Western Cascades Research Articles

Stream temperature responses to experimental riparian canopy gaps along forested headwaters in western Oregon

Streamside (riparian) areas in the western United States and across much of North America are dominated by young, regenerating forests with closed canopies, which shade the understory and reduce light to streams. The addition of canopy gaps has been suggested as a management tool to accelerate development of riparian forest complexity, create stream light conditions that mimic those in late successional forests, and enhance in-stream productivity. Although gaps form naturally in late-successional forests, explicitly adding gaps is a concern because the increases in light that accompany a canopy gap may have the potential to increases stream temperature, which is an important ecological driver and regulatory metric in streams. The goal of this study was to determine whether and to what degree riparian forest canopy gaps that reflect localized disturbance events (mortality of one to a few dominant canopy trees) affect stream temperatures. We created experimental gaps in young regenerating riparian forests along six replicate headwater streams in western Oregon. Gaps increased light along 90 m study reaches by 3.91 (±1.63) moles of photons m−2 day−1, similar to that of a naturally occurring gap in a late-successional forest. Using a Before-After-Control-Impact study design, we assessed stream temperature by tracking multiple responses in each reach including: maximum seven day moving average of daily maximums (T7DayMax), maximum seven day moving average of daily means (T7DayMean), daily maximum, and mean summer temperatures, as well as within-reach (every 30 m) responses, and downstream recovery. Over a 40-day period in summer (July 22nd - August 30th), the mean response in T7DayMax across the six replicate streams was 0.21 °C ± 0.12, and the mean response in T7DayMean was 0.15 °C ± 0.14. Although the mean response in T7DayMax (a key regulatory metric) was small, changes varied across individual study streams, and the magnitude of the relative increase in stream T7DayMax as a result of the canopy gap was strongly negatively correlated with stream size. T7DayMax was not correlated with the size of the canopy opening or change in reach-scale light availability (within the range of gap sizes from 514 m2 to 1,374 m2 (0.05 to 0.14 ha)). Overall, riparian forest canopy gaps have the potential to increase stream temperatures, but in the western Cascade Mountain headwaters studied here, gap effects were small (all < 0.5 °C), and temperature responses declined as stream size increased.

A land systems science approach to assessing forest governance and characterizing the emergence of social forestry in the Western Cascades of Oregon

National forests in the United States are undergoing a spatially and temporally uneven governance transition in response to Congressional policies, agency mandates, and social and economic pressures, with many moving from a wholly state-led ‘dominant federal’ model to a more collaborative networked governance model which we refer to as ‘social forestry’. While the broad contours of this transition have been observed and studied previously, there have been few attempts to characterize it using quantitative, qualitative, or geospatial methods. Here, we combine a novel remote sensing-based method with qualitative social science research to understand the emergence of social forestry and its implications for land use/land cover change associated with implementation of the Northwest Forest Plan (NWFP) in the Western Cascades of Oregon. We linked time-series satellite data with forest inventory data to track patterns of timber harvest at scales commensurate with timber management decision-making. We then compared these patterns to policy-based expectations. We found a significant disconnect between NWFP policy and actual timber harvest patterns, raising questions about the effectiveness of the NWFP land use allocation system and the ‘land sparing’ approach to managing tensions between conservation and production. Qualitative research, including semi-structured interviews with federal agency personnel and local stakeholders, shed light on the causal mechanisms and reciprocal relationships driving spatial patterns of timber harvesting, which we discuss in terms of the emergence of social forestry involving complex, place-based negotiations between the federal government and local veto actors advocating for conservation. Findings have implications for US Forest Service public engagement strategies and efforts to establish zones of agreement regarding timber harvesting, as well as broader discussions about the agency’s future.

