An experimental study of growth in relation to morphology and shoot water content in maritime Antarctic mosses

The dependence of shoot growth and growth form on water availability was studied experimentally in six species of maritime Antarctic moss. Under all conditions the largest growth increments were observed in the hydric species Brachythecium austro-salebrosum and Drepanocladus uncinatus. The xeric Andreaea depressinervis grew the least. Lateral shoot production varied within and between species. Over 50 % of the biomass produced in D. uncinatus was derived from lateral shoot production, whereas Polytrichum alpestre produced very few lateral shoots and A. depressinervis produced none. Leaf density and leaf size also varied with total water content. In all species growth ceased at total water contents of 100% d. wt or less. However, the total water content at which maximum growth was observed differed between species. Racomitrium austro-georgicum (mesic/xeric) had the lowest optimum for growth at 370% of d. wt and D. uncinatus (hydric) exhibited maximum growth between 890 and 2300% d. wt. Optimum total water contents for growth were greater than those at full turgor and published optima for net assimilation. Growth and total water content of these Antarctic mosses were similar to those reported for temperate species

Rapid population increases in native vascular plants in the Argentine Islands, Antarctic Peninsula

The number of individual plants and colonies of the two native Antarctic vascular plants, Colobanthus quitensis and Deschampsia antarctica, have been monitored between 1964 and 1990 on three islands in the Argentine Islands archipelago, western Antarctic Peninsula. The Deschampsia population increased by nearly 25-fold and Colobanthus by over 5-fold. Furthermore there was a considerable increase in the number of Deschampsia colonies, although no additional colonies of Colobanthus were recorded. An analysis of Colobanthus plant size in 1974 and 1990 indicated that recruitment was probably irregular although the population structure remained essentially the same. The reasons for this and the increases in population size of both species are discussed. The relatively rapid increase in the abundance and distribution of these species is considered to be a response to the increasing summer air temperatures being experienced in the region of the maritime Antarctic. In particular, there is probably improved success in reproductive behavior resulting from warmer and/or longer growing seasons