Cascade Range Research Articles

Differentiating spatial from environmental effects on foliar fungal communities of Populus trichocarpa

AbstractAimFoliar fungi – pathogens, endophytes, epiphytes – form taxonomically diverse communities that affect plant health and productivity. The composition of foliar fungal communities is variable at spatial scales both small (e.g. individual plants) and large (e.g. continents), yet few studies have attempted to tease apart spatial from climatic factors influencing these communities. Moreover, few studies have sampled in more than 1 year to gauge interannual variation in community structure.LocationThe Pacific Northwest of western North America.TaxonFoliar fungi associated with the deciduous tree Populus trichocarpa.MethodsIn two consecutive years, we used DNA metabarcoding to characterize foliar fungal communities of Populus trichocarpa across its geographic range, which encompasses a sharp climatic transition as it crosses the Cascade Mountain Range. We used multivariate analyses to (a) test for and differentiate spatial and environmental factors affecting community composition and (b) test for temporal variation in community composition across spatial and environmental gradients.ResultsIn both study years, we found that foliar fungal community composition varied among sites and between regions (east vs. west of the Cascades). We found that climate explained more variation in community composition than geographic distance, although the majority of variation explained by each was shared. We also found that interannual variation in community composition depended on environmental context: communities located in the dry, eastern portion of the tree's geographic range varied more between study years than those located in the wet, western portion of the tree's range.Main conclusionsOur results suggest that the environment plays a greater role in structuring foliar fungal communities than dispersal limitation.

The Chemistry of Sub-Alpine Streams in Mined Regions of the North Cascades Range

One hundred and fifty years of mineral extraction throughout the mountainous Ruby Creek watershed, Washington has left a legacy of historical hard rock mines and placer claims and their wastes. We conducted a watershed-scale chemical analysis of these gold-bearing tributaries, accounting for seasonal variability in streamflow, to identify spatial and temporal changes in stream chemistry and attribute them to natural processes or mining activities. We used hierarchical cluster analysis (HCA) to group chemically similar water samples based on concentrations of 23 metals, pH, and conductivity and compared the chemistry of HCA-generated clusters of water samples using pairwise comparisons to find chemical patterns. Total concentrations of As, Ba, Ca, Mg, Na, Sb, and Se, dissolved concentrations of Fe, and conductivity increased as streamflow progressed from snowmelt-influenced to baseflow. High total concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, V, and Zn during spring snowmelt and after rains were attributable to acid mine drainage at historical hard rock mines and prospect sites. Smaller-scale placer mining, by way of suction dredging and motorized gold panning, was associated with high concentrations of Al, Ba, Cd, Co, Fe, Mg, Mn, Mo, and Zn downstream. Stream biota may be adversely affected by exposure to Pb, which exceeded USEPA’s Aquatic Life Criteria, and exposure to particulate metals suspended in the water column.

Volcanic glass as a proxy for Cenozoic elevation and climate in the Cascade Mountains, Oregon, USA

After deposition, volcanic glass hydrates with ambient water, recording the average hydrogen isotope ratio (δD or δ2H) of local meteoric water during the hydration period. Previous researchers have used ancient glass δD values to reconstruct paleotopography and paleoclimate, while others have questioned the long-term reliability of the proxy as a recorder of ancient meteoric water. In this study, we sampled volcanic glasses ranging in age ~33 Ma to <50 ka from tuffs on the leeward (east) side of the Oregon Cascade Mountains. Our results strongly suggest that volcanic glass acquires and preserves δD values that are proportional to the stable isotopic composition of environmental water at the time of ash deposition based on 1) a 20‰ difference in δD values between samples of different ages (~8 Ma apart) from the same locality, 2) preservation of stable isotopic compositions consistent with lacustrine and non-lacustrine depositional environments in coeval samples, and 3) substantial differences between δD values of ancient volcanic glass (>1 Ma) and local meteoric water (converted to glass δD values) throughout the study area.We propose a paleoenvironmental interpretation of volcanic glass results that resolves previously published isotopic data and agrees well with the petrologic, structural, and stratigraphic record. Namely, the Oregon Cascades have been a significant topographic barrier since at least the mid-Miocene, and likely as far back as the Oligocene. Since reaching a topographic maximum during the eruption of Columbia River flood basalts in the mid-Miocene, surface elevations in Oregon have decreased, while the northern Cascades in Washington continue to rise.

