Journal
BIOGEOCHEMISTRY
Volume 131, Issue 1-2, Pages 103-119Publisher
SPRINGER
DOI: 10.1007/s10533-016-0267-8
Keywords
Organic matter decomposition; Peat; Greenhouse gas; Respiration; Methane; Dissolved organic carbon; Temperature sensitivity; Carbon quality; Nutrient availability
Funding
- National Science Foundation (NSF) [DEB 0841596]
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Estimates of gaseous carbon (C) fluxes in wetlands are heavily based on temperature. However, isolating specific effects of temperature on anaerobic C processing from other controls (C quality and nutrients) has proven difficult. Here, we test the hypothesis that temperature sensitivity of soil organic matter (SOM) decomposition is more influenced by C quality than nutrient availability in subtropical freshwater, sawgrass (Cladium jamaicense)-based peats. Carbon age (characterized by depth: 0-10 and 10-20 cm) was used as a surrogate of C quality while two sites were selected with contrasting levels of nutrient (P) availability. In anaerobic laboratory incubations temperature was increased in 5 degrees C steps to assess the proportion of C available at a given temperature (i.e. thermo-labile C) as productions of gaseous (CO2 and CH4) and dissolved organic C (DOC) fractions. Thermo-labile C increased 3.1-3.6 times from 15 degrees C to 30 degrees C in all soils. Disproportionate increase in the production of gaseous forms versus DOC as well as CH4:CO2 was observed with warming. Observed Q(10) values followed the trend of CH4 (similar to 14) >> CO2 (similar to 2.5) > DOC (similar to 1.7) and temperature sensitivity was more dependent on C quality than nutrient availability over the entire temperature range. Spectral analysis indicated more bio-available DOC production at higher temperature. Regression analysis also indicated that C quality primarily influenced SOM decomposition at lower temperature, while at higher temperature nutrient limitation dominantly controlled SOM decomposition. These findings confirm the role of C quality in temperature sensitivity of warm peat soils, but also indicate an increased importance of nutrient limitation at higher temperature.
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