Western Hemlock Research Articles

Tree species and soil nutrient profiles in old-growth forests of the Oregon Coast Range

Old-growth forests of the Pacific Northwest provide a unique opportunity to examine tree species – soil relationships in ecosystems that have developed without significant human disturbance. We characterized foliage, forest floor, and mineral soil nutrients associated with four canopy tree species (Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), western redcedar (Thuja plicata Donn ex D. Don), and bigleaf maple (Acer macrophyllum Pursh)) in eight old-growth forests of the Oregon Coast Range. The greatest forest floor accumulations of C, N, P, Ca, Mg, and K occurred under Douglas-fir, primarily due to greater forest floor mass. In mineral soil, western hemlock exhibited significantly lower Ca concentration and sum of cations (Ca + Mg + K) than bigleaf maple, with intermediate values for Douglas-fir and western redcedar. Bigleaf maple explained most species-based differences in foliar nutrients, displaying high concentrations of N, P, Ca, Mg, and K. Foliar P and N:P variations largely reflected soil P variation across sites. The four tree species that we examined exhibited a number of individualistic effects on soil nutrient levels that contribute to biogeochemical heterogeneity in these ecosystems. Where fire suppression and long-term succession favor dominance by highly shade-tolerant western hemlock, our results suggest a potential for declines in both soil Ca availability and soil biogeochemical heterogeneity in old-growth forests.

Riparian forest composition affects stream litter decomposition despite similar microbial and invertebrate communities

Cross-boundary flows of energy and nutrients link biodiversity and functioning in adjacent ecosystems. The composition of forest tree species can affect the structure and functioning of stream ecosystems due to physical and chemical attributes, as well as changes in terrestrial resource subsidies. We examined how variation in riparian canopy composition (coniferous, deciduous, mixed) affects adjacent trophic levels (invertebrate and microbial consumers) and decomposition of organic matter in small, coastal rainforest streams in southwestern British Columbia. Breakdown rates of higher-quality red alder (Alnus rubra) litter were faster in streams with a greater percentage of deciduous than coniferous riparian canopy, whereas breakdown rates of lower-quality western hemlock (Tsuga heterophylla) litter were independent of riparian forest composition. When invertebrates were excluded using fine mesh, breakdown rates of both litter species were an order of magnitude less and were not significantly affected by riparian forest composition. Stream invertebrate and microbial communities were similar among riparian forest composition, with most variation attributed to leaf litter species. Invertebrate taxa richness and shredder biomass were higher in A. rubra litter; however, taxa evenness was greatest for T. heterophylla litter and both litter species in coniferous streams. Microbial community diversity (determined from terminal restriction fragment length polymorphisms) was unaffected by riparian forest or litter species. Fungal allele richness was higher than bacterial allele richness, and microbial communities associated with lower-quality T. heterophylla litter had higher diversity (allele uniqueness and richness) than those associated with higher-quality A. rubra litter. Percent variation in breakdown rates was mostly attributed to riparian forest composition in the presence of invertebrates and microbes; however, stream consumer biodiversity at adjacent trophic levels did not explain these patterns. Riparian and stream ecosystems and their biotic communities are linked through exchange and decomposition of detrital resources, and we provide evidence that riparian forest composition affects stream ecosystem catabolism despite similarities in microbial and invertebrate communities.

Developing a sustainable irregular structure: an evaluation of three inventories at 6-year intervals in an irregular mixed-species stand in Scotland

The development of a mixed-species irregular stand in the latter stages of transformation was examined. Transformation of the stand, located in Faskally Forest, Scotland, began over 60 years ago and it is now managed under the selection system. The aim was to determine whether a sustainable irregular state has been reached based on a stable diameter distribution, basal area and stand increment and on whether sufficient regeneration of the desired species and recruitment into the canopy is present to maintain the distribution. Complete inventories at 6-year intervals were carried out in a 1-ha permanent sample plot established in 1997. Results from the 2009 inventory suggest that the stand has not reached a sustainable irregular condition based on the above criteria. A reduction in canopy tree number in the last harvesting intervention has slightly flattened the diameter distribution (q = 1.4 cf. 1.5 and 1.6 in 2003 and 1997 inventories, respectively). The reduction in overhead cover has increased the number of regenerating seedlings in the understorey and suggests that the stand is moving towards a more balanced structure. Shade-tolerant western hemlock and beech dominate the understorey followed by semi-shade-tolerant Douglas-fir and Norway spruce. Recommendations for future management are discussed.

