Oregon Coast Research Articles

Distribution of a Foliage Disease Fungus Within Canopies of Mature Douglas-Fir in Western Oregon.

Nothophaeocryptopus gaeumannii is a common native, endophytic fungus of Douglas-fir foliage, which causes Swiss needle cast, an important foliage disease that is considered a threat to Douglas-fir plantations in Oregon. Disease expression is influenced by fungal fruiting bodies (pseudothecia), which plug the stomata and inhibit gas exchange. Trees are impacted when pseudothecia plug stomates on 1-year-old and older needles resulting in early needle abscission. Mature (100 years+) trees appear to be less impacted from disease, and we hypothesize this is due to the greater emergence of pseudothecia on older than younger needles, which allows for more needle retention. We measured the density of pseudothecia occluding stomates across 2- to 5-year-old needles from upper, middle, and lower canopy positions of mature trees at three sites in the Oregon Coast Range and two sites in the western Oregon Cascade Mountains. Binomial generalized linear mixed model (GLMM) was used to test for the effects of canopy position (upper, middle, and lower), sites, needle age (2-5 years old), and years (2016 and 2017), and their interactions on the pseudothecia density. Pseudothecia density varied annually depending on sites, needle age and canopy positions. Pseudothecia density peaked on 3-, and 4-year-old needles, however, needles emerging from the same year, like 2-year-old needles in 2016 and 3-year-old needles in 2017 both emerged in 2014, had consistently similar patterns of pseudothecia density for both years, across site and canopy positions. Canopy position was important for 3-, and 4-year-old needles, showing less pseudothecia in the lower canopy. This research confirms that N. gaeumannii pseudothecia density is greatest in 3- and 4-year old needles in mature trees in contrast to plantations where pseudothecia density usually peaks on 2-year-old needles, and that pseudothecia density (disease severity) is generally lower in mature trees. Something about mature forest canopies and foliage appears to increase the time it takes for pseudothecia to emerge from the needles, in contrast to younger plantations, thus allowing the mature trees to have greater needle retention.

Otolith chemistry indicates age and region of settlement of immature shortspine thornyhead Sebastolobus alascanus in the eastern Pacific Ocean

Shortspine thornyhead Sebastolobus alascanus are widely distributed along the eastern Pacific coast and are assessed as a demographically homogeneous stock off the coasts of California, Oregon and Washington. The validity of this assumption has been questioned because data suggest complex ontogenetic movements. Otolith microchemistry applied to immature fish was used to determine the age of settlement and the population structure of S. alascanus. Samples were collected from 2011-2013 from bottom trawl surveys in 5 areas along the coasts of (1) Washington, (2) northern Oregon, (3) southern Oregon and northern California, (4) central California and (5) southern California. The Ba:Ca ratio, measured from the primordium to the margin of otoliths, corresponds to the pelagic and benthic phases of immature fish. This ratio decreased steadily before the formation of the first annulus and increased thereafter. Water masses along the bathymetric gradient mostly correlated with the distribution of otolith trace element (Mg:Ca, Ba:Ca) and stable isotope (δ18O and δ13C) ratios on the continental shelf. These results indicate that the population of immature fish belongs to 2 distinct groups, distributed north and south of Cape Mendocino. Accordingly, the performance of a k-nearest-neighbor classifier was highest when structured based on these 2 regions, with 94 and 69% cross-validated classification accuracy, respectively into the northern and southern groups. These results confirm that S. alascanus settle after nearly 1 yr of pelagic life and show that otolith chemistry can be used to test critical hypotheses regarding the migration and population structure of this species.

Assessing commercial fishery bait in Dungeness crab Cancer magister feeding ecology: δ13C and δ15N stable isotope and gut content analysis

Dungeness crabsCancer magistersupport the largest fishery in Oregon (USA), which inputs millions of pounds of bait into the coastal ocean every year. We assessed evidence for seasonal consumption of commercial Dungeness crab fishery bait off the Oregon coast by that target species through δ13C and δ15N stable isotope and gut content analysis. Using Dungeness crab samples collected on the Oregon inner to mid-continental shelf, variation in δ13C and δ15N values were assessed according to sex, size class, region, and season using nested ANOVA, Euclidean vector statistics, and Bayesian standard ellipse areas corrected for sample size (SEAc) in R. The isotopic signatures of sampled crabs showed statistically significant variation by sex, region, and season; the differences in the isotopic niches of large male versus female crabs (carapace width ≥159 mm) were especially pronounced. δ15N in female crabs peaked in spring and declined toward fall with similar mean δ13C, which could be indicative of higher trophic level bait consumption in the winter when the fishery is the most active, while δ13C varied seasonally in males with similar mean δ15N. The approximated trophic niches (based on SEAc) of both male and female crabs were greatest in fall, suggesting broader foraging in the absence of bait inputs. This work provides a step towards understanding the ecological role of fishery activities on one of the most economically valuable species on the US west coast.

