core and home-range sizes. Although no effect of the amount of late-seral stage forest on either survival or home-range size was detected, these results are the first to concurrently demonstrate increased forest fragmentation with decreased survival and increased home-range size of Northern Spotted Owls.En la provincia de Klamath, al suroeste de Oregón, Strix occidentalis caurina habita bosques complejos y productivos que históricamente han soportado incendios frecuentes de intensidad variable. Sin embargo, se sabe poco acerca de las relaciones entre la supervivencia de S. o. caurina y el tamaño del área de acción y las características de los bosques mixtos de coníferas propensos a incendios de la provincia de Klamath. Por ello, los objetivos de este estudio fueron estimar las tasas de supervivencia mensuales y el tamaño del área de acción en relación con las características del hábitat de S. o. caurina en el suroeste de Oregón. Se monitorearon el área de acción y la supervivencia de 15 individuos de S. o. caurina usando radiotelemetría en el Distrito de Guardabosque Ashland del Bosque Nacional Rogue River–Siskiyou desde septiembre del 2006 a octubre del 2008. Las clases de hábitat dentro de las áreas de acción de S. o. caurina fueron caracterizadas usando un mapa de vegetación del área de estudio elaborado con sensores remotos. Las estimaciones de supervivencia mensual oscilaron entre 0.89 y 1.0 y estuvieron positivamente correlacionadas con el número de parches de hábitat de la etapa sucesional tardía y la cantidad de hábitat de borde, y negativamente correlacionados con la distancia media al vecino más cercano entre hábitats sucesionales tardíos. El área de acción anual varió de 189 a 894 ha ( = 576; EE = 75), con una pequeña diferencia entre las áreas de acción reproductivas y no reproductivas. El área de acción de la época reproductiva se incrementó con la cantidad de borde tajante y con la cantidad de bosques viejos y maduros combinados. El área núcleo y las áreas de acción de la época reproductiva y no reproductiva se incrementaron con el aumento de hábitats de borde tajante, lo que sugiere que el incremento de la fragmentación se asocia con áreas núcleo y áreas de acción de mayor tamaño. Aunque no se detectó el efecto de la cantidad de bosque de la etapa sucesional tardía en la supervivencia o el tamaño del área de acción, estos resultados son los primeros en

The Pilot Joe Project: Dry Forest Restoration in Southwestern Oregon

T he US Department of the Interior (USDI) Bureau of Land Management (BLM) has recently begun to develop new resource management plans (RMPs) for western Oregon. In doing so, the BLM has specifically sought out a range of viewpoints and suggestions on new and innovative approaches to the management of their timberlands in western Oregon. One aspect of management being considered is the ecological forestry approach of Franklin and Johnson (this volume). The Pilot Joe Project, planned in 2011 and implemented in 2012, was designed under the conceptual framework of Franklin and Johnson’s Dry Forest restoration strategy. This demonstration project integrates ecosystem restoration, conservation of northern spotted owl (NSO) habitat, and commodity production over portions of the Middle Applegate watershed, an 80,000-ac landscape that is approximately 62% under control of USDI BLM. The rugged Middle Applegate landscape has cool, moist winters and hot, dry summers. Annual precipitation is 25–35 in. (varying with elevation), with less than 10% occurring from June through September. Because of these moisture limitations, slight changes in aspect and soil type dramatically affect forest productivity—cooler, moister north-facing slopes are typically covered by dense coniferous forest, while hot, dry south-facing slopes are usually dominated by hardwoods, shrubs, and grass. In the past, fire was the major disturbance agent affecting these plant communities. Alteration of historic fire regimes has allowed the proportion of Douglas-fir and dense closed-canopy forests to significantly increase, threatening old trees and increasing the possibility of crown fire. Hence, specific goals of this project included increasing the resistance and resilience of forests to wildfire, drought, and insects by reducing stand densities and ladder fuels; shifting species composition from the current dominance of Douglas-fir (Pseudotsuga menziesii) to include more ponderosa pine (Pinus ponderosa), sugar pine (Pinus lambertiana), California black oak (Quercus kelloggii), and Pacific madrone (Arbutus menziesii); and conserving and improving the survivability of older trees (more than 150 years). The Pilot Joe Project is the first “learning” and demonstration phase of a multiyear effort by BLM to apply the Franklin–Johnson approach within the Middle Applegate watershed. Fundamental to the success of this project was the ability to move forward on the treatments in a timely fashion. The relatively small size (890 ac) of Pilot Joe allowed it to be implemented more rapidly than a larger project that would take several years to plan and deploy—it was brought from public scoping to a sold timber sale in 8 months. Building stakeholder confidence was also needed to facilitate the process, so transparency was key—the BLM created and maintains a website for the Middle Applegate to post all meeting notes, official reports, National Environmental Policy Act of 1969 documents, and other related material for rapid, easy access to any interested party. Public participation was also critical to its success—extensive involvement occurred during the planning and development of Pilot Joe. More than a dozen field trips and public meetings were held to discuss, evaluate, and prioritize sites and conditions for treatment (Figure 1). Two in-depth meetings were held with the general public to specifically discuss the pilot goals and solicit criteria to be used for selection of forest stands to show the Franklin–Johnson restoration approach. Majority support existed for prioritizing treatment units most at risk to loss from wildfire, insects, or disease, especially those stands that could be accessed via the existing road network. Although there was general support for restoration forestry, there were many concerns. For example, some participants were very concerned about new road construction and skeptical that commercial harvest could be done while protecting residual stand characteristics such as large oak trees. Others felt restoration forestry does not provide high enough economic return. Developing partnerships outside of the agencies helped considerably. In the case of the Pilot Joe Project, the AppleJ. For. 110(8):442–445 http://dx.doi.org/10.5849/jof.12-081 Copyright © 2012 Society of American Foresters

