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Coastal marsh vegetation is an important component in maintaining marsh stability that is threatened by changes in sedimentation, sea level rise, natural and anthropogenic disturbances, and competition ...
Citation Citation
- Title:
- The Response and Effect of Emergent Coastal Vegetation to Sedimentation and the Distribution of Coastal Vegetation Communities along Environmental Gradients
- Author:
- Lemein, Todd
Coastal marsh vegetation is an important component in maintaining marsh stability that is threatened by changes in sedimentation, sea level rise, natural and anthropogenic disturbances, and competition from invasive species. Vegetation has been demonstrated to reduce wave energy, increase sedimentation, and decrease erosion in tidal environments under a range of conditions. Similarities and differences between the morphology of vegetation species may play an important role in understanding the mechanism between vegetation, sedimentation, and wave energy. Diversity of species within vegetation communities has been shown to reduce the success of biological invasions from invasive species as well as increase the ability of the community to adapt to environmental changes such as inundation period (period of time vegetation is submerged partially or fully by water). The species present along coastal marshes and specifically at the interface between vegetated marsh and unvegetated mudflat provide an opportunity to better understand the interactions between vegetation and its physical setting. In this dissertation I focus on the species and vegetation communities that are present at this interface of the terrestrial and aquatic boundary to better understand how plant communities may be characterized, how they respond to disturbance, how they are distributed, and how they may influence the physical environment in which they grow. In Chapter two, I explore the ability to use image analysis and the lateral obstruction of vegetation to describe a species density, height and diameter and evaluate the tradeoffs in using image analysis over more traditional methods. In Chapter three, I evaluate the response of an emergent vegetation species, threesquare bulrush (Schoenoplectus pungens), to different depths of complete burial as could be expected from extreme storms, hurricanes, tsunamis, or restoration efforts involving sediment amendment. Chapter four describes the distribution of coastal marsh communities of the Laurentian Great Lakes along an elevational gradient beginning at the terrestrial and aquatic boundary, identifying patterns of wetland distribution, species composition, and exotic plant invasion. In Chapter five, I conclude the dissertation with an evaluation of the effects of two morphologically distinct species of emergent marsh vegetation, threesquare bulrush and Lyngbye’s sedge (Carex lyngbyei), on the sedimentation rate and variability in Tillamook Bay, OR and compare the results to the current understanding of vegetation-sediment feedback. In Chapter two, I found that for morphologically simple species, such as S. pungens, image analysis of lateral obstruction can be used to determine important morphological characteristics of a stand of vegetation including the mean stem height, density, and mean diameter. The method provides a description of the vertical variation in morphologic structure, providing a rapid analytic tool for exploring the effects of vegetation on wave and sediment interaction. However, I note that more morphologically complex species, such as sedges and grasses may not be as easily described using image analysis. In Chapter three, I determined that aboveground biomass of S. pungens would return to pre-disturbance levels following burial by up to 40 cm of mineral sediment after two years. Vegetation was observed to survive burials depths of up to 80 cm, although initially at much lower density. The aboveground height of stems were statistically similar to unburied controls after two years, which is important for the continuation of ecosystem services such as wave attenuation. The results suggest that S. pungens is capable of returning to pre-disturbance levels of biomass following large natural sedimentation events such as extreme storms, hurricanes, or tsunamis, and that burying portions of marshes with sediment as a restoration tool is not likely to harm the buried vegetation. In Chapter four I refine and describe 21 coastal vegetation communities in the Laurentian Great Lakes and the ecological gradients along which they are distributed. Latitude, agricultural intensity, site geomorphology, substrate, and water depth were found to be the significant variables that determined community distribution. Additionally, we observed an expansion of invasive plant species near areas of high anthropogenic activity such as farms and urban centers. In Chapter five, I found that there were species-specific differences in sedimentation rate and variability in Tillamook Bay, OR. Schoenoplectus pungens was found to retain more sediment than C. lyngbyei. Sedimentation rate was observed to be variable by location within the estuary. Two patterns of sediment accumulation were observed. The first occurred along vegetation gradients, with increased sedimentation farther into vegetation beds. In the second pattern, sediment accumulation was observed to be greatest at the marsh/mudflat boundary where vegetation was dense and then decreased with increasing depth into the vegetation. In conclusion, this dissertation explores the interaction of emergent wetland vegetation with environmental factors. Image analysis provides a new tool for rapid characterization of vegetation structure, a burial experiment documents Schoenoplectus pungens’ tolerance to sand burial, a field study at Tillamook, OR documents the relationship between sediment accumulation and emergent vegetation beds, and a wetland classification is developed for coastal wetlands along the Great Lakes, which includes plant communities dominated by S. pungens.
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12312. [Article] Effects of spatial scale and heterogeneity on avian occupancy dynamics and population trends in forested mountain landscapes
Population trends and patterns in species distributions are the major currencies used to examine responses by biodiversity to changing environments. Effective conservation recommendations require that ...Citation Citation
- Title:
- Effects of spatial scale and heterogeneity on avian occupancy dynamics and population trends in forested mountain landscapes
- Author:
- Frey, Sarah Jean Kiuama
Population trends and patterns in species distributions are the major currencies used to examine responses by biodiversity to changing environments. Effective conservation recommendations require that models of both distribution dynamics and population trends accurately reflect reality. However, identification of the appropriate temporal and spatial scales of animal response, and then obtaining data at these scales present two major challenges to developing predictive models. In heterogeneous forested mountain landscapes I examined: A) the relative drivers of climatic variability at fine spatial scales under the forest canopy ('microclimate'), B) the influence of microclimate on local-scale occupancy dynamics of bird communities, and C) the effects of spatial scale and imperfect bird detection on long-term avian population trends. Climate change has been predicted to cause widespread biodiversity declines. However, the capacity of climate envelope models for predicting the future of biodiversity has been questioned due to the mismatch between the scale of available data (i.e., global climate models) and the scales at which organisms experience their environment. Local-scale variation in microclimate is hypothesized to provide potential ‘microrefugia’ for biodiversity, but the relative role of elevation, microtopography, and vegetation structure in driving microclimate is not well known. If the microrefugia hypothesis is true, I expected to see areas on the landscape that remained relatively cooler (i.e., buffered sites). To test this, I collected temperature data at 183 sites across elevation and forest structure gradients in complex terrain of the H. J. Andrews Experimental Forest in the Cascade Mountains of Oregon, USA (Chapter 2). I used boosted regression trees, a novel machine learning approach, to determine the relative influence of vegetation structure, microtopography, and elevation as drivers of microclimate and mapped fine-scale distributions of temperature across the landscape. Models performed extremely well on independent data - cross-validation correlations between testing and training data were 0.69 - 0.98 for ten selected climate variables. Elevation was the dominant driver in fine-scale microclimate patterns, although vegetation and microtopography also showed substantial relative influences. For instance, during the spring-summer transition, maximum monthly temperatures observed in old-growth sites were 2.6°C (95% CI: 1.8 - 3.3°C) cooler than plantation sites and minimum temperatures during winter months were 0.6°C (95% CI: 0.4 - 0.8°C) warmer. This suggests that older forest stands mediate changes in temperature by buffering against warming during summer months and moderating cold temperatures during the winter. Climate is generally considered most influential on species distributions at large spatial scales; however much microclimate variability exists within regional patterns. I tested whether this high degree of microclimate variability has relevance for predicting species distributions and occupancy dynamics of the Andrews Forest bird community. I collected bird occurrence data in 2012 and 2013 at all 183 sites with fine-scale temperature measurements. I used dynamic occupancy models to test the effects of temperature on occupancy and apparent within-season bird movement while statistically accounting for vegetation effects and imperfect bird detection (Chapter 3). Most species (87%) exhibited within-season shifts in response to local-scale temperature metrics. Effects of temperature on within-season occupancy dynamics were as large or larger (1 to 1.7 times) than vegetation. However, individual species were almost as likely to shift toward warmer sites as toward cooler sites, suggesting that microclimate preferences are species-specific. My results emphasize that high-resolution temperature data provide valuable insight into avian distribution dynamics in montane forest environments and that microclimate is an important variable in breeding season habitat selection by forest birds. I hypothesize that microclimate-associated distribution shifts may reflect species' potential for behavioral buffering from climate change in complex terrain. Factors influencing population trends often differ depending on the spatial scale under consideration. Further, accurate estimation of trends requires accounting for biases caused by imperfect detection. To test the degree to which population trends are consistent across scales, I estimated landscape-scale bird population trends from 1999-2012 for 38 species at the Hubbard Brook Experimental Forest (HBEF) in the White Mountains of New Hampshire, USA and compared them to regional and local trends (Chapter 4). I used a new method - open-population binomial mixture models - to test the hypothesis that imperfect detection in bird sampling has the potential to bias trend estimates. I also tested for generalities in species responses by predicting population trends as a function of life history and ecological traits. Landscape-scale trends were correlated with regional and local trends, but generally these correlations were weak (r = 0.12 - 0.4). Further, more species were declining at the regional scale compared to within the relatively undisturbed HBEF. Life history and ecological traits did not explain any of the variability in the HBEF trends. However, at the regional scale, species that occurred at higher elevations were more likely to be declining and species associated with older forests have increased. I hypothesize that these differences could be attributed to both elevated rates of land-use change in the broader region and the fact that the structure of regional data did not permit modeling of imperfect detection. Indeed, accounting for imperfect detection resulted in more accurate population trend estimates at the landscape scale; without accounting for detection we would have both missed trends and falsely identified trends where none existed. These results highlight two important cautions for trend analysis: 1) population trends estimated at fine spatial scales may not be extrapolated to broader scales and 2) accurate trends require accounting for imperfect detection.
