Environmental Engineering Reference
In-Depth Information
exposed summits and in the cryonival zone, where late-surviving snow severely
attenuates the growing season to less than 50 days. Mosses and crustose lichens are often
all that survive. Thoughts of survival also evoke the role of Quaternary plant refugia in
alpine environments, especially in mid-latitudes. Arctic-alpine flora retreat pole-wards
and upwards during temperate stages, and nunataks (alpine areas above glacier limits)
remain their last refuge over wide areas during mid- to high-latitude glaciation. This issue
is complex but it seems likely that some colonization spreads from alpine areas during
non-glacial cold stages and it has certainly sourced plagioclimax alpine communities
after deforestation. Arctic-alpine flora may have originated in Cretaceous low-latitude
Laurussia below 40° N and developed its modern character as less tolerant plants were
'sifted out' during poleward plate movement and Plio-Pleistocene glaciation.
ALPINE LANDSYSTEM
The Alpine landsystem develops its distinctive character through the integration of
glacial, cryonival, slope and fluvial elements within the higher and spatially more
restricted parts of the mountain systems. This is enhanced by close interaction with
mountain climates and ecosystems and by partial geomorphic isolation by the timber-line
and glacially excavated lake basins. The latter both act as major buffers, especially to
sediment transfer, from predominantly fluvial systems at lower altitude. However, the
landsystem is not isolated from endogenetic influences. Altitude, high gravitational
potential and recent or
Figure 25.15 Simplified vertebrate food web of the alpine
tundra, Beartooth plateau, Wyoming.
Source: After Hoffman (1974).
CLIMATE CHANGE AND ALPINE ENVIRONMENTS
new developments
The high diversity of mountain climates renders AOGCMs less useful in predicting the
impact of global climate change without nested regional models inside them
IPCC
Search WWH ::




Custom Search