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

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7. Scleropoa rigida-Populus nigra community
Fig. 4.16 Importance values <strong>of</strong> Scleropoa rigida-Populus nigra community (n=3)
This community comprises both very open, pioneer st<strong>and</strong>s as well as st<strong>and</strong>s, which are
to a higher degree vertically structured . It is a rather open community with a large
number <strong>of</strong> relatively small sized trees. Restricted to the riverbanks <strong>and</strong> open gravel beds
<strong>of</strong> the upper reaches <strong>of</strong> the fan it is subjected to frequent disturbances by flooding. The
substrate is considerably rough structured with a mean coarse soil fraction <strong>of</strong> 68 % <strong>and</strong>
a predomination <strong>of</strong> s<strong>and</strong>y fractions (80 %) within the fine soil. Due to the high degree <strong>of</strong>
disturbance the plants have to deal with strongly differing soil moisture conditions
during the course <strong>of</strong> the year. At least in summer soil moisture is relatively low. The
mean tree layer hight is about ten metres (pioneer st<strong>and</strong>s excluded). Some elder Populus
nigra or Populus alba individuals grow up to about 20 metres, both reaching maximal
circumference values <strong>of</strong> about 300 cm. With a mean <strong>of</strong> 18 species per plot it is a
moderately species rich community. Vegetation cover is usually very low, <strong>and</strong> bare
ground predominates (80 %). The absolute tree density amounts to a considerably high
value <strong>of</strong> 692 individuals per hectare (Fig. 4.6), though the amount <strong>of</strong> the total basal area
is strikingly low (11 m² per hectare). Particularly Populus nigra <strong>and</strong> Cotinus coggygria
turn out to be the most important woody species. Cotinus coggygria occurs with a large
number <strong>of</strong> individuals <strong>and</strong> Populus nigra with less but larger sized individuals.
Pyracantha coccinea, Conyza canadensis, Setaria viridis <strong>and</strong> Scleropoa rigida are
-<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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