The photosynthetic productivity and the factors affecting it are measured in the nival zone of the Alps. Patterns of CO2 exchange for several lichen species are determined whilst recording environmental factors such as light and temperature and lichen water content. Whilst these records will show the lichen response over the year they can most easily be interpreted when the photosynthetic ability of individual lichens is well known. To achieve this the response of each species to light intensity, temperature, thallus water content and humidity will be determined under fully controlled conditions in the laboratory. The final aim is to achieve an initial carbon balance model for the lichen species. This will be aided considerably by the deploying of a continuously recording chlorophyll fluorescence system that will provide activity data for one lichen species on a better than hourly basis throughout the year.
annual photosynthesis pattern, annual microclimatic data, carbon gain, xanthoria elegans, umbilicaria cylindrica, brodoa atrofusca, rhizocarpon geographicum, lecanora polytropa var. alpina, miriquidica garovaglii, sporastatia testudinea, lecidea lapicida, thamnolia vermicularis, cirriphyllum cirrosum
Diel courses of CO2 exchange of lichens are measured under natural conditions by means of a CO2/H20 porometer (CQP-130, Fa. WALZ, Effeltrich, Germany), with the air temperature and thallus temperature (in the cuvette), the relative humidity and the photosynthetic active photon flux density (PPFD) also being recorded. Lichen thalli are fixed in wire-mesh baskets and are positioned near the porometer chamber under similar illumination and water status as their original, unshaded, natural habitat. For CO2 exchange measurements, lichen samples are enclosed in the porometer cuvette, which tracks the ambient conditions of the sample thus approximating the air temperature and light levels of the external environment. A chlorophyll a fluorescence measurement system (Walz, MiniPam) isl monitoring the photosynthetic activity of the lichens in situ at the same sites as the CO2 exchange measurements. This method is non-destructive, provides a continuous measurement of activity and is particularly useful for remote or climatically extreme regions like the Alps and Arctic. The activity is treated as a qualitative on/off signal for photosynthesis and provides the time period during which the lichens are moist enough to carry out CO2 exchange. This method allows continuous unattended year round measurements of lichen activity. In addition to these activity signals, microclimatic measurements like irradiance, thallus temperature and relative humidity are also collected by a datalogger (Squirrel 1000, Grant).
Funded by FWF, Project Nr. P144637-BOT