Spectrum in the Strong Turbulence Region of Gross–Pitaevskii Turbulence

Numerical simulations of the Gross–Pitaevskii equation which describes the dynamics of quantum fluids are performed focusing on scales larger than the healing length. Dissipation and pumping of the mass are applied in high and low wavenumber ranges, respectively, in order to achieve turbulent states. In this setting of dissipation and pumping, it is found that the mass, or the particle number, cascades from low to high wavenumbers and a constant flux of the particle number is observed in the cascading wavenumber range. The spectrum F(k) (k is the wavenumber) of the order parameter field at the turbulent state is analyzed, and it is found that the obtained F(k) is consistent with the form $$\propto k^{-1}[\ln (k/k_0)]^{-1}$$ ( $$k_0$$ is the lower-end wavenumber of the scaling range) which is derived from a closure approximation of the particle-number transfer range of strong turbulence (Yoshida and Arimitsu in J Phys A Math Theor 46(33):335501, 2013).

Paleoecological implications of the first prehistoric record of water vole (Microtus richardsoni) from Washington state, USA

AbstractRemains of the North American water vole (Microtus richardsoni) have previously been recovered from late Pleistocene and Holocene deposits in southwestern Alberta, western Montana, and north-central Wyoming. All are within the historically documented modern range of the metapopulation occupying the Rocky Mountains; no ancient remains of this large microtine have previously been reported from the metapopulation occupying the Cascade Range. Four lower first molar specimens from the late Holocene Stemilt Creek Village archaeological site in central Washington here identified as water vole are from the eastern slope of the Cascade Range and are extralimital to the metapopulation found in those mountains. There is no taphonomic evidence indicating long-distance transport of the teeth, and modern trapping records suggest the local absence of water voles from the site area today is not a function of sampling error. The precise age of the Stemilt Creek Village water voles is obscure but climate change producing well-documented late Holocene advances of nearby alpine glaciers could have created habitat conditions conducive to the apparent modest shift in the range of the species represented by the remains.

Differential YAP nuclear signaling in healthy and dystrophic skeletal muscle.

Mechanical forces regulate muscle development, hypertrophy, and homeostasis. Force-transmitting structures allow mechanotransduction at the sarcolemma, cytoskeleton, and nuclear envelope. There is growing evidence that Yes-associated protein (YAP) serves as a nuclear relay of mechanical signals and can induce a range of downstream signaling cascades. Dystrophin is a sarcolemma-associated protein, and its absence underlies the pathology in Duchenne muscular dystrophy. We tested the hypothesis that the absence of dystrophin in muscle would result in reduced YAP signaling in response to loading. Following in vivo contractile loading in muscles of healthy (wild-type; WT) mice and mice lacking dystrophin (mdx), we performed Western blots of whole and fractionated muscle homogenates to examine the ratio of phospho (cytoplasmic) YAP to total YAP and nuclear YAP, respectively. We show that in vivo contractile loading induced a robust increase in YAP expression and its nuclear localization in WT muscles. Surprisingly, in mdx muscles, active YAP expression was constitutively elevated and unresponsive to load. Results from qRT-PCR analysis support the hyperactivation of YAP in vivo in mdx muscles, as evidenced by increased gene expression of YAP downstream targets. In vitro assays of isolated myofibers plated on substrates with high stiffness showed YAP nuclear labeling for both genotypes, indicating functional YAP signaling in mdx muscles. We conclude that while YAP signaling can occur in the absence of dystrophin, dystrophic muscles have altered mechanotransduction, whereby constitutively active YAP results in a failure to respond to load, which could be attributed to the increased state of "pre-stress" with increased cytoskeletal and extracellular matrix stiffness.

