Central Oregon Research Articles

The importance of fishing opportunity to angler utility analysis in marine recreational fisheries

Abstract Managers of recreational fisheries make assumptions about what anglers value, often emphasizing factors directly related to catch. Evaluations that include both catch and non-catch aspects of recreational fishing, as well as the trade-offs between attributes that are trip-based and those that measure opportunity over a season, are rarely be incorporated into management objectives and the design of management frameworks. A study of two marine recreational fisheries in the United States, Pacific halibut in central Oregon and red snapper in northeast Florida, comprised local interviews and a limited survey of recreational anglers to evaluate the relative importance of catch rates, season length, and the uncertainty around early closures. National meeting reports, interviews, and stated-preference survey results suggested that angling opportunity in the form of longer seasons may be more important to anglers than either catch rates or the uncertainty that results from mid-season changes to fishery closure dates. Results suggest that researchers evaluating economic benefits to anglers should consider including opportunity attributes directly in angler surveys. Issues associated with limited sample sizes and a lack of intermediate attribute values limit the use of this study for direct regulatory guidance, but it instead offers a potential methodology to be applied in future analyse.

Radial Growth Rate Responses of Western Juniper (Juniperus occidentalis Hook.) to Atmospheric and Climatic Changes: A Longitudinal Study from Central Oregon, USA

Research Highlights: In this longitudinal study, we explore the impacts of changing atmospheric composition and increasing aridity on the radial growth rates of western juniper (WJ; Juniperus occidentalis Hook). Since we sampled from study locations with minimal human agency, we can partially control for confounding influences on radial growth (e.g., grazing and logging) and better isolate the relationships between radial growth and climatic conditions. Background and Objectives: Our primary objective is to determine if carbon dioxide (CO2) enrichment continues to be a primary driving force for a tree species positively affected by increasing CO2 levels circa the late 1990s. Materials and Methods: We collected data from mature WJ trees on four minimally disturbed study sites in central Oregon and compared standardized radial growth rates to climatic conditions from 1905–2017 using correlation, moving-interval correlation, and regression techniques. Results: We found the primary climate driver of radial growth for WJ is antecedent moisture over a period of several months prior to and including the current growing season. Further, the moving-interval correlations revealed that these relationships are highly stable through time. Despite a trend toward increasing aridity manifested through significant increases in maximum temperatures during the summer growing season, WJ radial growth post-1960 exceeds growth pre-1960, especially during drought years. Our results support prior conclusions that increasing atmospheric CO2 increases water-use efficiency for this semiarid species, which allows the trees to continue to grow during climatic periods negatively associated with radial growth. Conclusions: Recent studies have shown that semiarid ecosystems are important for understanding global variations in carbon uptake from the atmosphere. As WJ woodlands cover an extensive region in western North America and have undergone rapid expansion during the 20th and 21st centuries, they may become an increasingly important carbon sink.

Cognition of complexity and trade-offs in a wildfire-prone social-ecological system

Wildfire risk is a defining environmental challenge throughout much of the American West, as well as in other regions where complex social and ecological dynamics defy simple policy or management solutions. In such settings, diverse forms of land use, livelihoods, and accompanying values provide the conditions for trade-offs (e.g. between protecting homes from uncontrollable fires and restoring low-severity fire to ecosystems as a natural disturbance process). Addressing wildfire risk requires grappling with these trade-offs at multiple levels—given the need for action by individuals as well as by large and diverse stakeholder groups—and under conditions of considerable complexity. We evaluated how individual and collective perception of trade-offs varies as a function of complexity through analysis of the cognitive maps—representations of perceived causal relationships among factors that structure an individual’s understanding of a system—of 111 stakeholders in the Eastern Cascades Ecoregion of central Oregon. Bayesian statistical analysis revealed a strong tendency against perception of trade-offs in individual maps, but not in a collective map that resulted from the aggregation of all individual cognitive maps. Furthermore, we found that lags (the number of factors that mediated the effect of an action on multiple valued outcomes) limited perception of trade-offs. Each additional intervening factor decreased the likelihood of a trade-off by approximately 52% in individual cognitive maps and by 10% in the collective cognitive map. However, the heterogeneity of these factors increased the likelihood of perception of trade-offs, particularly among individual cognitive maps, for which each unit increase of the Shannon diversity index translated into a 20-fold increase in the likelihood of perception of trade-offs. Taken together, these results suggest that features of complexity have distinct effects on individual—and collective-level perception of trade-offs. We discuss implications for wildfire risk decision-making in central Oregon and in other complex wildfire-prone social-ecological systems.