Field Observations of Oviposition and Early Development of the Coastal Tailed Frog (Ascaphus truei)

Key words: Ascaphus truei, clutch size,Coastal Tailed Frog, communal oviposition,early development, growth, Olympic Peninsula,Washington StateTailed frogs (genus Ascaphus) are stream am-phibians endemic to the Pacific Northwest (Jonesand others 2005) that are thought to represent thesister taxon of all other living anurans (Ford andCannatella 1993; Haas 2003). Among their uniquecharacteristics is their reproductive mode. Of the5912 described anuran species (AmphibiaWeb2010), the 2 species of tailed frog are the onlyanurans known to engage in copulation thatincludes intromission (Sever and others 2001).Further, the sperm storage capability of femalesallowstemporalseparationbetweenbreedingandoviposition, resulting in females depositing eggsalone (Metter 1964; Brown 1989).Knowledge of tailed frog oviposition sites,which are always concealed in streambeds, islimited (Karraker and others 2006 and referencestherein). What is known is based on theopportunistic discovery of sites during theexamination of instream substrates, a standardprocedure of various types of stream surveys (forexample, Adams 1993; Bury and others 2001).These haphazard discoveries have resulted inencountering various stages of clutch develop-ment, but have never involved field observationof oviposition. Observations of developmentfrom oviposition also have been restricted tofemales laying eggs in a laboratory via hormonalinduction (Wernz and Storm 1969; Brown 1975).Here we report the 1st field observation ofoviposition by tailed frogs, and selected fielddata on early development.Study AreaOur observations were made on Miller Creek(UTM Zone 10, 488225E, 5253553W, WGS84;elevation approximately 216 m), a 3rd-ordernon-fish-bearing stream on the east side of theOlympic Peninsula near Lake Cushman, MasonCounty, Washington. The site of our observa-tions consisted of a long riffle with steady fast-moving water. A bedrock step-pool was located5.5 m upstream and a small braided cascadewas located 5.9 m downstream of the site.Bedrock outcroppings lined the banks up- anddownstream for at least 40 m. Surroundinguplands are managed for timber production bythe Washington Department of Natural Re-sources; the local stand was last harvested in1945. Red Alder (Alnus rubra) and Vine Maple(Acer circinatum) dominate the riparian oversto-ry; understory is mostly Salmonberry (Rubusspectabilis), Devil’s Club (Oplopanax horridus),and Sword Fern (Polystichum munitum). Steephillslopes (50–65%) are blanketed with 2nd-growth Douglas-fir (Pseudotsuga menziesii),Western Hemlock (Tsuga heterophylla), andWestern Redcedar (Thuja plicata). Lithology ismostly Pleistocene age glacial till with large-clast material contributed from the basalt-basedCrescent Formation upstream.Initial Observations of OvipositionOn 29 July 2008, during rubble-rouse sam-pling (Quinn and others 2007) of a 2-m unit forstream-associated amphibians within this reach,we rolled a large (65 360 44 cm) boulder thatwas imbedded about 10 cm in surroundinggravel and sand. Four adult female A. truei andat least 183 A. truei eggs were found beneaththis boulder (Fig. 1). One female was activelylaying eggs. A spot water temperature taken atthis site at about 11:00 was 12.06C. A separategroup of 24 eggs was found beneath a 2ndboulder (55 3 40 3 24 cm) ,1 m downstreamthat was imbedded in approximately 20 cm of

Forest floor lichen and bryophyte communities in thinned Pseudotsuga menziesii - Tsuga heterophylla forests

While a great deal of research has illustrated the importance of late-successional forests for maintaining biodiversity in the Pacific Northwest of North America, over 76% of the forests in the region are less than 100 years old. To preserve landscape-level biodiversity, forest managers are increasingly interested in how young stands can be manipulated to favor late-successional species. We sought to understand how stand-level gradients in canopy structure, particularly those affected by thinning, relate to dominant forest floor bryophyte and lichen species composition and abundance. We sampled forest floor lichen and bryophytes ten years after alternative thinning treatments at two sites in western Oregon. Relationships of forest floor communities to canopy structure were site-specific. At the first site, moss and lichen abundance had small-scale geographic patterns and mosses were negatively associated with epiphytic cyanolichen species richness, however, we found no strong associations between forest floor communities and stand structural characteristics. At the second site, lichens, particularly Cladonia, was negatively associated with canopy cover and was most in thinned plots. Bryophyte abundance was positively associated with Tsuga basal area. This relationship was stronger in the thinned stands, which had a different community composition than those left unthinned. Overall, the forest floor communities were fairly homogeneous at both sites and relationships with stand structural variables were subtle, indicating that thinning did not have a strong impact.