Severity of Swiss needle cast in young and mature Douglas-fir forests in western Oregon, USA

Swiss needle cast (SNC), caused by Nothophaeocryptopus gaeumannii, is an important foliage disease of Douglas-fir (Pseudotsuga menziesii) forests of the Pacific Northwest. The fungus lives endophytically within the foliage, until forming reproductive structures (pseudothecia) that plug stomates and cause carbon starvation. When pseudothecia appear on one- and two-year-old foliage, significant needle abscission can occur, which reduces productivity of the tree. While there is considerable evidence of SNC disease in coastal Douglas-fir plantations, the severity of SNC in mature and old-growth forests is poorly understood. We compared tree crowns of mature and old-growth conifer forests and nearby young forests at three locations in the Oregon Coast Range and four locations in the western Cascade Range of Oregon. We assessed disease severity for N. gaeumannii on two-year-old foliage, incidence by presence of N. gaeumannii on all foliage, foliage retention for the first four years, and foliar nitrogen of one-year-old foliage. We also compared leaf wetness at three heights in one mature and one young tree at five of the seven sites. Disease severity was greater in young forests than mature forests at all sites except for high elevation Cascade Range areas. Incidence of disease was highest for two-year-old needles in young trees and 3–5 year-old needles in mature trees, except for one coastal site. Retention of 1–4 year-old needle cohorts differed between young and mature trees, and mature trees had much larger complements of > four-year-old needles. Total foliar nitrogen (TN) concentration did not differ in needles of young and mature trees, but at some locations total N differed between canopy positions. Leaf wetness differences were not consistent between young and mature tree crowns. However, at one study site in the core epidemic area, the younger stand had longer periods of wetness in the upper crowns than a nearby old stand. Leaf wetness and foliar N were hypothesized to play a role in SNC disease severity, but they do not explain differences in adjacent young and mature trees. Although the fungus is present in old and young trees, the likelihood of disease expression and lower foliage retention appears to be greater in younger plantation trees than mature and older trees in western Oregon Douglas-fir forests.

The evolutionary and systematic significance of hybridization between taxa ofSpiranthes(Orchidaceae) in the California Sierra Nevada and Cascade Range

The morphologically overlapping and frequently syntopic species ofSpiranthes(Orchidaceae) found in the Sierra Nevada of California and Cascade Range of Oregon—S.porrifolia,S.romanzoffiana, andS.stellata—have long been a source of taxonomic confusion. Much of this confusion is attributed to hypothesized hybridization between species, and a lack of agreement concerning the distinctiveness ofS.stellatafromS.romanzoffiana. We used molecular phylogenetics incorporating low‐copy nuclear, nuclear ribosomal, and chloroplast DNA sources, in addition to morphological data, to clarify the evolutionary relationships of this complex. Our results indicate that contrary to long‐held hypotheses, hybridization betweenS.porrifoliaandS.romanzoffianaappears to be rare or absent. Furthermore, a realignment of taxon status is necessary forS.stellatasubsp.stellataandS.stellatasubsp.perexilis, with subsp.perexiliselevated to full non‐hybrid species rank asS. perexiliscomb. &amp; stat. nov., and subsp.stellatachanged toS. ×stellata, indicating its likely recurrent allopolyploid origin between the sister speciesS.perexilisandS.romanzoffiana. We also describeS. ×sierraenothosp. nov., representing rare allopolyploid hybrids betweenS.perexilisandS.porrifolia, and provide the first pollinator records forS.perexilisandS. ×stellata.

Geothermal Abundance in the Cascade Range (Washington / Oregon / N. California)

Arc volcanism is typically associated with high geothermal potential and the Cascade Range of North America is no different. As an active continental arc, the Cascades have an abundance of mid-to-upper crustal heat sources. Yet the region has a scarcity of active hydrothermal systems that is typical in geologically similar areas. What is different about the Cascades? Elevated geothermal heat flow and few hydrothermal occurrences convey that heat from magmatic influence is mostly dissipating conductively. The region has low internal deformation with few extensional structures that would facilitate hydrothermal convection. The area is seismically quiet despite evidence of active subduction and frequent volcanism. A staccato extrusive history and a regional layer-cake of basalts and altered volcanoclastic deposits lack vertical permeability. This restricts the structures needed for the circulation of fluids from the underlying hot rock upward to the surface, limiting the development of hydrothermal systems. Hydrothermal systems that do exist have relatively small volumes and low-to-intermediate temperature, and are associated with esoteric structural features or recent near-surface volcanics.