Cost-effective fuel treatment planning: a theoretical justification and case study

Modelling the spatial prioritisation of fuel treatments and their net effect on values at risk is an important area for applied work as economic damages from wildfire continue to grow. We model and demonstrate a cost-effective fuel treatment planning algorithm using two ecosystem services as benefits for which fuel treatments are prioritised. We create a surface of expected fuel treatment costs to incorporate the heterogeneity in factors affecting the revenue and costs of fuel treatments, and then prioritise treatments based on a cost-effectiveness ratio to maximise the averted loss of ecosystem services from fire. We compare treatment scenarios that employ cost-effectiveness with those that do not, and use common tools and models in a case study of the Sisters Ranger District on the Deschutes National Forest in central Oregon, USA. Using cost-effectiveness not only increases the expected averted losses from fuel treatments, but it also allows a larger area to be treated for the same cost, simply by incorporating costs and cost-effectiveness into the prioritisation routine. These results have considerable implications for policymakers and land managers trying to minimise risk. Incorporating costs into the spatial planning of treatments could allow more effective outcomes without increasing fuel treatment budgets.

Ecosystem carbon in relation to woody plant encroachment and control: Juniper systems in Oregon, USA

The encroachment of western juniper (Juniperus occidentalis) trees represents a substantial problem in Oregon rangelands because of the displacement of understory vegetation of importance to wildlife and livestock. Therefore, the control of this species is a common ecological restoration practice. However, western juniper control may also affect the carbon sequestration capacity for an area, although this effect is not well understood. Our study site was a paired watershed in central Oregon where western juniper trees were cut in one watershed (treated, 116 ha) and were left intact in another (untreated, 96 ha). Thirteen years after control, we quantified aboveground carbon stocks for western juniper trees, shrubs, grasses, and litter in both the treated and untreated watersheds. We also quantified belowground carbon stocks (roots and soil) in both watersheds at two soil depths (0−25 cm and 25−50 cm). Aboveground carbon stocks were 5.8 times greater in the untreated than in the treated watershed. On the other hand, root carbon stocks were 2.6 times greater in the treated than in the untreated watershed. Soil carbon stocks at both 0−25 cm and 25−50 cm depth were not affected by juniper control. Overall, total ecosystem carbon stocks (average 137.6 Mg C ha−1) were not different between watersheds. Most carbon resided belowground (soil 0−50 cm and roots); 84% and 97% of the total ecosystem carbon, respectively, was found in the untreated and treated watershed. Juniper control represents benefits such as habitat restoration for native wildlife, increased forage for livestock, and restoration of hydrological functions. Our study provides basis to suggest that the benefits of juniper control can be attained without substantially affecting the potential for ecosystem carbon sequestration.

Judge decides administrators might have been reckless

Case name: Sawyer, et al. v. Central Oregon Community College, et al., No. 6:17‐cv‐1150 (D. Or. 06/11/18).

Widespread severe wildfires under climate change lead to increased forest homogeneity in dry mixed‐conifer forests

AbstractClimate warming in the western United States is causing changes to the wildfire regime in mixed‐conifer forests. Rising temperatures, longer fire seasons, increased drought, as well as fire suppression and changes in land use, have led to greater and more severe wildfire activity, all contributing to altered forest composition over the past century. To understand future interactions among climate, wildfire, and vegetation in a fire‐prone landscape in the southern Blue Mountains of central Oregon, we used a spatially explicit forest landscape model, LANDIS‐II, to simulate forest and fire dynamics under current management practices and two projected climate scenarios. The results suggest that wildfires will become more frequent, more extensive, and more severe under projected climate than contemporary climate. Furthermore, projected climate change generated a 20% increase in the number of extreme fire years (years with at least 40,000 ha burned). This caused large shifts in tree species composition, characterized by a decline in the sub‐alpine species (Abies lasiocarpa, Picea engelmannii, Pinus albicaulis) and increases in lower‐elevation species (Pinus ponderosa, Abies grandis), resulting in forest homogenization across the elevational gradient. This modeling study suggests that climate‐driven increases in fire activity and severity will make high‐elevation species vulnerable to decline and will reduce landscape heterogeneity. These results underscore the need for forest managers to actively consider climate change, altered fire regimes, and projected declines in sub‐alpine species in their long‐term management plans.