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12313. [Article] Active tectonics of the Kashmir Himalaya (NW India) and earthquake potential on folds, out-of-sequence thrusts, and duplexes
Active tectonics of a deformation front constrains the kinematic evolution and structural interaction between the fold-thrust belt and the most-recently accreted foreland basin. At the Himalayan deformation ...Citation Citation
- Title:
- Active tectonics of the Kashmir Himalaya (NW India) and earthquake potential on folds, out-of-sequence thrusts, and duplexes
- Author:
- Gavillot, Yann G.
Active tectonics of a deformation front constrains the kinematic evolution and structural interaction between the fold-thrust belt and the most-recently accreted foreland basin. At the Himalayan deformation front, the thrust front is blind, characterized by a broad fold (the Suruin-Mastgarh anticline (SMA)), and displays no emergent faults cutting the southern limb. Dated deformed terraces on the Ujh River constrain the structural style of deformation and shortening rates. Six terraces are recognized, and three yield OSL ages of 53 ka, 33 ka, and 0.4 ka. Terrace restorations through long profiles reveal a deformation pattern characterized by uniform uplift across the anticlinal axis and northern limb, and variable uplift due to rotation of the southern limb. Offset terraces occur between the fold trace and the northern limb. Bedrock dips, stratigraphic thicknesses, and cross sections suggest that a SW-directed duplex at depth drives uniform uplift in the north, and a NE directed wedge thrust drives variable tilt in the south. Localized faulting at the fold axis introduces asymmetrical fold geometry. Folding of the oldest dated terrace suggests rock uplift rates across the SMA range between 1.8 and 2.0 mm/yr. Assuming a 25°-dip for the duplex ramp on the basis of dip data constraints, the shortening rate across the SMA ranges between 3.8-5.4 mm/yr or ~4.6 mm/yr since ~53 ka. Of that rate, 2.7-1.1 mm/yr is likely absorbed by faulting at the fold axis. In comparison, long-term bedrock shortening rates are consistent with our data of Pleistocene shortening rates. Cross sections at the Ujh River transects and Chenab reentrant indicate 6.5 mm/yr and ~4 mm/yr, respectively, using an onset age of thrusting of ~ 3 Ma. Within the Sub-Himalaya deformation belt, new geomorphic mapping demonstrates that active emergent thrust faulting occurs north of the deformation thrust front in the Kashmir Himalaya. The Riasi thrust (RT) comprises the southeastern strand of a ~250 km-long seismically active fault system in Pakistan and Indian Kashmir. Multiple fault strands with Quaternary activity characterize the fault zone near the Chenab River. Vertical separation of ~272 m of Pleistocene fluvial deposits marks the main strand of the RT, or the Main Riasi thrust (MRT). A shortening rate of 10.8-2.8 mm/yr characterizes a ~91-39 ka time interval for the MRT at this location. A fault scarp and offset Holocene terrace mark the southernmost and frontal splay of the RT fault zone, called here the Frontal Riasi thrust (FRT). Differential uplift (21.6±1m) of a Holocene terrace yields a preferred shortening rate of 8.8-4.4 mm/yr. Contact relationships in a trench across the FRT date the last surface rupture of the RT fault zone at ~4,500 yrs ago. Average shortening rates since ~100 ka across the MRT and the FRT range from 10.8 mm/yr to 4.4 mm/yr (7.6±3.3 mm/yr), consistent with long-term bedrock shortening of ~10-14 mm/yr since 5 Ma. Given that Himalayan-Indian convergence is ~11-18 mm/yr, the sum of the intermediate-term shortening rates for the RT (10.8-4.4 mm/yr) and the deformation front (5.4-3.8 mm/yr), accounts for most of the total geological shortening in Kashmir. Using average rates, internal faults (RT) absorb 50% of the Himalayan shortening, comparatively more than the deformation front (~30%) in Kashmir. Similarities in the structural setting between the Riasi thrust and the Balakot-Bagh fault, including millennia recurrence, suggest the potential of Mw 7 to 8 earthquakes on the RT fault zone, similar to the source of the Mw 7.6 2005 Kashmir earthquake on the Balakot-Bagh fault segment. Lower rate at the deformation front may suggest an even longer recurrence interval, but nonetheless potentially devastating with predicted Mw of 7.5-7.6 along the 180-250 km-long structure. Apatite and zircon (U-Th)/He cooling ages are used to quantify the pattern of distributed deformation and overall thrust-belt kinematics at longer timescales across the Kashmir Himalayas. Apatite (U-Th)/He (AHe) cooling ages for the foreland molasse sediments are consistently younger than the sediment age, indicating that ages of Sub-Himalayan belt samples are reset. We interpret regional pattern of young AHe cooling ages (<3 Ma) in the foreland with peak cooling at 1.9-3.2 Ma to represent rapid coeval fault-related exhumation on multiple structures across the Sub-Himalaya. In the hinterland front ranges of the Pir Panjal, the MBT and MCT thrusts are characterized by older cooling (>4.7 Ma). For zircon (U-Th)/He (ZHe), probability density plots of samples from both detrital cooling ages in the foreland and reset cooling ages in the hinterland show a pronounced spike in cooling between ~16 and 20 Ma, a period where MCT motion is well documented throughout the Himalaya. Estimates of exhumation rates for the sum of Sub-Himalayan structures are higher (2.8-2.2 mm/yr) than across the MCT/MBT (<1 mm/yr) in the Pir Panjal Range. Cooling patterns across the Kashmir Himalayas do not correlate with monsoon precipitation gradients, suggesting climate forcing is decoupled from erosion and exhumation. Distributed rather than localized forward-propagating deformation characterizes fault-related exhumation for the orogenic wedge development in the Sub-Himalayan belt since at least ~2-3 Ma. In the hinterland, coeval young cooling ages (< 3 Ma) and high exhumation rates (2.8-1.3 mm/yr) across the Kishtwar Window, >100 km north of the deformation front, suggest tectonic-driven rapid exhumation across the orogenic wedge coincides with localities of predicted changes in ramp geometry and/or active orogenic growth. We attribute a pattern of distributed deformation and coeval faulting across the Sub-Himalaya to the effects of pre-existing basin architecture in Kashmir.
