Vol. 32 – 2006 - Ecologia Mediterranea

disturbance degree on Noy-Meir types? (iii)
What is the impact of seasonal drought and
disturbance degree on the CSR species strategies
(Grime types)?
Material and Methods
Studied zone
El Ouara communal rangelands
El Ouara region is a part of Presaharian
Tunisia following Floret and Pontanier’s definition
(1982); this region corresponds
roughly to the Tunisian part of the lower arid
zone of North-Africa, comprised between the
isohyets of 100 and 200 mm of annual rainfall
(Figure 1). Rainfall pattern and temperature
regime are Mediterranean. The rainfall
(256 mm) recorded in Sidi Toui National Park
during the studied period (from fall 2003 to
spring 2004) exceeds the annual averages of
the region (100 mm). The unique land use of
the area is rangeland. Topographically, this
region is mainly composed of vast encrusted
glacis with a thin sandy top layer (CNEA
1991). The vegetation, essentially constituted
of dwarf shrub steppe with perennial grasses,
covers about 12%, 23% and 37% during a dry,
medium and rainy year, respectively. Potential
productivity, which varies with dominant
plant species, is between 15 and 60 UF ha -1
ecologia mediterranea – Vol. 32 – 2006
A preliminary overview of the effects of seasonal drought and animal pressure around watering points
on plant species using adaptative strategy analyses in the Tunisian arid zone
an -1 (CNEA 1991) with 1UF: the equivalent
of the energy produced by 1 kg of barley.
Watering points
Three watering points situated in El Ouara
communal rangeland were retained for this
study. These wells differ by the duration of
exploitation, their geographical locations, the
nature of surrounding vegetation and the grazing
pressures. The first watering point (well
1, exploited for 150 years) is located in the
North of the studied zone, the second (well 2,
exploited for 100 years) and the third (well 3,
exploited for 5 years) are located in the south
of Sidi Toui National Park. Well 1 is located
on a stony soil with truncated top layer and
surfacing rock due to erosion with plants,
such as Anthyllis sericea Lag. subsp. henoniana
(Coss.) Maire and Gymnocarpos decander
Forssk. The east of this watering point is
occupied by Stipagrostis pungens (Desf.) de
Winter and Hammada schmittiana (Pomel)
Iljin. Wells 2 and 3 are located on a sandy
substratum with plants, such as S. pungens
and H. schmittiana. A. sericea is absent there
because of soil characteristics.
Data collection
Four transects were laid out in the four cardinal
directions and sampling points were
located at 250 m, 500 m, 1 km and 2 km from
each watering point (Figure 1). The choice of
Figure 1 – Location of the three studied watering points (W1 = Well 1; W2 = Well 2; W3 = Well 3),
Sidi Toui National Park and the sampling design around them.
300 mm
200 mm
100 mm
100 mm
W1
Sidi Toui
W2
W3
200 mm
0 50 100 Km 0 30 60 Km 0 1 2 Km
W
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