Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Hydrology and landscape structure control subalpine catchment carbon export(Montana State University - Bozeman, College of Agriculture, 2009) Pacific, Vincent Jerald; Chairperson, Graduate Committee: Brian L. McGlynn.Carbon export from high elevation ecosystems is a critical component of the global carbon cycle. Ecosystems in northern latitudes have become the focus of much research due to their potential as large sinks of carbon in the atmosphere. However, there exists limited understanding of the controls of carbon export from complex mountain catchments due to strong spatial and temporal hydrologic variability, and large heterogeneity in landscape structure. The research presented in this dissertation investigates the control of hydrology and landscape structure and position on two major avenues of carbon loss from mountain watersheds: soil respiration and stream dissolved organic carbon (DOC) export. Measurements of soil respiration and its biophysical controls (soil water content, soil temperature, vegetation, soil organic matter, and soil physical properties) and stream and groundwater DOC dynamics are presented across three years and multiple riparian-hillslope transitions within a complex subalpine catchment in the northern Rocky Mountains, Montana. Variability in soil respiration was related to hydrologic dynamics through space and time and was strongly influenced by topography and landscape structure. Cumulative soil CO 2 efflux was significantly higher from wet riparian landscape positions compared to drier hillslope locations. Changes in hydrologic regimes (e.g. snowmelt and precipitation timing and magnitude) also impacted soil respiration. From a wet to a dry growing season, there were contrasting and disproportionate changes in cumulative growing season surface CO 2 efflux at wet and dry landscape positions. Stream DOC export was also influenced by landscape structure and hydrologic variability. The mobilization and delivery mechanisms of DOC from the soil to the stream were dependent upon the size of DOC source areas and the degree of hydrologic connectivity between the stream and the riparian and hillslope zones, which varied strongly across the landscape. This dissertation provides fundamental insight into the controls of hydrology and landscape structure on carbon export from complex mountain watersheds. The results of this research have large implications for the carbon source/sink status of high elevation mountain ecosystems, the influence of changing hydrologic regimes on soil respiration, and the use of landscape analysis to determine the locations of large source areas for carbon export.Item A review of landscape influences on riparian zone processes in mountainous headwater catchments(Montana State University - Bozeman, College of Agriculture, 2012) Stoy, Padraic Fitzgerald; Chairperson, Graduate Committee: Lucy Marshall.Understanding the drivers of riparian zone hydrology is crucial for informed management of water quality, especially in headwater catchments. This study reviews landscape influences on riparian zone processes in mountainous headwater catchments, and combines recent findings and management techniques into a conceptual analysis of riparian zone hydrology and nutrient export. A case study synthesizing recently published work in Tenderfoot Creek Experimental Forest (TCEF) is developed outlining riparian zone hydrology, riparian buffering, and nutrient export. We demonstrate that a major influence on the hydrology and nutrient export in mountainous catchments can be landscape structure, and use this finding as a framework to develop a conceptual approach to riparian zones in mountainous areas. The conceptual analysis is intended to inform management through the identification of riparian areas that are important for stream water quality depending on hydrologic drivers in the catchment. Understanding the variability of riparian zone hydrology and subsequent water quality impacts will allow for more focused and informed management decisions for riparian areas.