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12314. [Article] Landscape-Level Approaches to Desert Bighorn Sheep (Ovis canadensis nelsoni) Conservation in a Changing Environment
Landscape characteristics can strongly influence demographic and genetic processes in wildlife populations. Climate change and human land use are causing many landscapes to change rapidly, and the effects ...Citation Citation
- Title:
- Landscape-Level Approaches to Desert Bighorn Sheep (Ovis canadensis nelsoni) Conservation in a Changing Environment
- Author:
- Creech, Tyler Graydon
Landscape characteristics can strongly influence demographic and genetic processes in wildlife populations. Climate change and human land use are causing many landscapes to change rapidly, and the effects on wildlife populations must be understood to properly manage these threats and design effective conservation strategies. In this dissertation, I explored the implications of landscape heterogeneity for desert bighorn sheep (Ovis canadensis nelsoni), an ecologically and culturally important ungulate species in the southwestern United States, and demonstrated new approaches that can be applied to landscape-level conservation of many wildlife species in changing landscapes. This research focused on populations within and surrounding U.S. national parks, comprising a large portion of the desert bighorn sheep's geographic range, and utilized a genetic dataset including > 1,600 individuals that was developed during this and previous projects. Landscape resistance models have been used extensively to predict potential linkages among fragmented wildlife populations, including desert bighorn sheep, but have rarely been used to guide systematic decision-making such as prioritizing conservation actions to maximize regional connectivity. In Chapter 1, I combined network theory and landscape resistance modeling to prioritize management for connectivity, including protection and restoration of dispersal corridors and habitat patches, in a desert bighorn sheep metapopulation in the Mojave Desert. I constructed network models of genetic connectivity (potential for gene flow) and demographicconnectivity (potential for colonization of empty habitat patches). I found that the type of connectivity and the network metric used to quantify had substantial effects on prioritization results; however, I was able to identify high-priority habitat patches and corridors that were highly ranked across all combinations of the above factors. Potential diet quality varies across landscapes and through time for desert bighorn sheep and other ungulates, but is difficult to measure at fine spatial and temporal resolution using traditional field-based methods. The remotely sensed vegetation index NDVI can potentially overcome these limitations, but its relationship to diet quality has never been empirically validated for desert herbivores. In Chapter 2, I examined how strongly NDVI was associated with diet quality of desert bighorn sheep in the Mojave Desert using fecal nitrogen data from multiple years and populations, and considered the effects of temporal resolution, geographic variability, and NDVI spatial summary statistic. I found that NDVI was more reliably associated with diet quality over the entire growing season than with instantaneous diet quality for a population, and was positively associated with population genetic diversity (a proxy for long-term diet quality). Although NDVI was a useful diet quality indicator for Mojave Desert bighorn sheep, my analysis suggested that it may be unreliable if satellite data are too spatially coarse to detect microhabitats providing high-quality forage, or if diet is strongly influenced by forage items that are weakly correlated with landscape greenness. Landscape genetic studies typically rely on neutral genetic markers to explore gene flow and genetic variation, but the potential for species to adapt to changing landscapes depends on how natural selection influences adaptive genetic variation. In Chapter 3, I optimized landscape resistance models for desert bighorn sheep in three regions with different landscape characteristics, and then used genetic simulations incorporating natural selection to determine how the spread of adaptive variation is influenced by differences among landscapes. Optimized landscape resistance models differed between regions but slope, presence of water barriers, and major roads had the greatest impacts on gene flow. Differences among landscapes strongly influenced the spread of adaptive genetic variation, with faster spread in landscapes with more continuously distributed habitat and when a pre-existing allele (i.e., standing genetic variation) rather than a novel allele (i.e., mutation) served as the source of adaptive genetic variation. Climate change presents a substantial threat to desert bighorn sheep and wildlife worldwide, and adaptation may be required to persist in novel environmental conditions. Knowledge of how adaptive capacity - the potential to cope with climate change by persisting in situ or moving to more suitable ranges or microhabitats - varies across populations is needed to establish conservation priorities for minimizing climate change impacts to individual species. In Chapter 4, I explored variation in the evolutionary component of adaptive capacity for 62 desert bighorn sheep populations on and near U.S. national parks. I measured adaptive capacity of populations as a function of two factors that are strongly associated with the potential for evolutionary adaptation, genetic diversity and connectivity (estimated using a landscape resistance model from Chapter 3). Genetic diversity and connectivity were highly variable across regions and populations. I identified populations with high adaptive capacity that could serve as genetic refugia from climate change impacts (e.g., those in Death Valley and Grand Canyon National Parks), but also populations with low adaptive capacity that may require conservation actions to improve their potential for adaptation (e.g., those in eastern Utah and the southern Mojave Desert). Genetic structure analyses suggested that populations in eastern Utah were genetically distinct from the rest of the study area, likely resulting from restricted gene flow following regional population extinctions. This dissertation highlighted the effects of landscape heterogeneity on genetic and demographic processes in desert bighorn sheep populations. Collectively, the information in these chapters should help guide management of desert bighorn sheep in the face of climate change and human land use. The landscape-level approaches demonstrated here may be useful for managing many other wildlife species.
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12315. [Article] Biological Soil Crusts of the Great Basin : An Examination of their Distribution, Recovery from Disturbance and Restoration
We are at risk of losing the sagebrush steppe in the floristic Great Basin to the invasion of Bromus tectorum L., cheatgrass. The floristic Great Basin includes the Central Basin and Range, the Northern ...Citation Citation
- Title:
- Biological Soil Crusts of the Great Basin : An Examination of their Distribution, Recovery from Disturbance and Restoration
- Author:
- Condon, Lea A.