Small carnivoran fauna of the Mascall Formation, Crooked River Basin, central Oregon

ABSTRACTThe Hemingfordian North American Land Mammal Age is a poorly known time period, although recently discovered sites in central Oregon have begun to cast light on a diverse mammalian fauna. Here, we describe four small carnivorans new to this region, one of which is a new species. Cryptailurus tinaynakti, sp. nov., is a hypercarnivorous feliform. UOMNH F-70218 is the dp4 of a diminutive mustelid similar in morphology to that of extant martens, but likely of a new species based upon discussed patterns in mustelid deciduous dentition. The occurrence of two additional species, Leptocyon leidyi and Bassariscus antiquus, increases both their geographic and temporal ranges. The early to middle Miocene was a time of transition from sparse woodland to grassland ecosystems in much of North America. The Hemingfordian fauna of the Pacific Northwest inhabited a diverse wet woodland ecosystem, surprisingly rich in carnivorans. With the description of these additional small taxa, we can now get a clearer picture of what must have been a diverse assemblage of mammals with a variety of ecological roles in an undersampled period of time.

Using generalized additive models for interpolating microclimate in dry-site ponderosa pine forests

Microclimate in the understory of forests can be an important mediating influence for ecological attributes such a vegetation composition, wildlife habitat, fuel moisture, and downed wood and forest floor decomposition processes. Several tools exist for interpolating data from regional, broad-scale weather stations to derive geospatial climate surface maps representing mesoclimate variations at the earths’ surface. While useful, these tools typically do not provide interpolations that account for variations in forest canopy cover and therefore often fail to provide for higher resolution characterization of near-surface, understory microclimate conditions. In this paper we explore the development of understory microclimate surface maps from a dispersed set of microclimate sensors in a 991-ha managed landscape dominated by ponderosa pine forest patches of various densities in central Oregon, USA. We used generalized additive models (GAM) to interpolate microclimate at 50 m resolution from 2013 to 2016 using elevation, heat load, and normalized difference vegetation index (NDVI) as covariates. Models for all years revealed that air temperature trends were dependent on complex interactions of forest cover, site physiography and time, and produced interpolations closer to observed conditions than freely available coarse-scale models. We analyzed sub-canopy air temperature interpolation maps for trends in the context of differing canopy structures arising from five fuels mitigation treatments implemented between 2011–2014. Variations in NDVI within the treatments had statistically significant and visually discernible influence on sub-canopy temperature as evidenced by spatial temperature trends that were congruent with NDVI maps, and indicates the model accounted for the influence of canopy. The ability to develop higher resolution understory microclimate surface maps is of value to many aspects of ecosystem monitoring and the methods presented here may be of use to researchers and managers who work in forested environments.

Space use of Pacific harbor seals (Phoca vitulina richardii) from two haulout locations along the Oregon coast.