How do logging and fire affect soil stability? Insights from a 2000 years charcoal record in Southwestern Oregon, USA

How do logging and fire affect soil stability? Insights from a 2000 years charcoal record in Southwestern Oregon, USA

Influence of forest structure and experimental green-tree retention on northern flying squirrel (Glaucomys sabrinus) abundance

In many regions of the world, forest management has shifted from practices emphasizing timber production to more sustainable harvesting that integrates ecological values, including maintenance of biodiversity, wildlife habitat, and ecological goods and services. To this end, management strategies emphasize retention of stand structures that meet the needs of forest-obligate wildlife species and enhance connectivity across landscapes. However, little is known about the effects on arboreal rodents of varying the amount or spatial distribution of retained structures. We quantified the responses of northern flying squirrels (Glaucomys sabrinus) to retention harvests of varying levels (15%, 40%, 75%, and 100% of original basal area) and spatial patterns (trees uniformly dispersed vs. aggregated in 1-ha patches), using six experimental treatments replicated at three locations in southwestern Oregon and Washington. Relative abundance of northern flying squirrels decreased following harvest; minimum number of squirrels known alive (MNKA) in the control (100%) and 75% retention treatment was significantly higher than in the 15% or 40% treatments. In mixed-effects regression models, MNKA increased with treatment-unit basal area and amount of surrounding mature (>80-year-old) forest, suggesting that squirrel abundance was influenced by local structure and landscape-scale variables. However, only basal area contributed to best-fit models of reproductive female abundance. Our results suggest a threshold response of northern flying squirrels to green-tree retention somewhere between 40% and 75% that is likely to be influenced by the spatial pattern of retention and landscape context. This study underscores previous conclusions that northern flying squirrels are sensitive to logging at both local and larger landscape scales, and demonstrates the current minimum retention standard of 15% will not provide suitable habitat for this species.

Kicking the Commodity Habit: On Being Grown Out of Place

Wheat is a crop that has been put into its place. That place is the Wheat Belt, the center of the country. It can grow where most crops don't do well and where there is no economic incentive to grow anything else. At one time, wheat was grown as part of a diverse cropping system in virtually every region of the country. Today, wheat is returning to places such as the hills of North Carolina, Vermont, Maine, Northern California, southwestern Oregon, the Skagit Valley, and San Juan Islands of Washington. These areas are “out of place,” and there is value to wheat grown out of place. That value can be indirect—for example, when used as a rotational crop that reduces diseases and other pests. Its value can also come more directly in unexpected forms, such as flavor and unique functional properties. The new focus on wheat production is helping farmers produce value where before they were bit players in a brutal commodity market geared only toward larger producers.

