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

摘要

This study uses long-term water chemistry records for a circum-neutral peat stream to reconstruct a 7-year record of dissolved CO_2 and DIC flux from the catchment. Combining catchment flux with a knowledge of in-stream metabolism and gas evasion fromthe stream surface enables an estimate of the dissolved CO_2 content of water emerging from the peat profile to be made; furthermore, these can be used to estimate soil CO_2 respiration. In this way multi-annual records of CO_2 production can be reconstructed, and therefore inter-annual controls on production examined. The results suggest that: (i) Stream evasion of CO_2 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; ii) Export of dissolved CO_2 emerging from the soil profile, above that expected at equilibrium with the atmosphere, varies between 9.6 and 25.6 tonnes,C/km~2/yr; and iii) The export of dissolved CO_2 implies a soil respiration rate of between 64.2 and 94.9 tonnesC/km~2/yr. The inter-annual variation in both dissolved CO_2 flux and soil CO_2 respiration suggests that severe drought has no long-term effect on CO_2 production and that temperature-based models of soil CO_2 respiration will be adequate in all but theseverest of summer droughts. The inter-annual variation in CO_2 flux shows that CO_2 production is decoupled from dissolved organic carbon (DOC) production. The decoupling of DOC and dissolved CO_2 production shows that enzymatic-latch production of DOC is an anaerobic process and will not increase soil CO_2 respiration.