Graduate Thesis Or Dissertation
 

Lake classification in the glacially influenced landscape of the north Cascade mountains, Washington, USA

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/nc580r69h

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  • Factors affecting physical, chemical, and biological characteristics of lakes were investigated through the development of a lake-classification system for 162 lakes in North Cascades National Park Service Complex. A conceptual view of lake development and its relationship to the expression of lake and watershed characteristics was derived. Water quality and biological assemblages of these primarily glacially formed high-mountain oligotrophic lakes were influenced by elevation, lake morphology, and certain watershed characteristics: aspect, vegetation, soils, hydrology, and degree of glacial influence. Lakes continually evolve relative to changes in their watershed environments. A watershed-based, three-level hierarchical classification was created to include 1) lake position relative to the hydrologic crest of the North Cascade Mountain Range, 2) vegetation zone (alpine, subalpine, low elevation forest, high elevation forest), and 3) basin origin. Hydrologic crest position differentiated broad-scale climatic differences in precipitation and air temperature. Vegetation zones reflected the localized geology (soil maturation) and climate (precipitation, aspect). Morphogenetic class identified differences in lake morphology, landscape position, and potential for persistence, and were unequally distributed across vegetation zones with forest zones most diverse. Time of ice-out increased from low-forest lakes to alpine lakes; eastslope lakes iced-out earlier. Epilimnetic temperature was warmest in low-forest lakes and coolest in alpine lakes. Classification did not clearly order lakes relative to chemical characteristics, though westslope low-forest lakes differed significantly from other lake classes and were most productive. Little seasonal or annual variation for most chemical characteristics were found. However, chemical differences did mirror environmental and physical differences between lakes. High phosphorus levels separated glacially influenced lakes. Total Kjeldahl-N and total phosphorus concentrations decreased with increasing lake depth. For a given flushing ratio, Kjeldahl-N decreased from low-forest to alpine zones. Depth and vegetation class ordered the diversity and composition of phytoplankton, zooplankton, and benthic macroinvertebrate assemblages. Nutrients, conductivity, pH, alkalinity, and cations were correlated with phytoplankton and zooplankton assemblages. Non-native trout presence was associated with large, deep [greater than or equal to] 3 m) lakes.
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