Long and Short-Term Effects of Fire on Soil Charcoal of a Conifer Forest in Southwest Oregon

In 2002, the Biscuit Wildfire burned a portion of the previously established, replicated conifer unthinned and thinned experimental units of the Siskiyou Long-Term Ecosystem Productivity (LTEP) experiment, southwest Oregon. Charcoal C in pre and post-fire O horizon and mineral soil was quantified by physical separation and a peroxide-acid digestion method. The abrupt, short-term fire event caused O horizon charcoal C to increase by a factor of ten to >200 kg C ha−1. The thinned wildfire treatment produced less charcoal C than unthinned wildfire and thinned prescribed fire treatments. The charcoal formation rate was 1 to 8% of woody fuels consumed, and this percentage was negatively related to woody fuels consumed, resulting in less charcoal formation with greater fire severity. Charcoal C averaged 2000 kg ha−1 in 0–3 cm mineral soil and may have decreased as a result of fire, coincident with convective or erosive loss of mineral soil. Charcoal C in 3–15 cm mineral soil was stable at 5500 kg C ha−1. Long-term soil C sequestration in the Siskiyou LTEP soils is greatly influenced by the contribution of charcoal C, which makes up 20% of mineral soil organic C. This research reiterates the importance of fire to soil C in a southwestern Oregon coniferous forest ecosystem.

Holocene winter climate variability in mid-latitude western North America

Water resources in western North America depend on winter precipitation, yet our knowledge of its sensitivity to climate change remains limited. Similarly, understanding the potential for future loss of winter snow pack requires a longer perspective on natural climate variability. Here we use stable isotopes from a speleothem in southwestern Oregon to reconstruct winter climate change for much of the past 13,000 years. We find that on millennial time scales there were abrupt transitions between warm-dry and cold-wet regimes. Temperature and precipitation changes on multi-decadal to century timescales are consistent with ocean-atmosphere interactions that arise from mechanisms similar to the Pacific Decadal Oscillation. Extreme cold-wet and warm-dry events that punctuated the Holocene appear to be sensitive to solar forcing, possibly through the influence of the equatorial Pacific on the winter storm tracks reaching the US Pacific Northwest region.

Short‐term response of Dicamptodon tenebrosus larvae to timber management in southwestern Oregon

AbstractIn the Pacific Northwest, previous studies have found a negative effect of timber management on the abundance of stream amphibians, but results have been variable and region specific. These studies have generally used survey methods that did not account for differences in capture probability and focused on stands that were harvested under older management practices. We examined the influences of contemporary forest practices on larval Dicamptodon tenebrosus as part of the Hinkle Creek paired watershed study. We used a mark–recapture analysis to estimate D. tenebrosus density at 100 1‐m sites spread throughout the basin and used extended linear models that accounted for correlation resulting from the repeated surveys at sites across years. Density was associated with substrate, but we found no evidence of an effect of harvest. While holding other factors constant, the model‐averaged estimates indicated; 1) each 10% increase in small cobble or larger substrate increased median density of D. tenebrosus 1.05 times, 2) each 100‐ha increase in the upstream area drained decreased median density of D. tenebrosus 0.96 times, and 3) increasing the fish density in the 40 m around a site by 0.01 increased median salamander density 1.01 times. Although this study took place in a single basin, it suggests that timber management in similar third‐order basins of the southwestern Oregon Cascade foothills is unlikely to have short‐term effects of D. tenebrosus larvae. © 2011 The Wildlife Society.

Fire exclusion effects on riparian forest dynamics in southwestern Oregon

Euro-American settlement and organized fire suppression have been associated with structural and compositional changes in many upland forests of the western United States, but little is known about the impacts on riparian forests, portions of the landscape protected for habitat and water quality. In this study, we used dendro-ecological methods to characterize the pre-settlement disturbance and tree recruitment processes of riparian forests in the Rogue River basin of southwestern Oregon and to identify changes to the forest structure and composition post-settlement. Our results suggest riparian forests in our study area developed with frequent disturbance by fire and that Euro-American land management shifted these forests onto a new successional trajectory. Our findings indicate the current hands-off management regime for riparian forests under the Northwest Forest Plan will continue along this altered trajectory and have ecologically undesirable consequences. We suggest that the restoration of pre-settlement forest dynamics in fire-prone forests of southwestern Oregon will be most effective where it includes density reductions in overstory trees and prescribed fire in both upland and riparian forests.