The Sensitivity of Terrestrial δ18O Gradients to Hydroclimate Evolution

AbstractTerrestrial gradients in the oxygen isotopic composition of meteoric water (δ18O), as reconstructed through proxies, reflect characteristics of ancient hydrologic conditions. These gradients are primarily influenced by the atmospheric transport of water vapor and the balance of precipitation and evapotranspiration, which are linked to climate and topography. We incorporate these effects into a one‐dimensional model that predicts the spatial evolution of δ18O based on local topography and the regional water‐energy budget. Specifically, we build on existing reactive transport models by incorporating parameterizations of orographic precipitation and energetic constraints on evapotranspiration following the Budyko water balance framework. We test our model on three modern transects that represent topographically distinct environments. These are the Amazon Basin (lowlands), the Cascade Range (mountains), and the eastern Himalayan Range (lowlands and mountains). Comparisons among these gradients demonstrate that the topographic regime determines how sensitive isotope records are to hydroclimate evolution. As a result, isotope records differentially express signatures of topography and the regional water balance, and we present a quantitative framework to predict this trade‐off. Finally, we link these effects to climate evolution and discuss how our model may help disentangle topographic and climatic signals through Earth history.

Applying Andragogy to an Outdoor Science Education Event

Andragogy provides a framework for how adults learn, and contemporary researchers have explored its validity and usefulness in varied contexts. This article joins the discussion by examining andragogy in an as-yet-unstudied setting—an outdoor science education event (HJA Day). In this mixed-methods study, we examine how andragogy applies to HJA Day at the H.J. Andrews Experimental Forest in the Oregon Cascades. HJA Day reflects many aspects of andragogy, with some inconsistencies. For example, many participants preferred learning sessions applicable to their work or personal interests, reflecting the assumption that adults prefer learning content with strong personal relevance. However, some participants attended sessions to be with their friends or to experience a specific learning style, demonstrating a diversion from the andragogical model. Overall, our results affirm the relevance of andragogy for adult field-based science outreach and offer context-specific suggestions for the use of andragogy in outdoor science education.

Tree traits influence response to fire severity in the western Oregon Cascades, USA

Wildfire is an important disturbance process in western North American conifer forests. To better understand forest response to fire, we used generalized additive models to analyze tree mortality and long-term (1 to 25 years post-fire) radial growth patterns of trees that survived fire across a burn severity gradient in the western Cascades of Oregon. We also used species-specific leaf-area models derived from sapwood estimates to investigate the linkage between photosynthetic capacity and growth response. Larger trees and shade intolerant trees had a higher probability of surviving fire. Trees that survived fire tended to experience a reduction in growth immediately following fire, with the most pronounced growth suppression found in trees within stands burned at high severity. Radial growth response to fire over time differed markedly as a function of tree size. Smaller trees that survived fire generally experienced enhanced radial growth relative to small trees in unburned stands. Conversely, larger trees that survived fire experienced significant and persistent reductions in growth relative to large trees in unburned stands. There was a linear relationship between diameter and tree leaf area in stands burned at low severity, but a non-linear relationship between diameter and leaf area in stand burned at high severity. Generalized additive models are well suited to modeling non-linear mortality and growth responses to fire. This research provides a better understanding of how fire severity influences tree-growth, forest succession, as well as the long-term resilience of forests to disturbances.

