The ecology of Ramalina menziesii. V. Estimation of gross carbon gain and thallus hydration source from diurnal measurements and climatic data

All subsets regression analysis was used to determine the set of meteorological variables that best predicted daily gross carbon fixation of the lichen Ramalina menziesii Tayl. measured on 23 days at Hastings Reservation in central coastal California. The regression equation containing the two best predictor variables, the duration of diurnal atmospheric humidities equal to or above 90% and daily precipitation, was then used in conjunction with weather records to estimate daily, seasonal, and annual gross CO2 gain of R. menziesii at Hastings for the years 1981 – 1983. Calculated average annual gross CO2 fixation for these 3 years was 2756 mg CO2∙g dry weight−1. For 66% of this total gain, the most likely source of thallus hydration was rainfall. Dewfall was responsible for 15%, atmospheric water vapor uptake for 11%, and for the remaining 8% the source was uncertain. Three-fourths of the annual carbon fixation took place during the 6 months of the rainy season.