Runoff-initiated post-fire debris flow Western Cascades, Oregon

Wildfires dramatically alter the hydraulics and root reinforcement of soil on forested hillslopes, which can promote the generation of debris flows. In the Pacific Northwest, post-fire shallow landsliding has been well documented and studied, but the potential role of runoff-initiated debris flows is not well understood and only one previous to 2018 had been documented in the region. On 20 June 2018, approximately 1 year after the Milli fire burned 24,000 acres, a runoff-initiated debris flow occurred on the flanks of Black Crater in the Oregon Cascade Range. The debris flow was initiated via dispersed rilling on > 30-degree slopes near the crater rim and traveled > 1.5 km downslope. We measured exceptionally low soil infiltration rates at the study site, likely due to high burn severity during the Milli fire. Based on nearby 5-min rain gage data, we quantified rainfall rates for the storm event that triggered the debris flow. Our results show that peak 15-min rainfall rates were 25.4 mmh−1, equaling or exceeding the measured infiltration rates at the study site, which had a geometric mean of ~ 24 mmh−1. Field mapping shows that high burn severity resulted in the initiation of the debris flow and that convergent and steep topography promoted the development of a debris flow at this site. As wildfires increase in frequency and intensity across the western USA, the Pacific Northwest could become more susceptible to runoff-initiated debris flows. Therefore, characterization of the conditions that resulted in this debris flow is crucial for understanding how runoff-initiated debris flows may shape terrain and impact hazards in the Pacific Northwest.

AWWA Water Science Author Spotlight

Laboratory Simulation of Postfire Effects on Conventional Drinking Water Treatment and Disinfection Byproduct Formation Amanda K. Hohner, R. Scott Summers, and Fernando L. Rosario-Ortiz My research group evaluates the effects of extreme events and watershed disturbances on the resilience of drinking water systems. We study how events such as wildfire, floods, and droughts affect source water quality and treatment process performance, and how utilities can best adapt to address these disruptions in water quality. Our research was motivated by the needs of water utilities across North America, but especially utilities in the West that have experienced wildfires or are concerned about the risk of future wildfires to their water treatment system. The rise in wildfire activity has created new and unknown risks to source water quality, and there was a lack of scientific knowledge of the postfire impacts on treatment processes. Our goal was to develop a systematic approach to understand the effects of forest floor heating on water quality and treatment and to provide guidance to utilities that are vulnerable to wildfire. Amanda (Mandi) pauses with her dog, Holly, during a hike to Ice Lake in the Wallowa Mountains in northeast Oregon. I love spending time hiking and camping in forest watersheds. In the Pacific Northwest and in Colorado, we are fortunate to rely on these forest watersheds for high-quality drinking water supplies. When driving or hiking in wilderness areas, you often come across areas that have burned, and I want to understand how these drastic changes and visible changes affect downstream communities. With climate-change-related wildfires and other extreme weather events becoming more frequent, it will be increasingly important for water utilities to be prepared to adapt to climatic impacts. Our research in AWWA Water Science is a step toward understanding the potential risk of wildfire to water treatment and finished water quality. Our goal is to influence how water utilities and regulators are investing their resources as they now have to prepare for more uncertainty and greater variability in source water quality. I grew up in the state of Washington and have always lived out West, where there is a focus on the importance of water resources. Watching the effects of climate change through the rise in wildfire activity in areas that haven't burned historically—like the western Cascades—truly highlights the rapid changes and challenges we face as a scientific community. Adapting to consequences of climate change within the drinking water community will only become more important in the coming years. For fun and to clear my head, we like to spend time outdoors, hiking and running with our pup. In the winter, we cross-country ski around where we live, and in the summer we head to the lake to do stand-up paddle boarding. To learn more about this research, see the abstract on page 25 of the December issue of Journal AWWA and visit the article, available online at https://doi.org/10.1002/aws2.1155.

Corralling a black swan: natural range of variation in a forest landscape driven by rare, extreme events.