Influence of Atmospheric Rivers on Mountain Snowpack in the Western United States

In the coastal mountains of western North America, most extreme precipitation is associated with atmospheric rivers (ARs), narrow bands of moisture originating in the tropics. Here we quantify how interannual variability in atmospheric rivers influences snowpack in the western United States in observations and a model. We simulate the historical climate with the Model for Prediction Across Scales (MPAS) with physics from the Community Atmosphere Model, version 5 [CAM5 (MPAS-CAM5)], using prescribed sea surface temperatures. In the global variable-resolution domain, regional refinement (at ~30 km) is applied to our region of interest and upwind over the northeast Pacific. To better characterize internal variability, we conduct simulations with three ensemble members over 30 years of the historical period. In the Cascade Range, with some exceptions, winters with more atmospheric river days are associated with less snowpack. In California’s Sierra Nevada, winters with more ARs are associated with greater snowpack. The slope of the linear regression of observed snow water equivalent (SWE) on reanalysis-based AR count has the same sign as that arrived at using the model, but is statistically significant in observations only for California. In spring, internal variance plays an important role in determining whether atmospheric river days appear to be associated with greater or less snowpack. The cumulative (winter through spring) number of atmospheric river days, on the other hand, has a relationship with spring snowpack, which is consistent across ensemble members. Thus, the impact of atmospheric rivers on winter snowpack has a greater influence on spring snowpack than spring atmospheric rivers in the model for both regions and in California consistently in observations.

Evaluation of Rootstocks on Harvest Metrics of ‘Pinot Noir clone 02A’ Wine Grapes in Maritime Western Washington

The Puget Sound American Viticulture Area (AVA), located west of the Cascade Mountain Range in Washington State, is a large and uniquely situated area with diverse topography and mesoclimates. Given the young age of the AVA, little formal information exists on the appropriate rootstock–scion combination in wine grapes (Vitis vinifera) for the region. This project reports on a series of rootstock trials from 2003 to 2007, which evaluated the influence of ‘420A Millardet et de Grasset’, ‘3309 Couderc’, ‘101-14 Millardet et de Grasset’ (all Vitis hybrids), and a self-rooted control on basic harvest metrics of the wine grape scion ‘Pinot noir clone 02A’. At the warmer site in Everson, WA, rootstocks had no effect on final juice harvest metrics measured by soluble solids, titratable acidity (TA), and pH. At the cooler site in Mount Vernon, WA, the use of rootstocks did not always influence soluble solids or pH but did reduce final harvest TA, a desired effect for the region that is typified by low sugar–high TA wines. Even with a reduction in TA in some rootstock–scion combinations, overall, TA remained at the upper end or above the range typically desired for many wine styles.

Projections of water, carbon, and nitrogen dynamics under future climate change in an old-growth Douglas-fir forest in the western Cascade Range using a biogeochemical model

Statistically downscaled climate change scenarios from four General Circulation Models for two Representative Concentration Pathways (RCP) were applied as inputs to a biogeochemical model, PnET-BGC, to examine potential future dynamics of water, carbon, and nitrogen in an old-growth Douglas-fir forest in the western Cascade Range. Projections show 56% to 77% increases in stomatal conductance throughout the year from 1986–2010 to 2076–2100, and 65% to 104% increases in leaf carbon assimilation between October and June over the same period. However, future dynamics of water and carbon under the RCP scenarios are affected by a 49% to 86% reduction in foliar biomass resulting from severe air temperature and humidity stress to the forest in summer. Important implications of future decreases in foliar biomass include 1) 20% to 71% decreases in annual transpiration which increase soil moisture by 7% to 15% in summer and fall; 2) decreases in photosynthesis by 77% and soil organic matter by 62% under the high radiative forcing scenario; and 3) altered foliar and soil carbon to nitrogen stoichiometry. Potential carbon dioxide fertilization effects on vegetation are projected to 1) amplify decreases in transpiration by 4% to 9% and increases in soil moisture in summer and fall by 1% to 2%; and 2) alleviate decreases in photosynthesis by 4%; while 3) having negligible effects on the dynamics of nitrogen. Our projections suggest that future decrease in transpiration and moderate water holding capacity may mitigate soil moisture stress to the old-growth Douglas-fir forest. Future increases in nitrogen concentration in soil organic matter are projected to alleviate the decrease in net nitrogen mineralization despite a reduction in decomposition of soil organic matter by the end of the century.