Den use and selection by northern flying squirrels in fragmented landscapes

We studied den use and den-habitat selection by the Prince of Wales Island flying squirrel (Glaucomys sabrinus griseifrons) at multiple spatial scales in fragmented temperate rain-forest habitats because of the role dens play in the distribution, reproduction, and population density of this endemic subspecies. We observed differences in spatial patterns associated with den use between juveniles and adults: juvenile core denning areas were almost an order of magnitude larger than those of adults, and juveniles used about one-half the number of dens per month as adults. Female juveniles exhibited both the largest mean and maximum movements between consecutive dens among all age and sex classes. At the microhabitat scale of den selection snags were not selected over live trees, but flying squirrels primarily used cavities in snags and live trees. Flying squirrels also selected dens in the largest diameter live trees and snags, in snags with intermediate levels of decay, in live trees with more conks and visible bole entries, and in western hemlock (Tsuga heterophylla). At the broader scale of den selection flying squirrels chose den locations in neighborhoods with higher-volume forests and lower levels of fragmentation, although not lower absolute amounts of edge, than was available across the landscape. Our results suggest that extensive modification of landscapes from clear-cut logging and the creation of an early-seral matrix appeared to influence spatial patterns of den use in flying squirrels and den selection at the broader scale. When compared to patterns in a more-intact landscape, den selection at the microhabitat scale did not relate to differences in landscape context, suggesting additional factors might play an important role in den use across the region.

Restocking with broadleaved species during the conversion of Tsuga heterophylla plantations to native woodland using natural regeneration

The removal of conifers planted during the twentieth century on sites that had been woodland for many centuries, with the intention of restoring native broadleaved species, is an important aim of forestry policy in Great Britain. Current guidance generally advocates gradual removal of plantation trees using continuous cover silviculture and restocking by natural regeneration, but methods are largely untested. This study investigated natural regeneration of trees and shrubs at sites where western hemlock had been established either pure or in mixture with native broadleaved species. Western hemlock had been cleared from 70% of the sites. There were c. 10–300 stems ha−1 providing canopy cover of 10–90%; the predominant broadleaved canopy trees were ash, beech, birch and oak. The ground flora of all sites was species poor; bramble was the predominant vegetation type overall, but grasses, rushes and shrubs were relatively more abundant on open sites. A total of 15 native tree species were regenerating, birch was most common and at most sites there were few valuable broadleaved timber species. Although combined numbers of seedlings and saplings varied from 200 to 20,000 ha−1, large areas of most sites had few regenerating trees and <10% of their area was becoming restocked with timber species. Relationships between seedling numbers and site characteristics were complex and varied with species, but there was a consistent positive relationship between the presence of nearby parent trees and the frequency and abundance of seedlings. The results indicate that the current reliance on natural regeneration may be unwise especially for those broadleaved species such as oak and beech which are valued for their timber.

The impact of black cottonwood on soil fertility in coastal western hemlock forest

Black cottonwood ( Populus trichocarpa Torr. and Gray) is a deciduous tree species that extends from Alaska through coastal regions of western Canada into the northwestern United States and as far south as Baja California. We examined the influence of black cottonwood on soil fertility within a forest dominated by Douglas-fir [ Pseudotsuga menziessi (Mirb.) Franco], western hemlock [ Tsuga heterophylla (Raf.) Sarg], and western red cedar ( Thuja plicata Donn ex. D. Don.). Six circular 0.008 ha plots with a single cottonwood tree in the center of conifers were paired with six conifer plots (of the same size) without cottonwood. Litterfall, litter decomposition, properties of forest floor and mineral soil, and N mineralization were compared between plot types. Cottonwood litter had higher concentrations of almost all elements relative to conifer litter. Mass loss did not differ between cottonwood and fir/hemlock litter on cottonwood sites. Twice the amount of mull-like humus form (vermimull and mullmoder, 56%) was found in cottonwood plots compared to 28% in conifer plots. Higher pH (4.4) was found in the forest floor under cottonwood compared to conifer (3.9). Total N concentration (3.33 g/kg) and base saturation (68%) were higher in the mineral soil under cottonwood compared to conifers (2.98 g/kg total N and 50% base saturation). Net ammonification and net mineralization were both lower under cottonwood. These results suggest a variable effect of cottonwood on soil fertility within coastal western hemlock forests with some soil variables changed in a favourable direction and some in an unfavourable direction.

