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

-Discussion-
N
E
S
W
6 0 0 m
4 0 0 m
S l o p e
2 0 0 m
V a l l e y F l o o r
1 0 k m
S c l e r o p o a r i g i d a - P o p u s n i g r a
c o m m u n i t y
Q u e r c u s i b e r i c a - C a r p i n u s o r i e n t a l i s
c o m m u n i t y
E q u i s e t u m t e l m a t e i a - A l n u s b a r b a t a
c o m m u n i t y
S w i d a s a n g u i n e a - P o p u l u s a l b a
c o m m u n i t y
C o t i n u s c o g g y g r i a s h r u b l a n d Q u e r c u s r o b u r - C a r p i n u s b e t u l u s
c o m m u n i t y
F r a x i n u s e x c e l s i o r - P t e r o c a r y a p t e r o c a r p a
c o m m u n i t y
O p l i s m e n u s u n d u l a t i f o l i u s - A c e r v e l u t i n u m
c o m m u n i t y
w a t e r f l o w r o c k s , s t o n e s g r a v e l , s a n d s i l t , c l a y
Fig. 5.3 Longitudial section <strong>of</strong> the fan
Direct effects <strong>of</strong> flooding include reduced oxygen exchange <strong>and</strong> hampered soil water
movement (Hughes et al. 2001) uprooting (Karrenberg et al. 2003) as well as burial by
sediments (Marigo et al. 2000). Indirect effects are the creation <strong>of</strong> bare substrates due to
sedimentation (Johnson 2000), decreased vegetation cover <strong>and</strong> increased nutrient supply
(Thoms 2003). The response to the above mentioned factors varies among species. The
s<strong>of</strong>twood species Salix spp. <strong>and</strong> Populus spp. tend to be better adapted to flooding than
the hardwood broad leafed deciduous species Quercus spp, Ulmus spp. <strong>and</strong> Fraxinus
spp. (Vreugdenhil et al. 2006). In Europe, this results in a typical zonation <strong>of</strong> the
s<strong>of</strong>twood species Salix spp. <strong>and</strong> Populus spp. near the main channel <strong>and</strong> the hardwood
species Quercus spp., Ulmus spp. as well as Fraxinus spp. dominating the less
frequently flooded sites (Ward et al. 2002; Ellenberg 1988). These observations could
be affirmed within this study, though the s<strong>of</strong>twood zone was <strong>of</strong>ten narrow <strong>and</strong>
sometimes completely lacking, possibly due to already reduced river dynamics. Both
poplar species were obviously restricted to bare soils in, or adjacent to the open riverbed
where flood dynamic is greatest. Populus nigra prefers the upper sites (Fig. 5.3 , Fig.
5.4 <strong>and</strong> Fig. 5.6), obviously better adapted to survive drier periods in summer. Glenz et
al. (2006) indicate its flooding tolerance with high (4) (Table 5.1).
-<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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