biological diversity and tropical forests in tunisia - PART

PART I1
TROPICAL FORSSTS
Before the oligocece era the climate of Tucisia was tropical (~1-
Hamrouci 1978). Fossil flora at Ichked cocsists of 265 tropical
elemects, such as:
Salj x cacariersis
Cassia sp.
Sapicdus sp.
Pittospo-un sp.
Diiricg the epoch of the Capsiecce civilizati3c, : 5,300 gears ag3, !hcjsia
still had 1~x;rjais abxdart vegetati3c that s~pport.ed mar? specles of
acimels that are co large- foxd ir. Africa ro-th of the Sahara fccludicg
elephacts, rhinocg-aes, liors ard beax (3ir. For. : 376).
Chacgirg climates, ircludirg the peri ods of the g~est glacjatiors,
brought nary F'editerraceac, Saharar acd Fliropear elenerts acd ever. some
boreal elemerts to the forest flora. The last great climate charge was
7000 years ago. Sicce that time, nost of the charges Sc forest erea ard
species comp3siti3r have beer ce~sed by mar.
The presect climate ard domicect forest species a x Kediterraceac, bat
theye are still some t-ee acd shrib species with tropical afficities. Two
primsly remcarts of the txpical forests are thuya Callit-is a~ticiilata
ard Chamae-ops hunllis; others irclade ( ~ e ~ e - i m h o f f r
Zizyph~s (the gecGs ic gece~al) Rhus sp.
Acacia ~addiara (~aha-o-tropi cel) Myrtus conmuci s
Periplnca laevigata " Jasnicum fr~ticacs
E~icaceaes (~rica a-borea grws ir Lyci~n SF
sub-Saharec Af ri ce) Ficxs carica (ictrodaced)
Of the above species, ocly th;ya acd Acacia raddiara are txe rative
tree species, ard neithe~ form what ~oild be cocsidered tropical forests
by mary deficitiors. However, accordicg to the deficitior used for FAA
amerdments 118 acd :19 (state Cable 7183241, 1967) tropical forests
include "all tree acd woody sh~ub formations, whethe? opec or closed,
occurrirg ic humid, subhumid OY semi-arid u~lacds or lowlards". Roughly
the ro~thex 25: of T~cisia is ir the ab3ve bioclimates, so the-e are
about 4 rnillioc ha that coald scpport 'It-opical fo-ests" by the above
defiritioc. Kzch of that lard is cultivated, developed or occupied by
steppe vegetatioc, but there aY? c.680,000 ha with woody vegetatioc (Dir.
For. 1976). Species ic those areas jccl~de thase previo~sly mectioced
nithttrpical aff:ritles (except raddla~a, whlch occd-s 5r arid areas)
acd all 3f the najor forest spec! es -"edi ter-arezr elerr.er.ts).