Photosynthetische Primärproduktion der Flechte Cladonia portentosa an einem Dünenstandort auf der Nordseeinsel Baltrum: II. Photosynthesemodell: Entwicklung, Parametrisierung durch Messungen des CO2-Gaswechsels unter kontrollierten Bedingungen und Test

Abstract

Summary Photosynthesis and dark respiration of the lichen Cladonia portentosa was studied under controlled conditions in the laboratory. There was good agreement with respect to the absolute rates of CO 2 exchange as well as in response to single factors between the laboratory results and performance of the lichen in the field (see part I). The dependencies of CO 2 -gas exchange on incident photosynthetically active radiation, thallus temperature, and thallus-water content were described with a series of equations. These functions were combined in a general model which simulates net photosynthesis in response to all three environmental factors. The model was validated against observed diurnal courses of CO 2 exchange which were obtained in the natural habitat of the lichen. Field performance is reproduced well by the model although deviations may occur in extreme environmental situations.