Assimilation and productivity in selected species of lichen in relation to ecological amplitude
Distribution patterns of Cetraria islandica (L.) Ach.: Cladonia arbuscula (Wallr.) Harm.; Cladonia impexa, Harm.; and Cladonia gracilis (L.) Willd., through a relatively limited environmental gradient represented by four sites at Dinnet moor, Aberdeenshire have been investigated. These sites were chosen because of an unusual occurrence of a lichen community dominated by Cetraria islandica (L.) Ach., present on only one site. The influence of environmental factors on distribution patterns has been investigated both in the laboratory and in the field. Laboratory investigations included determination of gas exchange in relation to various levels of PHAR, temperature and thallus moisture content, at intensities equivalent to those experienced in the field. Field work included a transplant experiment, designed to measure productivity (and therefore survival) of the four species on three sites in the area (their respective sites of origin and two other sites). Also, in the field light, temperature, moisture and wind regimes of the sites were monitored once monthly for one year. The moisture content of the four species throughout the designated day and the rate of water loss from artificially hydrated lichens was measured on one site, for six months.