biological diversity and tropical forests in tunisia - PART

A. Vegetation
Most of Jerba has been cultivated to date palms, olives, various fruit
trees and vegetables. The rest is so overgrazed that only a poor
representatioc of the native vegetation remains. Inland, on the higher
ground, a group of nitrophilic species is found. Thoae species include
- Malva parviflora, Aizoon hispanicum and Peganum hannala. Around the areas
of nitrophilic species are warmer locations with 5460 ha characterkzed by
a ~ituranthos tortuosa and Haplophgllum venniculata association (~u~horbia
eerrata v a r i a n m ha with an Artemesia herba-alba and Arthrophytum
scoparium association (~ymnocar~os decander sub association, Asphodelis
microcarpos variant) and 34,000 ha characterieed by an A. microcarpus
variant of the Zarzis peninsula association ( ~ Houerou e and Froment 1969).
Van Berghen (1977) noted two major associatkons on the dunes between
Bordj Kastil and Bordj Djellidj composed of 32 species: one on the low
dunes charactsrized by Agropyron farctum and the other on the high dunes,
characterized by Ammophila arenaria. Annuals compose 56% of the
vegetetioc.
Oc the wsst and north sides of Jerba there are coastal dunes vegetated
by spscies groaps characterized by A. arenaria and Agropyrum unceum or
Cakile maritima ar.d Medicago marina7~e Houerou and Proment ;*Where
the dune sands are more salkne, such as in the northwest corner and on the
east side of Jerba, a gypso-halophile associatkon of Nitraria retusa,
Suaeda vsrmiculata and Salsola sieberi var vesceritensis is found. In the
depressiocs betwsec the dunes there are 6 major plant associations
compossd of 83 species (van Bsrghsn 1979):
1. A single species aquatic association (water 1-4 m deep) of Ruppia
cirrhosa var drepansis.
2. A pionser community on wet sands with Riella notarissi and some
Chare vulgaris.
3. Very open cover with Limonium tunetanurn and Aeluropus lagopoides.
4. Alocg depression edges, Juncus maritimus var arabius occurs.
5. A Schoenus nigrans association on water-holding substrates.
6. A pioneer cornmucity with Frankenia pulverulenta.
Along the coast are found:
Halocnemum etrobilaceum Juncus maritimus
Limoniastrum guyonianum Atriplex halimus
Zygophyllum album Limoniurn ep.
Tamarix africana (sparse)
Rare placts include Peganum hamala var. garamanteum.
Mammals. Nary fox have been released on Jerba by departing tourists
who p~rzhased fox kits and found that they were unable to take them out of
the coactry. The introdxed fox are now so numerous that they have
virtaally elirnicated barbary partridge from the island (A. Abed, pers.
corn). Brom hares were similarily ictrodaced by tourists, but have been