Environmental Engineering Reference
In-Depth Information
Figure 25.12
The geoecological zones of mid- to high-
latitude mountains in the northern hemisphere.
Source: Modified from Ives and Barry (1974).
400 g m
−2
yr
−1
(alpine meadow). This compares with montane/boreal forest ranging
between 800 g m
−2
yr
−1
and 1800 g m
−2
yr
−1
. Geomorphologists, however, incorporate
this belt into the
cryonival
zone of permanent snow cover, permafrost and associated
alpine glaciers and mountain icefields and an
alpine landsystem
dominated by cryogenic
processes.
MONTANE FOREST
Mountain forest zones reflect temperature and moisture limitations; their lower boundary
experiences
c
. 245 growing days per year. In the European Alps summer temperatures
generally determine the timberline, especially in extra-tropical mountains. Thermal
effects are also implicit in tropical
tierra
zonation, with its
t. caliente
(hot/
tropical forest
),
t. templada
(temperate/
submontane- montane forest
),
t. fria
(cool-temperate/
montane-
sub-alpine
) and
t. helada
(frozen/
alpine
) (Figure 25.13). Montane forest on cool
mountain slopes mirrors the latitudinal temperate-boreal zone transition by replacing
more thermophilous species (oak, beech, pine) with boreal communities (spruce, larch,
fir, birch), or with rhododendron and giant
ericaceae
in Asian and African tropical
mountains. A parallel transition from closed to open forest, with a strong incursion of
alpine tundra vegetation, marks the approaching timberline. Moisture effects create
interesting regional or topoclimate variations. Low moisture indices are reflected by more
xeric
(arid-tolerant)