From the redwood forest to the gulf stream waters - drought resistance in coast redwoods and giant sequoias.

From the redwood forest to the gulf stream waters - drought resistance in coast redwoods and giant sequoias.

Statistical analysis and modeling of underwater wind noise at the northeast pacific continental margin.

Approximately 11 400 h of acoustic recordings from two sites off the Oregon coast have been evaluated to characterize and model the frequency and wind dependence of wind noise in the northeast Pacific continental margin. Acoustic data are provided by two bottom-mounted broadband hydrophones (64 kHz sampling frequency) deployed at depths of 81 and 581 m at the continental shelf and slope, respectively. To describe the spectral level versus frequency relation, separate linear models for the 0.2-3 kHz and 3-25 kHz frequency range are fitted to the data. While spectral slopes for the 0.2-3 kHz range generally decrease with increasing wind speed, slopes remain constant (shallow location) or increase with increasing wind speed (deep location) above 3 kHz. The latter is in strong contrast to results from previous studies. The relation between spectral level and wind speed is described by a piecewise linear model where spectral levels are approximately constant below a critical wind speed vc and increase linearly with logarithmic wind speed above vc. It is shown that the critical wind speed and the slopes of the piecewise linear model strongly depend on the acoustic frequency.

Using a difference-in-differences and synthetic control approach to investigate the socioeconomic impacts of Oregon's marine reserves

As Marine Protected Areas (MPAs) expand in size and number, it is critical that we understand how they are impacting local communities. However, social impact evaluations on MPAs are often conducted with limited data points before and after MPA implementation, which can weaken the reliability of their results. To address this gap, we collected longitudinal American Community Survey (ACS) socioeconomic data on coastal communities and counties adjacent to marine reserves in Oregon. Oregon has both limited-take MPAs and stricter no-take marine reserves. This study focused solely on the marine reserves. We compared treatment and control units before and after marine reserve implementation using both difference-in-differences (DID) and synthetic control approaches. Each approach yielded different results, potentially providing a more complete picture of marine reserve impacts and long-term trends while also highlighting the need to consider the variability of ACS data collected from small communities. The percent of the population employed in tourism-related industries was the only significant model in both the DID and synthetic control approaches. Tourism employment increased post marine reserve implementation more in communities adjacent to the marine reserves than in more distant coastal communities. This result could indicate that marine reserves are bringing more visitors to the coast, thereby increasing the need for a more tourism-based economy. However, this may not be the case since most coastal visitors are unaware of Oregon's marine reserves and fewer than 10% of business owners think the reserves have impacted their business. An alternative hypothesis is that the marine reserves were placed near communities with a prominent land-sea connection that were already shifting their economic base to focus more on tourism. This study contributes to the literature by demonstrating how secondary data sources can be used to aid in a more comprehensive MPA impact evaluation, how two different impact evaluation approaches (i.e., synthetic control and DID) can result in differing conclusions, and how the robust synthetic control approach can be easily applied to improve MPA impact evaluations. As one element of a large-scale assessment of marine reserve impacts, this study also broadens our understanding of underlying trends on the Oregon coast and how the recently implemented marine reserves may be impacting nearby communities.

