Date of Award
Master of Science (MS) in Biology
Wetlands are biodiverse ecosystems that play a key role in the biogeochemical cycling of carbon. In the face of global warming, wetland hydroperiods could shift causing changes in their functionality. My field experiment surveyed 3 plots within 12 wetlands of each hydroperiod class (i.e. 12 permanent, 12 semi-permanent, 12 ephemeral). This survey was paired with a warming experiment by placing open top warming chambers on half of each wetland type. In chapter one, I compared carbon dynamics across hydroperiods and treatment by measuring soil organic carbon (in Summer 2018) and effluxes of carbon dioxide and methane (in Summer 2018, Fall 2018, and Spring 2019). I found no differences across wetland type or warming treatment in soil organic carbon. Results also showed that when comparing wetland fluxes within each season, there were no differences between wetland types or warming treatments. CO2 fluxes were consistently higher than CH4 fluxes within and across all seasons. The seasonality of CO2 and CH4 fluxes differed, which lead to a significant interaction between gas and season. In chapter two, I report on differences in both wetland soil microbial abundance and diversity between treatments. Total abundance was measured by qPCR to quantify 16S rRNA gene copy numbers. Soil microbial diversity, composition, and relative abundance was determined using Illumina sequencing protocol for the amplification of the V4-V5 region of the 16S rRNA gene. Results showed that both abundance and diversity decreased with warming and depth within permanent wetlands, although no variation in species composition was found. Abundance also decreased with warming in ephemeral wetlands, but diversity did not. Although Chapter 1 highlights a general stability in carbon dynamics with warming, Chapter 2 illustrates that the microbial communities are changing with warming and that they might not be as stable over time. As global warming progresses, it is important to continue wetland ecosystem research in longer term studies due to its high potential for climate change mitigation.
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Medina, Marissa A., "The effects of warming on carbon and microbial community wetland dynamics at Turnbull National Wildlife Refuge, Washington" (2019). EWU Masters Thesis Collection. 571.