Theses and Dissertations at Montana State University (MSU)
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Item Spatiotemporal mapping of mountain pine beetle infestation severity and probability of new infestation in the central U.S. Rocky Mountains(Montana State University - Bozeman, College of Agriculture, 2018) Bode, Emma Taylor; Chairperson, Graduate Committee: Rick L. LawrenceSynchronous, widespread, and severe mountain pine beetle (MPB; Dendroctonus ponderosae) outbreaks impacted forests of western North America at unprecedented levels in recent decades. Severe MPB epidemics can degrade ecosystem services and socio-economic assets. Mapping outbreak progression informs mitigation efforts and enables analysis of MPB attack processes on a landscape scale. Existing time-series methods for mapping disturbance focus on extent rather than severity. Infestation severity, expressed as within-pixel mortality percentage, is more robust for answering a variety of ecological questions. Our objectives were to: (1) map infestation severity from 2005-2015 using a time-series regression; and (2) analyze MPB attack processes by modeling new infestation probability using spatial and environmental variables in the central U.S. Rocky Mountains. We used spectral data from all available Landsat images, topographic data, and data from U.S. Forest Service aerial detection survey (ADS) polygons to model infestation severity. We collected reference data by interpreting National Agricultural Imagery Program images. We then employed logistic regression model-based recursive partitioning (MOB) to determine: (a) to what degree nearby infestation severity increased probability of new infestation; (b) the degree of variation in probability across space and time with respect to other spatial and environmental risk factors; and (c) the extent to which these effects were directional relative to prevailing winds. Validation of our infestation severity model against a randomly selected subset of the data resulted in no statistical difference between predicted and observed severity. Our raster maps allowed us to identify lower severity infestation not recorded by the ADS. The final MOB model obtained 72.1% accuracy in predicting new infestation. Nearby infestation severity strongly influenced the probability of new infestations. This effect varied with elevation, aspect, temperature, phase of the outbreak, and spatial location. Variation in probability of infestation was highest when surrounding infestation severity was low. Use of wind-informed directional effects did not improve the model. This analysis establishes the efficacy of mapping an infestation severity time series and demonstrates that severity maps facilitate novel analyses of MPB attack processes. The processes developed here can support management decisions with timely maps of MPB infestation severity and probability of new infestation.Item Effects of mountain pine beetle on elk habitat and nutrition in the Elkhorn Mountains of Montana(Montana State University - Bozeman, College of Letters & Science, 2018) Cascaddan, Brent Morris; Chairperson, Graduate Committee: Robert A. GarrottMountain pine beetle (Dendroctonus ponderosae, MPB) outbreaks have become increasingly prevalent in western North America, resulting in ecological changes in pine forests that have important implications for wildlife populations and habitat. The potential effects of MPB-caused tree mortality on ungulate populations and habitat are relatively unstudied, and the possibility exists for both beneficial changes to ungulate habitat such as increased production of forage (i.e., forage availability) through the opening of the forest canopy and negative impacts such as accelerated phenology of herbaceous plants that may reduce forage quality. Using data collected during 2015 - 2017 in MPB-impacted National Forests in west-central Montana, I quantified the effects of MPB outbreaks on elk summer forage resources and use. To accomplish this objective, I 1) evaluated differences in herbaceous plant communities between mature uninfested lodgepole pine stands and two temporal classes of MPB-impacted forest stands (i.e., lodgepole pine cover classes: mature uninfested, old infested: > or = 10 years old, recent infested: <10 years old), 2) evaluated differences in elk summer forage availability and herbaceous vegetation quality, and 3) compared current elk use of lodgepole cover classes (2015 - 2017) to a previous elk telemetry study conducted during 1980 - 1991 before the MPB epidemic. I found that herbaceous forage plant communities did not differ in plant species composition but did differ in forage abundance in each cover class. Forage abundance was significantly different between cover classes and was highest in the old-infested cover class, and lowest in the mature uninfested cover class. The dominant phenology stage of forage species did not change across cover classes by a biologically meaningful amount, but herbaceous quality differed across cover classes, however the amount of difference was small. During the 2015 - 2017 study, elk used all three lodgepole pine cover classes in proportion to how much of each cover class was available. Elk use of lodgepole pine during the 1980 - 1991 study was approximately double what was estimated to be available and suggests elk are using the beetle-killed forest less than prior to infestation. My results indicate MPB does not negatively affect elk nutrition during later summer (July and August), and active management of beetle-killed forest is not necessary for the benefit of elk during this time period, but may be needed for improving elk habitat in other ways during other times of year.Item Demographic responses of woodpeckers in relation to a mountain pine beetle epidemic in the Elkhorn Mountains of Montana(Montana State University - Bozeman, College of Letters & Science, 2015) Dresser, Matthew Alan; Chairperson, Graduate Committee: Jay J. RotellaMountain pine beetle (Dendroctonus ponderosae; MPB) epidemics in coniferous forests of western North America have recently increased in size