The natural range of variation (NRV) is an important reference for ecosystem management, but has been scarcely quantified for forest landscapes driven by infrequent, severe disturbances. Extreme events such as large, stand-replacing wildfires at multi-century intervals are typical for these regimes; however, data on their characteristics are inherently scarce, and, for land management, these events are commonly considered too large and unpredictable to integrate into planning efforts (the proverbial "Black Swan"). Here, we estimate the NRV of late-seral (mature/old-growth) and early-seral (post-disturbance, pre-canopy-closure) conditions in a forest landscape driven by episodic, large, stand-replacing wildfires: the Western Cascade Range of Washington, USA (2.7million ha). These two seral stages are focal points for conservation and restoration objectives in many regions. Using a state-and-transition simulation approach incorporating uncertainty, we assess the degree to which NRV estimates differ under a broad range of literature-derived inputs regarding (1) overall fire rotations and (2) how fire area is distributed through time, as relatively frequent smaller events (less episodic), or fewer but larger events (more episodic). All combinations of literature-derived fire rotations and temporal distributions (i.e., "scenarios") indicate that the largest wildfire events (or episodes) burned up to 105 -106 ha. Under most scenarios, wildfire dynamics produced 5th-95th percentile ranges for late-seral forests of ~47-90% of the region (median 70%), with structurally complex early-seral conditions composing ~1-30% (median 6%). Fire rotation was the main determinant of NRV, but temporal distribution was also important, with more episodic (temporally clustered) fire yielding wider NRV. In smaller landscapes (20,000ha; typical of conservation reserves and management districts), ranges were 0-100% because fires commonly exceeded the landscape size. Current conditions are outside the estimated NRV, with the majority of the region instead covered by dense mid-seral forests (i.e., a regional landscape with no historical analog). Broad consistency in NRV estimates among widely varied fire regime parameters suggests these ranges are likely relevant even under changing climatic conditions, both historical and future. These results indicate management-relevant NRV estimates can be derived for seral stages of interest in extreme-event landscapes, even when incorporating inherent uncertainties in disturbance regimes.

Disentangling effects of forest harvest on long-term hydrologic and sediment dynamics, western Cascades, Oregon

The magnitude of sediment yield following forest timber harvest is controlled by increases in both sediment supply and streamflow. Since the relation between sediment transport and streamflow typically follows a power law, small increases in streamflow may translate into large increases in sediment transport. Interpreting the geomorphic effects of streamflow increases is confounded by the fact that timber harvest influences both the hydrologic regime and sediment supply of a watershed simultaneously, making it difficult to isolate the streamflow effect alone. Here we report on a novel approach to this problem using long-term data from two paired catchments located in the H.J. Andrews Experimental Forest, Oregon, USA. We use observed streamflow from the treated (clearcut) and control watersheds to reconstruct a natural streamflow time series for the treated watershed, one that represents streamflow response in conditions prior to harvest. We combine this reconstructed natural streamflow time series with observed relations between streamflow and sediment transport to quantify the background sediment yield and disentangle the relative effects of changes in hydrology and sediment supply. Results indicate that while increases in streamflow can account for modest increases in sediment transport, this is dwarfed by the increased supply of sediment that accompanies most timber harvest. These results have broad relevance to forest timber harvest and fuel management practices worldwide and can be used to constrain or set bounds on likely effects of more modest (i.e., thinning) techniques.

Forest structure and biomass reflects the variable effects of fire and land use 15 and 29 years following fire in the western Cascades, Oregon

The mixed severity fire regime of western Oregon forests creates a complex post-fire landscape mosaic with patches of low, moderate and high overstory tree mortality. Conversion of old-growth forests into plantations and post-fire salvage logging are widespread land uses that dramatically affect structure, biomass and carbon stocks. Few studies, however, have quantified the complex responses to wildfire and land management (i.e. logging and post-fire salvage logging) over long time periods. We quantified total aboveground biomass and composition in forest stands following low, moderate, and high severity fires 15 (2002 Apple Fire) and 29 years (1991 Warner Creek Fire) following fire in low elevation, old-growth forests dominated by Douglas-fir (Pseudotsuga menziesii). We also sampled post-fire responses in forest plantations (harvested prior to fire) and salvage-logged sites (harvested after fire) in the same fires. Fire severity had dramatic effects on the partitioning of total aboveground biomass (TAGB). Most of the TAGB in high severity fires was sequestered in dead trees (>43%) and downed wood (>29%) while live trees comprised the largest component of TAGB (>62%) in low severity fires. In spite of differences in overstory mortality, there was no significant difference in the TAGB between the low, moderate and high severity fires 15 years following fire (Apple Fire). Similarly, there was no significant difference between the low and high severity burns 29 years following fire (Warner Creek Fire). Managed forests (salvage and plantations) had significantly lower post-fire aboveground biomass and carbon storage that the natural forests. The TAGB of salvage logged sites was 49% and 42% that of the high severity sites at the Apple Fire and Warner Creek Fire, respectively. The mean TAGB of plantations was lowest of all fire and land use scenarios. At the Warner Creek Fire, TAGB of the plantations were <30% of that of the high severity fire sites (e.g. 326 and 984 Mg ha−1, respectively). This equates to a difference in aboveground carbon in the managed compared to the natural stands of 553 Mg CO2e ha−1 at the Apple Fire and 781 Mg CO2e ha−1 at the Warner Creek Fire. This research highlights the management tradeoffs involving values relating to carbon storage and wood harvest following fires.