Modeling mortality in mixed-species stands of coastal British Columbia

Individual-tree distance-independent models were developed to estimate regular mortality for western hemlock ( Tsuga heterophylla (Raf.) Sarg.), Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii), and western redcedar ( Thuja plicata Donn ex D. Don) in the coastal temperate rain forests of British Columbia, Canada. Permanent plots remeasured at intervals ranging from 1 to 17 years were used. Because of the irregular remeasurement intervals, survival was estimated using a generalized logistic model and mortality was calculated by subtraction. Basal area of trees larger than the subject tree provided reasonably accurate mortality estimates for larger trees. However, poor results were obtained for trees less than 7.5 cm in diameter at breast height, which had higher mortality rates than the larger trees. Since the implementation of a survival (or mortality) model within a growth and yield model environment can largely affect estimation accuracy, three methods of implementing the model were also evaluated. A probability multiplier approach where the stems per hectare surviving to the next period is estimated by multiplying the probability of survival by the stems per hectare at the beginning of the time period is recommended. This is equivalent to a stochastic approach averaged over many repetitions but with much less processing time.

Understory abundance, species diversity and functional attribute response to thinning in coniferous stands

Alternative strategies for stand density management in even-aged coniferous forests may increase plant species and functional diversity. We examined the effects of fixed and variable density thinning on tree seedling regeneration as well as on abundance (indexed by cover) and richness of understory vascular plants 11 years after harvesting 45- to 66-year old forests dominated by Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) or western hemlock ( Tsuga heterophylla (Raf.) Sarg.) at three sites in western Oregon. Each site contained an unthinned control (CON), and thinning treatments selected to enhance overstory structural diversity and spatial variability within stands (HD, high density treatment at 300 trees ha −1; MD, moderate density treatment at 200 trees ha −1; VD300, VD200 and VD100, variable density treatments at 300, 200 and 100 trees ha −1). Leave islands are included in HD and the other thinning treatments contain both leave islands and gap openings. Tree seedling regeneration was highly variable and generally increased with thinning. Cover of all understory species was greater in VD100 than in the control whereas richness was greater in HD and MD. Cover and richness of early seral species were greater in most thinning treatments than in the control. Understory plant communities were overwhelmingly dominated by native species. In general, vegetation dynamics was accelerated by thinning, especially in variable density treatments. Cover of N-fixing understory species was greater in VD200 than in the other treatments, and in MD and VD300 than in the control, whereas richness of understory N-fixing species increased in all thinning treatments. Cover of understory species with intermediate soil water requirements was greater in MD, VD200 and VD100 than in the control, whereas richness of these species increased in VD200 compared to the control, HD and VD300. Thinning promoted higher diversity of understory conditions without reducing density and species richness of crop tree regeneration, and seemed to increase functional effect and response diversity.

A closer look at site index - biogeoclimatic site series correlations: Douglas-fir in the Coastal Western Hemlock Zone, xm2 variant, 01 site series

The Site Index - Biogeoclimatic Ecosystem Classification (SIBEC) model predicts site index from species and biogeoclimatic site series. The purpose of this project was, for Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) in the CWHxm2/01 site series, to: 1) verify that the current SIBEC site index estimate of 32.90 m is accurate, 2) create a more site-specific SIBEC model by including additional variables in the model to capture within-site series variation, and 3) compare the SIBEC site index estimates and their variability when the estimates are obtained using stem analysis data versus data from Bruce’s (1981) height-age model. The data set consisted of 40 Douglas-fir plots established in the CWHxm2/01 site series. The analysis shows that the current SIBEC site index estimate should be changed to 34.68 m. No relationship was found between site index and ecological variables within this site series, hence the model could not be made more site-specific. The BEC system aggregates sites into relatively homogeneous units with respect to productivity. The comparison of the SIBEC site index estimates and their variances when estimated using stem analysis and a height-age model were not statistically different. Obtaining a site index estimate from Bruce’s model is as accurate as obtaining a site index estimate from stem analysis when the Douglas-fir sample trees are between 50 and 80 years of age.Key words: Biogeoclimatic Ecosystem Classification, Douglas-fir, model error, site index, site series, stem analysis