BackgroundThere are approximately 10,000–12,000 Pacific harbor seals (Phoca vitulina richardii) inhabiting the Oregon coast, and unlike other species of pinnipeds in this region, are reliably present year-round. Despite this, and drastic rebounds in population since the enactment of the Marine Mammal Protection Act, limited data is available for the present period regarding their space use at sea, and within estuarine, riverine, or bay areas within the state.ObjectiveTo examine site-based differences in space use for 24 adult Pacific harbor seals captured and outfitted with satellite transmitters at two predominant haulout sites on the Oregon Coast, USA.DesignWe captured 24 adult harbor seals from two haulout sites on the Central Oregon coast between September 2014–16 and fitted them with external Wildlife Computers SPOT5 satellite transmitters to track movement. Using state-space modeled locations derived from satellite telemetry data, we evaluated spatial behavior of these animals using a correlated random walk model via R package crawl. Kernel density estimation was subsequently used to calculate home range and core area for each animal. Percent use of open ocean habitat versus use of estuaries, rivers and bays was quantified, as was an initial examination of presence within five newly-established marine reserves in Oregon. Examination of haulout site-related differences in spatial behavior were examined for seals captured in Netarts and Alsea Bays, Oregon and haul out behavior related to time of day, season, and tidal level was also investigated.ResultsThe average individual home range for seals was 364.47 ± 382.87 km2 with seals captured in Alsea bay demonstrating a significantly higher home range area than those captured in Netarts Bay. Alsea bay seals also tended to range farther from shore than Netarts Bay animals. The average calculated core area for seals encompassed on average 29.41 ± 29.23 km2 per animal, however the home range of one animal was so small, core area could not be calculated. Use of marine reserves was limited for animals in this study, representing less than 2% of locations with a majority occurring in Cape Perpetua Marine Reserve and North Marine Protected Area. Seals were more likely to haul out during low tides and periods of low light (dusk, night and dawn), and hauling out behavior increased in winter months.SignificanceThese findings demonstrate the first major documentation of space use of harbor seals in the state for nearly three decades, and lends itself to future comparison and formation of mechanistically-based hypotheses for behavior of a common marine mammal in the highly productive northern California Current System.

Retracted: Factors Influencing Angler Satisfaction and Catch Rates in Arizona Stream Put‐and‐Take Trout Fisheries

AbstractThe following article has been retracted by agreement between the authors, Zachary S. Beard and Ryan D. Mann, the journal editor‐in‐chief, Daniel J. Daugherty, and the American Fisheries Society:“Factors Influencing Angler Satisfaction and Catch Rates in Arizona Stream Put‐and‐Take Trout Fisheries,” by Zachary S. Beard and Ryan D. Mann, Early View. DOI: 10.1002/nafm.10322.The retraction has been agreed to due to unattributed overlap between this article and the following article published in the North American Journal of Fisheries Management:Volume 34(5), October 2014: “Effect of Fishing Success on Angler Satisfaction on a Central Oregon Rainbow Trout Fishery: Implications for Establishing Management Objectives,” by Joshua L. McCormick and Timothy K. Porter, pages 938–944. DOI: 10.1080/02755947.2014.932869.

Differential Species Responses to Aspects of Resistance to Invasion in Two Columbia Plateau − Protected Areas

Protected-area sagebrush steppe ecosystems are few in number and increasingly important to the North American conservation network as sagebrush steppe faces growing threats from land use, climate change, and invasive species. We analyzed the distribution and abundance of native perennial and invasive annual plants to better understand patterns of plant invasion within two protected areas: John Day Fossil Beds National Monument (JODA), located in central Oregon, and Craters of the Moon National Monument and Preserve (CRMO), located in southeast Idaho. We used multivariate analysis to examine vegetation monitoring datasets and illuminate geographic variation in plant cover along gradients of well-known aspects of resistance to plant invasion (elevation, exposure [slope and aspect], precipitation and proximity to disturbance). Topographically mediated resistance to invasion appeared to manifest in the park with greater topographic variability (JODA), while increased elevation was more strongly associated with resistant sites in the park, which spanned a greater elevational gradient (CRMO). Factors that may mitigate moisture-mediated resistance also differed between sites. Slope and aspect were factors of apparent resistance for bunchgrass communities in JODA, while high crop year precipitation appeared to benefit medusahead (Taeniatherum caput-medusae [L.] Nevski) and the weedy native subshrub broom snakeweed (Gutierrezia sarothrae [Pursh] Britton & Rusby) over bunchgrasses and Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young). Increased elevation and distance to disturbed areas were the most important factors of resistance in forb-rich communities at CRMO, with the invasive annuals cheatgrass (Bromus tectorum L.), tumblemustard (Sisymbrium altissimum L.), and Descurainia spp. Webb & Bethel. invading in low elevations and in close proximity to roads or agricultural fields. Such complexity underscores the idiosyncratic nature of the manifestation of resistance and the need for place-based empirical studies to provide information for guiding protected-area management.

