Thesis (M.S.) University of Alaska Fairbanks, 2012Permafrost and organic soil layers are common to most wetlands in interior Alaska, where wetlands have functioned as important long-term soil carbon sinks. Boreal wetlands are diverse in both vegetation and nutrient cycling, ranging from nutrient-poor bogs to nutrient- and vascular-rich fens. The goals of my study were to quantify growing season ecosystem respiration (ER) along a gradient of vegetation and permafrost in a boreal wetland complex, and to evaluate the main abiotic and biotic variables that regulate CO₂ release from boreal soils. Highest ER and root respiration were observed at a sedge/forb community and lowest ER and root respiration were observed at a neighboring rich fen community, even though the two fens had similar estimates of root biomass and vascular green area. Root respiration also contributed approximately 40% to ER at both fens. These results support the conclusion that high soil moisture and low redox potential may be limiting both heterotrophic and autotrophic respiration at the rich fen. This study suggests that interactions among soil environmental variables are important drivers of ER. Also, vegetation and its response to soil environment determines contributions from aboveground (leaves and shoots) and belowground (roots and moss) components, which vary among wetland gradient communities.Introduction -- Introduction to boreal wetlands -- Ecosystem respiration and its role in peatland function -- Brief rationale for this study -- Goals, objectives, and hypotheses -- Methods -- Description of study site and the gradient design -- Atmospheric and soil environmental variables -- Ecosystem respiration fluxes -- Root respiration fluxes and aboveground vegetation measurements -- Results -- Soil environmental variables along the gradient -- Ecosystem respiration -- Contributions of root respiration to ER -- Discussion -- Patterns of ecosystem respiration along the wetland gradient -- The role of roots in ecosystem respiration of CO₂ -- Study limitations and ideas for future research -- Conclusions
