Along the coasts there is a fringe of Manglares (man- 
groves), succeeded inland by a narrow zone of Selva Baja 
Caducifolia. This predominantly deciduous forest type 
generally covers the sides of the highlands or almost flat 
land, especially in the Central Depression, where the an- 
nual precipitation is less than 1200 mm. Also prominent 
on the coastal plains and in the Central Depression are 
Sabanas and Selva Alta Subcaducifolia, occurring along 
the floodplains of the larger river valleys. The Sabanas 
are xerophytic grasslands with scattered low-growing 
trees typically developed in areas with an annual precipi- 
tation of about 1200 mm. The deep soils are often flooded 
during temporary rains, but during the dry season the 
water table is deep, and the top soil is very dry. During 
the dry season, this vegetation type, and others that have 
a dense grass cover, are constantly being burned. Palm- 
ares are often interspersed within the Sabana. The sepa- 
rate patches of palms are usually characterized by differ- 
ent species, and hence the groves vary from one locality 
to another. 
The Selva Alta Subcaducifolia contains a number of 
trees that are common in both the Selva Alta Perenni- 
folia and Selva Baja Caducifolia, and consequently ap- 
pears to be a transition forest assemblage between the 
last two types. The most extensive humid lowland vege- 
tation is the Selva Alta Perennifolia, which Miranda 
considers a northern extension of the equatorial tropical 
rain forests. He also believes that this vegetation type 
covered at least one third of Chiapas in recent times, but 
has been largely destroyed by human occupation. This 
forest develops in an area with an annual precipitation 
of at least 2000 mm. It has relatively few shrubs and 
herbs in the understory, and its composition varies greatly 
from one locality to another. Trees from temperate re- 
gions descend into the humid lowlands along the rivers. 
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