Glacial‐Isostatic Adjustment Models Using Geodynamically Constrained 3D Earth Structures

AbstractGlacial‐isostatic adjustment (GIA) is the key process controlling relative sea‐level (RSL) and paleo‐topography. The viscoelastic response of the solid Earth is controlled by its viscosity structure. Therefore, the appropriate choice of Earth structure for GIA models is still an important area of research in geodynamics. We construct 18 3D Earth structures that are derived from seismic tomography models and are geodynamically constrained. We consider uncertainties in 3D viscosity structures that arise from variations in the conversion from seismic velocity to temperature variations (factor r) and radial viscosity profiles (RVP). We apply these Earth models to a 3D GIA model, VILMA, to investigate the influence of such structure on RSL predictions. The variabilities in 3D Earth structures and RSL predictions are investigated for globally distributed sites and applied for comparisons with regional 1D models for ice center (North America, Antarctica) and peripheral regions (Central Oregon Coast, San Jorge Gulf). The results from 1D and 3D models reveal substantial influence of lateral viscosity variations on RSL. Depending on time and location, the influence of factor r and/or RVP can be reverse, for example, the same RVP causes lowest RSL in Churchill and largest RSL in Oregon. Regional 1D models representing the structure beneath the ice and 3D models show similar influence of factor r and RVP on RSL prediction. This is not the case for regional 1D models representing the structure beneath peripheral regions indicating the dependence on the 3D Earth structure. The 3D Earth structures of this study are made available.

And now, co-occurrence and functionality of discourse markers on the Oregon Coast

This paper compares the usage patterns or usage dynamics of discourse markers and their combinations in Alsea and Siuslaw, two dormant languages of the Oregon Coast with a long history of contact and convergence. Like many languages of the Pacific Northwest Coast, Alsea and Siuslaw have a set of clause-initial markers mostly used for adverbial and pragmatic functions. These markers often co-occur, and in both languages clauses in connected discourse have zero to four such markers. Despite the similar potential range for combinations, the patterns by which these markers are used in the two languages differ: discourse markers co-occur much more frequently in Alsea, in more varied combinations, and their relative order tends to be more set. We propose that this is correlated with the coding means used to structure discourse in the two languages, particularly the different functions of individual markers and of their common combinations. We illustrate this by comparing the uses of two discourse markers, Alsea tem and Siuslaw ᵘɬ roughly translatable to English by “and”, and the uses of their combination with Alsea múⁿhū and Siuslaw wàn, roughly translatable to English by “now, then”.

Little evidence for genetic variation associated with susceptibility to sea star wasting syndrome in the keystone species Pisaster ochraceus.

The keystone species Pisaster ochraceus suffered mass mortalities along the northeast Pacific Ocean from Sea Star Wasting Syndrome (SSWS) outbreaks in 2013-2016. SSWS causation remains of debate, leading to concerns as to whether outbreaks will continue to impact this species. Considering the apparent link between ocean temperature and SSWS, the future of this species and intertidal communities remains uncertain. Surveys of co-occurring apparently normal and wasting P. ochraceus along the central Oregon coast in 2016 allowed us to address whether variation in disease status showed genetic variation that may be associated with differences in susceptibility to SSWS. We performed restriction site-associated DNA sequencing (2bRAD-seq) to genotype ~72,000single nucleotide polymorphism (SNP) loci across apparently normal and wasting sea stars. Locus-specific analyses of differentiation (FST ) between disease-status groups revealed no signal of genetic differences separating the two groups. Using a multivariate approach, we observed weak separation between the groups, but identified 18 SNP loci showing highest discriminatory power between the groups and scanned the genome annotation for linked genes. A total of 34 protein-coding genes were found to be located within 15kb (measured by linkage disequilibrium decay) of at least one of the 18 SNPs, and 30 of these genes had homologies to annotated protein databases. Our results suggest that the likelihood of developing SSWS symptoms does not have a strong genetic basis. The few genomic regions highlighted had only modest levels of differentiation, but the genes associated with these regions may form the basis for functional studies aiming to understand disease progression.

Six years of low-frequency underwater noise off the Oregon coast from the OOI Regional Cabled Array System (RCA) and interpretive linkage with RCA Oceanographic Data

Approximately 6 years of underwater noise data recorded from the Regional Cabled Array (RCA) network, at the site known as Hydrate Ridge, is studied for purposes of examining long term trends. The acoustic data originate from station HYS14 located on the seabed at a depth of approximately 800 m and 80 km offshore of Newport, OR. The sample rate is 200 Hz, setting the analysis limit to less than 100 Hz. Seasonal warming results in a highly repeatable annual change in the levels at shipping frequencies (50–70 Hz) of order 4 dB which is out-of-phase with concurrent observations of shipping density. Using data from the shallow-water profiler (RCA station SF03A) the influence seasonal warming on the acoustic observations are studied. It is shown how higher ocean surface temperatures cause mode excitation support to move deeper and away typical ship source depths resulting in less efficient transmission of underwater sound. Deviations in the seasonal trends are also observed and shown to be correlated to atypical climatic events such as the warm water blob event of 2015–2016, and suppressed shipping activity during economic downturns, such as observed during COVID-19.

