Studies on lichen-dominated systems. XIII. Seasonal and geographical variation of net CO2 exchange of Alectoria ochroleuca

Abstract

By using a new gas-exchange method, the seasonal changes in net photosynthetic rates of Alectoria ochroleuca were examined in relation to thallus moisture content, thallus temperature, and light intensity. These experiments were run using samples collected from both the top and bottom positions of a raised-beach ridge and showed very little intraspecific variation. Collections made from other geographical locations, however, showed that considerable intraspecific variation was possible within this species.At the Pen Island site, A. ochroleuca shows patterns of net photosynthesis adapted to the xeric ridge-top environments on which it is most abundant.Rapid seasonal acclimation to temperature and changes in the response to light intensity were found for both ridge-top and ridge-bottom collections of A. ochroleuca. The ecological significance of these findings is discussed.