Vol. 32 – 2006 - Ecologia Mediterranea

MOHAMED TARHOUNI, AZAIEZ OULED BELGACEM, BELGACEM HENCHI, MOHAMED NEFFATI
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distances is explained by the fact that while
in the grazed woodlands the cover of perennial
plant patches remains low for a considerable
distance from water (5-8 km), in grasslands,
like in our case, plant cover reaches its
expected maximum within 2 km from water
(Ludwig et al. 2001). Two perpendicular
measuring tapes, 20 m of length each, were
installed at each sampling point. Eight 20meter
transects by distance and 32 20-meter
transects by well were sampled and monitored
during the spring (rainy season) and fall (dry
season) 2004 using the point intercept method
as define by Daget & Poissonnet (1971) and
Floret (1988). A fine pin was descended to the
ground every 20 cm along the tape. Each of
the 100 hits per tape was recorded according
to the plant species and type of ground
touched. The specific frequency of presence
(SFP) is the number of hits of the specific
species: SFPi = (ni /N) * 100 with ni : the number
of hits of species i and N: the total number
of hits (100 hits in our case). The Grime
adaptive strategies were determined according
to Jauffret (2001), Jauffret & Visser
(2003). Plant species and their nomenclature
are identified with flora books (Cuenod et al.
1954; Quezel & Santa 1962, 1963; Ozenda
1977; Pottier-Alapetite 1979, 1981).
We ran one-way ANOVA on two separate
models: one testing the effects of season on
plant types and one testing the effects of distance
on plant types (SPSS Inc 2002). The
various plant types were treated as categorical
explanatory variables. When significant,
ANOVA were followed by Fisher LSD
Posthoc tests. The Multivariate General Linear
Model Test was used to show the crossed
effect of season and distance on plant strategies.
Results
The cover of chamaephytes, hemicryptophytes
and therophytes increase in the spring
(rainy season) compared to the fall (dry season)
(Figure 2). This is significant at well 3
for chamaephytes, at wells 3 and 2 for
hemicryptophytes and at wells 1, 2 and 3 for
therophytes (Table 1). During the dry season,
when animals frequent wells one day every
three days and induce the destruction of vegetation
cover, the flora is mainly composed of
hemicryptophytes at wells 2 and 3.
Both chamaephyte and hemicryptophyte covers
increase significantly with increasing distance
from the watering point at wells 1 and
2, particularly between 250 m and 500 m
from the wells (Table 1; Figure 3). Therophytes
are not significantly influenced by distance
from watering points. The cover of
hemicryptophyte plants was the highest
(24%) in the spring far from well 2 while it
was the lowest close to this well in both the
rainy and the dry season (Table 1; Figure 4).
Contrarily the cover of therophyte plants was
the highest (28%) in the spring close to well
3 while it was the lowest far from this well.
During the dry season the cover of therophyte
plants is null (Table 1; Figure 5).
Figure 2 – Percent cover of plants classified with Raunkiaer biologic spectrum depending on the season.
See Table 1 for ANOVA results. Values are means ±IC. a/b indicate differences for Therophyte
plants; 1/2 indicate differences for Hemicryptophyte plants and α/β for chamaephyte plants.
Plant cover (%)
40
35
30
25
20
15
10
5
0
Fall String Fall
b
1
a a
a
Ch H Th Ch H Th Ch H Th Ch H Th Ch H Th Ch H Th
String Fall String
Well 1 Well 2 Well 3
b
ecologia mediterranea – Vol. 32 – 2006
β
2
b