Botany of Bouvetøya, South Atlantic Ocean. II. The terrestrial vegetation of Bouvetøya

Abstract

Bouvetøya (54°25'S, 3°20'E), the northernmost land in the maritime Antarctic, has a climate typical of oceanic islands south of the Antarctic convergence, and a non-vascular vegetation of maritime Antarctic composition and structure. Mean vegetation temperatures during the growing season are from + 1 to +4.S°C on the low ground, whereas elevations above 200 m a.s.1. are more prone to freezing and show regular diurnal freeze/thaw cycles. Radiative heating of the ground is important in some well-drained lichen communities with a northward aspect, but generally the mean diurnal temperatures registered in the superficial part of substratum and vegetation are low because of the prevailing cloudiness and high windspeeds. Some geothermally heated communities are described. The soil reaction ranges from slightly acid on silicic lava and leached basalt ground. to alkaline on calcitebearing pyroclastic rocks, with a correspondingly different vegetation. The main plant communities of Bouvetøya are documented by quadrat analyses, and a classification is proposed. Local distribution patterns of 26 cryptogamic species arc discussed and related to soil chemistry and elevation, as well as to the time elapsed for their establishment and the development of communities undisturbed by volcanism, landslides, glacierization, and animal influence.