Theses and Dissertations at Montana State University (MSU)
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Item The effect of permafrost thaw and geologic substrate on dissolved organic carbon mobilization and transformation in northern streams(Montana State University - Bozeman, College of Agriculture, 2019) Wologo, Ethan Andrew; Chairperson, Graduate Committee: Stephanie A. Ewing; Sarah Shakil, Scott Zolkos, Sadie Textor, Stephanie Ewing, Jane Klassen, Robert G.M. Spencer, David C. Podgorski, Suzanne E. Tank, Michelle A. Baker, Jonathan A. O'Donnell, Kimberly P. Wickland, Sydney S.W. Foks, Jay P. Zarnetske, Joseph Lee-Cullin, Futing Liu, Yuanhe Yang, Pirkko Kortelainen, Jaana Kolehmainen, Joshua F. Dean, Jorien E. Vonk, Robert M. Holmes, Gilles Pinay, Michaela M. Powell, Jansen Howe, Rebecca Frei and Benjamin W. Abbott were co-authors of the article, 'No evience of dissolved organic matter priming in permafrost stream networks: a circumpolar assessment' submitted to the journal 'Global biogeochemical cycles' which is contained within this thesis.; Stephanie Ewing, Jonathan A. O'Donnell, Jim Paces, Rob Striegl, Duane Froese and Joshua Koch were co-authors of the article, 'Groundwater connection and doc transport in the Yukon River Basin: uranium and strontium isotopes in permafrost catchments' submitted to the journal 'Global biogeochemical cycles' which is contained within this thesis.Permafrost landscapes exhibit unique hydrology that is linked both chemically and physically to nutrient cycling and geochemical processes. Permafrost thaw is expected to result in a positive feedback to Earth's climate system through carbon release to the atmosphere; this potential demands better understanding of hydrologic pathways in permafrost landscapes in the face of global change. The work that follows is divided into two main bodies of research that explore both carbon dynamics and isotope geochemistry of river waters draining permafrost catchments in the Yukon River Basin (YRB). The first study uses in-vitro incubations of stream water from seven permafrost regions to investigate how biolabile carbon additions (acetate) and inorganic nutrients (nitrogen and phosphorus) 'prime' water-column dissolved organic carbon (DOC) decomposition. No priming effect from biolabile carbon addition was evident through changes in DOC concentrations or compositional transformations, but consumption of added acetate was correlated with ambient nutrient concentrations. Sites with fine-textured, ice-rich substrate and proximal thermokarst features had higher ambient DOC and nutrient concentrations, and consequently the fastest rates of acetate consumption. We conclude that the fate of biolabile DOC released from degrading permafrost will depend largely on inorganic nutrient availability in receiving waterbodies. The second part of this thesis focuses on hydrology of intermediate-sized catchments in the YRB. We evaluate uranium isotope activity ratios ([234U/238U]) as tracers of groundwater-surface water connection in thawing permafrost landscapes. Streams draining loess-mantled areas had [234U/238U] values moderately increased relative to meteoric values. Streams draining low-order catchments with rocky substrate and surface disturbance exhibit dramatically increased [234U/238U] values, consistent with groundwater connection. In addition, we observed higher DOC concentrations both in areas influenced by recent thaw and where flow is restricted by ice-rich silt. The transformation of northern stream chemistry will likely continue as northern permafrost environents warm, with greatest resilience of ground ice in loess-blanketed areas not subject to thermal erosion by groundwater. As subsurface storage expands and groundwater exchange intensifies, ecosystems within and connected to northern streams will also be transformed, with implications for resource managers concerned with fish and wildlife management in these systems.Item Effect of permafrost thaw on methane and carbon dioxide exchange in two western Alaska peatlands(Montana State University - Bozeman, College of Agriculture, 2013) Johnston, Carmel Eliise; Chairperson, Graduate Committee: Stephanie A. Ewing; Stephanie A. Ewing, Jennifer W. Harden, Paul C. Stoy, Ruth K. Varner, Kimberly P. Wickland, Joshua Koch, Christopher Fuller and Mark T. Jorgenson were co-authors of the article, '2.0 effect of permafrost thaw on CO 2 and CH 4 exchange in a western Alaska peatland chronosequence' submitted to the journal 'Environmental research letters' which is contained within this thesis.; Stephanie A. Ewing, Merritt R. Turetsky, Jennifer W. Harden, A. David McGuire and Miriam Jones were co-authors of the article, '3.0 effect of recent permafrost thaw on the spatial distribution of CO 2 and CH 4 exchange in a western Alaska