Plume-modified mantle flow in the northern Basin and Range and southern Cascadia back-arc region since ca. 12 Ma

AbstractBimodal volcanism and rhyolite migration along the High Lava Plains in central Oregon (United States) lie above a broader feature defined by low seismic velocity in the upper mantle that emanates from the Yellowstone hotspot (northwest United States) and extends westward across the northern Basin and Range. It was emplaced by a westward current, driven in part by rapid buoyancy-driven flow across the east-west cratonic boundary of North America. Geothermometry studies and geochemical considerations suggest that the low-velocity feature may be composed of moderately hot, low-density mantle derived from the Yellowstone plume but diluted by thermomechanical erosion and entrainment of colder mantle lithosphere. Finger-like conduits of plume-modified mantle beneath Quaternary eruption sites delineate flow-line channels that have developed across the broader mantle structure since 2 Ma. These channels have allowed low-density mantle to accumulate against the Cascades arc, thus providing a heated mantle source for mafic magmatism in the Newberry (Oregon) and Medicine Lake (California) volcanic fields.

Biotic factors influencing the unexpected distribution of a Humboldt marten (Martes caurina humboldtensis) population in a young coastal forest.

Pacific martens (Martes caurina) are often associated with mature forests with complex structure for denning, resting, and efficient hunting. Nonetheless, a small isolated population of the Humboldt subspecies of Pacific martens (Martes caurina humboldtensis) occupies a narrow strip of young, coastal forest (< 70 years old) but not inland mature forest in the central Oregon Coast Range. We examined factors contributing to this unexpected distribution of martens by 1) analyzing marten diets using DNA metabarcoding to assess 90 scats, 2) using camera traps to assess differences in the relative abundances of prey, competitors, and predators across a coastal to inland gradient of vegetation types, and 3) quantifying differences in extent of fruit-producing shrubs and vegetation structure within vegetation types. Diets of martens were diverse (12, 10, and 3 species of birds, mammals, and amphibians respectively), and most fall and winter scats contained fruit. Voles, mice, and varied thrushes (Ixoreus naevius) were dominant prey items. Voles, mice, and most birds, but not varied thrushes, were more commonly observed in the coastal shrub-dominated forest than in inland forest. The coastal shrub-dominated forest had the highest diversity of vertebrates and potential prey overall. Bobcats (Lynx rufus), a key potential predator, were more commonly detected in inland forest. Of potential competitors, western spotted skunks (Spilogale gracilis) were more commonly detected in inland forest, with gray foxes (Urocyon cinereoargenteus) and raccoons (Procyon lotor) detected almost exclusively in coastal forests. Vegetation in coastal forests appears to provide, at least seasonally, more prey and fruit, and more overhead shrub cover compared with inland forest. Remaining plausible hypotheses for the restricted distribution of marten to coastal forests include increased prey, fruit, and overhead cover, and reduced predation risk from bobcats.

Water Stress Patterns of Xerophytic Plants in an Urban Landscape

Efficient water use in urban landscapes is a common objective throughout the western United States. Vegetative species promoted for their drought tolerance characteristics are often included in landscapes designed for resource conservation. However, water requirements of most common landscape species have not been quantified. This is especially true for xerophytic species. This lack of landscape plant water requirement data is a significant constraint on the design of efficient irrigation systems and management practices affecting urban landscape water use. Current irrigation practices often fail to consider the unique physiology of xerophytic species, and irrigation scheduling models may not be appropriate for xeric landscapes using xerophytic vegetation as the primary method of reducing water use. This work describes the seasonal patterns of growth and xylem water status for four regionally native xeric shrub species planted in an unirrigated urban landscape in the semi-arid environment of central Oregon. The four species (Artemisia tridentata, Holodiscus microphyllus, Ericameria nauseosa, and Ribes cereum) exhibited substantial growth over the course of 18 months without irrigation in a heavily modified urban soil profile. Water potential of the four species was strongly correlated with surface (10 cm) soil moisture (r ≥ 0.90), less so with reference monthly evapotranspiration (r ≤ 0.55), and only weakly with water vapor deficit (r ≤ 0.22). In A. tridentata and H. microphyllus, xylem water potential became more negative during the growing season and tracked the seasonal decline in soil moisture. In contrast, the xylem water potential of E. nauseosa and R. cereum tracked soil moisture early in the season but became less responsive to soil moisture in the driest months, suggesting different drought adaptation strategies in these species. Three of the four species showed no visual signs of drought stress and maintained acceptable aesthetics even as soil moisture decreased to less than 10%. However, R. cereum exhibited a drought dormancy strategy that made it less aesthetically desirable. These results suggest that extreme xerophytic shrubs provide an opportunity for significant reductions in water use in urban landscapes.

