Ecology and regeneration of forest communities on the alluvial fan ...

-Study area-
Alluvial fans are typical l<strong>and</strong>forms <strong>of</strong> regions with a considerably high amount <strong>of</strong>
mechanical weathering. They are composed <strong>of</strong> fluvial sediments build up by means <strong>of</strong>
river sedimentation processes (Fig. 2.3). They preferentially appear in semiarid areas, at
the foot slopes <strong>of</strong> high mountain ranges <strong>and</strong> also in periglacial regions. Not the whole
fan surface is active at a given time. Eventually, accumulation <strong>of</strong> sediments downstream
makes it easier for a new flood to flow over another part <strong>of</strong> the fan. This switch from
one part to another is called avulsion. The typical cone shape <strong>of</strong> most alluvial fans
results from regular avulsion <strong>of</strong> the river. Due to decreasing erosion <strong>and</strong> transportation
rates <strong>of</strong> the rivers towards their distal margins a characteristic series <strong>of</strong> sediments is
given. The coarsest material is dropped at the top <strong>of</strong> the fan, s<strong>and</strong> <strong>and</strong> gravel in the midfan,
<strong>and</strong> fine material at the lower reaches (Ahnert 1996).
Fig. 2.3 Outline <strong>of</strong> an alluvial fan (Strahler 1975)
2.3 Climate
The warm temperate climate <strong>of</strong> the Alasan-Awtoran depression with sufficient rainfall
during the whole vegetation period provides excellent conditions for <strong>forest</strong> growth. The
Greater Caucasus mountain ranges protect it from cold weather <strong>and</strong> strong winds.
Duration <strong>of</strong> the vegetation period varies between eight <strong>and</strong> ten months. Spring, summer
<strong>and</strong> fall receive each about one third <strong>of</strong> the annual rainfall. Mean temperature in January
is 0°C, the mean temperatures in July range from 22,5°C to 25°C. The end <strong>of</strong> summer
-<strong>Ecology</strong> <strong>and</strong> <strong>regeneration</strong> <strong>of</strong> <strong>forest</strong> <strong>communities</strong> on the alluvial fan near Qakh (Northwestern Azerbaijan)-
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