Estimating ocean variables using ambient noise interferometry

Ambient noise interferometry is a method of estimating the time domain Greene's function (TDGF) by correlating and averaging sound from adjacent hydrophones. These averaged cross correlations are called noise cross correlation functions (NCCFs). Noise interferometry has been used in ocean acoustics to estimate ocean variables such as water temperature by measuring propagation times. In this talk, a 6-year NCCF stack between two Ocean Observatories Initiative cabled array hydrophones is investigated. The hydrophones are separated by 3.2 km, and are bottom mounted at a depth of 1500 meters. They are located in the caldera of the Axial Seamount volcano approximately 470 km off the Oregon coast. The TDGF estimate from the NCCF stack contains clear, multipath arrivals. Fluctuations in the arrival time over the six years are on the order of a single time bin. However, if the signal to noise ratio is high enough, it is possible to measure the arrival times with more accuracy than a single time bin. In this presentation, signal processing methods to accurately estimate the propagation time will be explored, as well as the viability of inverting these multipath arrival times to estimate ocean variables such as water temperature. [Work supported by ONR.]

A comparison of EAR and SoundTrap performance for acoustic monitoring of resident killer whales

Since 2006, a network of hydrophones has been deployed along the outer coasts of Washington, Oregon, and California to improve our understanding of endangered Southern Resident killer whale (SRKW) movements outside the inland waters of the Salish Sea and refine Critical Habitat designation. During this time period, improvements in methods and equipment have resulted in longer deployments, improved ability to detect resident killer whales (RKW) and monitor their acoustic behavior, and added the capability to characterize ambient and ship noise throughout SRKW range. It is important to understand how these changes might impact the results of long term studies on RKW movements and distribution. In this study, we co-located Ecological Acoustic Recorders (EARs) and SoundTraps at five locations along the Washington coast, analyzed each data set separately, and compared the results. Preliminary analysis of these data resulted in a 1.6 to 3.4 times increase in the number of days with RKW detections in the SoundTrap data compared to the EAR data depending on location. We will present the results of this comparison, investigate potential causes of the differences between recorder type, and highlight the implications of these differences to previous knowledge of RKW movements along the Washington coast.

Abundance Trends for Adult Pacific Lamprey in Western Oregon (USA): Historic Declines, Recent Increases, and Relative Contributions from Coastal Rivers

AbstractThe anadromous Pacific Lamprey Entosphenus tridentatus is native to the northern Pacific Ocean and its drainages, returning each spring to spawn in streams along the West Coast of North America. We analyzed abundance trends of adult Pacific Lamprey from dam counts and redd surveys in western Oregon, USA. We compared a series of generalized additive models (GAMs) to describe lamprey abundance trends. Lamprey counts varied considerably among dams but showed steep declines over 70+ years (1949–2019) at Bonneville Dam on the Columbia River, over 50+ years (1965–2019) at Winchester Dam on the North Umpqua River, and over 17 years (1993–2009) at Gold Ray Dam on the Rogue River. By contrast, redd surveys displayed synchronous abundance trends of different magnitudes among geographic management areas on the Oregon coast, with an overall increasing abundance over 13 years (2007–2019). This corroborates pre‐existing notions that Pacific Lamprey spawning in Oregon coast rivers are from a single mixed population. The most supported GAM included a fixed effect for location and allowed abundance to vary over years as a function of location. These results suggest that abundance trends among dam counts are more variable than coastal redd surveys and that dam counts and redd surveys across this large region are not useful proxies for each other. Furthermore, counts across dams may be more variable because they record prespawning lamprey and thus may be recording a mixture of cohorts. Redd surveys, by contrast, provide a metric of a single cohort of spawning lamprey.

