Vol. 35 – 2009 - Ecologia Mediterranea - Université d'Avignon et des ...

HANADI ISMAÏL, HUSSEIN ABOU-HAMDAN, AHMAD KOUBAYSSI, STÉPHANIE FAYOLLE, GABY KHALAF, ARLETTE CAZAUBON, JACQUES HAURY
Figure 3 – Seasonal variations in the taxonomic richness in the stations according to different groups (the values are the sum of
species for each macrophyte type of each season). Spring = April, May, June. Summer = July, August, September. Autumn
= October, December. Winter = January, March.
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the macrophytes with respect to some environmental
parameters. It also made it possible
to establish macrophytic associations
which exist in several sectors of Litani, and to
distinguish the stations by their floristic characteristics.
Figure 4 – Average percentage of macrophytic cover (average + SD) among
the different stations (L1, L2, L3 & L4). (a) all taxa, (b) for each
type of macrophytes categories at the four stations.
On the map of the CCA (axis 1 inertia 41%;
axis 2 inertia 32%) L1 is separated from L2-
L3 and L4 on axis 1, and L2-L3 are separated
from L4 on axis 2. In addition the axis 1 (41%
inertia) describes a gradient of mineralisation
and eutrophication on its negative part and a
gradient of oxygenation on its positive part.
Thus, the degree of pollution effect is strongly
increased through the axis 1 which opposes a
sector strongly polluted on the rhithral (L2,
L3, L4) to a sector lightly polluted on L1.
Thus, the ecological determinism is clear. In
one hand, we can individualize the spring,
characterized by its depth and its well oxygenated
water and on the other hand, the stations
of the rhithral characterized by a high
conductivity, nitrates and phosphates concentrations,
and by a relatively faster water.
From there we distinguished 3 groups:
– The group (G1) positively correlated with
the depth. It is made up primarily by
hydrophytes colonizing the stagnant mediums
and/or with weak current (Chara sp.)
and of the helophytes which correspond to
the rhithral of the small rivers with a very
good shining and a low flow (Phalaris arundinacea,
Phragmites australis).
– The group (G2) includes macrophytes generally
announced in the rhithral of large
rivers (here rhithral of Litani on L4) characterized
by a strong representation of
hydrophytes (Ranunculus fluitans, Myriophyllum
spicatum, Potamogeton crispus,
Potamogeton pectinatus, etc.).
ecologia mediterranea – Vol. 35 – 2009