5.9.1.2. Alpine Ecosystems
Climatic changes observed in alpine areas generally have paralleled climatic
patterns in surrounding regions, with the most pronounced warming at high latitudes,
in the Alps, and in Asia and the least pronounced changes in tropical alpine
regions (Diaz and Bradley, 1997). Precipitation generally has increased, with
the most pronounced changes in winter, leading to increased snow depth (Beniston,
1997).
Regional trends in climate have led to shrinkage of alpine and subpolar glaciers,
equivalent to a 0.25 ± 0.1 mm yr-1 of sea-level change or
16% of the sea-level rise in the past 100 years (Dyurgerov and Meier, 1997).
This trend has been regionally variable, with Asia contributing 45% of this
sea-level rise and arctic islands an additional 18%. The net mass reduction
of the alpine glaciers has been most pronounced since 1980, when regional warming
was greatest.
Climatic warming observed in the Alps has been associated with upward movement
of some plant taxa of 1-4 m per decade on mountaintops and loss of some
taxa that formerly were restricted to high elevations (Braun-Blaunquet, 1956;
Grabherr et al., 1994). In general, direct human impacts on alpine vegetation
from grazing, tourism, and nitrogen deposition are so strong that climatic effects
on goods and services provided by alpine ecosystems are difficult to detect
(Körner, 1999). Soil carbon stocks per unit area in alpine ecosystems are
only one-third as great as those in the arctic because greater topographic relief
promotes greater drainage and decomposition than in the arctic (Körner,
1995b).
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