The effects of climatic pattern on lichen productivity: Cetraria cucullata (Bell.) Ach. in the arctic tundra of northern Alaska

Abstract

The climatic control of productivity for two populations of the lichen Cetraria cucullata (Bell.) Ach. growing in the arctic tundra of northern Alaska (70°28'N, 157°23'W) was examined. Respiratory losses of carbon vary with tissue temperature, tissue water content, and time since wetting. Potential net photosynthetic gains of carbon are affected by photon flux density, tissue temperature, and water content. The net CO exchange responses of populations growing on ridge tundra and on upland tundra differ and these differences reflect possible adaptation to the normal environmental regimes in the two habitats. Simulation of the lichen's net carbon balance using continuous hourly records of photon flux density, temperature, and water content for the unusually dry period June 28 through July 17, 1977 show that lichen biomass is actually lost during climatic regimes leading to frequent but short periods of lichen metabolic activity. This result is confirmed by the negative relative growth rates measured for C. cucullata over the same monitoring period. This observed loss of biomass may be attributable to depletion of carbon reserves to reactivate dormant metabolism without sufficiently long periods favorable for net photosynthetic activity to replenish the lost reserves. These results illustrate that environmental limits exist on the success of the dormancy strategy characteristic of lichen and moss carbon metabolism.

Nocturnal respiration of lichens in their natural habitat is not affected by preceding diurnal net photosynthesis

“…Resaturation respiration is one of the largest and best known (Ried 1960;Smith and Molesworth 1973) but it does not seem to be of substantial ecological significance in nature as it occurred only rarely in our analyses and did not substantially affect carbon balance (Lange 2003a(Lange , 2003b; however, see Lechowicz 1981). Strong transient increases of DR are also reported when temperature is quickly raised experimentally (Sundberg et al 1999), but we never observed steep changes in the temperature of wet, metabolically active lichen thalli in the field.…”

Water relations and CO2 exchange of the terrestrial lichen Teloschistes capensis in the Namib fog desert: Measurements during two seasons in the field and under controlled conditions

“…However, thalli of T. capensis, which had been kept artificially dry for 10 days in the field, did exhibit a significant depression in their carbon income when they were exposed again to natural condition. As described by Lechowicz (1981), reactivation after desiccation appears to have the potential to also affect the productivity of a fog-desert lichens. However, in our data we found no examples of this effect, possibly it had been ameliorated through nocturnal hydration at high humidity, even during the dry periods.…”

“…180 per year) were the main source of water for lichen productivity (Kappen et al, 1979). Whilst there are no records available for dew occurrence for the Swakopmund region, the mean monthly maximal relative air humidity at Pelikan Point is 100% throughout the year (1976-1981Lancaster et al, 1984), suggesting that the dew point is also reached every day. Waibel (1922) recorded 295 days with dew fall (including fog precipitation) during one year (1913/14) for Anichab (30 km north of Lu¨deritzbucht).…”

In situ studies of water relations and CO2 exchange of the tropical macrolichen, Sticta tomentosa

“…The importance of the resaturation respiration under natural conditions is under debate. For example, Lechowicz (1981) studied the post-desiccation recovery of the CO # gas exchange of the arctic lichen, Cetraria cucullata, in the laboratory. His predictions on the in situ gas exchange, however, could not be verified by observations in the field (Hahn et al, 1993).…”