Cryptogamic carbohydrate release and microbial response during spring freeze-thaw cycles in antarctic fellfield fines
The soluble carbohydrate and polyhydric alcohol (polyol) content of fruticose lichens, cushion mosses and early vegetative colonizers of maritime Antarctic fellfield soils were examined by gas-liquid chromatography during 18 months. The total sugar plus polyol content in lichens varied significantly with season, ranging from 62 to 236 mg g−1 dry wt. Although such total seasonal changes were not significant in a cushion moss its polyol concentration increased from 4.0 to 37.0 mg g−1 dry wt. The major polyol present in the cryptogams was arabitol reaching II5.4mgg−1 dry wt, equivalent to 71% of the total sugars plus polyols. The amounts of polyols found in Antarctic lichens were up to three times those reported in temperate lichens, providing considerable potential for frost tolerance. The soluble sugars and polyols leached into fellfield soil fines from the surrounding vegetation were quantified during the spring. These were sometimes in excess of 1 % fresh wt and were compared with the composition and population size of the bacterial, yeast, fungal and algal microflora. Significant relationships were found between the algal and bacterial populations in conjunction with the water content of the fines. The implications of large amounts of sugar within the fines and the possible consequences for microbial and cryptogamic colonization are discussed.