Consequences of reduced light for flower production in conifer-invaded meadows of the Pacific Northwest, U.S.A

Woody-plant encroachment threatens the biodiversity and ecosystem functioning of grasslands and meadows worldwide. An important but rarely described consequence of the transition to woody-plant dominance is the reduction in flowering of herbaceous species. We modeled community-wide relationships between flowering and light in two tree-invaded meadows (BG and M1) in the western Cascade Range, Oregon (USA). At BG, trees established over two centuries, forming a gradient of encroachment states (open meadow to old forest) and declining levels of light (91% to 8%), with most (85%) of the decline occurring within 2–4 decades of tree establishment. At M1, where trees formed distinct edges, we also tested whether distance from edge can serve as proxy for light in modeling flowering response. Flowering declined significantly with reductions in light at both sites: for a 10-percentage-point reduction in light, probability of flowering decreased by 35% (BG) and 21% (M1), median flowering density (flowers per m2) by 15% and 8%, and median flowering effort (density per unit cover) by 10% and 9%, respectively. At M1, distance to edge was a poorer predictor of flowering due to its nonlinear relationship with light: > 80% of the reduction in light occurred within 4.5 m of the edge. Our results reveal strong, nonlinear relationships of flowering in time (most rapid early in the invasion process) and space (steepest at the forest edge). In a landscape dominated by forests, conifer invasion of mountain meadows can reduce the local and larger-scale diversity of plants and their insect pollinators.

North American Douglas-fir (P. menziesii) in Europe: establishment and reproduction within new geographic space without consequences for its genetic diversity

Genetic admixture and plasticity along with propagule pressure, large seed dispersal distances and fast adaptation support successful establishment and spread of introduced species outside their native range. Consequently, introductions may display climatic niche shifts in the introduced range. Douglas-fir, a controversial forest and ornamental conifer represented by two ecologically different and hybridising varieties, was transferred multiple times outside the native range in North America. Here, we compare climatic and genetic patterns of 38 native populations from North America with six old Pseudotsuga menziesii populations with natural regeneration in the introduced range in Central Europe. Following variety and geographic origin assessment of introduced populations, genotypic and climatic data were examined for signatures of inter-varietal gene flow, reduced genetic diversity, presence of fine-scale spatial genetic structure (SGS), dispersal patterns, and climate similarities between native and introduced range. In the introduced range, dominating coastal variety originated from a restricted area in the US, whereas the interior variety, with limited presence in the European sites, displayed wider geographic origin. Variety hybrids with contributing coastal, but not the interior parent were identified. Differences in genetic diversity between both ranges, but also among the parent and their respective offspring populations in Europe were not found. Old populations in general lacked any SGS, whereas natural regeneration revealed different patterns of SGS. Distances of propagule dispersal ranged between 2.5 and 92 m. The climate of the studied European introduced range was most similar to the climate of the coastal variety from the western Cascade range from which the majority of the analysed coastal European Douglas-fir, but not the European interior variety, was assigned to originate. The results we present here shed not only light on dynamics of invasive species in the introduced range in general, but also allow for refinement of climatic niche modeling when using lower than species level.

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.