Hilltop curvature as a proxy for erosion rate: wavelets enable rapid computation and reveal systematic underestimation

Abstract. Estimation of erosion rate is an important component of landscape evolution studies, particularly in settings where transience or spatial variability in uplift or erosion generates diverse landform morphologies. While bedrock rivers are often used to constrain the timing and magnitude of changes in baselevel lowering, hilltop curvature (or convexity), CHT, provides an additional opportunity to map variations in erosion rate given that average slope angle becomes insensitive to erosion rate owing to threshold slope processes. CHT measurement techniques applied in prior studies (e.g., polynomial functions), however, tend to be computationally expensive when they rely on high-resolution topographic data such as lidar, limiting the spatial extent of hillslope geomorphic studies to small study regions. Alternative techniques such as spectral tools like continuous wavelet transforms present an opportunity to rapidly document trends in hilltop convexity across expansive areas. Here, we demonstrate how continuous wavelet transforms (CWTs) can be used to calculate the Laplacian of elevation, which we utilize to estimate erosion rate in three catchments of the Oregon Coast Range that exhibit varying slope angle, slope length, and hilltop convexity, implying differential erosion. We observe that CHT values calculated with the CWT are similar to those obtained from 2D polynomial functions. Consistent with recent studies, we find that erosion rates estimated with CHT from both CWTs and 2D polynomial functions are consistent with erosion rates constrained with cosmogenic radionuclides from stream sediments. Importantly, our CWT approach calculates curvature at least 103 times more quickly than 2D polynomials. This efficiency advantage of the CWT increases with domain size. As such, continuous wavelet transforms provide a compelling approach to rapidly quantify regional variations in erosion rate as well as lithology, structure, and hillslope sediment transport processes, which are encoded in hillslope morphology. Finally, we test the accuracy of CWT and 2D polynomial techniques by constructing a series of synthetic hillslopes generated by a theoretical nonlinear transport model that exhibit a range of erosion rates and topographic noise characteristics. Notably, we find that neither CWTs nor 2D polynomials reproduce the theoretically prescribed CHT value for hillslopes experiencing moderate to fast erosion rates, even when no topographic noise is added. Rather, CHT is systematically underestimated, producing a power law relationship between erosion rate and CHT that can be attributed to the increasing prominence of planar hillslopes that narrow the zone of hilltop convexity as erosion rate increases. As such, we recommend careful consideration of measurement length scale when applying CHT to estimate erosion rate in moderate to fast-eroding landscapes, where curvature measurement techniques may be prone to systematic underestimation.

Physiological responses of Douglas-fir to climate and forest disturbances as detected by cellulosic carbon and oxygen isotope ratios.

Swiss needle cast (SNC), caused by a fungal pathogen, Nothophaeocryptopus gaeumannii, is a major forest disease of Douglas-fir (Pseudotsuga menziesii) stands of the Pacific Northwest (PNW). There is mounting concern that the current SNC epidemic occurring in Oregon and Washington will continue to increase in severity, frequency and spatial extent with future warming. Nothophaeocryptopus gaeumannii occurs wherever its host is found, but very little is known about the history and spatial distribution of SNC and its effects on growth and physiological processes of mature and old-growth forests within the Douglas-fir region of the PNW. Our findings show that stem growth and physiological responses of infected Douglas-fir to climate and SNC were different between sites, growth periods and disease severity based on cellulosic stable carbon and oxygen isotope ratios and ring width data in tree rings. At a coastal Oregon site within the SNC impact zone, variations in stem growth and Δ13C were primarily influenced by disproportional reductions in stomatal conductance (gs) and assimilation (A) caused by a loss of functioning stomates through early needle abscission and stomatal occlusion by pseudothecia of N. gaeumannii. At the less severely infected inland sites on the west slopes of Oregon's Cascade Range, stem growth correlated negatively with δ18O and positively with Δ13C, indicating that gs decreased in response to high evaporative demand with a concomitant reduction in A. Current- and previous-years summer vapor pressure deficit was the principal seasonal climatic variable affecting radial stem growth and the dual stable isotope ratios at all sites. Our results indicate that rising temperatures since the mid-1970s has strongly affected Douglas-fir growth in the PNW directly by a physiological response to higher evaporative demand during the annual summer drought and indirectly by a major SNC epidemic that is expanding regionally to higher latitudes and higher elevations.

