Patterns of Sulfur and Carbon Biogeochemistry in Three Wetland Types Across an Alpine Landscape, Niwot Ridge, Colorado

Huber, Molly Elizabeth

Graduate Thesis Or Dissertation

Patterns of Sulfur and Carbon Biogeochemistry in Three Wetland Types Across an Alpine Landscape, Niwot Ridge, Colorado Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/1j92g8771

Abstract

Wetlands serve as important locations of disproportionately high biogeochemical activity and plant productivity in many lowland regions. However, little is known about the function of alpine wetlands, or about how their biogeochemical cycling compares with the broader alpine landscape, which is usually composed of thin, rocky soils and tundra vegetation. In my thesis research, I compared the soil and water biogeochemistry among three types of alpine wetlands at Niwot Ridge, CO: alpine wet meadow (AWM), periglacial solifluction lobe (PSL), and subalpine wetland (SAW). Each wetland type exhibited unique biogeochemical characteristics. SAWs had high organic matter, high carbon concentrations, and low bulk density. Mean loss on ignition from SAW samples (70%) was significantly higher than AWM and PSL samples (17% and 13%, respectively), mean soil %C and DOC in surface water from SAW samples (37.2% and 12.8 mg L^-1, respectively) was higher than in AWMs (9.4% and 6.5 mg L^-1), and in PSLs (7.0% and 7.3 mg L^-1), and soil bulk density was lower in SAWs (0.16 g cm-3) than in AWMs (0.48 g cm-3) and PSLs (1.06 g cm-3). PSLs had very high sulfur concentrations in soil and water as sulfate, at 0.603 mg S g^-1 dry soil and 16.4 mg S L^-1, compared to 0.016 mg S g^-1 dry soil and 0.5 mg S L^-1 in AWMs and 0.042 mg S g^-1 dry soil and 0.2 mg S L^-1 in SAWs. PSLs also had low soil pH, with a mean pH of 3.95 in interior soil samples from PSLs, compared to 4.56 and 4.23 in the AWMs and SAWs, respectively. Compared to surrounding alpine dry meadow, all wetlands had higher water content, higher organic matter, lower pH, and higher soil extractable sulfur as sulfate in interior pools, and AMWs and SAWs had higher total soil carbon. These findings suggest that wetlands may have a disproportionate effect on biogeochemical and ecological processes in alpine landscapes.

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