Impacts of Surrounding Land-use on Denitrification and Carbon Storage in Headwater Wetlands of Central Pennsylvania
Open Access
- Author:
- Britson, Aliana Jocelyn
- Graduate Program:
- Ecology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- July 16, 2014
- Committee Members:
- Denice Heller Wardrop, Dissertation Advisor/Co-Advisor
Elizabeth Weeks Boyer, Committee Chair/Co-Chair
Patrick Joseph Drohan, Committee Member
Christopher J Duffy, Committee Member - Keywords:
- Denitrification
Carbon Storage
Wetlands
Anthropogenic Disturbance
Ecosystem Services
Ecosystem Functional Assessments - Abstract:
- There is increasing evidence that elevated levels of nitrate are degrading aquatic ecosystems while increasing atmospheric carbon levels are leading to global climatic shifts. Riparian wetlands may alleviate the impacts of elevated nitrate and atmospheric carbon through denitrification and long-term carbon storage. However, anthropogenic impacts in the surrounding landscape likely affect the ability of riparian wetlands to provide these ecosystem services. Changes in land-use regimes surrounding riparian wetlands has been known to alter plant communities, hydrology, and soils. However, few studies examine whether the different plant communities associated with land-use regime affect decomposition or total carbon inputs and outputs within these wetlands and whether these differences lead to differential carbon storage. For denitrification, surrounding-land use likely influences the concentration of important abiotic parameters such as nitrate and dissolved organic carbon. However, it is not understood how surrounding land-use influences the distribution of these parameters and thus the distribution of denitrification in space and time. To better understand the influences of land-use on denitrification and carbon storage, three high disturbance and three low disturbance headwater wetlands were selected. Factors known to affect denitrification in shallow groundwater were analyzed at a meter scale and used to construct functional habitats to examine the combined effects of multiple parameters on denitrification. To examine effects of plant community on carbon storage I classified the sites by plant community, performed a yearlong decomposition experiment, and measured organic carbon inputs and outputs at each site. Five distinct denitrification functional habitats were identified across the six sites. Distribution of three out of five functional habitats differed between high and low disturbance sites, indicating that surrounding land-use regime likely influences the spatial characteristics of biogeochemical parameters important to denitrification. Carbon storage differed between the plant communities, with low disturbance sites dominated by Tsuga canadensis having the highest soil carbon levels. The differences in carbon storage were likely due to differential decomposition and carbon inputs and outputs between the different plant communities. Litter quality was found to be a large driver of decomposition dynamics, as litter with greater percent C, percent lignin, C:N ratios, and lignin:N ratios decomposed more slowly. Furthermore, significant differences in dissolved organic carbon concentration and quality, as well as soil carbon content and quality between high and low disturbance sites indicate shifts in carbon dynamics which can likely be attributed to differences in plant community. Overall, large changes were seen in carbon dynamics and biogeochemical parameters associated with denitrification between high and low disturbance sites, indicating that surrounding land use has a large effect on C and N cycling in headwater wetlands.