biological diversity and tropical forests in tunisia - PART

Betweec 1890 and 1973, 2.7 millioc ha of grazicg lands we-e put ucdez
cultivation, fozcicg he~ders to brlcg the5r livestock to the forests to
gzaze (~iz. For. 1976). Aftez the tzees or shrubs have beec cut,
ictecsjve grazicg by domestic livestock disrupts the regeceratioc process.
Grazicg also occars ic umu stands, stopping the natural replacement of
old acd dyicg t~ees. In 1976 more thac 50% of the pine acd oak were of
declicicg age; therefore, 20 - 5% should have been regenerated.
From 1962 to 1984 ac average of 9400 ha/yeaz were planted (OMJPAA
l985), but this practice has beec chacging the f orest species composition
and still falls short of the deforestation rate. Trees commonly selected
for placting are fast g-owing noc-cative species of eacalyptus, acacia acd
pice. Some species native to Tunisia are placted, but often this is doce
outside the coma1 racge of the species.