Measurements of climate data and the effect of high light and low temperature on the photosynthetic response (photosynthetic gas exchange rates and fluorescence) of mosses and lichens at Granite Harbour

The winter snowfall (during 1994) was unusually large and the area of Botany Bay was uniformly covered to a depth of 50 to 70cm. Furthermore, air temperatures were low being rarely above -6° C. These conditions allowed the opportunity to study the effects of high light at low temperatures on lichens and to track lichen performance at low temperatures. Daily photosynthetic performance was measured from a crustose lichen that covers many rock surfaces, Buellia frigida. A number of thalli were labelled on a large rock with fluorescence yield, temperature and light recorded several times a day for nine days. The position of the edge of the snow bank was also recorded as it retreated each day. A second boulder was fitted with a datalogger with light and temperature probes. The response of photosynthesis to temperature (-5°C to +25°C) and light was investigated using gas exchange and fluorescence techniques and making concurrent measurements on a lichen (Umbilicaria aprina) and a moss (Bryum argenteum) at saturating light and temperatures. Frozen specimens of U. aprina were collected from a depth of 50cm in snow to ensure the plants had not received sunlight. The specimens were exposed to full sunlight for 8-10 hour periods and their CO2 exchange and fluorescence parameters were continuously measured. Several data loggers were deployed to gain climate information (local and microclimates) where the plants are found. Chlorophyll a fluorescence activity of selected plants was recorded for about three weeks. Fluorescence measurements are non-contact and a positive signal indicates that the photosystems of the lichen or moss are active.