biological diversity and tropical forests in tunisia - PART

B. Icfluences
Humac influences include hunting and cultivation to within 5 m of the
waterline, which leaves only a narrow band of vegetation. The ecosystem
would be sensitive to heavy concentratiocs of fertilizers or pesticides in
the ranoff water from farmlands if large scale chemical use was initiated.
3 . 2 4 Sebkhet Kelbia 35'50' N 10°17' E
Kelbia is located at the edge of the Low Steppes, 20 km northeast of
Kairouac and 30 km west of Sousse. It has an area of 13,000 ha and a
maximum depth of 2.52m. Three intermittent rivers drain the adjacent
watershed (15,000 km ) into Kelbia - the Nebhana, Merguellil and Zeroud.
Before the rivers were dammed, they flooded after heavy rains, causing
erosior and resulting in a delta of silt deposited at the south end of the
lake (~or~ac 1982). During the summer the lake occasionally dries,
leaving a light salt crust on the bottom. Water salinity varies from 1
g/l ic the spring to saturation as the lake dries (~aouali 1976).
A. Vegetatioc
Alocg with the halophile vegetatioc typical of sebkhas, there are
bands of tamarisk along the edge and emergents such as cattails Typha
angustifolia, reed Phragmites communis and Scirpus lacustris covering
about 10% of the edge. When there is water in Kelbsa, a dense prairie of
Zacichella palustris covers aboat 9% of the bottom and dominates over
Potamogetoc pecticatus and Tolypella (~aoaali 1976, Morgac 1982). A
floating mass of Spyrogyra often forms during the spring.
B. Fauca
Zaoaali (1 976 ) acd Morgan (1 982) reported several specses of fauna:
Z O O D ~ ~ ~ ~ O R :
Arctiodiaptomus wierzejskii Dapcia rnagna
Dapcia atkicsi Diacyclops crassicaudis
Irvertebrates:
Cymatia bocsdorffi
Micronecta sp.
Ilyocoris sp.
Sigara sp.
S. dorsalis
Plea sp.
Berosus sp.
Palaemonetes varians (crustacean)
Gyrinus sp.
Palaemonetes and the insects are adapted in such a manner that after
dry periods they can recolonize Kelbia from nearby water bodses. The
zooplankton has resistant eggs.
In former times, before the construction of the dams, up to 82 metric
tons of fish have been taken from Kelbia by commercial fishermen. Fish
species include:
Fucdalus hispacicus Cambus3a affixis
Barbus barbas Cypricus carpio
hgil cephal-JS Anguilla a~guilla
Y. ramada