Habitat selection by northern spotted owls in mixed‐coniferous forests

AbstractConservation planning for the federally threatened northern spotted owl (Strix occidentalis caurina) requires an ability to predict their responses to existing and future habitat conditions. To inform such planning we modeled habitat selection by northern spotted owls based upon fine‐scale (approx. 1.0 ha) characteristics within stands comprised primarily of mixed‐aged, mixed coniferous forests of southwestern Oregon and north‐central California. We sampled nocturnal (i.e., primarily foraging) habitat use by 71 radio‐tagged spotted owls over 5 yr in 3 study areas and sampled vegetative and physical environmental conditions at inventory plots within 95% utilization distributions of each bird. We compared conditions at available forest patches, represented by the inventory plots, with those at patches used by owls using discrete‐choice regressions, the coefficients from which were used to construct exponential resource selection functions (RSFs) for each study area and for all 3 areas combined. Cross‐validation testing indicated that the combined RSF was reasonably robust to local variation in habitat availability. The relative probability that a fine‐scale patch was selected decreased nonlinearly with distances from nests and streams; varied unimodally with increasing average diameter of coniferous trees and also with increasing basal area of Douglas‐fir (Pseudotsuga menziesii) trees; increased linearly with increasing basal areas of sugar pine (Pinus lambertiana) and hardwood trees and with increasing density of understory shrubs. Large‐diameter trees (>66 cm) appeared important <400 m from nest sites. The RSF can support comparative risk assessments of the short‐ versus long‐term effects of silvicultural alternatives designed to integrate forest ecosystem restoration and habitat improvement for northern spotted owls. Results suggest fine‐scale factors may influence population fitness among spotted owls. © 2011 The Wildlife Society.

Stand Structures of Oregon White Oak Woodlands, Regeneration, and their Relationships to the Environment in Southwestern Oregon

Although Oregon white oak (Quercus garryana) woodlands are a characteristic landscape component in southwestern Oregon, little is known about their current or historical stand structures. Meanwhile, fuel reduction thinning treatments that change stand structures in non-coniferous communities are ongoing and widespread on public lands in this region; some of these treatments also have restoration objectives. Managers need baseline information on which to base prescriptions that have a restoration focus. We inventoried 40 Oregon white oak dominated woodlands across two study areas in southwestern Oregon, and describe here their stand characteristics and age structures. We assessed whether these varied systematically with site conditions or recorded fire history. Stands included various proportions of single- and multiple-stemmed trees and a range of tree densities and diameter- and age-class distributions. Variables that may indicate site moisture status were weakly associated with multivariate gradients in stand structure. Peak establishment of living Oregon white oaks generally occurred during 1850–1890, sometimes occurred in the early 1900s, and recruitment rates were low post-fire suppression (∼1956). Recruitment of sapling-sized oak trees (< 10 cm diameter at breast height, ≥ 1.3 m tall) was generally low and their ages ranged from 5 to 164 yr; they were not necessarily recent recruits. The observed wide range of variability in stand characteristics likely reflects the diversity of mechanisms that has shaped them, and suggests that a uniform thinning approach is unlikely to foster this natural range of variability.

Geographic Variation in Type I Songs of Black-throated Gray Warblers

We studied songs of Black-throated Gray Warblers (Dendroica nigrescens) in a fragmented landscape in southwestern Oregon and northern California where each male sings a single Type I song consisting of two phrases. Fourteen variants of Type I songs were distributed in a complex geographic pattern across 19,400 km2 of the region. Variants differed in number of notes/syllables in the A-phrase (range 2–5), and the B-phrase differed in both the number and structure of syllables. Several variants occurred in well-defined areas and differed from neighboring songs; others overlapped adjacent variants or graded from one form to another across a narrow zone. Distinct variants could be identified, but the diversity of Type I songs and the pattern of distribution throughout the region does not describe a clear system of dialects. Geographic extent of the variants differed considerably; some occurred as small scattered populations occupying <250 km2 while the largest exceeded 3,000 km2. Variants in the most restricted area and having the most fragmented distribution had the least consistent structure among individuals both within local populations and across the range of the variant. Ridges >1,000–1,200 m in elevation served as effective barriers and separated sets of similar song variants. Fire also likely had a role in generation of variants as reflected by multiple variants occurring in areas lacking obvious geographic barriers.