peatland' submitted to the journal 'Environmental research letters' which is contained within this thesis.Methane (CH 4) causes about 20% of greenhouse gas radiative forcing despite its relatively short lifetime (~10 y) and low concentration (1800 ppb) in the atmosphere. Wetlands are the largest natural source of CH 4, amounting to 22% of CH 4 production globally, with emission of CH 4-C by both diffusion and ebullition pathways. Permafrost peatlands store about 10% of permafrost C and 5% of global belowground C; hence CH 4- C emission with peatland permafrost thaw is of concern. We quantified temporal and spatial aspects of CH 4 and CO 2 emissions from northern peatlands using two approaches: (1) a ~1000 y thaw chronosequence in remote western Alaska (Innoko Flats Wildlife Refuge; May-September, 2011), and (2) lateral transects in intermediate age (~20-500 y) collapse-scar bog features at a well-instrumented site near Fairbanks, Alaska (Alaska Peatland Experiment (APEX)/Bonanza Creek Long Term Experimental Research site; June-September, 2012). At Innoko Flats, peak CH 4 production was observed in features aged 30-590 y since thaw, which had warmer soils than younger sites and shallower water tables than older sites. Average surface flux at these 30-590 y sites (+2.52 ± 0.98 mg CH 4-C m -2 hr -1) was greater than estimated ebullition flux (0.13 ± 0.05 mg CH 4-C m -2 hr -1) based on an observed rate of 0.78 ± 0.33 mL m -2 hr -1. Net ecosystem exchange of CO 2-C (NEE) did not differ among chronosequence features, and offset CH 4-C emissions by a factor of 2 to 400 when considered as 100-y global warming potential. At APEX, bogs reflecting <100 y since most recent thaw showed high variability in CH 4 exchange, but rates were generally consistent with levels at the Innoko 30-590 y sites (mean of 5.42 ± 1.16 mg CH 4-C m -2 hr -1). APEX bogs showed greater balance between CH 4-C efflux and CO 2-C influx, with CH 4-C fluxes offsetting 80-140% of NEE during the growing season when considered as 100-y global warming potential. We argue that CH 4 contributes most significantly to post-thaw C loss over timescales of decades to centuries in these northern peatlands.Item Regional context, internal structure, and microbiological investigation of the Lone Peak Rock Glacier, Big Sky, Montana(Montana State University - Bozeman, College of Letters & Science, 2011) Florentine, Caitlyn Elizabeth; Chairperson, Graduate Committee: Mark L. Skidmore; Mark Skidmore, Marvin Speece, Curtis Link, William Locke, Christina Carr, and Colin Shaw were co-authors of the article, 'The role of geology in rock-glacier distribution and internal structure: a case study from SW Montana' in the journal 'Journal of geophysical research earth surface' which is contained within this thesis.; Mark Skidmore and Scott Montross were co-authors of the article, 'Rock-glacier ice as a microbial habitat' in the journal 'Journal of glaciology' which is contained within this thesis.This thesis is the first to the author's knowledge to conduct a holistic investigation of the physical, chemical and microbial properties of a rock glacier. The Lone Peak Rock Glacier (LPRG) is located in the Madison Range of southwest Montana on Big Sky Resort property. This thesis focuses on three scales of investigation: regional, landform, and micro. Regional-scale analysis assessed the role of geology and topography as factors in determining rock-glacier distribution in SW Montana above 2000m. Rock glaciers across alpine landscapes in southwest Montana are preferentially distributed according to rock type, with more rock glaciers occurring in intrusive, foliated intrusive and metamorphic catchments relative to the areal proportion of these rock types than in extrusive and sedimentary catchments. This preferential distribution according to catchment geology is likely due to the affect that geology has on topography and provision of talus. Landform-scale analysis focuses on internal structure, flow dynamics and surface topography of the LPRG. The relationship between surface topography and subsurface structure is explained by passive roof duplex faulting. This finding has implications for rock-glacier flow dynamics and the development of transverse ridges, a common surface feature of rock glaciers studied worldwide. Micro-scale analysis characterizes microbiological and geochemical properties of rock-glacier ice and evaluates it as a microbial habitat, exploring potential associations between debris content and microbial activity. Amber ice (containing 0.1% debris by weight) appears to be a more suitable microbial environment than debris-poor ice (containing < 0.01% debris). This finding highlights the importance of debris as a potential nutrient and energy source to enhance microbial viability in rock-glacier ice.