Doctor of Philosophy, The Ohio State University, 2012, Environment and Natural Resources

Wetland ecosystems are significant carbon sinks. Their high productivity and presence of water gives them the ability to efficiently sequester carbon in the soil, serving as a potential tool to mitigate the net greenhouse effect of carbon emissions to the atmosphere and abate climate change. We explored the efficiency of freshwater wetlands sequestering carbon under different climates, wetland types, and vegetation communities, in order to assess the conditions that favor carbon accumulation. We also studied the ability of created freshwater wetlands to sequester carbon and the effect of their vegetation communities on this task. We found significant differences on carbon sequestration between wetland types in temperate and tropical regions, being consistently higher in the studied forested wetlands (260 ± 58 gC m-2 y-1) than the riverine ones (113 ± 27 gC m-2 y-1), indicating the importance of wetland productivity and the type of organic matter entering the system. Our temperate wetlands were also consistently more efficient in sequestering carbon than similar tropical ones (233 ± 89 and 151 ± 57 gC m-2 y-1, respectively), suggesting that higher temperatures in tropical climates may hinder carbon sequestration by intensifying organic matter decomposition rates. Within the tropical climates, we found that the tropical humid wetland sites had significantly higher carbon sequestration rates (306 ± 77 gC m-2 y-1) than those located in the tropical dry regions, were there is a marked wet and dry season (63 ± 10 gC m-2 y-1 on average). Our comparison between vegetation communities show that wetland productivity and permanent anaerobic conditions are key in enhancing soil carbon sequestration, being 214 ± 54 gC m-2 y-1 in the open water sites (with prolonged anaerobic conditions) and 184 ± 72 gC m-2 y-1 in the edges (typically more productive due to their fluctuating water levels). In the tropics, where temperature might to be a limiting factor for carbon sequestration (open full item for complete abstract)

Committee: William J. Mitsch (Advisor); Rattan Lal (Committee Member); Richard P. Dick (Committee Member); Eric Toman (Committee Member) Subjects: Environmental Science

Master of Science, The Ohio State University, 2008, Natural Resources

Wetlands are a large terrestrial carbon pool and play an important role in global carbon cycles as natural carbon sinks. Previous carbon studies have mainly focused on boreal peatlands; little is known about carbon pools in temperate and tropical wetlands and their soil profiles. This study analyzes the variation of soil carbon with depth in two temperate (Ohio) and three tropical (humid and dry) wetlands in Costa Rica, and compares their total soil C pool as a first step toward determining C accumulation in wetland soils. The results indicate that these temperate wetlands have significantly greater (P < 0.01) C pools (17.6 kg C m-2) than wetlands located in tropical climates (9.7 kg C m-2) in the top 24 cm of soil. Carbon profiles showed a rapid decrease of concentrations with soil depth in the tropical sites, whereas in the temperate wetlands they tended to increase with depth, up to a maximum at 18-24 cm, after which they started decreasing. The two wetlands in Ohio had about ten times the mean total C concentration of adjacent upland soils (e. g., in Gahanna Woods, 161 g C kg-1 were measured in the wetland, and 17 g C kg-1 in the upland site), and their soil C pools were significantly higher (P < 0.01). Among the five wetland study sites, three main wetland types were identified – isolated forested, riverine flow-through, and slow-flow slough. In the top 24 cm of soil, isolated forested wetlands had the greatest pool (10.8 kg C m-2), significantly higher (P < 0.05) than the other two types (7.9 kg C m-2 in the flow-though and 8.0 kg C m-2 in the slough), indicating that the type of organic matter entering into the system and the type of wetland may be key factors defining its soil C pool. The flow-through wetland in Ohio (Old Woman Creek) showed a significantly higher C pool (P < 0.05) in the permanently flooded location (18.5 kg C m-2), than in the edge location with fluctuating hydrology, where the soil is inttermitently flooded (14.6 kg C m-2).

Committee: William Mitsch (Advisor); Rattan Lal (Committee Member); Richard Dick (Committee Member) Subjects: Ecology; Environmental Science; Soil Sciences