Middle Holocene menus: dietary reconstruction from coprolites at the Connley Caves, Oregon, USA

Multiproxy data from coprolites at the Connley Caves in central Oregon provide new evidence for diet, seasonal subsistence strategies, and human health during the middle and late Holocene. Macrobotanical, palynological, and faunal components show that plant taxa from wetland and dryland habitats functioned as dietary staples. Repeated and abundant representation of wetland resources coupled with small dryland seeds provide strong evidence for dietary continuity between ~ 5700 and 3200 calendar years ago. Seasonal availability of represented taxa indicates late summer and early fall habitation. Minimal evidence for parasitic infection and unusual constituents such as cordage raise questions regarding health and cultural behavior. As the first coprolite analysis for this time period in the northern Great Basin, this study contributes unique datasets that complement and clarify the regional understanding of hunter-gatherer settlement-subsistence strategies and food economy.

Describing Fine‐Scale Patterns of Genetic Structure and Introgression of Redband Trout in a Complex River System

AbstractThe conservation status of Redband Trout Oncorhynchus mykiss gairdneri has been an increasing concern of fish managers. Effective fish management first requires an understanding of the spatial distribution of distinct populations and the processes influencing gene flow. We performed a genetic analysis of Redband Trout from the Deschutes River basin in central Oregon to discern population genetic structure and the genetic impacts of an extensive hatchery stocking program and several potential barriers to dispersal. Conducting surveys in lateral habitats, we sampled over 1,400 young‐of‐the‐year Redband Trout and genotyped them at a panel of 269 SNPs using genotyping‐in‐thousands by sequencing. We found that within this section of the Deschutes River basin there were multiple distinct genetic groups of Redband Trout, with an irrigation diversion dam and only one of eight waterfalls in the study area acting as complete barriers to gene flow. Within these distinct genetic groups there was a strong signal of isolation by distance. Despite the extensive stocking of large numbers out‐of‐basin hatchery Rainbow Trout Oncorhynchus mykiss, our results indicated that introgression of wild fish occurred only with a locally derived hatchery strain of Redband Trout. Hatchery influence was greatest in Fall River and in neighboring portions of the Deschutes River. The combination of spatially explicit sampling in lateral habitat with genotyping via high‐throughput sequencing provided an effective sampling design for this large river and its tributaries. Such an approach may be useful elsewhere for identifying genetic management units of Redband Trout and other widespread freshwater fishes.

Investigating old-growth ponderosa pine physiology using tree-rings, δ13 C, δ18 O, and a process-based model.

In dealing with predicted changes in environmental conditions outside those experienced today, forest managers and researchers rely on process‐based models to inform physiological processes and predict future forest growth responses. The carbon and oxygen isotope ratios of tree‐ring cellulose (δ13Ccell, δ18Ocell) reveal long‐term, integrated physiological responses to environmental conditions. We incorporated a submodel of δ18Ocell into the widely used Physiological Principles in Predicting Growth (3‐PG) model for the first time, to complement a recently added δ13Ccell submodel. We parameterized the model using previously reported stand characteristics and long‐term trajectories of tree‐ring growth, δ13Ccell, and δ18Ocell collected from the Metolius AmeriFlux site in central Oregon (upland trees). We then applied the parameterized model to a nearby set of riparian trees to investigate the physiological drivers of differences in observed basal area increment (BAI) and δ13Ccell trajectories between upland and riparian trees. The model showed that greater available soil water and maximum canopy conductance likely explain the greater observed BAI and lower δ13Ccell of riparian trees. Unexpectedly, both observed and simulated δ18Ocell trajectories did not differ between the upland and riparian trees, likely due to similar δ18O of source water isotope composition. The δ18Ocell submodel with a Peclet effect improved model estimates of δ18Ocell because its calculation utilizes 3‐PG growth and allocation processes. Because simulated stand‐level transpiration (E) is used in the δ18O submodel, aspects of leaf‐level anatomy such as the effective path length for transport of water from the xylem to the sites of evaporation could be estimated.

