Method for Field Measurements of CO₂-Exchange. The Diurnal Changes in Net Photosynthesis and Photosynthetic Capacity of Lichens under Mediterranean Climatic Conditions

Abstract

The determination and interpretation of patterns in photosynthetic primary production which are characteristic of different lichen species within their respective habitats may lead to a better understanding of habitat preferences and species distributions. However, the necessary photosynthetic CO₂ exchange measurements are difficult to accomplish in the field. Thus, only a few examples of diurnal courses of photosynthetic CO₂ uptake by poikilohydric organisms may be found in the ecophysiological literature. Recently mathematical models have been developed which have been used to simulate the net photosynthetic performance of lichens under natural conditions. Because such models are usually based upon physiological parameters obtained from laboratory experiments, their validity can only be established by comparing simulated rates of photosynthesis with rates actually measured in the field. Thus, the development of instrumentation and methods which allow accurate determination of CO₂ exchange of lichens under natural conditions is essential.