Survey of Fragile Geologic Features and Their Quasi-Static Earthquake Ground-Motion Constraints, Southern Oregon

ABSTRACTFragile geologic features (FGFs), which are extant on the landscape but vulnerable to earthquake ground shaking, may provide geological constraints on the intensity of prior shaking. These empirical constraints are particularly important in regions such as the Pacific Northwest that have not experienced a megathrust earthquake in written history. Here, we describe our field survey of FGFs in southern Oregon. We documented 58 features with fragile geometric characteristics, as determined from field measurements of size and strength, historical photographs, and light detection and ranging point clouds. Among the surveyed FGFs, sea stacks have particular advantages for use as ground-motion constraints: (1) they are frequently tall and thin; (2) they are widely distributed parallel to the coast, proximal to the trench and the likely megathrust rupture surface; and (3) they are formed by sea cliff retreat, meaning that their ages may be coarsely estimated as a function of distance from the coast. About 40% of the surveyed sea stacks appear to have survived multiple Cascadia megathrust earthquakes. Using a quasi-static analysis, we estimate the minimum horizontal ground accelerations that could fracture the rock pillars. We provide context for the quasi-static results by comparing them with predictions from kinematic simulations and ground-motion prediction equations. Among the sea stacks old enough to have survived multiple megathrust earthquakes (n = 16), eight yield breaking accelerations lower than the predictions, although they generally overlap within uncertainty. FGFs with the lowest breaking accelerations are distributed uniformly over 130 km of coastline. Results for inland features, such as speleothems, are in close agreement with the predictions. We conclude that FGFs show promise for investigating both past earthquake shaking and its spatial variability along the coasts of Oregon and Washington, where sea stacks are often prevalent. Future work can refine our understanding of FGF age and evolution.

Reevaluating the antiquity of the Palmrose site: Collections-based research of an early plank house on the northern Oregon Coast.

Large-scale excavations conducted by Smithsonian Institution archaeologists and avocational archaeologists during the 1960s and 1970s at three sites in Seaside, Oregon, resulted in the recovery of a diverse range of material culture curated by multiple institutions. One site, known as Palmrose (35CLT47), provides compelling evidence for the presence of one of the earliest examples of a rectangular plank house along the Oregon Coast. Previous research suggests habitation of the Palmrose site occurred between 2340 cal BC to cal AD 640. However, recent research highlights significant chronometric hygiene concerns of previously reported radiocarbon dates for the Seaside area, calling into question broader regional chronologies. This paper presents a revised chronology for the Palmrose site based on 12 new accelerator mass spectrometry (AMS) radiocarbon dates of ancient cervid bones. I evaluate these new dates and previously reported radiocarbon dates from the site, applying chronometric hygiene assessments and Bayesian statistics to build a refined chronology for the Palmrose site. Calibration of the 12 AMS radiocarbon dates suggests an initial occupation range from 345−55 cal BC and a terminal occupation range from cal AD 225−340−. Bayesian modeling of the Palmrose sequence suggests initial occupation may have spanned from 195−50 cal BC and the terminal occupation from cal AD 210−255. Modeling suggests the maximum range of occupation may span from 580−55 cal BC to cal AD 210−300 based on the start and end boundary calculations. Bayesian modeling of radiocarbon dates directly associated with the plank house deposits suggests the plank house’s occupation may have spanned from 160−1 cal BC to cal AD 170−320. The new radiocarbon dates significantly constrain the Palmrose habitation and alter regional chronologies.

Mycelial DNA persistence in a forest soil

AbstractLiving fungi can be identified and monitored in their soil habitat using an array of molecular methods. However, DNA originating from dead fungal tissue may become stabilized in the soil and remain detectable for some time after cell death rendering species detections with molecular methods difficult to interpret. Very little data exist about the persistence time of DNA from dead mycelium as it decomposes within the soil ecosystem. We placed soil containing the heat‐killed mycelium of two mycorrhizal fungal species, Phaeocollybia scatesiae A.H. Sm. & Trappe and P. fallax A.H. Sm., in mesh bags and buried them at a forested site in the Oregon Coast Range. The detectability of Phaeocollybia DNA in the soil bags was monitored over 8 months using PCR with species‐specific primers. We found that after 2 months of burial, P. scatesiae was undetectable, while P. fallax was barely detected. No Phaeocollybia DNA was detected at 3 months or thereafter. With the determination of this fungal DNA persistence time, treatment effect studies with an appropriate post‐treatment waiting period can be designed. The applicability of this fungal DNA persistence time to other studies depends on many factors, but we provide a reference point for the soil/ fungus environmental DNA system where very few exist.