and severity, which affects wildlife habitat. Development of meaningful habitat-conservation strategies therefore requires information on wildlife population responses to mountain pine beetle. Over nine years (2003-2006, 2009-2013), we monitored 355 nests of 5 woodpecker species: American three-toed woodpecker (Picoides dorsalis), hairy woodpecker (P. villosus), downy woodpecker (P. pubescens), red-shafted northern flicker (Colaptes auratus cafer), and red-naped sapsucker (Sphyrapicus nuchalis) in the Elkhorn Mountains of Montana. In our study area, a MPB epidemic began in 2006 and peaked in 2008. We investigated the relationships between daily survival rate (DSR) and metrics of epidemic severity and timing (epidemic period, annual and cumulative estimates of tree-mortality, and red squirrel [Tamiasciurus hudsonicus] counts) while accounting for other potentially important covariates identified in previous studies (temperature, precipitation, time within the breeding season, nest height, diameter at breast height of the nest tree, and nest-tree species). Additionally, we examined trends in densities of hatched nests concurrent with the epidemic. In general, we found little support for a relationship between DSR and variables that described MPB epidemic timing and severity. Red-naped sapsucker was the only species to show a relationship between DSR and a MPB-related variable (cumulative tree-mortality). In contrast, densities of hatched nests for American three-toed, hairy, and downy woodpeckers increased following the epidemic, whereas, nest densities for red-naped sapsucker did not change. We found stronger support for nest survival relationships with covariates unrelated to the MPB epidemic (temperature, nest height, diameter at breast height of the cavity tree), but even these relationships were only weakly supported. As is commonly the case for cavity-nesting birds, nest survival was relatively high, leaving little room for covariate relationships. Our findings suggest that woodpecker populations tend to relate positively with MPB epidemics, although these relationships may often be the result of numerical increases in nest densities rather than functional increases in nest survival rates.Item Studies on the biology of the mountain pine beetle, Dendroctonus monticolae Hopkins (Coleoptera: Scolytidae)(Montana State University - Bozeman, College of Agriculture, 1960) Reid, Robert WilliamItem The impacts mountain pine beetle on forested snowpacks : accumulation and ablation(Montana State University - Bozeman, College of Agriculture, 2013) Welch, Christopher Michael; Chairperson, Graduate Committee: Paul C. StoyThe future of water resources in the west is tenuous, as climatic changes have resulted in earlier spring melts that have exacerbated summer droughts. Associated with climate changes to the physical environment are changes to the biological environment that may impact snow dynamics; namely via the massive outbreaks of Mountain Pine Beetle (MPB; Dendroctonus ponderosae) that have devastated several million hectares of Lodgepole Pine forests in the western U.S. and Canada. If snow accumulation and melt are determined by the physical environment of the snowpack, and forest canopies define in part this physical environment, how might recent insect outbreaks alter the timing and intensity of snowmelt? MPB often attack in large numbers, and within a few years, the canopy of an infected forest will turn from green but dying, to red, to grey. As needles fall, impacts on the snow pack include changes to wind driven transport, temperature gradients, and snow interception. Additionally, the shifting canopy alters the radiated physics of the canopy, specifically the shortwave/longwave flux density. Combined with a corresponding decrease of snow reflectance (albedo) from litter fall, the dying canopy will provide more energy available to the surface and likely drive snowpacks to melt more rapidly. Conversely, the diminished canopy cover will presumably decrease net longwave radiation of the snowpack. Canopy interception of snow is expected to decrease, and an increase in accumulation will result. I investigate the impacts of MPB disturbance on snow melt through modeling and micrometeorological measurements in intact lodgepole pine and mixed coniferous forests, a MPB-infested forest in the red stage, and a clearcut stand. Albedo at the homogenous intact stand is found to be 16 and 34% higher than the red stand during the melt periods of 2011 and 2012, but no significant difference is found between the red stand and the more heterogeneous 'healthy' stand. Modeled sensible heat over-predicts sensible heat by over 300% during the melt period of 2012. Results highlight the role of beetle-infested and mixed stands on altering snow albedo, and additionally suggest that model formulations for turbulent exchange between snow and atmosphere below forest canopies require improvement.Item Forest disturbance history in the Sawtooth Mountains of Central Idaho and the Beaverhead Range of Western Montana(Montana State University - Bozeman, College of Letters & Science, 2008) Gage, Joshua Albert; Chairperson, Graduate Committee: Cathy WhitlockStudies of disturbance history are important because they provide a framework for understanding the ecological response to past, present, and future climate change, and this information is useful for paleoecological researchers and land-use managers. Fire and insect outbreaks are common occurrences in western forests, and three studies were undertaken to increase our knowledge of their history in the northern Rocky Mountains. In the first study, sediment cores were sampled from 21 lakes located in forests experiencing mountain pine beetle infestation in the Sawtooth Mountains, Idaho. Cores were analyzed to determine whether or not mountain pine beetle remains were accumulating in the lake sediments in association with recent outbreaks. The study found that insect remains were sparse in the lake sediments, even in sites surrounded by heavily infested forests. These results cast doubt on whether paleo-beetle records