We are at risk of losing the sagebrush steppe in the floristic Great Basin to the invasion of Bromus tectorum L., cheatgrass. The floristic Great Basin includes the Central Basin and Range, the Northern Basin and Range, and the Snake River Plain. The Great Basin receives most of its precipitation as winter snow and experiences hot and dry summers. Early accounts of invasion by cheatgrass associated it with farming and grazing practices. The non-farmed areas in the region are still actively grazed and referred to as rangelands. On invaded sites, cheatgrass changes the flammability of fuels on invaded landscapes, across the Great Basin, from coarser fuels that are widely spaced to fine fuels that are continuous, filling interspaces between perennial plants. The fuel load created by cheatgrass regenerates annually. This has resulted in a change in the fire regime of the Great Basin from infrequent, small fires to more frequent large fires. In arid lands globally, soil interspaces between perennial plants are typically filled by biological soil crusts (biocrusts). This is also true for ecoregions in and surrounding the Great Basin. Biocrusts are known to influence many ecosystem processes that cheatgrass influences, specifically nutrient cycling and availability of soil moisture. However, little work has been done on biocrusts of the Great Basin and to my knowledge, no one had restored biocrusts within the Great Basin. I attempt to fill some of this knowledge "interspace" by relating biocrust presence to disturbances and cheatgrass invasion and to demonstrate the potential for biocrust restoration within this region. Previous work in eastern Oregon demonstrated relationships between declines in biocrusts and increases in cheatgrass with increasing grazing intensity, soil temperature, and decreasing soil moisture. Grazing intensity influences the cover of biocrusts as well as the abundance and composition of native bunchgrasses. Native bunchgrasses influence the interspace gap size between perennial herbaceous vegetation which is directly associated with the cover of cheatgrass. In a region where grazing records may be incomplete and may exist in various forms of data, having a simple indicator of grazing impacts would be useful. It is also crucial that we have an understanding of what leads to loss of site resistance to cheatgrass. This previous work suggested that cover of biocrusts, in addition to bunchgrass composition, were associated with increased site resistance to cheatgrass. In Chapter 2, I used current grazing records from a range of suspected grazing intensities, to examine the ability of both biocrusts and perennial vegetation to maintain site resistance to cheatgrass after fire. I examined the ability of mosses and lichens to maintain site resistance separately given that these are two very different kinds of organisms. Mosses are non-vascular plants and early colonizers of sites in primary succession. Lichens have a symbiotic relationship between a fungus and a photosynthesizing partner, a cyanobacteria, an algae or both. Using structural equation models, I corroborated that perennial vegetation and lichens are associated with increased site resistance to cheatgrass and that mosses are associated with and may facilitate both lichens and perennial herbaceous vegetation. Also in Chapter 2, I identified that burned sites were associated with increased grazing pressure by livestock as shown by increases in cow dung density and increases in gap size between perennial herbaceous vegetation. The Great Basin is managed for cover of perennial vegetation but it could also be managed for morphogroups of biocrusts. Considering morphogroups of biocrusts, which were shown in the Chapter 2 to be important for site resilience and resistance, I wanted to determine if there were site characteristics associated with biocrust distribution and recovery from disturbance, across the Great Basin. Outside of the Great Basin on the Columbia Plateau, others had found that mosses were still present on disturbed sites whereas lichens were often lost. In addition, biocrust species were more associated with soil properties than with grazing by livestock. Given that grazing by livestock and fire are common disturbances across the region, I wanted to know if the same relationships between biocrusts, soil properties and disturbance were true in the Great Basin. I found that cover of the lichen component of biocrusts was higher on sites that were both ungrazed and unburned. Factors related to disturbance characteristics were correlated with the recovery of biocrusts, even after accounting for time since fire. Factors related to disturbance, a composite of grazing and fire, were more important for structuring the cover and composition of morphogroups as opposed to environmental conditions. Lichens were the most sensitive morphogroup, compared to tall mosses, followed by short mosses which were favored by some disturbance but reduced in cover immediately after fire. Perennial grasses were also favored by some disturbance and perennial forbs did not show an obvious relationship with a disturbance gradient. Chapter 3 highlights that grazing by livestock and fire are common disturbances across the region so much so that the effects of one on the abundances of morphogroups could not be separated from the other. Given the observed contributions of biocrusts to site resilience and resistance, I wanted to know if we could restore biocrusts in the field. Others have grown mosses in a lab setting but this was the first study to restore mosses in the Great Basin. I tested the influence of factors that are commonly used in the field of restoration for facilitating plant establishment. I tested the influence of season of inoculation (fall versus spring), the addition of organic matter (in the form of jute net), irrigation (in the spring season) and the climatic setting of moss the collection sites (for moss propagation), in comparison to the experiment site (warm, dry versus cool, moist) on moss growth. I used two moss species: a ruderal (Bryum argenteum) and a later successional species (Syntrichia ruralis). Moss cover increased when the climatic setting of the collection site matched the experiment site. Mosses were facilitated by the addition of the organic jute netting, putting on most of their growth in winter. Although there is still a great deal of work to be done developing moss material for restoration and working out inoculation rates of moss fragments, similar to seeding rates, land managers have another tool to consider when rehabilitating sites after disturbance. Managing the Great Basin for biocrusts in the presence of grazing and fire will not only increase site resistance to cheatgrass but it will add to the conservation of ecosystem functions related to nutrient cycling, hydrologic cycling and soil erosion. Site resistance will be improved with increased periods of rest from grazing following fire. The lichen component of biocrusts is a more sensitive indicator of disturbance when compared with mosses or perennial vegetation but we are currently actively managing for perennial vegetation and not biocrusts. The moss component of biocrusts can be successfully restored in the Great Basin, without irrigation. This dissertation shows that land managers should consider a suite of organisms, in addition to perennial plants to achieve management goals and maintain site resistance to cheatgrass.
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12316. [Article] Evaluating tools used to estimate and manage browse available to wintering moose on the Copper River Delta, Alaska
Ungulates comprise some of the most well researched and intensely managed wildlife populations on earth. As such, they are recognized as ideal study subjects for developing and modifying management tools ...Citation Citation
- Title:
- Evaluating tools used to estimate and manage browse available to wintering moose on the Copper River Delta, Alaska
- Author:
- Smythe, Sharon E.
Ungulates comprise some of the most well researched and intensely managed wildlife populations on earth. As such, they are recognized as ideal study subjects for developing and modifying management tools or theories (Danell et al. 1994, Shipley 2010). An introduced moose (Alces alces gigas) population on the Copper River Delta (CRD; Delta) of south-central Alaska functions as a valuable resource for the residents of Cordova and an isolated research population on which to test managerial techniques. Since its introduction (1949-1958), the founding population of 23 moose has grown to over 830 in 2013, divided into two sub-populations. However, in 1964, the largest earthquake recorded in U.S. history (9.2 magnitude) uplifted the Delta by 1.0-4.0 m, initiating delta-wide changes in hydrology, vegetation distributions, and successional processes. The proportion of stands dominated by woody species, especially alder (Alnus viridis sinuata) and spruce (Picea sitchensis), increased visibly. Furthermore, previous research (1987-89) observed that 90% of the moose on the western region of the Delta wintered within 9-24% of the total land area, possibly restricting their available winter browse. Because moose diets on the CRD are dominated by willows (Salix spp.), managers were concerned that the combined effects of a restricted winter range and earthquake-initiated vegetation changes would negatively influence the population. Managers have responded to this concern by 1) supporting work to estimate the nutritional carrying capacity (NCC; i.e., the forage available to a population within a specified area and time) of the Delta, and 2) by exploring the feasibility of mechanical treatment as a means of stimulating browse production for the moose. Thus, the objectives of this thesis were to 1) explore the factors influencing NCC for moose on the west CRD while combining updated digital and field-collected data to estimate NCC, and 2) to assess the effects of mechanical treatment on the production of moose browse across stand types and over time. We collected field data and evaluated differences in the past (1988-89) and present (2012-13) biomass-predicting regression equations for two willow species (Barclay's and Hooker's willow, Salix barclayi and hookeriana) used within NCC models to determine 1) whether past and present models of Barclay's willow predicted similarly and 2) whether Hooker’s and Barclay's willow differed in average available biomass, nutritional quality, and utilization by moose. The linear coefficients for the current (2013) Barclay’s willow, Hooker's willow, and combined equations were 2.2x, 1.6x, and 1.9x larger, respectively, than that derived from the 1988 model for Barclay’s willow (which possibly included Hooker's willow data). Thus, willows on the CRD may now be supporting more biomass per stem than predicted by prior models. Hooker's and Barclay's willow did not differ in mean available biomass, nutritional values, or utilization rates. These results suggest a need to evaluate the accuracy of older allometric regressions, though separate identification of the visually-similar Barclay's and Hooker's willow may be unnecessary for future biomass-estimating efforts on the CRD. To further explore the factors influencing the biomass available to moose and their associated NCC estimates, we compared 5 NCC model types across 4 winter ranges and under 3 winter-severity scenarios for the western CRD moose population. We conducted a sensitivity analysis (Sx) of our final model to determine the relative influence of factors affecting NCC estimates. Lastly, we compared current (2012-13) browse available biomass, stand type areas (2011), and NCC results to those obtained by past research (1987-89, MacCracken et al. 1997 