Landscape Genetics of American Beaver in Coastal Oregon

ABSTRACTAmerican beaver (Castor canadensis) have been translocated for population restoration, reduction of human‐wildlife conflict, and enhancement of ecosystem function. Yet few studies have assessed dispersal of beaver, making it difficult to determine at what scale translocations are appropriate. Genetic studies can provide inferences about gene flow, and thus dispersal. We used a landscape genetic approach to evaluate whether landscape features influenced gene flow among beaver in the Coast Range of western Oregon, USA, using samples collected April–September 2014. We collected genetic samples from live‐captured (n = 232), road‐killed (n = 2) and trapper‐provided (n = 58) tissue samples and genotyped them at 10 microsatellite loci. We mapped records of beaver translocations into or within the study area during the twentieth century to consider the effect of those movements on genetic structure. We used population assignment tests to delimit genetic clusters, evaluated correspondence of those clusters with watershed boundaries and translocation history, and then estimated differentiation between clusters and between watersheds using model‐based and model‐free approaches. We evaluated how individual genetic differences varied with geographic distance, and investigated related pairs within clusters. We developed landscape resistance models incorporating slope, distance to water, and watershed boundaries at 2 scales, and estimated effective distances between sample locations with least cost path and circuit theoretic analyses. We evaluated the correlation of individual genetic distances with effective distances using a pseudo‐bootstrapping approach. Landscape genetic models did not explain spatial variation in genetic structure better than geographic distance, but hierarchical genetic structure corresponded with watershed boundaries and suggested influences from historical translocations. Pairwise individual genetic distances were positively correlated with geographic distances to 61 km; highly‐related pairs mostly were detected <1 km apart (median = 1.0 km, = 14.6 ± 2.3 [SE] km, n = 77). We concluded that slope and distance to water did not strongly limit dispersal and gene flow by beaver in this system, but concordance of genetic structure with watershed boundaries suggests that dispersal is more common within than between watersheds. Genetic differentiation of beaver within this topographically complex system was much greater than reported in a study at similar spatial scales in relatively flat topography. We recommend that translocation efforts of American beaver in topographically complex landscapes occur within watersheds when possible but conclude that dispersal can occur across watersheds. © 2021 The Wildlife Society. This article is a U.S. Government work and is in the public domain in the USA.

Predicted distribution of a rare and understudied forest carnivore: Humboldt marten (Martes caurina humboldtensis).

BackgroundMany mammalian species have experienced range contractions. Following a reduction in distribution that has resulted in apparently small and disjunct populations, the Humboldt marten (Martes caurina humboldtensis) was recently designated as federally Threatened and state Endangered. This subspecies of Pacific marten occurring in coastal Oregon and northern California, also known as coastal martens, appear unlike martens that occur in snow-associated regions in that vegetation associations appear to differ widely between Humboldt marten populations. We expected current distributions represent realized niches, but estimating factors associated with long-term occurrence was challenging for this rare and little-known species. Here, we assessed the predicted contemporary distribution of Humboldt martens and interpret our findings as hypotheses correlated with the subspecies’ niche to inform strategic conservation actions.MethodsWe modeled Humboldt marten distribution using a maximum entropy (Maxent) approach. We spatially-thinned 10,229 marten locations collected from 1996–2020 by applying a minimum distance of 500-m between locations, resulting in 384 locations used to assess correlations of marten occurrence with biotic and abiotic variables. We independently optimized the spatial scale of each variable and focused development of model variables on biotic associations (e.g., hypothesized relationships with forest conditions), given that abiotic factors such as precipitation are largely static and not alterable within a management context.ResultsHumboldt marten locations were positively associated with increased shrub cover (salal (Gautheria shallon)), mast producing trees (e.g., tanoak, Notholithocarpus densiflorus), increased pine (Pinus sp.) proportion of total basal area, annual precipitation at home-range spatial scales, low and high amounts of canopy cover and slope, and cooler August temperatures. Unlike other recent literature, we found little evidence that Humboldt martens were associated with old-growth structural indices. This case study provides an example of how limited information on rare or lesser-known species can lead to differing interpretations, emphasizing the need for study-level replication in ecology. Humboldt marten conservation would benefit from continued survey effort to clarify range extent, population sizes, and fine-scale habitat use.