can be reconstructed from lake-sediment cores. In the second study, one-meter-long sediment cores were taken from three lakes in Pinus contorta forests in the Sawtooth Mountains, Idaho, to reconstruct a historical record of fire spanning the last 2000 years. High-resolution charcoal analysis of the cores indicated changes in fire activity, but there was not a significant difference in fire occurrence during the relatively dry Medieval Climate Anomaly (1050 - 650 cal yr BP), the cooler Little Ice Age (750 - -50 cal yr BP), and the present day. Results suggest that the current fire regime has persisted for at least 2000 years, with little modification by humans or climate. In the third study, a high-resolution charcoal record was analyzed from Reservoir Lake in the Beaverhead Mountains, Montana to reconstruct the fire history of the last 15,000 years at the lower forest-steppe boundary. The charcoal record indicates relatively low fire frequency between 13,500 cal yr BP and 6000 cal yr BP and increased fire activity from 6000 to 1500 cal yr BP, suggesting increasing aridity in the middle and late Holocene. The fire-climate linkages observed in the paleoecological record provide insights that are useful in understanding future fire regimes with projected climate changes.Item Avian community response to a mountain pine beetle epidemic(Montana State University - Bozeman, College of Letters & Science, 2011) Mosher, Brittany Ann; Chairperson, Graduate Committee: Jay J. RotellaRecent epidemics of mountain pine beetles (Dendroctonus ponderosae) will fundamentally alter forests of the Intermountain West, impacting management decisions related to fire, logging, and wildlife conservation. We evaluated effects of a recent mountain pine beetle epidemic on site occupancy dynamics of 49 avian and one mammal species in forests dominated by ponderosa pine (Pinus ponderosa) on the Helena National Forest, Montana. Point count data were collected during the avian breeding seasons (May-July) of 2003-06 (pre-epidemic) and again during 2009-10 (during epidemic). We used a Bayesian hierarchical model that accounts for detection probability to obtain occupancy estimates for rare species as well as common ones. We used one model to investigate changes occupancy for all species with respect to the timing of the beetle outbreak and then used a second model to determine whether the relationships seen were associated to changes in snag density. Results show that 30% of species exhibited strong short-term associations between occupancy probability and the occurrence of the beetle epidemic and 12% of species exhibited strong short-term associations between occupancy probability and snag density. Predictions were partially met, as we saw short-term increases in occupancy probability for beetle-foraging species, decreases for some foliage-gleaning canopy insectivores, and intermediate amounts of change for many ground and shrub insectivores. While short-term ecological changes caused by a mountain pine beetle outbreak were associated with changes in occupancy rates for individual species, the overall species richness of native avifauna was unaffected. Though further study over a longer period of time will be necessary to understand the complete dynamics of this disturbance, our results suggest that well-planned salvage operations after beetle outbreaks could also maintain suitable habitat for successfully breeding avian species.Item Spatiotemporal relationships between climate and whitebark pine mortality in the greater Yellowstone ecosystem(Montana State University - Bozeman, College of Agriculture, 2009) Jewett, Jeffrey Thomas; Chairperson, Graduate Committee: Rick L. Lawrence.Whitebark pine (Pinus albicaulis) serves as a subalpine keystone species by regulating snowmelt runoff, reducing soil erosion, facilitating the growth of other plants, and providing food for wildlife, particularly grizzly bears (Ursus arctos horribilis). Mountain pine beetle (Dendroctonus ponderosae) is an ideal bio-indicator of climate change, as its life cycle is entirely temperature dependent. Western North America is currently experiencing the largest outbreak of mountain pine beetle on record, and evidence suggests that a changing climate has accelerated the life-cycle of this bark beetle, allowing it to expand into new habitat. This study explored the relationships between climate, mountain pine beetles, and whitebark pine mortality in the Greater Yellowstone Ecosystem (GYE). A time-series of Landsat satellite imagery was used to monitor whitebark pine mortality in the GYE from 1999 to 2008. The patterns of mortality were analyzed with respect to monthly climate (temperature and precipitation) variations over the 9-year period. The impacts of topography and autocorrelation (both spatial and temporal) were also analyzed with respect to whitebark pine mortality. Whitebark pine mortality was assessed using the Enhanced Wetness Difference Index (EWDI), a Landsat-derived measure of canopy moisture. Regression tree models were built to predict yearly changes in EWDI. Thirty-eight percent of the deviance in whitebark pine was explained by a regression tree with 10 predictor variables. The most important predictor variables were autocorrelation terms, indicating a strong host-tree depletion effect, where mountain pine beetles were much less likely to attack recently attacked areas. Topographic variables (elevation, slope, aspect) were not useful in predicting whitebark pine mortality. Climate variables alone were used to construct a regression tree with 14 predictor variables which predicted 15% of the dataset deviance in whitebark pine mortality. Drier climatic conditions favored increased whitebark pine mortality, likely due to the decreased ability of whitebark pine to repel beetle attacks. Warmer climatic conditions also favored increased whitebark pine mortality, likely due to a decrease in winter mortality of mountain pine beetle. These results show for the first time a statistical link between climate variability and whitebark pine mortality, likely mediated by mountain pine beetles.