Landscape patterns and diversity of meadow plants and flower-visitors in a mountain landscape

Wild flowering plants and their wild insect visitors are of great importance for pollination. Montane meadows are biodiversity hotspots for flowering plants and pollinators, but they are contracting due to tree invasion. This study quantified flowering plants and their flower-visitor species in montane meadows in the western Cascade Range of Oregon. Species diversity in small, isolated meadows was expected to be lower and nested relative to large meadows. Alternatively, landform features may influence richness and spatial turnover. Flowering plants and their visitors were sampled in summers of 2011–2017 in twelve montane meadows with varying soil moisture. All flowering plants and all flower-visitors were recorded during five to seven 15 min watches in ten 3 × 3 m plots in each meadow and year. A total of 178 flowering plant species, 688 flower-visitor species and 137,916 interactions were identified. Richness of flower-visitors was related to meadow patch size, but neither plant nor flower-visitor richness was related to isolation measured as meadow area within 1000 m. Species in small meadows were not nested subsets of those in large meadows. Species replacement accounted for more than 78% of dissimilarity between meadows and was positively related to differences in soil moisture. Although larger meadows contained more species, landform features have influenced meadow configuration, persistence, and soil moisture, contributing to high plant and insect species diversity. Hence, conservation and restoration of a variety of meadow types may promote landscape diversity of wild plants and pollinators.

Survival dynamics of mechanically topped Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) snags in Douglas-fir plantations, Oregon, USA

Structural enrichment in commercial tree plantations is a potential tool to increase snag numbers but relatively little information is available about how species, size, and spatial distribution of created snags are associated with longevity of these structures. We created 1197 snags in 31 harvest units from 1997 to 1999 in the Cascade and Coast Ranges, Oregon, USA, by topping live trees with harvesting equipment. We used an experimental design to distribute created snags at three densities and as either single or clumped created snags. We fit Weibull and log-logistic Accelerated Failure Time models and found that the median failure time was insensitive to the choice of distribution. We found a small positive effect of diameter at breast height (DBH) and a slight negative effect of increasing distance between created snags on survival. Assuming Weibull and log-logistic distributions at mean observed values of DBH and distance between snags, median survival times for Douglas-fir (Pseudotsuga menziesii) were 21.0 (95% confidence interval: 19.3, 22.8) years and 21.2 (19.7, 22.8) years, respectively. For western hemlock (Tsuga heterophylla), median survival times were 13.0 (11.9, 14.2) years and 12.5 (11.4, 13.7) years, respectively. Although the two failure distributions had similar median failure times, the log-logistic implies a higher survival probability over time for snags that remained standing at the end of the study period. Created snags can be a useful supplement for harvest units rotated at ∼45 years and Douglas-fir will be available for longer as standing structures. For example, under the log-logistic model, a predicted 5% of Douglas-fir snags are retained to rotation age, so that 40 snags per hectare would be required at harvest to maintain 2 snags per hectare through stand rotation. Snags created from western hemlock will provide an early rotation pulse but are unlikely to last longer than 20 years. Our results suggest that longevity can be increased by maximizing the snag size within the safety constraints of harvesting equipment. Scattering of snags may have a slightly negative effect on snag survival but this outcome should be weighed against potential ecological benefits of variation in snag distributions.

Magma storage below Cascades shield volcanoes as inferred from melt inclusion data: A comparison of long-lived and short-lived magma plumbing systems