Impact and recovery of western hemlock following disturbances by forestry and insect defoliation

Impact and recovery of juvenile western hemlock stands were measured 5 years after the end of an outbreak of western blackheaded budworm Acleris gloverana (Walsingham) (Lepidoptera: Tortricidae) and hemlock sawfly Neodiprion tsugae Middleton (Hymenoptera: Diprionidae) on Haida Gwaii, British Columbia, Canada. Overall, whole-tree mortality was infrequent (3.6–6.8%) but aggregated in a few, severely defoliated stands. Top-kill of the apical leader of surviving trees was more frequent (7.2–22.1%) and many of these trees had not recovered a growing dominant leader 5 years after the original damage. These severe impacts were most common in the largest trees in the youngest stands which had been spaced just before the outbreak. Radial growth was also reduced for 2 years following defoliation. However, mean annual ring width and basal area increment in surviving trees recovered quickly and was even enhanced in post-defoliation stands, particularly in spaced stands that had been moderately defoliated. Management recommendations include planning for likely outbreaks by avoiding creation of expanses of young regenerating stands of western hemlock during harvest and modifying spacing treatments when an insect outbreak is imminent to reflect the greater risk to trees <20 years of age.

Lichen habitat may be enhanced by thinning treatments in young Tsuga heterophylla-Pseudotsuga menziesii forests

Abstract Forest structural characteristics manipulated by alternative thinning treatments were associated with increases in cyanolichen and alectorioid species richness and changes in lichen community compositions. At two sites in moist conifer forests of western Oregon, lichen community monitoring plots were established before thinning treatments; the most diverse plots in each treatment were retained as diversity islands whereas the less diverse plots were treated in the thinning prescription. We resampled these plots approximately 10 years after thinning. At one site we found that lichen communities in diversity plots were quite similar to those in the surrounding treated forest and that the proportion of Tsuga heterophylla in the stand was negatively associated with alectorioid and cyanolichen richness. At both sites, hardwood gaps and open-grown trees were positively associated with cyanolichen species richness. At the other site, surrounding plots were more like diversity “leave-islands” after thinn...

Carbon isotope discrimination in western hemlock and its relationship to mineral nutrition and growth

Western hemlock (Tsuga heterophylla [Raf.] Sarg.) is a major component of temperate rainforests in coastal British Columbia. Forest fertilization can enhance the growth of forest trees, but results are inconsistent for western hemlock. We investigated the relationship between delta13C (foliage and stemwood), growth response and tree nutritional status in this species. To establish a sampling protocol for stemwood, we first assessed spot-to-spot variation around and along the bole, which exceeded 1 per thousand. We utilized the reaction wood (high lignin content) and adjacent normal wood in two curved western hemlock stems to evaluate whether this variation was related to wood composition. There was a consistent 3.43 per thousand difference between lignin and holocellulose, but the isotopic mass balance of whole wood was conserved and, therefore, did not vary with lignin content. Therefore, extraction of cellulose or holocellulose prior to analysis can introduce (not remove) bias. In a detailed study of a third stem, circumferential and longitudinal variation in delta13C was associated with spiral grain indicating limited physiological mixing of isotopic signatures originating from the crown. Wood was subsequently pooled from four cardinal positions around each stem. Eight even-aged western hemlock stands were selected and fertilized with different combinations of nitrogen (N), phosphorous (P) and a blend of S, K, Mg, Zn and Cu. Fertilization was effective in increasing foliar N, P, K and S depending on treatment. At the end of the first growing season after fertilization, the effect of treatments on foliar delta13C was nearly significant (P = 0.054), but did not persist into a second year. Effects on tree-ring delta13C were more obvious and persisted for about 3 years, averaging approximately 0.2-0.4 per thousand over this period, depending on treatment. Combinations of N, P and blend had the greatest effect, consistent with relative increases in basal area increment. Effects of fertilizer additions on delta13C, though clear, were superimposed on larger site and annual weather-related patterns in delta13C. Large tree-to-tree variation in delta13C was positively correlated with basal area increment, both before and after treatment imposition, suggesting that high water-use efficiencies are associated with greater growth.