and 1959/1986, Stephenson et al. 2006) to determine changes over time, while evaluating the effects of models incorporating satellite-based estimates of stand areas and forage nutritional values on NCC estimates. Because recent aerial survey observations suggest expansion of the moose winter range, our final model estimated NCC between 2,198-3,471 moose depending on winter severity within a winter range encompassing the entire west Delta. These results suggest the current western moose population (approximately 600 in 2013) is below NCC. Model components with the largest and smallest Sx were snow depth and tannin- and lignin-caused reductions in forage nutritional quality, respectively. Changes from 1987-2013 in available biomass of forage species ranged from -66-493%, while changes from 1959-2011 in stand type areas ranged from -60-661%. Overall, NCC estimates only declined by 2% from 1959-2013, however inclusion of forage nutritional quality in models reduced NCC estimates by 60%. Lastly, we assessed the use of hydraulic-axing (i.e., hydro-axing) as tool for increasing the available willow biomass. We evaluated treatment effects on biomass, height, nutritional quality (crude protein, lignin, and tannin levels), utilization, and snow burial of the winter forage species within 3 winter-severity scenarios. Sites were treated in 4 winters (1990-92, 2008, 2010, and 2012) within 5 stand types in 20 locations varying from 0.86-63.40 ha in size. Results indicate few significant differences relative to controls, though treatment significantly increased the ratio of willow to alder. Our results may be limited by sample sizes (n = 1-9 per stand type or treatment year) as visual comparison suggests treatment via hydraulic-axing may be an effective method for increasing willow biomass without influencing nutritional quality. However, willows 20-23 years post-treatment are still significantly shorter than untreated willows (P = 0.03). Thus, treatment may result in decreased forage available to moose in severe winters. Management concerns regarding continued earthquake-initiated changes in vegetation distributions and successional processes prompted our investigation. However, studies on the vegetation dynamics of the CRD suggest the vegetation distribution of the Delta may be relatively stable (Boggs 2000, Thilenius 2008). If so, our current estimates of NCC suggest the west Delta can support a larger moose population than is currently present. Hydro-axing may not be necessary to ensure the future of the moose population, though it could be used to counter increases in alder (Alnus viridis sinuata) which are likely within certain successional sequences. However, together with earthquakes, the processes determining the future forage available on the CRD include complex, interactive forces such as glaciers, the Copper River, oceanic tides, and zoological- and human-caused influences. These forces and their effects on the vegetation create a dynamic ecosystem for the moose population, are difficult to predict, and may be further complicated by climate change. As a result, application of any managerial tool may be temporary and often difficult. However, this guarantees a constant need for further revision and redevelopment of the tools used to manage the moose population, ensuring that the moose of the CRD will remain an important resource for researching and refining ungulate management worldwide.
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12317. [Article] The optimal allocation of watershed conservation funding : a case study of the John Day River Basin, Oregon
This study determines the optimal allocation of watershed conservation funds in the John Day River Basin, Oregon. Fund managers can use a variety of targeting schemes to allocate their limited resources. ...Citation Citation
- Title:
- The optimal allocation of watershed conservation funding : a case study of the John Day River Basin, Oregon
- Author:
- Skelton, Katharine
This study determines the optimal allocation of watershed conservation funds in the John Day River Basin, Oregon. Fund managers can use a variety of targeting schemes to allocate their limited resources. Depending on which targeting criteria is used, they may or may not be achieving the maximum environmental benefits per dollar expended, a policy goal that is increasingly being adopted for conservation programs. Previous studies have provided the theory behind this optimal allocation of funds, but none, to the researcher's knowledge, have attempted a case study to illustrate the optimal allocation of funds as well as the misallocations that could result. Watershed conservation policies are very important, especially here in the Pacific Northwest where salmonid populations are endangered. As stream temperatures are lowered, salmonid recruitment increases. Improvements in riparian vegetation provide stream shade and bank stability. Shade decreases stream temperatures by preventing solar radiation from reaching the stream, while bank stability allows streams to become narrower and deeper, with more vegetative overhang. Narrower streams have less surface area to come in contact with solar radiation and vegetative overhang provides additional shade. A simultaneous equation system was used to estimate stream temperature and fish recruitment models for the thirteen streams studied, classified into three environmental attribute clusters. Fish recruitment models were developed for rainbow trout, Chinook salmon and speckled dace. Marginal values for rainbow trout and Chinook salmon from previous studies were used to calculate the total marginal benefits to society from increasing cold-water salmonid species. The analytical models were the basis for determining the optimal fund allocation, after considering the cumulative, indirect and correlated benefits derived from improving riparian vegetation conditions. Policy managers and previous studies have failed to consider these additional environmental benefits, particularly jointly produced benefits. Two scenarios were determined for the optimal fund allocation, based on the riparian conditions of the surveyed stream reaches. The riparian conditions are reported using a vegetative use index from one (the worst conditions) to four (the best conditions). Under the first scenario, which assumes a full range of riparian conditions, Granite Creek should receive funding priority with $51,756 in marginal social benefits received from improving the streamside vegetative use rating from one to four, for one mile of stream. Deerdorff Creek and Reynolds Creek would be the next two streams to receive funding, respectively, both for a vegetative use improvement from one to two. The second scenario assumes that only vegetative conditions in the surveyed segments exist in the stream. Under these circumstances, only six of the thirteen streams would even be considered for funding, with Granite Creek again receiving priority. Improving the vegetative use rating in Granite Creek from three to four, for one stream mile, will produce $9355 in marginal social benefits. Murderer's Creek and Camp Creek would be the next streams to receive funding for a vegetative use improvement from three to four and one to two, respectively. In addition to determining the optimal fund allocation, discussion is included about the policy implications that would result from ignoring the cumulative, indirect and correlated benefits. For the fund misallocation discussion Granite Creek was assumed to be the stream that should be given funding priority for an improvement from three to four only, with Murderer's Creek and Camp Creek receiving funds second and third, respectively. If an on-site, physical criterion is used as the targeting criteria, such as stream temperatures or the riparian vegetation conditions, then the cumulative benefits will be ignored. Two possible misallocations could result when the cumulative effects are ignored. First, streams with very high temperatures may receive funding, even if improvements in the vegetative use index will not lower temperatures enough so that salmonids can survive. Second, streams that have temperatures below the optimal range for salmonids, but have poor riparian vegetation may be funded. Improving streamside vegetation in those streams would be a misallocation of funds. Targeting based on the highest stream temperature criteria would only consider the direct benefits received from improving streamside vegetation. Under a temperature- based targeting criteria, Alder Creek would be the first stream funded with Mountain and Murderer's Creek following. If we assume only two streams could be funded, then there will be a loss of almost all marginal benefits per stream mile. If the change in the stream temperatures is used as the targeting criteria, and indirect benefits are ignored, then Camp Creek would receive funding priority, with Mountain Creek, Granite Creek and Murderer's Creek following. If it is again assumed that only two streams could be funded, this targeting scheme would result in an approximate loss to society of up to 87 percent in marginal benefits, per stream mile Additionally, all of the indirect benefits need to be taken into consideration in order to optimally allocate funds. If Chinook salmon are ignored, and rainbow trout are the only cold-water species taken into account, then society will forgo around 50 percent of marginal social benefits, per stream mile. This is if we assume two streams are funded, and the South Fork is the second stream to receive funds, rather than Murderer's Creek. Granite Creek would still receive funding priority. Finally, correlated benefits, or warm-water species, need to be considered. In this study ignoring the warm-water species would not effect fund allocation, as a marginal social value for speckled dace was not found. Even if we assume the speckled dace is a proxy for warm-water sport fish, such as bass, and the correlated benefits are taken into consideration, funding priority would still be given to Granite Creek. However, under the same assumptions, if the correlated benefits are ignored in Camp Creek, then society will misallocate funds and lose a small portion of marginal social benefits per stream mile. This study points towards small, high elevation streams being given funding priority. Granite Creek should be the first stream to receive funds in the John Day River basin, when funds are optimally allocated. However, if not all of the environmental benefits are taken into consideration, different streams may be targeted. When a temperature-based targeting scheme is used, Alder Creek would be given funding priority, even though no marginal social benefits would be derived. If the change in stream temperatures is used, Camp Creek will receive funds, with a large loss to society in marginal benefits. If not all of the indirect benefits are considered, the South Fork will be funded over Murderer's Creek, and only half of the possible marginal benefits will be received. Finally, when correlated benefits were ignored, the fund allocation in this study was not affected. However, fund managers still have to consider the tradeoffs involved between warm and cold-water adapted fish species. This is especially true if warm-water sport fish or endangered species are the jointly produced benefits. Failing to include all of the environmental benefits that are produced when conservation programs are initiated will lead policy managers to target the wrong streams or basins, and misallocate funds. In addition, using the wrong criteria to prioritize watersheds will also lead managers to misallocate funds. Funds should be allocated so that the total value of environmental benefits is maximized, and not the total amount of resources saved.