Tanoak Target: The Rise and Fall of Herbicide Use on a Common Native Tree

Despite over a century of conservation efforts and scientific forest management, a keystone nut tree common to California and southwestern Oregon is threatened by the 1995 introduction of an exotic disease. This is after decades of overharvesting of bark for industrial tanning beginning with American settlement, then of a full-scale tanoak eradication campaign by the mid-1900s. In addition to herbicide use, twentieth-century fire suppression favored conifers over tanoak. This article explores the limits and failures of governmental regulation to reverse devastating assaults on tanoak by examining the interplay of economic, ecological, and cultural factors that informed use and abuse.

Mixed-severity fire regimes: lessons and hypotheses from the Klamath-Siskiyou Ecoregion

Although mixed-severity fires are among the most widespread disturbances influencing western North American forests, they remain the least understood. A major question is the degree to which mixed-severity fire regimes are simply an ecological intermediate between low- and high-severity fire regimes, versus a unique disturbance regime with distinct properties. The Klamath-Siskiyou Mountains of southwestern Oregon and northwestern California provide an excellent laboratory for studies of mixed-severity fire effects, as structurally diverse vegetation types in the region foster, and partly arise from, fires of variable severity. In addition, many mixed-severity fires have occurred in the region in the last several decades, including the nationally significant 200,000-ha Biscuit Fire. Since 2002, we have engaged in studies of early ecosystem response to 15 of these fires, ranging from determinants of fire effects to responses of vegetation, wildlife, and biogeochemistry. We present here some of our important early findings regarding mixed-severity fire, thereby updating the state of the science on mixed-severity fire regimes and highlighting questions and hypotheses to be tested in future studies on mixed-severity fire regimes. Our studies in the Klamath-Siskiyou Ecoregion suggest that forests with mixed-severity fire regimes are characterized primarily by their intimately mixed patches of vegetation of varied age, resulting from complex variations in both fire frequency and severity and species responses to this variation. Based on our findings, we hypothesize that the proximity of living and dead forest after mixed-severity fire, and the close mingling of early- and late-seral communities, results in unique vegetation and wildlife responses compared to predominantly low- or high-severity fires. These factors also appear to contribute to high resilience of plant and wildlife species to mixed-severity fire in the Klamath-Siskiyou Ecoregion. More informed management of ecosystems with mixed-severity regimes requires understanding of their wide variability in space and time, and the particular ecological responses that this variability elicits.

Short-term bryoid and vascular vegetation response to reforestation alternatives following wildfire in conifer plantations

Question: How are dynamics of early-seral post-fire vascular plant and bryoid (terrestrial mosses, lichens, and fungi) vegetation impacted by reforestation activities, particularly manual vegetation removal and planting density? Does the relationship between vegetation dynamics and vegetation removal differ between harsh (west-facing) and moderate (east-facing) aspects? Location: Five high-severity burn plantation forests of Pseudotsuga menziesii in southwestern Oregon, USA. Methods: Plantations severely burned in a recent wildfire were planted with conifer seedlings as a four-species mixture or a monoculture, at two different densities, with and without manual vegetation removal. A subset of plots was also planted on a contrasting aspect within each plantation. The contrasting aspects differed in potential solar insolation and were indicative of moderate (eastern exposure) and harsh (western exposure) site conditions. Covers of shrub, herbaceous and bryoid vegetation layers were measured during reforestation activities 2‐4yr after the fire. Dynamics of structural layer cover and community composition were compared among treatments with analysis of variance and multivariate analyses (non-metric multidimensional scaling and blocked multi-response permutation procedure). Results: Structural layer cover and community composition differed between areas that received reforestation treatments and untreated areas. However, variability within treatments in a plantation was greater than variability within treatments across plantations. Effects of vegetation removal on composition and structure were more evident than effects of planting or altering planting density. Vegetation removal decreased cover of tall and low shrub and the bryoid layer, and increased herbaceous layer cover. Bryoid community and low shrub structural layer responses were more pronounced on moderate aspects than on harsh aspects. Vegetation removal shifted vascular plant community composition towards exotic and annual species. Conclusions: These reforestation treatments may be implemented without substantially altering early-seral vegetation community composition dynamics, especially in areas with harsh site conditions. Site conditions, such as aspect, should be evaluated to determine need and potential effects of reforestation before implementation. Monitoring for exotic species establishment should follow reforestation activities.

