Environmental factors affecting flower and seed production in Deschampsia antarctica and Colobanthus quitensis on Livingston Island (South Shetland Islands, Antarctica)

Abstract

The variation in floral and seed development, as well as the seed bank, along an altitudinal gradient (10 to 147 m) and on different orientations (NE and SW), of the two native vascular species was studied on Hurd Peninsula at Livingston Island, Antarctica. The phenological cycles have been described quantifying the flower and seed production. Flower density in both species increased during the austral summer from early January until the end of February, except for C. quitensis at the highest altitude. The more advanced flower and seed maturation at lower sites suggests an important effect of temperature on reproduction through seed production. The production of ripe seeds from the current and previous seasons’ seed decreased with altitude. Seeds of both species at lower sites can reach full maturation in one growing season. A higher production of ripe seeds was found on NE orientated slopes (warmer than the other orientations) and in less compacted soils. A better development of the reproductive structures at the lower altitudes, with more probability to complete the full maturation of seeds in the current year than at the higher sites (altitudinal gradient about 1º C) shows that the Antarctic vascular plants are highly sensitive to temperature. An increase in reproduction through seed production over the last decades (mean summer temperature rise of more than 1 ºC over the last three decades) appears closely linked to the rapid expansion of both species (distribution and abundance) in the Antarctic Peninsula area.