Drought impacts to trout and salamanders in cool, forested headwater ecosystems in the western Cascade Mountains, OR

Climate change projections for the western United States suggest that many regions will experience increasing frequency and severity of droughts. In summer 2015, the Pacific Northwest experienced a drought with early onset of stream low flows, reduced summer discharge, and elevated temperatures. We evaluated population responses of two dominant stream predators—coastal cutthroat trout (Oncorhynchus clarkii clarkii) and coastal giant salamander (Dicamptodon tenebrosus)—across nine Cascade Mountain streams. Drought conditions impacted both trout and salamanders, but their responses differed. Adult trout abundance and biomass were significantly lower in 2015 relative to 2014, a year with discharge and temperature closer to historical norms. Juvenile trout abundance did not differ between years but juveniles were significantly larger in 2015. Salamander abundance and biomass were not significantly different between years but body condition was lower in all nine streams in 2015. Differences in temperature among streams did not explain trout or salamander responses. Habitat was important for trout responses with trout abundance and biomass experiencing smaller declines in systems with more deep pool area. Despite notable short-term drought impacts to trout and salamanders in 2015, populations recovered to pre-drought conditions within two years in all but the smallest stream.

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.

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.

Near-future forest vulnerability to drought and fire varies across the western United States.

Recent prolonged droughts and catastrophic wildfires in the western United States have raised concerns about the potential for forest mortality to impact forest structure, forest ecosystem services, and the economic vitality of communities in the coming decades. We used the Community Land Model (CLM) to determine forest vulnerability to mortality from drought and fire by the year 2049. We modified CLM to represent 13 major forest types in the western United States and ran simulations at a 4-km grid resolution, driven with climate projections from two general circulation models under one emissions scenario (RCP 8.5). We developed metrics of vulnerability to short-term extreme and prolonged drought based on annual allocation to stem growth and net primary productivity. We calculated fire vulnerability based on changes in simulated future area burned relative to historical area burned. Simulated historical drought vulnerability was medium to high in areas with observations of recent drought-related mortality. Comparisons of observed and simulated historical area burned indicate simulated future fire vulnerability could be underestimated by 3% in the Sierra Nevada and overestimated by 3% in the Rocky Mountains. Projections show that water-limited forests in the Rocky Mountains, Southwest, and Great Basin regions will be the most vulnerable to future drought-related mortality, and vulnerability to future fire will be highest in the Sierra Nevada and portions of the Rocky Mountains. High carbon-density forests in the Pacific coast and western Cascades regions are projected to be the least vulnerable to either drought or fire. Importantly, differences in climate projections lead to only 1% of the domain with conflicting low and high vulnerability to fire and no area with conflicting drought vulnerability. Our drought vulnerability metrics could be incorporated as probabilistic mortality rates in earth system models, enabling more robust estimates of the feedbacks between the land and atmosphere over the 21st 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.

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.

A long‐term perspective on microclimate and spring plant phenology in the Western Cascades

AbstractPhenology—recurring seasonal events in an organism's life cycle—is largely driven by local climates &lt;1 km2 (microclimates), and changes in phenology are frequently used to indicate a species’ or community response to climate change. Phenological shifts can result in trophic asynchrony, population declines of higher‐level consumers, and reduction of plant fitness. While timing of phenological events is often correlated with elevation, studies have shown that microclimates created by areas of heterogeneous topography can be decoupled from regional climate patterns and that the distribution of microclimates does not always follow the elevation gradient. To examine the interaction between regional weather patterns and microclimate, and the subsequent effect of microclimate on phenology, we conducted standardized weekly spring phenology surveys of 18 native forest plants at the H.J. Andrews Experimental Forest in the Western Cascades from 2009 to 2016. We saw a high degree of inter‐annual variability of microclimate within and across sites, resulting in a changing pattern of microclimate diversity across the landscape from year to year. Most importantly, we saw that years with regional conditions predicted by continued climate change showed a loss of diversity in both microclimate and phenological events, with a more rapid advancement in bud break occurring at higher elevation sites. This study highlights the importance of understanding the interactions between regional and local processes that determine microclimate conditions and how those conditions influence patterns of plant phenology within forest communities, across mountain landscapes and over time, with implications for the capacity of mountainous regions to buffer local communities against the effects of climate change.

Intestinal microbiota lipid metabolism varies across rainbow trout (Oncorhynchus mykiss) phylogeographic divide.

