305-4
Temperature Sensitivity Of Anaerobic Carbon Processing: The Importance Of Carbon Quality Vs. Nutrient Availability.

Tuesday, November 5, 2013: 10:05 AM
Marriott Tampa Waterside, Grand Ballroom J, Second Level

Debjani Sihi, University of Florida, Gainesville, FL, Kanika S. Inglett, Soil and Water Science, Wetland Biogeochemistry Laboratory, University of Florida, Gainesville, FL and Patrick W. Inglett, Department of Soil and Water Science, University of Florida, Gainesville, FL
Anaerobic carbon (C) processing in warmer peatlands is relatively unexplored compared to northern systems. Temperature has a dominant influence on CO2 and CH4 fluxes in northern wetlands. However, specific effects of temperature on C mineralization in warmer wetlands remain difficult to isolate from other factors such as C quality and nutrients. Our objective was to assess the temperature sensitivity of soil organic carbon (SOC) decomposition in relation to C quality and phosphorus (P) availability over 15°-30°C range in freshwater, Cladium-based peats of the Everglades. We hypothesized that C quality will interact more with temperature sensitivity of SOM decomposition than nutrient level in warmer wetlands. Depth (0-10 cm and 10-20 cm) was used as a surrogate of C quality while two sites were selected to represent soils with contrasting P availability. Temperature was increased in 5°C steps to assess proportion of C considered available at a given temperature (i.e. thermo-labile C) and production estimates of gaseous (CO2 and CH4) and dissolved organic C (DOC) fractions were determined by anaerobic incubation of samples. Results confirmed that temperature significantly controlled SOC decomposition rate, where higher temperature increased the proportion of gaseous forms vs. DOC and CH4 vs. CO2. As a percentage of total SOC, thermo-labile C increased from 0.37-0.84 % at 15°C to 1.24-2.98 % at 30°C. Higher Q10 was observed for CH4 (~14) followed by CO2 (~2.5), and DOC (~1.7). Spectral slope ratios (S275–295) of DOC increased 1.2-2 fold over 15°C-30°C range, thus indicating more bio-available DOC production at higher temperature. The temperature response of SOC decomposition was more influenced by C quality than nutrient availability. At lower temperature, SOC decomposition was limited by C quality, while at higher temperature it was mainly influenced by P limitation. These findings have potential to advance our understanding of climate-C feedback in warmer peatlands.
See more from this Division: SSSA Division: Wetland Soils
See more from this Session: General Wetland Soils: I

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