Behaviour of carbon dioxide and water vapour flux densities from a disturbed raised peat bog

Abstract

Measurements of carbon dioxide and water vapour flux densities were carried out for a disturbed raised peat bog in the north of the Netherlands during an 18 month continuous experiment. Tussock grass (sp. Molinea caerulae) mainly dominated the vegetation of the bog area. The maximum leaf area index (LAI) of the vegetation reached a numerical value of about 1.7 in mid-August. When the LAI is large enough (LAI > 0.2), a mean net uptake of carbon dioxide is observed with a clear daily pattern. The total evapotranspiration consists of a soil, an open water, and a plant transpiration part. When the LAI is large enough (LAI > 0.2), plant transpiration dominates the total evapotranspiration. The mean daily transpiration pattern, however, is not similar to the carbon dioxide uptake pattern. During the summer months, the daytime carbon dioxide uptake shows a single early morning maximum value followed by a decline in uptake during the rest of the day. The evapotranspiration, however, follows more or less the incoming short-wave radiation pattern. Effects of the vapour pressure deficit are suggested as a possible cause of this discrepanc