Hahn, SC/ Tenhunen, JD/ Popp, PW/ Meyer, A/ Lange, OL 1993: Upland tundra in the foothills of the Brooks Range, Alaska: diurnal CO2 exchange patterns of characteristic lichen species. - Flora188: 125-143. [RLL List # 152 / Rec.# 7313] Keywords: CO2 EXCHANGE/ DRYING PERIOD/ PHOTOSYNTHESIS/ WATER RELATIONS
Abstract: 9 fig. 6 tab. [Detailed field study of CO2 exchange relative to water content and microclimate conditions in seven lichen species: Masonhalea richardsonii, Cetraria cucullata, Stereocaulon alpinum, Thamnolia vermicularis, Dactylina arctica, Peltigera aphthosa, P. malacea. "Even short periods of favourable hydration were used by lichens for positive net photosynthesis (NP). There was no indication of adverse consequences of "resaturation respiration." Even after a dry period of 3 days, sudden rehydration resulted in carbon gain without delay. For short periods of time, the combinations of water content, temperature and light imposed on the lichens enables high rate of NP. Individual species differed greatly in their maximal NP rate, which correlated with chlorophyll and nitrogen content. At favourable times in the field, observed NP rates approached the maximum capacity found in the laboratory experiments at natural ambient CO2. Often with sufficient hydration, carbon gain was limited by light. CO2 exchange became negative even during daylight hours due to the effects of fog and clouds with light below compensation levels. Reduced but still positive rates of NP were observed with snow and with frozen lichens."]