Ecological variables
The
main
ecological
variables
related
to
the
floristic
composition
of
the
vegetation
in
the
inlan
d
Delta
of
the
Niger
River
are
as
follows:
•
The topomorphological position: (9 classes)
The
probability
of
the
occurrence
of
each
vegetation
association
in
a
“topomorphological"
position
was
established
for
9
of
these
positions:
river
bed,
levee,
bank,
flood
plain,
sedimentation
basin,
shoal,
loamy
clay
mound
,
sandy
mound,
irrigated
rice
field.
For
example,
the
probability
of
occurrence
of
the
vegetation
association
BP,
“burgu”
with
Vossia
cuspidata
,
in
the
topomorphological
positions
is
figured
in
the
rectangles
on
top
of
the
following
drawing.
The
probability
is
assessed
by
the
indexed
profile
method
previously
described.
For
example
BP
occurs
more
significantly
in
sedimentation
basins
(p
<0.001)
and
secondarily in the river beds (p <0.01).
•
Flood: it includes the following headings:
- regularity: 5 classes
- duration: 6 classes
- water height: 7 classes
- date and speed of rising water (6 classes and 5 classes)
- date and speed of water fall (6 classes and 5 classes)
Table 1 : Flood characteristics of the vegetation association B (« Burgu » Echinocloa stagnina)
The
floods
linked
with
the
vegetation
association
B
(“Burgu”
with
Echinochloa
stagnina
),
taken
as
an
example,
are
typically
very
regular,
with
a
6
to
7
months
'
duration,
and
a
maximum
height
between
1.5
m
and
2.8
m.
The
food
rise
is
rapid
and
takes
place
in
July,
while
the
fall
is
gradual
and
takes
place
between
February
and
April.
(These
characteristics
in
terms
of
dates
were
determined
in relation to the plains of Moura, Ténenkou, Diafarabé, Kadial, Kakagnan, Walado and Saya).
•
Soil
drainage
and
hydromorphy:
the
types
of
soil
drainage
and
hydromorphy
are
noted
for
the
non-flooded
vegetation
associations
Table
2:
soil
drainage
and
hydromorphic
characteristics
of
vegetation
association
TB
(Palm
grove
with
Borassus
aethiopum).
![Type of soil hydromorphy p N ot hydromorph ic ( deep water table ) +++ W ater table reaching [0,1 to 0,3 m ] seasonally 0 W ater table reaching top soil seasonally 0 S easonal flood 0 A quati c 0](index_htm_files/13272.png)
The
soil
drainage
and
hydromorphy
of
the
flooded
vegetation
association
are
systematically
set
to
zero.
Conversely
the
flood
variables are set to zero for the non flooded vegetation associations.
Example
of
a
complete
ecological
file
of
a
vegetation
association
with
the
field
titles
as
they
appear
in
the
database.
All
these data can be downloaded (excel file "ecology").
Ecology_EN.rar
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