Influence of precommercial thinning on understory vegetation of young-growth Sitka spruce forests in southeastern Alaska

The effects of precommercial thinning on the understory vegetative cover of 16- to 18-year-old spruce–hemlock ( Picea sitchensis (Bong.) Carrière – Tsuga heterophylla (Raf.) Sarg.) stands were studied in seven replicate areas over seven growing seasons postthinning. Vegetative cover was analyzed at the class level, but species-specific effects were examined in relation to their value as food for Sitka black-tailed deer ( Odocoileus hemionus sitkensis Cowan). When compared with unthinned controls, thinned stands (3.6–6.3 m spacing) had significantly greater understory cover. However, all thinned spacings led to similar understory cover. Conifer cover recovered to about two-thirds of its prethinning level within seven growing seasons posttreatment. Understory nonconiferous cover increased during the first 2–4 years postthinning but began to decline with increasing conifer cover during the next 3 years, nearly reaching pretreatment levels by year 7. In unthinned understories, vegetative cover had declined and was significantly lower than that beneath thinned stands. Summer food resource values for deer were increased by thinning. Winter food resource values were increased by thinning for snow-free conditions but were unaffected for conditions when herb-layer forbs were buried by snow.

Systematics and ecology of the genus Dendrozetes (Acari: Oribatida: Peloppiidae) from arboreal habitats in Western North America

We present the systematics and ecology of a new species of arboreal oribatid mite in the family Peloppiidae (Acari: Oribatida), Dendrozetes jordani n. sp., a dominant arthropod on branch tips and arboreal lichens associated with western hemlock (Tsuga heterophylla (Pinaceae)) and Pacific silver fir (Abies amabilis (Pinaceae)) in the coniferous temperate and montane forests of the Pacific Northwest of North America. Dendrozetes jordani represents the first record of the genus Dendrozetes in North America. The species is described on the basis of morphology of all active instars plus molecular sequence data for the mitochondrial cytochrome oxidase I (COI) gene. Dendrozetes jordani is compared with type specimens of D. caudatus Aoki from Japan, and a revised diagnosis of the genus Dendrozetes is given. Dendrozetes jordani has a stable, overlapping population structure through the year, and its association with trees in Pinaceae is an ecological characteristic shared with D. caudatus from Japan.

Spectrophotometric assay of a wood preservative, didecyldimethylammonium chloride (DDAC), in aqueous solution

A spectrophotometric assay based on the color reaction between didecyldimethylammonium chloride (DDAC) and 4-[4-(dipropylamino)phenylazo]-benzenesulfonic acid (propyl orange) was used for the determination of DDAC as a wood preservative. The assay was carried out using a propyl orange solution at pH 2.9. The visible absorbance spectrum of propyl orange showed an absorbance maximum at 510 nm, which decreased continuously with increasing DDAC concentration from 0 to 20 ppm. A linear correlation was observed at a DDAC concentration lower than 8 ppm. To apply this assay method to determine DDAC retention in treated wood, the influence of wood extractives on the assay was investigated. Wood extractives from sapwood and heartwood of Japanese cedar, Hinoki cypress, Japanese larch, and Western hemlock showed no influence on DDAC determination except in the case of heartwood from Japanese cedar and Hinoki cypress, which gave apparent DDAC concentrations higher than the actual values. However, it was also found that absorbance measurement at 477 nm solved this overestimation and gave precise values. It was concluded that this assay is a viable alternative to the current methods for DDAC determination.

Modeling Shrinkage Response to Tensile Stresses in Wood Drying II. Stress–Shrinkage Correlation in Restrained Specimens

This article reports on the effect of tensile stresses, temperature, and target moisture content on shrinkage behavior of short and thin Western hemlock specimens as part of a series of papers dealing with these issues. All tests were performed perpendicular to fiber grain while drying at 40, 60, and 80°C to 17, 11, and 5% final moisture contents at each temperature. Four matched specimens were subjected to different restraints during each drying experiment, namely, zero restraint (free shrinkage), two static restraints of 3 and 6 daN and a dynamic restraint controlled by the drying process. The resulting shrinkage was measured by pairs of resistive transducers located on the middle part of each specimen. Shrinkage percentages, obtained after the tensile stress was released and all the viscoelastic strain recovered, were proven to be a strong function of stress value, moisture, and temperature. The analytical fit yielded high coefficients of determination (R 2 = 0.83–0.85, p < 0.05) for both structural directions tangential and radial, respectively.

