Northwest Science - Accepted Articles and Notes
Northwest Science 99(1)
Native plant association with Lupinus rivularis on coarse sediments following dam removal; Elwha River, Washington - Karson Nicpon, Joey Lane, Bruce Cudkowicz, John McLaughlin
Facilitating native revegetation is important in restoration following dam removal, which exposes large areas of bare sediment vulnerable to invasion by exotic species. Coarse sediments in drained reservoirs provide a hostile growth substrate due to low moisture retention, low nutrient concentrations, low organic matter, and exposure to wind and intense sun. Revegetation on the Mills Reservoir bed, the largest restoration site in the Elwha River dam removal project, included seeding of riverbank lupine (Lupinus rivularis) to ameliorate harsh sediment conditions and facilitate succession. We assessed relationships between L. rivularis and other plants. We measured cover of native and introduced plants in coarse sediment plots stratified by three levels of L. rivularis density. We quantified relationships between lupine density and plant cover using a linear mixed model with sampling areas treated as a random factor. We evaluated relationships with species richness using a Kruskal-Wallis test. Our results revealed positive associations between L. rivularis and native species but not introduced species. The mechanism for these results needs further study, particularly determining whether the relationships are correlative or causal. Regardless of the mechanism, seeding with native nitrogen-fixing species could have broad application as dam removal projects increase in coming decades and revegetation of former reservoirs becomes a pervasive challenge.
The complete pre-print version of this article is available here.
Quaking aspen clonal expansion in the Greater Yellowstone Ecosystem - Hunter H. Holcomb, Autumn L. Keller, Dan Tyers, Daniel Z. Atwater
Quaking aspen is a widely distributed tree that provides valuable ecosystem services in Western landscapes, including forage for ungulates. It forms multi-shoot clones that can cover large areas and live for centuries. Although individual shoots die back, stands are maintained through asexual reproduction. Current threats include drought, ungulate browsing, and conifer competition. Owing to its ecological importance and sensitivity to disturbance, aspen has been the subject of a 34-year monitoring effort in the Custer-Gallatin National Forest in the Greater Yellowstone Ecosystem. To assess aspen status on this landscape, we used remote sensing to monitor changes in stand area from 1990–2023 and related the increase in 60 % of the stands to long-term changes in stand size-class composition, browsing, and conifer encroachment. Stand area in 2023 was associated with more intermediate-sized shoots and absence of encroaching conifers 18 years prior. Larger stands also tended to have more mature trees and experience less contemporaneous browsing. However, higher past browsing was associated with larger and faster-growing stands, indicating that browsing may have complex and conditional effects on aspen stand growth. Other site factors including slope, aspect, and elevation did not have detectable effects. Our results suggest that management promoting intermediate size classes and removing conifer competition could be important for the long-term health of aspen. Browsing affected stand area and structure but was not necessarily harmful. We hypothesize that intermediate browsing that stimulates suckering may be beneficial, provided it does not prevent regeneration of the mid-sized shoots that appear vital for long-term stand health.
Northwest Science 98(4)
Environmental DNA sampling identifies different nonnative and native salmonid species assemblages in two eastern Oregon wilderness areas - Ben C. Wiley, Kellie J. Carim, Kathleen G. O’Malley
Wilderness areas often provide critical habitat for native fishes. However, remoteness of wilderness areas can limit fish monitoring efforts, such that changes in nonnative and native fish distributions may not be detected and management responses may be delayed. Environmental DNA (eDNA) sampling offers a non-invasive and efficient method to monitor aquatic species across remote waterways. We used eDNA sampling and species-specific qPCR analysis to assess distributions of nonnative brook trout (Salvelinus fontinalis) and native bull trout (S. confluentus) and Columbia River redband trout (Oncorhynchus mykiss gairdneri) across sections of Monument Rock and Strawberry Mountain Wilderness Areas in eastern Oregon. In Monument Rock, we did not detect brook trout or bull trout eDNA, supporting previous findings of brook trout non-invasion and bull trout extirpation. Redband trout eDNA was detected at 29 of 34 sites despite recent environmental disturbances. Environmental DNA from all species was detected in Strawberry Mountain. Brook trout eDNA was detected at 10 of 17 sites, indicating upstream expansion of this nonnative species in Meadow Fork Big Creek. Bull trout eDNA was detected at seven sites and redband trout eDNA was detected at four sites, confirming native salmonid persistence despite decades of co-occurrence with brook trout. Brook trout eDNA concentrations were highest in samples closer to High Lake where the species was first introduced, while native salmonid eDNA concentrations were higher at locations further from the lake. This study provides baseline distributions for these species and a framework for using eDNA sampling to monitor fish distributions in remote areas.
