Abstract

The world's southernmost tree has been documented along with the condition and growth pattern of the world's southernmost forest on Isla Hornos, Chile. The distribution of trees at broad scales is strongly influenced by the abiotic environment and determining the position and condition of tree limits around the world is an important way to monitor global change. This offers an ideal way to test the relationship between the biogeography of individual species and the effects of climate/climate change. The limits of trees, as all ecotones, are also useful communication points - easily understood signposts of ecosystems and their change through time. The southernmost trees in the world exist at soil temperatures that correspond to the low range of global treeline temperatures, with a climate analogous to equatorial treeline despite the high latitude (56 degrees S). However, their fine-scale distribution is strongly influenced by wind exposure rather than simply aspect and/or elevation, as one would expect if temperature were limiting the range. Recent establishment further south was found from core forest areas, however significant dieback along wind-exposed edges of the contiguous forest was also noted. In contrast to the wide extension of land where boreal or subarctic forests grow in the Northern Hemisphere, in the Southern Hemisphere Isla Hornos represents a single point embedded in the ocean under much milder climatic conditions. Documented shifts in wind intensity and direction as result of larger-scale climate change will likely continue to strongly shape the condition of these unique forests.