Water vapour and carbon dioxide fluxes over bog vegetation

During a period of 18 months observations have been made above bog vegetation in The Netherlands. The observations have been used to evaluate an assimilation model in which nitrogen shortage has been taken into account
In this study we analyse observations of water vapour and carbon dioxide fluxes over bog vegetation in the Netherlands. The observations are used to evaluate an assimilation photosynthesis (so-called A-g(s)) model on the canopy scale. Next, a simple estimate for the soil respiration has been added to the A-g(s) model. Leaf sample analysis showed that nitrogen concentration was well below optimum conditions, so the A-g(s) model was adjusted appropriately. Transpiration calculations with the adjusted model result in an excellent agreement with the measurements over the bog area. The total simulated fluxes of plant assimilation and soil respiration have been compared with the measured total CO2 flux. The agreement between simulations and experiments appears to be reasonably good. For practical applications a simplified relationship has been derived between the transpiration and the net assimilation rates. This relation has been tested and appears to work well for practical purposes. (C) 2002 Elsevier Science B.V. All rights reserved.