Postglacial vegetation history of Mitkof Island, Alexander Archipelago, southeastern Alaska

An AMS radiocarbon-dated pollen record from a peat deposit on Mitkof Island, southeastern Alaska provides a vegetation history spanning ∼12,900 cal yr BP to the present. Late Wisconsin glaciers covered the entire island; deglaciation occurred &gt; 15,400 cal yr BP. The earliest known vegetation to develop on the island (∼12,900 cal yr BP) was pine woodland (Pinus contorta) with alder (Alnus), sedges (Cyperaceae) and ferns (Polypodiaceae type). By ∼12,240 cal yr BP, Sitka spruce (Picea sitchensis) began to colonize the island while pine woodland declined. By ∼11,200 cal yr BP, mountain hemlock (Tsuga mertensiana) began to spread across the island. Sitka spruce-mountain hemlock forests dominated the lowland landscapes of the island until ∼10,180 cal yr BP, when western hemlock (Tsuga heterophylla) began to colonize, and soon became the dominant tree species. Rising percentages of pine, sedge, and sphagnum after ∼7100 cal yr BP may reflect an expansion of peat bog habitats as regional climate began to shift to cooler, wetter conditions. A decline in alders at that time suggests that coastal forests had spread into the island's uplands, replacing large areas of alder thickets. Cedars (Chamaecyparis nootkatensis, Thuja plicata) appeared on Mitkof Island during the late Holocene.

Doug Bake and Red Tree Voles: A Tale of Discovery in the Pacific Northwest

In 2002, we began compiling a database on all historical locations of Red Tree Voles (Arborimus longicaudus) and Sonoma Tree Voles (A. pomo) in Oregon and California. Part of that exercise involved visiting museums that had Tree Vole specimens and reading the old field notes of previous researchers who had collected museum specimens. As we began reading field notes and looking at specimens, we noticed that a remarkable number of Red Tree Voles had been collected around Tillamook, OR, in the 1960s and 1970s by a logger named Doug Bake. Most of the Red Tree Voles that Doug collected were prepared by Murray Johnson, then curator of mammals at the Slater Museum of Natural History at the University of Puget Sound in Tacoma, WA. Prior to preparing them as study skins, Murray kept many of Doug’s voles in captivity to study their behavior. He even used them in experimental crosses with Sonoma Tree Voles that he collected in California and found that these matings were not very successful, suggesting a reproductive barrier between Red and Sonoma Tree Voles (Johnson and George 1991). Murray also used some of Doug’s voles in feeding trials to see if individuals that normally fed on needles of Western Hemlock (Tsuga heterophylla) could switch to Douglas-fir (Pseudotsuga menziesii); he discovered that they did poorly at this. Though Murray had passed away by the time we started compiling our database, we were curious about whether Doug Bake was still alive, and, if so, we hoped to talk to him about how he came to be interested in Red Tree Voles and how he was able to capture so many of them. So we checked the Tillamook phone directory and found him listed. Because we knew that he had to be quite old, we were reluctant to simply call him up, so we decided to write him instead. About a week after we sent him a letter, we got a response back from Doug, written in his distinctive block print, saying that ‘‘It’s been over 20 years since I fell timber and my memory is a little rusty. However, if I can recollect anything beneficial, I’d be glad to talk with you.’’ We were elated by Doug’s quick response, so we immediately called him up and arranged to meet with him at his home on the outskirts of Tillamook. We met on 1 August 2003 and spent a couple of hours sitting on Doug’s couch, talking to him about his days in the woods and his interactions with Murray Johnson and Alex Walker, another Tillamook resident and one of the earliest naturalists to study mammals in northwest Oregon (Walker 1928, 1930). After our visit, we were so impressed with Doug and his unique contribution to science that we were inspired to write the following article. It is part obituary, but more than that, it is an example of what an ordinary lay person can contribute to science if they really desire to.