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12318. [Article] Evaluating Coastal Protection Services Associated with Restoration Management of an Endangered Shorebird in Oregon, U.S.A.
Coastal sand dunes and beaches offer a variety of ecosystem services such as coastal protection, sand stabilization, species conservation, and recreation. However, the management and balance of ecosystem ...Citation Citation
- Title:
- Evaluating Coastal Protection Services Associated with Restoration Management of an Endangered Shorebird in Oregon, U.S.A.
- Author:
- Carroll, Lindsay J.
Coastal sand dunes and beaches offer a variety of ecosystem services such as coastal protection, sand stabilization, species conservation, and recreation. However, the management and balance of ecosystem services offered by dunes and beaches is challenging when ecosystem services interact across the landscape. Management focusing only on one ecosystem service may result in unintended consequences and trade-offs between other key services. Understanding the magnitude of the trade-offs and linkages between services provides a more holistic approach for reducing unintended consequences and maximizing function. The degradation of habitats and land use changes associated with expanding human populations has resulted in the need for species conservation. However, species conservation techniques can sometimes have unintended consequences for other services. Given the mandate of the Endangered Species Act to restore habitat structure and function essential to endangered or threatened species, it becomes critical to evaluate the implications of species conservation management initiatives to reduce negative implications to other key services. The coastal dune systems of the Pacific Northwest (PNW) are a prime example of how ecosystem services, such as species conservation and coastal protection, can interact with one another. Over the last 125 years in the Pacific Northwest (PNW), the intentional introduction of two non-native congeneric beach grasses (Ammophila arenaria and A. breviligulata) has increased coastal protection through the creation of foredunes, but also dramatically altered the dune ecosystem. Both invasive grasses build taller dunes that range from 3 - 18 m in height compared to the native grass, Elymus mollis. Increased foredune elevations generate greater coastal protection services that are increasingly important given sea level rise and extreme storm events on the PNW coast. However, the beach grasses have dramatically changed the beach/dune community, resulting in the decline of several native dune plants and animals. One species that is negatively affected by the grass invasion is the Western snowy plover (Charadrius nivosus nivosus), an endemic shorebird living on beaches and dunes in the Pacific Northwest. This shorebird was listed threatened under the Endangered Species Act in 1993 and a recovery plan was established that employed multiple recovery techniques. The most important part of the plan involves establishing habitat restoration areas (HRAs) where dunes are bulldozed, reducing dune elevations, burying the grass, and returning the dunes to an open shifting sand environment, historically preferred by the plover. Recent coastal hazards modeling revealed that the changes in beach and dune shape associated with plover restoration increases coastal exposure to flooding and erosion at certain locations along the Oregon coast, particularly under projected climate change scenarios of sea level rise and extreme storms. As part of future plover management, four critical habitat areas were proposed for Tillamook County, Oregon: Nehalem River Spit, Bayocean Spit, Netarts Spit, and Sand Lake South. Given the interest in plover habitat restoration in Tillamook County, this research project addresses the following questions: (1) What is the present day dune geomorphology and exposure to coastal hazards at four proposed critical habitat (PCH) areas in Tillamook County, Oregon; and (2) how do changes in beach geomorphology associated with different restoration scenarios alter coastal exposure today, under projected sea level rise and storm scenarios? To address the coastal geomorphological impacts of HRA installation on the four proposed areas, multiple restoration scenarios that reduce foredune elevation were evaluated under present day sea level and potential future sea level rise and extreme storminess scenarios, using coastal exposure modeling techniques. The model projections provide site-specific information on the exposure of HRAs to overtopping under different restoration conditions. We determined that exposure to flooding was dependent on proposed HRA site and restoration scenario, and was exacerbated by sea level rise and extreme storms. Empirical models projected the greatest flooding exposure would occur at Nehalem River Spit, followed by Netarts Spit, and then Bayocean Spit and Sand Lake South, which did not differ. Exposure to flooding at present day dunes was low across all sites, but with increasing exposure to flooding as foredune elevations were reduced to 6.0 m or below, as could happen with plover habitat restoration. Under present day water levels, restoring foredune elevations to 6.0 m or below would likely result in roughly 5 days of overtopping per year at Nehalem River Spit, Bayocean Spit, and Netarts Spit, and 4 days of overtopping at Sand Lake South. Flooding under various foredune restoration scenarios increased under higher sea level rise scenarios. Flooding exposure for the 6.0 m restoration scenario exceeded 10 days per year at Nehalem River Spit and 5 days per year at Bayocean Spit, Netarts Spit, and Sand Lake South. Overall exposure to flooding under the extreme storm scenarios was dependent on proposed HRA site, restoration scenario, and increased wave conditions, such as wave height, period, and water level. Similar to the empirical model, flooding exposure under extreme storm scenarios increased when foredune elevations were reduced to 6.0 m or below, across all sites. The site with the greatest overall flooding exposure during extreme storms was Bayocean Spit. Flooding distance was dependent on restoration scenario and site while flooding duration was only dependent on restoration scenario. The 5.5 m restoration scenario under higher storm water levels resulted in one hour or more of flooding exposure at least one day per year at Nehalem River Spit, Netarts Spit, and Bayocean Spit. The overall likelihood of overwash extending to 150 m or more into the dune field during extreme storms was at least 5 days when selecting to reduce foredune to restoration elevations of 7.0 m or below across all sites. The effect of higher wave heights and greater wave periods was more important to overtopping distance than restoration scenario. Learning from current plover management, combined with the coastal exposure analysis we conducted here, could enable managers to develop site-specific restoration plans that maximize plover recovery while minimizing coastal exposure. This research will give resource managers information on the coastal exposure associated with proposed HRAs and the foredune reduction scenarios they might want to employ at the different sites. It will allow them to identify the best restoration scenarios to maximum habitat restoration without compromising coastal protection, and thus balance some important services of dunes and beaches. Regardless of management objective, identifying the unintended consequences of restoration to key ecosystem services is necessary for the holistic management of our dynamic coasts, especially with projected sea level rise and the uncertainty of frequent and extreme storms.
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12319. [Article] The effects of enhanced expression of the GluN2B (NR2B) subunit of the N-methyl-D-aspartate (NMDA) receptor on memory in aged animals
As the aging population continues to grow worldwide, age-related complications are becoming more apparent within the aging population. One of the first age-related complications to become apparent is age-associated ...Citation Citation
- Title:
- The effects of enhanced expression of the GluN2B (NR2B) subunit of the N-methyl-D-aspartate (NMDA) receptor on memory in aged animals
- Author:
- Brim, Brenna L.
