This riverside vegetation also commonly tends to have 
abundant tall bamboo and cane-type grasses, such as 
Guadua and Gynerium, as ground cover. 
The most widespread vegetation in the temperate re- 
gions of Chiapas are Encinares and Pinares. Considerable 
areas of the mountains in the north, the Central Mesa 
and peaks of the Central Depression, and the Sierra 
Madre are covered with oak and pine forests. In most 
of these locations, oaks usually occupy the deep soils and 
pines the shallow soils, although the two types can be 
mixed with the pines occupying more area than the oaks. 
The oak forests are extremely variable in composition. 
Forests dominated by oaks may occur in contact with 
either the Selva Alta Perennifolia in the hot country or 
with the Bosque Caducifolio in temperate regions. Cer- 
tain species of oak, however, occur in patches intercalated 
within the Selva Alta Perennifolia, and other species are 
a normal component in the Bosque Caducifolio. Both 
the oak and pine forests generally have a grass understory 
and are marked by repeated burning. The lower altitu- 
dinal limit of pines is in a transition area between hot and 
temperate zones. Pines extend to about 4000 m., which 
is the upper limit of tree growth. In the more humid 
areas at high elevations (2800-8500 m. ), 4 bes and Cupres- 
sus rnay occur with the pines. Species of Juniperus form 
a low forest on dry sites between 1600-2200 m., as well 
as occurring in dense stands at tree line. 
The Bosque Caducifolio is characterized by the clear- 
cut dominance of a relatively few tall, typically temper- 
ate, deciduous species. This type of vegetation occupies 
a considerable area in Chiapas, especially on the escarp- 
ments of the Central Mesa between 1000-2000 m., most 
exposed to northerly, moisture-laden winds. 
Living producers of abundant resin in Chiapas occur 
in most of these vegetation types (Plate XLV). In some 
[ 269 ] 
