Expanding forests and changing growth forms of Siberian larch at the polar Urals treeline during the 20th century. Global Change Biology 14

• Main Authors: Nadezhda Devi, Frank Hagedornw, Pavel Moiseev, Harald Bugmannz
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2008
• Subjects: Tundra
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.362.4859; http://wattsupwiththat.files.wordpress.com/2009/11/devi_081119_gcb_ural.pdf

The ongoing climatic changes potentially affect plant growth and the functioning of temperature-limited high-altitude and high-latitude ecosystems; the rate and magnitude of these biotic changes are, however, uncertain. The aim of this study was to reconstruct stand structure and growth forms of Larix sibirica (Ledeb.) in undisturbed forest–tundra ecotones of the remote Polar Urals on a centennial time scale. Comparisons of the current ecotone with historic photographs from the 1960s clearly document that forests have significantly expanded since then. Similarly, the analysis of forest age structure based on more than 300 trees sampled along three altitudinal gradients reaching from forests in the valleys to the tundra indicate that more than 70 % of the currently upright-growing trees are o80 years old. Because thousands of more than 500-year-old subfossil trees occur in the same area but tree remnants of the 15–19th century are lacking almost entirely, we conclude that the forest has been expanding upwards into the formerly tree-free tundra during the last century by about 20–60 m in altitude. This upward shift of forests was accompanied by significant changes in tree growth forms: while 36 % of the few trees that