Abstract
Hydrological conditions are considered to be among the main drivers influencing the export of dissolved organic carbon (DOC) from terrestrial to aquatic ecosystems, and hydrology is likely to alter due to climate change. We built a mesocosm experiment by using peat profiles from a pristine and from a drained (drained in 1978) peatland. A several-week-long low water table period followed by a high water table period, that is, a setting mimicking drought followed by flood, released relatively more DOC from pristine peat than from drained peat. From pristine peat profiles DOC was released into soil water in such quantities that the concentration of DOC remained stable despite dilution caused by added spring water to the mesocosms. In drained peat the DOC concentrations decreased during the high water table period indicating stronger dilution effect in comparison to pristine peat. At the landscape level DOC load from a drained peatland to the recipient water body may, however, increase during flooding because of high water runoff out of the peatland containing high DOC concentrations relative to the forest and agricultural areas. During the high water table period neither peat type nor water table had any clear impact on carbon dioxide (CO2-C) fluxes.
Highlights
Northern peatlands comprise about one-third of the world’s soil organic carbon (C) pool [1]
Compared to the spring water, which was used for water additions to the mesocosms, dissolved organic carbon (DOC) concentrations in mesocosm soil waters were 10 to 50 times higher, indicating that substantial amounts of DOC were released from the peat
At the end of the low water table period (WL(37)), DOC concentrations in profiles with control conditions (PrCtrl) and profiles with fluctuating water table (PrFluc) mesocosms were at about the same level (Figure 2)
Summary
Northern peatlands comprise about one-third of the world’s soil organic carbon (C) pool [1]. As the decomposition and leaching of organic matter from peatlands greatly affect DOC fluxes entering water systems [3, 4], any major changes in hydrology on the peatlands and/or in the composition and properties of the peat itself modify the loading of C from these ecosystems to the recipient water bodies. This is especially important in the boreal areas where the projected change in climate seems to be considerable [5]. If consumption outweighs or is in balance with production or the conditions are dry enough, the altered production may not be seen in DOC export at least when viewed over a short period of time
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