As the aging population continues to grow worldwide, age-related complications are becoming more apparent within the aging population. One of the first age-related complications to become apparent is age-associated memory impairment and it can make the elderly more dependent on caregivers early on. The N-methyl-D-aspartate (NMDA) receptor is important to learning and memory and appears to be especially vulnerable to the process of aging. The density of NMDA receptors declines with age more than any other ionotropic glutamate receptor. Both the density of NMDA receptors and the mRNA and protein expression of its subunits decline with age. In particular, the GluN2B subunit of the NMDA receptor shows the greatest age-related declines in expression across multiple brain regions, including the frontal lobe (including the prefrontal and frontal cortices), caudate nucleus and hippocampus. These declines are strongly correlated to age-related declines in spatial memory. Specifically, age-related decreases in the protein expression of the GluN2B subunit within crude synaptosomes of the frontal cortex of C57BL/6 mice show a relationship to the declines in performance in a long-term spatial memory task across age groups. However, within the population of aged mice, there was a subpopulation of aged mice in which higher expression of the GluN2B subunit within the synaptic membrane of the hippocampus was associated with poorer performance in the same task. Moreover, transgenic mice designed to express higher levels of the GluN2B subunit from birth also possess superior memory, including spatial memory, across adulthood to middle-age. Taken together, these data led to the hypothesis that increasing the expression of the GluN2B subunit within the aged brain could potentially alleviate age-related declines in memory. However, increasing its expression regionally was first examined since higher expression of the GluN2B subunit within the hippocampus has been associated with poorer memory in aged animals. Since age-related decreases in the protein expression of the GluN2B subunit within the frontal cortex show a relationship to impaired memory function, the first study was designed to determine if increasing GluN2B subunit expression in the frontal lobe would improve memory in aged mice. Mice received bilateral injections of either an adenoviral vector, containing cDNA specific for the GluN2B subunit and enhanced Green Fluorescent Protein (eGFP) (GluN2B vector); an adenoviral vector containing only the cDNA for eGFP (control vector); or vehicle into their frontal lobe. Spatial memory, cognitive flexibility and associative memory were assessed using the Morris water maze. Aged mice, with increased GluN2B subunit expression in the frontal lobe, exhibited improved long-term spatial memory, comparable to young mice, in the second day of training. Moreover, a higher concentration of the specific GluN2B antagonist, Ro 25-6981, was required to impair long-term spatial memory in aged mice with enhanced GluN2B subunit expression, as compared to aged controls. The requirement for greater antagonism in aged mice to block memory performance suggests that the number of GluN2B-containing receptors in their frontal lobe was enhanced and contributed to the improved memory. This study provides suggestive evidence that therapies that enhance GluN2B subunit expression within the aged brain could have the potential to ameliorate age-related memory loss. Since higher expression of the GluN2B subunit within the hippocampus of aged mice is associated with poorer memory, the second study was designed to determine if increasing GluN2B subunit expression in the hippocampus would improve or further impair memory in aged mice. This would help to determine if a therapy aimed at enhancing the GluN2B subunit expression or function of GluN2B-containing receptors throughout the aged brain could help ameliorate age-associated memory loss. Mice were injected bilaterally with either the GluN2B vector, a control vector or vehicle into the hippocampus. Spatial memory, cognitive flexibility and associative memory were assessed using the Morris water maze. Aged mice, with increased GluN2B subunit expression in the hippocampus, exhibited improved long-term spatial memory, comparable to young mice, early in training. However, there was a trend for impaired memory later in the long-term spatial memory trials. Still, these data suggest that enhancing GluN2B subunit expression in the aged hippocampus could be more beneficial to memory than harmful. In addition, the results of this study suggest that enhancing GluN2B subunit expression in different brain regions may improve memory at different phases of learning. Therefore, therapies that enhance GluN2B subunit expression throughout the aged brain could help ameliorate age-related memory loss. The first two studies demonstrated that enhancing the expression of the GluN2B subunit within either the frontal lobe or hippocampus of the aged brain has the potential to reduce age-related memory declines. However, the increase was not global nor specific to the synapse. Therefore, a third study was developed with the intent of garnering a more global increase in GluN2B subunit expression that was localized to the synapse. Cyclin dependent kinase 5 (Cdk5) enhances endocytosis of the GluN2B subunit-containing NMDA receptors from the synapse. Previous research has shown that inhibiting Cdk5 increases the number of GluN2B subunits at the synapse and within the whole cell and improves memory in young mice. This study was designed to determine if using antisense phosphorodiamidate morpholino oligomers (Morpholinos) to decrease the expression of Cdk5 protein within the brain would improve memory in aged mice. Morpholinos were conjugated to a cell penetrating peptide, which enhances cellular uptake, and delivered bilaterally to the lateral ventricles of both young and aged mice via acute stereotaxic injection. Treatments consisted of equivalent volumes and concentrations of either vehicle, control Morpholino or a Morpholino targeting the mRNA of Cdk5 (Cdk5 Morpholino). Memory was evaluated in the Morris water maze and using a novel object recognition task. Aged mice treated with the Cdk5 Morpholino exhibited improved early acquisition and spatial bias in the long-term spatial memory trials, as well as improved performance overall, compared to control Morpholino-treated aged animals. However, aged mice treated with the Cdk5 Morpholino performed similarly to vehicle-treated aged animals. The presence of the peptide-conjugated Morpholinos within the brain may have worsened performance in the Morris water maze task since control Morpholino-treated animals performed significantly worse than vehicle-treated animals. In concurrence, there was significantly greater gliosis in peptide-conjugated Morpholino-treated animals over vehicle-treated brains, suggesting it was neurotoxic. In contrast, young mice treated with the Cdk5 Morpholino showed impaired early acquisition and spatial bias but a trend for improved later learning in the long-term spatial memory task compared to control Morpholino-treated animals. Treatment with the Cdk5 Morpholino had no significant effect on cognitive flexibility, associative memory or novel object recognition for young or aged animals. Immunohistochemistry revealed increased GluN2B subunit expression within cells with characteristics of neurons and astroglia in regions of the frontal lobe, caudate nucleus and hippocampus of aged mice who received the Cdk5 Morpholino compared to control treatments. However, the increased GluN2B subunit expression appeared to be greater within the hippocampus. These results suggest that inhibiting the translation of Cdk5 using Morpholinos increased GluN2B subunit expression in both young and aged mice and may have contributed to the improved long-term spatial memory observed in aged mice, despite the Morpholino being administered at a presumably toxic concentration. An additional group of mice was used to determine a non-neurotoxic dosage of the peptide conjugated Morpholino. However, future studies are needed to determine the efficacy of the Cdk5 Morpholino at this dosage. Taken together, the studies presented here suggest that increasing expression of the GluN2B subunit within the aged brain does improve age-associated memory declines. In addition, cell penetrating peptide- conjugated Morpholinos show promise as tools for genetic manipulation within the brain and Cdk5 could prove to be a novel target for enhancing GluN2B subunit expression within the aged brain. Though future studies are needed, the studies presented here do suggest that therapies that enhance GluN2B subunit expression within the aged brain have the potential to help ameliorate memory loss. However, since enhanced GluN2B subunit expression itself can increase the potential for excitotoxicity, an optimal dose of such a therapeutic would need to be determined.
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12320. [Article] Implications of cougar prey selection and demography on population dynamics of elk in northeast Oregon
Mule deer (Odocoileus hemionus hemionus) and Rocky Mountain elk (Cervus canadensis nelsoni; hereafter elk) populations in northeast Oregon have declined in the past 10 to 20 years. Concurrent with these ...Citation Citation
- Title:
- Implications of cougar prey selection and demography on population dynamics of elk in northeast Oregon
- Author:
- Clark, Darren A.