Western oak mistletoe (Phoradendron villosum subsp. villosum) on non-native urban trees of western Oregon - David C. Shaw, Max Bennett, Don Goheen, Alan Kanaskie, Scott Altenhoff
Western oak mistletoe (Phoradendron villosum subsp. villosum) (WOM) occurs on native oaks (Quercus spp., Fagaceae) from Baja California, Mexico to the northern Willamette Valley, Oregon, USA. A variety of other native and non-native hardwoods within its native range are also hosts. We used the diverse urban forests of western Oregon (Salem, Corvallis, Eugene, Medford, Central Point, Rogue River, and Ashland) as a natural laboratory to investigate the host range of WOM and to assess the effects of WOM on tree health. During the leaf-off period of deciduous hardwood trees, we surveyed these urban forests for the occurrence of WOM in crowns of non-native trees. We collected data on tree species, tree size, height, mistletoe abundance, and tree condition. We observed WOM in 227 non-native trees, of which 85 percent were pin oak (Q. palustris) or northern red oak (Q. rubra), 12 percent were other oak species, and only 3 percent were individuals of non-oak species, despite the fact that non-oak genera represented from 81 to 96 percent of the urban trees in four cities with tree inventories. WOM tended to occur in larger trees which is consistent with the literature. We found no observable effects of mistletoe infestation on tree condition. The decision to manage WOM should involve oaks only, and depends on whether tree owners are concerned about potential negative effects of heavy infestations on tree health or desire increased biodiversity. Urban forest managers could also consider alternatives to red oak group species if WOM is abundant in the area.
The complete pre-print version of this article is available here.
Ecological, demographic, and physical characteristics of Sierra Nevada red foxes in the Oregon Cascades - Jamie L. Bowles, Corey Heath, Tim L. Hiller
Little is known about the montane subspecies, Sierra Nevada red fox Vulpes vulpes necator (SNRF). The SNRF is a habitat specialist putatively limited to sky islands of alpine and subalpine meadows and parklands in the Cascades of Oregon and California, and the Sierra Nevada of California. Populations in California have experienced substantial range contractions for unknown reasons in recent decades, complicating research and management, whereas populations in Oregon are more widespread, thereby allowing for accumulation of basic knowledge with conservation and management benefits. We collected data on radiomarked SNRF in Oregon during 2016–2020. Using a biased random bridge approach, SNRF showed patterns of larger areas used during the breeding (e.g., 95% utilization distribution, x̄ = 138.3 km2; n = 10) vs. nonbreeding (x̄ = 79.5 km2; n = 12) season. Based on selection ratios to assess second-order cover selection, SNRF most strongly selected for parkland and meadow (alpine and subalpine), woodland (alpine and subalpine), grassland (alpine and subalpine), forest (hemlock dominated), and rock (volcanic, other), regardless of season. For third-order selection, SNRF often strongly selected for developed land-cover types, potentially associated with anthropogenic food sources. The most common cause of mortality was potential predation (3 of 7 foxes), and mean annual survival probability was 0.69. Given that SNRF are generally limited to sensitive, linear-shaped alpine and subalpine areas primarily on federal lands, multi-agency coordination for management decisions are necessary to address or mitigate impacts from humans, including impacts from increasing levels of recreational use and development.