| Summary: | Specialization: Microbiology and Biotechnology Degree: Master of Science Abstract: Alpine glaciers have been retreating since the Little Ice Age, leading to exposure of foreland soils. Microorganisms are the primary below ground biological influence on nutrient cycling in recently deglaciated soil and are linked to down valley vegetation colonization. Previous studies demonstrate high turnover rates of bacterial communities within the first 50 years following glacier retreat, coinciding with plant colonization. It thus remains unclear whether turnover occurs as a result of changing conditions after glacier retreat, or from the effects of plant colonization. Using high throughput sequencing of 16S rRNA genes and standard soil chemistry analysis, I examined the trends in both bacterial diversity and soil chemistry to address my central hypothesis: bacterial community turnover will be linked to glacier retreat in newly deglaciated soils and plant colonization in more developed soils. Changes in bacterial community structure were examined in 42 samples collected from two chronosequences within the foreland soils of Duke River, located in Kluane National Park Reserve, Yukon. The chronosequences contain up to 220 years of non-vegetated soils before an appreciable grassline, therefore allowing extended assessment of bacterial succession in bare soils before analyzing changes following plant colonization. I determined the existence of three successional groups within both chronosequences; an “early” group in soils of less than approximately 50 years since deglaciation; an “intermediate” group within bare soils after deglaciation but before the grassline; and a “grassline” group following plant colonization. These results suggest the high turnover after glacier retreat occurs as a result of glacier retreat itself, and the later colonization by plants is associated with a second period of turnover linked with changes in soil chemistry properties. This work elucidates and provides further insight into the processes of ...
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