biological diversity and tropical forests in tunisia - PART

have been made of medicinal plants (~abli 1987) such as:
A juga iva Urginea maritima
Zygophyllum album Nerium oleander
Daphne gnidium
Export of medicinal plants is also a source of foreign exchange. Oil
from Myrtus communis is highly valued in some european countries. Each
year, branches are cut from thousands of ha (9,000 in 1984) of Hyrtus for
extraction of oil reputed to help treat rheumatism and other ailments.
C. Fiber Plants
Vegetable fiber is obtained from dwarf palm Chamaerops humilis. In
1975 over 350 metric tons of dwarf palm leaves were harvested at a value
of 30,000 Tunisian Dinars. Valuable leaves and somewhat slow regeneration
make dwarf palm sensitive to overharvesting. It is a species warranting
special attention to ensure its continued abundance.
Esparto grass Stipa tenacissima (also called alfa grass) is a fibrous
plant, used traditionally for weaving. A modern use of large quantities
of esparto fiber is the production of high quality paper. Paper mills in
Kasserini use such great quantities of esparto grass that more than half
of the esparto grasslands of Tunisia are exploited. Esparto regenerates
fairly well, but overharvesting followed by grazing or cultivation has
lead to serious degradation of the grasslands in many areas.
D. Forage Plants
Many of ~unisia's grazing lands are degraded and occupied by poor
quality forage plants. Some plants, such as Saccharum ravennae and
Andropogon sp. are becoming rare due to o v e r g m a b l i 1987). In
desertic areas, important sand-fixing species are being decreased with
serious consequecces to the ecosystem. Pasture improvement and rational
grazicg strategies are needed throughout Tunisia. Pastures can be
improvsd by improving the water regime and nutrients of an area, and by
increasing high quality forage species.
The developmect of high quality forage plants is a concern of several
icternatiocal organizations and seed companies. Attention has been
focused on producing hybrids of several types of highly palatable and
nutritional plants. To determine favorable forage plants for cultivation
and produce optimum hybrids, a large number of species are being tested
and efforts are being made to inventory the geographic distribution and
availability of some of the more desirable genera. The International
Bureau for the Protection of Genetic Resources is currently conducting
such a study on the genus Medicago. Tunisia's flora includes many species
of plants in genera of interest, including 24 species of Medica~o, 34
species of Trifolium, 6 species of Hedysanun (two of which are of high
interest for local propagation) and many subspecies of these and other
forage plants (Festuca, Dactylis, etc.).
Many spsciis in Tunisia are of high forage value without hybridization
and need only be increased in suitable ecosystems (ex. Hedysarum
carnosum). Nabli (1987) suggested the propagation of several species of