The Use of Low-Altitude UAV Imagery to Assess Western Juniper Density and Canopy Cover in Treated and Untreated Stands

Monitoring vegetation characteristics and ground cover is crucial to determine appropriate management techniques in western juniper (Juniperus occidentalis Hook.) ecosystems. Remote-sensing techniques have been used to study vegetation cover; yet, few studies have applied these techniques using unmanned aerial vehicles (UAV), specifically in areas of juniper woodlands. We used ground-based data in conjunction with low-altitude UAV imagery to assess vegetation and ground cover characteristics in a paired watershed study located in central Oregon, USA. The study was comprised of a treated watershed (most juniper removed) and an untreated watershed. Research objectives were to: (1) evaluate the density and canopy cover of western juniper in a treated (juniper removed) and an untreated watershed; and, (2) assess the effectiveness of using low altitude UAV-based imagery to measure juniper-sapling population density and canopy cover. Ground- based measurements were used to assess vegetation features in each watershed and as a means to verify analysis from aerial imagery. Visual imagery (red, green, and blue wavelengths) and multispectral imagery (red, green, blue, near-infrared, and red-edge wavelengths) were captured using a quadcopter-style UAV. Canopy cover in the untreated watershed was estimated using two different methods: vegetation indices and support vector machine classification. Supervised classification was used to assess juniper sapling density and vegetation cover in the treated watershed. Results showed that vegetation indices that incorporated near-infrared reflectance values estimated canopy cover within 0.7% to 4.1% of ground-based calculations. Canopy cover estimates at the untreated watershed using supervised classification were within 0.9% to 2.3% of ground-based results. Supervised classification applied to fall imagery using multispectral bands provided the best estimates of juniper sapling density compared to imagery taken in the summer or to using visual imagery. Study results suggest that low-altitude multispectral imagery obtained using small UAV can be effectively used to assess western juniper density and canopy cover.

Effects of underburning on habitat use of mule deer during migration

ABSTRACTMule deer (Odocoileus hemionus hemionus) populations have been declining throughout their range and deteriorating habitat conditions are likely one cause of these declines. Reductions in food and cover availability along traditional routes may especially influence habitat use during migration by mule deer. Forest management practices such as underburning, the practice of using low‐severity fires to reduce fuel loads, are often assumed to be beneficial to deer through enhancement of forage quality and quantity. However, these practices may be detrimental to mule deer through decreases in food and cover availability. Currently, little is known about the effects of underburning on habitat use by mule deer during migration. We analyzed Global Positioning System tracking data from 187 adult female mule deer in central Oregon, USA, from 2005 to 2012 in relation to 243 areas that were underburned between 1977 and 2009 to assess effects of underburning on habitat use during seasonal migrations. During spring migration, mule deer decreased use of recently underburned (i.e., ≤7 years‐since‐burned) areas compared with pretreatment use. There was not a difference in use of recently underburned areas before and after treatment during autumn migration. In spring, the proportion of used underburned areas declined postburn without recovering to preburn levels up to 20 years after treatment. The proportion of underburned areas used in autumn was much more variable, with use of postburn areas fluctuating above the preburn mean but never reaching the preburn maximum. We contend that reductions in forage and cover availability from underburning may negatively affect migrating mule deer, especially during spring. Thus, efforts should be taken to minimize burning large, continuous areas along migration routes and avoid burning adjacent areas during the same year to maintain a diverse mosaic of understory age classes, which will allow deer to make habitat use choices during migration. © 2019 The Wildlife Society.