Theses and Dissertations at Montana State University (MSU)
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Item Biogeochemistry and hydrology of three alpine proglacial environments resulting from glacier retreat(Montana State University - Bozeman, College of Letters & Science, 2008) Bruckner, Monica Zanzola; Chairperson, Graduate Committee: Mark L. SkidmoreProglacial environments, formed by glacier retreat, exhibit distinct characteristics in discharge, water temperature, water residence time, and dissolved ion, carbon, and suspended sediment concentrations. The unnamed alpine glacier at the headwaters of the Wheaton River, Yukon, Canada, provides an ideal setting to compare deglaciation processes that result in three different proglacial environments. The glacier has evolved from occupying one large catchment (~4 km²) to two smaller catchments (each ~2 km²) via glacier thinning and net mass loss, forming two lobes separated by a medial moraine. Field observations revealed neither crevasses nor evidence of subglacial drainage outlets and suggested this glacier had a non-temperate thermal regime with meltwater predominantly flowing from supraglacial and ice marginal sources. Climate and bedrock geology were similar for the subcatchments, providing a natural laboratory to compare deglaciation processes. This study compared the hydrology and biogeochemistry of three outlet streams from this glacier: one stream drained a proglacial lake which is fed by meltwater from the lower west lobe, a second stream drained the upper west lobe, and a third stream was the major drainage outlet for the east lobe. Hydrologic monitoring over the 2006 melt season (June-August) and analyses of water samples for dissolved ion content and carbon indicated that the meltwaters are dominated by Ca²+ and HCO 3-, which are derived from biogeochemical weathering of crustal materials. The study demonstrated that the presence of the proglacial lake, which acted as a meltwater reservoir, measurably modified meltwater residence time, water temperature, water chemistry, and bacterial biomass relative to the proglacial streams. Rock:water interaction between meltwater and medial morainal sediment and fine-grained, reactive glacial flour suspended in the streams and the lake water column also enhanced biogeochemical weathering within the catchment. Thus, this study provided a small-scale example for how differences in proglacial environments and water flow paths affect headwater hydrology and biogeochemistry. This study was the first of its kind in the Coast Mountains, Yukon, Canada, and results presented here aid in the understanding of how proglacial environments created by climate-induced glacier retreat affect hydrochemistry, hydrology, and carbon dynamics in remote high elevation environments.Item Classification of the grasslands, shrublands, woodlands, forests and alpine vegetation associations of the Custer National Forest portion of the Beartooth Mountains in Southcentral Montana(Montana State University - Bozeman, College of Letters & Science, 2012) Williams, Kristin Louise; Chairperson, Graduate Committee: David Roberts; Dave W. Roberts was a co-author of the article, 'Classification of shrubland associations of the Beartooth Mountains study area and comparison to existing grassland and shrubland habitat type classifications' in the journal 'Western North American naturalist' which is contained within this thesis.; Dave W. Roberts was a co-author of the article, 'Classification of woodland and forested vegetation associations of the Beartooth Mountains study area and comparison with existing woodland and forested habitat type classifications' in the journal 'Western North American naturalist' which is contained within this thesis.; Dave W. Roberts was a co-author of the article, 'Classification of the alpine vegetation associations of the Beartooth Mountains study area' in the journal 'Western North American naturalist' which is contained within this thesis.The purpose of this thesis was to classify and describe low-elevation grassland and shrubland vegetation, mid-elevation woodland and forested vegetation, and high elevation alpine vegetation associations of the Beartooth Mountains study area and to compare newly derived associations with existing habitat type and community type classifications of ecologically relevant environments in Montana, Wyoming and Idaho. Five grassland/shrubland associations, twelve woodland/forested associations and thirteen alpine associations were classified and described for the Beartooth Mountains study area. Prior to this thesis, no comprehensive vegetation association classification of the Beartooth Mountains, the highest, largest and easternmost alpine region in Montana, has been conducted.