Phytophthora species in forest streams in Oregon and Alaska

Eighteen Phytophthora species and one species of Halophytophthora were identified in 113 forest streams in Alaska, western Oregon and southwestern Oregon that were sampled by baiting or filtration of stream water with isolation on selective media. Species were identified by morphology and DNA characterization with single strand conformational polymorphism, COX spacer sequence and ITS sequence. ITS Clade 6 species were most abundant overall, but only four species, P. gonapodyides (37% of all isolates), P. taxon Salixsoil, P. taxon Oaksoil and P. pseudosyringae, were found in all three regions. The species assemblages were similar in the two Oregon regions, but P. taxon Pgchlamydo was absent in Alaska and one new species present in Alaska was absent in Oregon streams. The number of Phytophthora propagules in Oregon streams varied by season and in SW Oregon, where sampling continued year round, P. taxon Salixsoil, P. nemorosa and P. siskiyouensis were recovered only in some seasons.

Estimating Within Tree Spatial Changes in Acoustic Velocity in Felled Douglas-fir Stems

Sorting logs for stiffness in the woods using acoustic devices mounted on harvesters and processors could improve the allocation of logs to their most appropriate processing destinations. Estimating spatial changes in acoustic velocity in felled stems, based on a limited number of measurements, will be essential if they are not to unduly impact harvesting or processing productivity and costs. The effect of five variables (length from butt, bark percentage, moisture content, green density, and oven dry density) and four velocity measurement approaches (time of flight [TOF] across the tree bole, resonance of the full tree length, resonance of the first 3 m butt log segment, and resonance of a log segment between 6 and 9 m above the butt) on the ability to estimate spatial changes in acoustic velocity were evaluated in felled Douglas-fir stems from five stands in southwestern Oregon. Distance from the butt was a significant predictor of acoustic velocity along the stem. TOF acoustic velocity measured across the bole had little value in predicting the longitudinal resonance acoustic velocity of a section of the tree. Full tree length resonance acoustic velocity, or single log acoustic velocity (either 3 m butt log or 3 m log 6 m above the butt) were found to be statistically significant and strongly correlated predictors of acoustic velocity of a section of a tree (R2 ranging from 0.68 to 0.89). The models were found to be stand-dependent, indicating a possible need for calibration for each stand to be harvested.

Susceptibility of Conifers to Three Dwarf Mistletoes in the Klamath-Siskiyou Mountains

Abstract Dwarf mistletoes (Arceuthobium spp., Viscaceae) are parasitic flowering plants that infect members of the Pinaceae family in the western United States. This article reports additional host susceptibility data for three dwarf mistletoes found in the Klamath-Siskiyou Mountains of southwestern Oregon and northwestern California. Three mixed conifer stands, each infested with either mountain hemlock dwarf mistletoe, western white pine dwarf mistletoe, or Wiens' dwarf mistletoe (nine stands total) were sampled to evaluate the susceptibility of conifers to these parasites. At each of the study sites, 10–20 temporary circular plots with a 6-m radius (0.012 ha) were established around large, severely infected trees. Within plots, species, dbh, and dwarf mistletoe rating (six-class system) were determined for each live tree. On the basis of the incidence of infection, conifers were assigned to host susceptibility classes. Western white pine and mountain hemlock were principal hosts of western white pine and mountain hemlock dwarf mistletoes, respectively. Brewer spruce and red fir were principal hosts of Wiens' dwarf mistletoe. Other conifers sampled were less susceptible to these mistletoes. This information can be used by forest managers to mitigate the damage associated with infestations of these dwarf mistletoes in mixed conifer forests of the Klamath-Siskiyou Mountains.