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

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 (S_275–295) 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.