This study focused on intestinal microbiome variation across the phylogeogrpahic divide of rainbow trout and its potential functional effects on ocean migration. Hindgut intestinal contents were analysed using the 16S V4 hypervariable ribosomal gene region. Core microbiome taxonomies and overall microbial diversity were identified across the species phylogeographic divide with increased diversity found in Eastern Cascade fish. To determine potential functional differences between groups PICRUSt metagenomics analysis was utilized, revealing significant enrichment of lipid and fatty acid metabolism genes in Western Cascade fish microbiomes. Decreased levels of intestinal microbial lipid metabolism in Eastern Cascade rainbow trout suggests increased lipid absorption in these fish given the consistent diets. Such absorption, and potential storage, would be an evolutionary benefit for increased migration distances experienced by Eastern Cascade fish. Core microbiome differences, and their functional associations, suggest evolutionary differences at the genetic level noticeably contribute to intestinal microbial community diversity. The possibility of genetic variation controlling intestinal microbiome diversity could have significant impacts on strain selection for rainbow trout aquaculture, especially given the consistent rearing conditions experienced in our sample populations likely result in differences in intramyocellular lipid storage.

Increased microbial uptake and plant nitrogen availability in response to simulated nitrogen deposition in alpine meadows

As global industry and intensive agriculture increase in response to an expanding human population, oligotrophic ecosystems such as alpine and subalpine habitats are increasingly vulnerable to transported atmospheric nitrogen (N) pollution. Even at low levels, N deposition can alter soil chemistry via changes in decomposition rates and mineralization of N from soil organic matter. We used fertilization to mimic N deposition in three National Park alpine meadow ecosystems in the Pacific Northwest (PNW) of the United States (an area of low ambient N deposition) over a 3-year period. Our sites were two moist heath meadow ecosystems in the western Cascade Mountains and one dry meadow ecosystem in the eastern Olympic Mountains. We assessed alpine soil chemistry and N cycling responses to simulated N deposition, using soil inorganic N availability to plants as a critical loads indicator. Soil solution inorganic N supply as measured by resin probes increased in response to N treatment at all sites by Year 3 in plots fertilized at the 10 kg N ha−1 yr−1 treatment level. At the heath meadow sites, we observed increased soil NO3-N during the summer and decreased extractable organic carbon (C) during the fall in response to applied N. We also observed seasonal increases in the proportion of soil N contained in microbial biomass in response to treatment. These data indicate season-specific increases in microbial N uptake and mineralization in response to fertilizer treatment. The carbon-rich, fine-ash volcanic soils of the North Cascades were the most sensitive to N treatment with low microbial N uptake. From those soils, we derived an empirical critical load of 6 kg N per ha−1 yr−1 for increased soil N availability. However, alpine meadow soils in the Western Cascades undergo N limitation in the fall and may have less potential for N leaching with fall rains. In contrast, soils at the dry meadow site had much greater potential for N mineralization, and are temperature- and moisture-limited rather than N limited. Changes in soil chemistry in response to N deposition were site-specific and resulted from differences in plant uptake and soil N mineralization capacity, indicating two very different regimes for response to N deposition for N-limited alpine meadows vs moisture-limited alpine meadows.

Tracking an atmospheric river in a warmer climate: from water vapor to economic impacts

Abstract. Atmospheric rivers (ARs) account for more than 75 % of heavy precipitation events and nearly all of the extreme flooding events along the Olympic Mountains and western Cascade Mountains of western Washington state. In a warmer climate, ARs in this region are projected to become more frequent and intense, primarily due to increases in atmospheric water vapor. However, it is unclear how the changes in water vapor transport will affect regional flooding and associated economic impacts. In this work we present an integrated modeling system to quantify the atmospheric–hydrologic–hydraulic and economic impacts of the December 2007 AR event that impacted the Chehalis River basin in western Washington. We use the modeling system to project impacts under a hypothetical scenario in which the same December 2007 event occurs in a warmer climate. This method allows us to incorporate different types of uncertainty, including (a) alternative future radiative forcings, (b) different responses of the climate system to future radiative forcings and (c) different responses of the surface hydrologic system. In the warming scenario, AR integrated vapor transport increases; however, these changes do not translate into generalized increases in precipitation throughout the basin. The changes in precipitation translate into spatially heterogeneous changes in sub-basin runoff and increased streamflow along the entire Chehalis main stem. Economic losses due to stock damages increase moderately, but losses in terms of business interruption are significant. Our integrated modeling tool provides communities in the Chehalis region with a range of possible future physical and economic impacts associated with AR flooding.