Theses and Dissertations at Montana State University (MSU)
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Item Breeding bird populations in logged and unlogged forest stands in southwestern Montana(Montana State University - Bozeman, College of Letters & Science, 1993) Mulqueen, Kathleen ElizabethItem GIS modeling of bison habitat in southwestern Montana : a study in ranch management and conservation(Montana State University - Bozeman, College of Letters & Science, 2000) Phillips, Linda BowersItem Graph-theoretic modeling of functional habitat connectivity for lynx on the Okanogan Highlands, northern Washington(Montana State University - Bozeman, College of Letters & Science, 2004) Jones, Aaron Paul; Chairperson, Graduate Committee: Richard J. AspinallMaintenance of habitat connectivity over various geographic scales is a conservation imperative for the long-term persistence of many species. Functional linkages for a given focal species may not be readily apparent or spatially coincident with explicit structural patterns in a landscape. In species-level habitat connectivity modeling, therefore, techniques derived from empirical data are needed to sustain a species-centric perspective on landscape mosaics. This study demonstrates an empirically-based, combined Bayesian and graph-theoretic approach to modeling functional habitat connectivity. The case study focused on a subpopulation of Canadian lynx resident to a subalpine plateau in north-central Washington. Using data collected during two prior radiotelemetry studies, habitat selection by individual lynx was analyzed at two spatial scales using a combination of compositional analysis, chi-squared tests, and Neu's method. Significant habitat associations were used to create probability models for lynx presence using Bayes theorem. These provided a composite index of habitat suitability and enabled data-driven definition of habitat patches and an impedance surface for lynx movement in the study landscape. To address gradual variation in habitat quality, multiple study-wide and within-home-range patch surfaces were derived in accord with minimum percentages of areas of known lynx presence. Patches and cost-weighted interpatch distances were then converted to lattice data structures (graphs) and used as frameworks for hierarchical analyses of functional connectivity. Mapped probabilities of lynx presence indicated higher quality habitat in the northward interior of the study area and in several drainages along its northern periphery. Areas most significant to study-wide connectivity were identified in terms of core linkages and those along which the habitat network is most susceptible to disruption. A general divergence between these areas suggests that the former, "parsimoniously-connected" cores of lynx habitat may also be the areas most resilient to fragmentation. Places where these areas co-occur, however, are "hotspots" supported by dual justifications for conservation prioritization. In measuring global connectivity, three indices were relatively insensitive to changes in patch surface definition until the graph based on seven percent areas of known presence was reached, after which point fragmentation was marked. A critique of the Bayesian graph-theoretic modeling approach concludes the study, with emphasis given to its applicability for identifying subregional habitat linkages for far-ranging carnivores.Item The influence of riparian-canopy structure and coverage on the breeding distribution of the southwestern willow flycatcher(Montana State University - Bozeman, College of Letters & Science, 2005) Brodhead, Katherine May; Chairperson, Graduate Committee: Richard J. AspinallThere is a long history of relating bird species diversity and distributions to heterogeneity in foliage structure as seen from within the habitat and measured from the ground up. There is also an overwhelming contribution in the literature promoting and justifying a broad-scale approach to characterizing spatial patterns, especially for the purpose of relating to, and predicting, species distributions. This study draws from the relationship between birds and habitat structure but assesses heterogeneity in structure from a broader perspective. For this analysis, I compared the spatial distribution of a breeding population of the southwestern willow flycatcher (Empidonax extimus traillii) to the structure of a riparian zone with an emphasis on capturing patterns that are measured horizontally across the zone. Riparian zones are dynamic by nature and are structurally diverse in a natural, healthy system, and support a high density of breeding birds. The flycatcher prefers dense riparian habitat in close proximity to lentic water. The structural characteristics of the riparian zone where dense vegetation and water are present were hypothesized to be more structurally heterogeneous and to support a broader riparian zone. Riparian zone structure was mapped and stand characteristics were extracted, with the intent of relating spatial patterns in stand heterogeneity and riparian extent to the spatial distribution of the southwestern willow flycatcher. A moving window function in a GIS assessed the stand characteristics, which were imported as attributes to presence/absence data points. The extent of the analysis window was varied to determine the scale at which the habitat characteristics were most highly correlated with flycatcher presence. Correlation between the structural characteristics of the stand and the presence/absence of the flycatcher was modeled with logistic regression. Results show the flycatcher is more likely to occupy habitat that is structurally heterogeneous and has more riparian vegetation. The results also show that selection is most sensitive to habitat characteristics within a relatively close proximity.