In the central Oregon Cascades, mafic volcanic edifices include both short-lived cinder cones and a spectrum of much larger, longer-lived volcanoes. We analyzed olivine-hosted melt inclusions from explosive eruptions from three of the larger edifices to compare crystallization, volatile contents, and storage depths to those of the shorter-lived cinder cones. The melt inclusions were sampled from calc-alkaline basalt to basaltic andesite tephra collected from Belknap, Mount Washington, and North Sister volcanoes. Olivine host compositions are Fo80–83, Fo79–82, and Fo74–81, respectively. These Fo values are lower than the published values for nearby cinder cones (mostly Fo83–85), indicating greater extents of differentiation beneath the longer-lived edifices. The H2O contents of melt inclusions from each of the three volcanoes form a continuous range of values from ≤0.5 to ~2.5 wt% H2O. Many of the inclusions contain a vapor bubble, and the bubbles are mostly in the range of 1.0–6 vol% of the inclusion. After correcting bubble-bearing inclusions for the amounts of CO2 lost to the bubbles, our data show that variable degassing and olivine crystallization occurred beneath the larger edifices over a wide range of depths from > 7 km (> 2–5 kbar) to as shallow as ~0.1 km (~10–30 bars). In contrast, olivine-hosted melt inclusions from nearby cinder cones record entrapment at > 4–5 km depth, with no evidence for shallow crystallization and storage (e.g. Ruscitto et al., 2010). Our results demonstrate that the longer-lived edifices develop a vertically extensive zone of storage and crystallization that extends from the middle to the upper crust and continues into the core of the edifice itself. Modeled primary magma compositions for Belknap, Mount Washington, and North Sister are similar to those from nearby cinder cones, indicating that shield volcanoes and nearby cinder cones are supplied by the same magma sources. The results demonstrate that the shield volcanoes have more complex, shallow magmatic plumbing systems than that of the cinder cones.

Estimating economic impact of black bear damage to western conifers at a landscape scale

Black bear (Ursus americanus) damage to trees in the Pacific Northwest is common, although volume and economic losses are unknown. Common measures to quantify bear damage to conifers at large scales rely solely on aerial estimates of red tree crowns (caused by complete girdling) and broad assumptions about stand characteristics. We surveyed 122 vulnerable stands in the Coast Range and western Cascades of Oregon using both aerial surveys and ground surveys. Then, we modeled 4 damage scenarios (Salvage; Total Loss; Root Disease; and Combined Damage) with the Forest Vegetation Simulator (FVS) growth and yield model and the Fuel Reduction Cost Simulator (FRCS). Damage polygons, digitized in real time from aerial surveys identifying red (dead or dying) tree crowns, overestimated bear damage by approximately 5-fold due to misclassification with root disease, and failed to detect partially peeled trees that contributed to economic loss. Damage polygons assessed from the air generally did not include red crowns, and were a mean distance of 58.8 m (SE = 8.8) from damage polygons’ outer edges to the nearest red crown. We accounted for mortality and volume losses from partially girdled trees that did not show red crowns in our Salvage scenario, whereas we assumed that all bear-peeled trees resulted in complete loss in the Total Loss scenario. At the landscape scale, economic loss was ≤0.35% of net present value under both damage scenarios, while processing bear damage trees (Salvage) was the most efficacious option. At the landscape scale, our worst-case scenario (Total Loss) resulted in an estimated loss of $56/ha to bear damage, 10-fold less than a previously reported estimate of $585/ha. Root disease was a more prevalent damage agent than bear damage but did not affect net present value at harvest. The majority (92%) of bear damage observed in ground surveys was older (>2 yrs) and existed at a low frequency (1.5 bear damaged trees/ha) and severity across the landscape. Our results suggest that black bear damage is not uniformly distributed and that perceived impact varies with spatial scale. On-the-ground monitoring of the status of bear damage across the western Oregon landscape will identify hot spots of severe peeling and provide an understanding of these changes over time.

Active fault mapping and reconnaissance paleoseismic investigations in the La Pine graben, Oregon Cascades, USA

Despite geologic and geodetic evidence of ongoing extension across the Oregon Cascades, the late Quaternary structural expression of this deformation is not well constrained. High resolution airborne lidar-derived bare earth topography enables examination of densely forested portions of the Cascade Range to test for the presence of late Quaternary fault-related deformation.We target a portion of this extensional system by mapping evidence for recent faulting across the La Pine graben on the eastern flank of the central Oregon High Cascades. Our mapping documents >20 new Quaternary fault traces across the graben, illustrating that late Quaternary deformation is distributed across a wide zone. Paleoseismic investigations on the Twin Lakes maars fault within the La Pine graben provide evidence for a mid-late Holocene earthquake based on the offset of the 7.6 ka Mazama tephra. Potential temporal and genetic relationships between faulting and volcanic activity remain unclear because of limited age control, but this research provides a critical foundation for future paleoseismic efforts, targeted geochronologic studies, and basin structure and development investigations.