Fluxes of dissolved carbon dioxide and inorganic carbon from an upland peat catchment : implications for soil respiration.

Abstract

This study uses long-term water chemistry records for a circum-neutral peat stream to reconstruct a 7-year record of dissolved CO2 and DIC flux from the catchment. Combining catchment flux with a knowledge of in-stream metabolism and gas evasion from the stream surface enables an estimate of the dissolved CO2 content of water emerging from the peat profile to be made; furthermore, these can be used to estimate soil CO2 respiration. In this way multi-annual records of CO2 production can be reconstructed, and therefore inter-annual controls on production examined. The results suggest that:(i) Stream evasion of CO2 within the catchment varied between 80 and 220 g C/m of stream/yr, while in-stream metabolism produces between 1.0 and 2.9 g C/m of stream/yr; Export of dissolved CO2 emerging from the soil profile, above that expected at equilibrium with the atmosphere, varies between 9.6 and 25.6 tonnes,C/km2/yr; and The export of dissolved CO2 implies a soil respiration rate of between 64.2 and 94.9 tonnes C/km2/yr. The inter-annual variation in both dissolved CO2 flux and soil CO2 respiration suggests that severe drought has no long-term effect on CO2 production and that temperature-based models of soil CO2 respiration will be adequate in all but the severest of summer droughts. The inter-annual variation in CO2 flux shows that CO2 production is decoupled from dissolved organic carbon (DOC) production. The decoupling of DOC and dissolved CO2 production shows that enzymatic-latch production of DOC is an anaerobic process and will not increase soil CO2 respiration.