Mule deer (Odocoileus hemionus hemionus) and Rocky Mountain elk (Cervus canadensis nelsoni; hereafter elk) populations in northeast Oregon have declined in the past 10 to 20 years. Concurrent with these declines, cougar (Puma concolor) populations have apparently increased, leading to speculation that predation by cougars may be responsible for declining ungulate populations. However, empirical data on cougar diets, kill rates, and prey selection are lacking to support this speculation. Furthermore, the common assumption that cougar populations have increased in northeast Oregon may not be well founded because cougar populations in other areas within the Pacific Northwest region have declined in recent years. My primary research objectives were to (1) estimate kill rates and prey selection by cougars in northeast Oregon, (2) document causes of mortality and estimate survival rates for cougars, (3) estimate population growth rates of cougars in northeast Oregon and simulate the effects of hypothetical lethal control efforts on the cougar population, and (4) investigate the relative influence of top-down, bottom-up, and climatic factors for limiting population growth rates of elk in northeast Oregon. Results from my research will help guide cougar and elk management in northeast Oregon and provide a framework for assessing relative effects of top-down, bottom-up, and abiotic factors on population growth rates of ungulates in this and other areas. I implemented a 3-year study in northeast Oregon to investigate diets, kill rates, and prey selection of cougars in a multiple-prey system to better understand mechanisms by which cougars may influence ungulate populations. During my research, 25 adult cougars were captured and fitted with Global Positioning System (GPS) collars to identify kill sites. I monitored predation sequences of these cougars for 7,642 days and located the remains of 1,213 prey items killed by cougars. Cougars killed ungulates at an average rate of 1.03 per week (95% CI = 0.92 – 1.14); however, ungulate kill rates were variable and influenced by the season and demographic classification of cougars. Cougars killed ungulates 1.55 (95% CI = 1.47 – 1.66) times more frequently during summer (May-Oct) than during winter (Nov-Apr), but killed similar amounts of ungulate biomass (8.05 kg/day; 95% CI = 6.74 – 9.35) throughout the year. Cougars killed ungulates more frequently in summer because juvenile ungulates comprised most of the diet and were smaller on average than ungulate prey killed in winter. Female cougars with kittens killed more frequently (kills/day) than males or solitary females. After accounting for the additional biomass of kittens in cougar family groups, male cougars killed on average more biomass of ungulate prey per day than did females (R = 0.41, P < 0.001), and female cougars killed more biomass of prey per day as a function of the number and age of their kittens (R = 0.60, P < 0.001). Patterns of prey selection were influenced by season and demographic classification of cougars. Female cougars selected elk calves during summer and deer fawns during winter. In contrast, male cougars selected elk calves and yearling elk during summer and elk calves during winter. My results strongly supported the hypothesis that cougar predation is influenced by season, gender, and reproductive status of the cougar and these patterns in cougar predation may be generalizable among ecosystems. The observed selection for juvenile elk and deer suggested a possible mechanism by which cougars could negatively affect population growth rates of ungulates. I investigated survival and documented causes of mortality for radio-collared cougars at 3 study areas in Oregon during 1989 – 2011. Mortality due to hunter harvest was the most common cause of death for cougars in the Catherine Creek study area and the study area combining Wenaha, Sled Springs, and Mt. Emily Wildlife Management Units (WSM study area) in northeast Oregon. In contrast, natural mortality was the most common cause of death for cougars in the Jackson Creek study area in southwest Oregon. Annual survival rates of adult males were lowest at Catherine Creek when it was legal to hunt cougars with dogs (Ŝ = 0.57), but increased following the prohibition of this hunting practice (Ŝ = 0.86). This latter survival rate was similar to those observed at Jackson Creek (Ŝ = 0.78) and WSM (Ŝ = 0.82). Regardless of whether hunting of cougars with dogs was permitted, annual survival rates of adult females were similar among study areas (Catherine Creek Ŝ = 0.86; WSM Ŝ = 0.85; Jackson Creek Ŝ = 0.85). I did not document an effect of age on cougar survival rates in the Catherine Creek study area, which I attributed to selective harvest of prime-aged, male cougars when it was legal to hunt cougars with dogs. In contrast, I observed an effect of age on annual survival in both the WSM and Jackson Creek study areas. These results indicate that sub-adult males had significantly lower survival rates than sub-adult females, but survival rates of males and females were similar by age 4 or 5 years. My results suggest that survival rates of cougars in areas where hunting cougars with dogs is illegal should be substantially higher than areas where use of dogs is legal. I used estimates of cougar vital rates from empirical data collected in northeast Oregon to parameterize a Leslie projection matrix model to estimate deterministic and stochastic population growth rates of cougars in northeast Oregon when hunting cougars with dogs was legal (1989 - 1994) and illegal (2002 - 2011). A model cougar population in northeast Oregon that was hunted with dogs increased at a mean stochastic growth rate of 21% per year (λ[subscript s] = 1.21). Similarly, I found that a model cougar population that was subjected to hunting without dogs increased at a rate of 17% per year (λ[subscript s] = 1.17). Given that hunting cougars with dogs typically results in increased harvest and reduced survival rates of cougars, it was unexpected that the cougar population subjected to hunting with dogs was increasing at a faster rate than one that was not hunted with dogs. However, cougar populations in Oregon were subjected to low harvest rates when hunting cougars with dogs was legal and harvest was male biased. This resulted in high survival rates of female cougars and correspondingly high population growth rates. The Oregon Cougar Management Plan allows the Oregon Department of Fish and Wildlife to administratively reduce cougar populations to benefit ungulate populations, reduce human-cougar conflicts, and limit livestock depredation. Consequently, I was interested in modeling the effects of a hypothetical lethal control effort on a local cougar population. Using empirically-derived vital rates and a deterministic Leslie matrix model, I found that the proportion of the cougar population that would need to be removed annually to achieve a 50% population reduction within 3 years was 28% assuming a closed population, and 48% assuming maximum immigration rates into the population. Using a stochastic Leslie matrix model, I also determined that the model cougar population would likely return to its pre-removal size in 6 years assuming a closed population, and 2 years assuming maximum immigration rates. These model results indicate that current management practices and harvest regulations, combined with short-term, intensive, and localized population reductions, are unlikely to negatively affect the short-term viability of cougar populations in northeast Oregon. However, at this time, it is not known if intensive lethal control efforts funded by state agencies will be cost-effective (i.e., increased sales of tags to hunt deer and elk will offset the costs of control efforts). Further research is needed to investigate the cost-effectiveness of cougar control efforts in Oregon. I developed a Leslie matrix population model, parameterized with empirically-derived vital rates for elk in northeast Oregon, to investigate the relative influence on elk population growth rates of (1) survival and pregnancy, and (2) top-down, bottom-up, and climatic variables. I then estimated the effect of varying the strength of top-down factors on growth rates of elk populations. Growth rates of the model elk population were most sensitive to changes in adult female survival, but due to the inherent empirical variation in juvenile survival rates explained the overwhelming majority of variation in model population growth rates (r² = 0.92). Harvest of female elk had a strong negative effect on model population growth rates of elk (r² = 0.63). An index of cougar density was inversely related to population growth rates of elk in my model (r² = 0.38). A delay in mean date of birth was associated with reduced juvenile survival, but this had a minimal effect on population growth rates in my model (r² = 0.06). Climatic variables, which were used as surrogates for nutritional condition of females, had minimal effects on population growth rates. Likewise, elk density had almost no effect on population growth rates (r² = 0.002). The results of my model provided a novel finding that cougars can be a strong limiting factor on elk populations. Wildlife managers should consider the potential top-down effects of cougars and other predators as a limiting factor on elk populations.