Geoscience Reference
In-Depth Information
and, as its name implies, the species present are diverse. This type of tropical sea-
sonal forest has a high, closed canopy layer at 80-100 ft (25-30 m) or higher, and a
relatively open understory of small trees, and bamboo reaching above 23 ft (7 m) in
height with few epiphytes and lianas. The forest floor tends to be open with little
low-growing vegetation. The dominant tree in this community is also teak. Other
important trees include
Xylia kerrii
(locally known as daeng), tropical almond, and
a species of crape myrtle (loosestrife family). Diversity of tree species is high.
Mixed deciduous forests dominated by teak have been heavily disturbed due to log-
ging this valuable wood.
Dipterocarp forests are the most extensive deciduous forest type, covering more
area in northeast India, Myanmar, and Thailand, as well as Laos, Cambodia, and
Vietnam, than any other forest type. This dipterocarp forest is characterized by 40-
60 in (1,000-1,500 mm) of highly seasonal annual rainfall, and a five- to seven-
month dry season. Most areas where dipterocarp forests occur are mountainous or
hilly and are dry with shallow soils. Most trees are leafless between February and
April. Fires commonly occur in this forest type between December and March at
intervals of one to three years. The structure of the deciduous dipterocarp forest
can range from a closed canopy to more open woodland. The canopy is typically
low at 16-26 ft (5-8 m) in height with emergents reaching 33-40 ft (10-12 m). The
deciduous dry forests in Thailand, Laos, Cambodia, and Vietnam contain all six
deciduous dipterocarp species. Four species including taengwood, dark red mer-
anti,
Dipterocarpus obtusifolius,
and
D. tuberculatus
(no common names) dominate.
Smaller trees in this forest are from the legume family and include
Sindora siamensis
(locally called tete hoho) and
Xylia xylocarpa
(pyinkado). The leaves of these trees
tend to be large and thick. Cycads and palms are common in the understory.
Where the forest is more open, grasses dominate the understory.
Other dry deciduous forests in India are located on the geologically ancient
Decca Plateau. They include woodlands with an open canopy dominated by two
members of the legume family (Fabaceae),
Hardwickia binata
and
Albizia amara
,
and having an upper canopy of 50-80 ft (15-25 m) and an understory 32-50 ft
(10-15 m) tall.
Dry evergreen forests contain a mix of deciduous and evergreen trees. The ever-
green trees tend to have smaller leaves that are leathery. The forest canopy can be
quite tall at 82-98 ft (25-30 m), with a mix of dipterocarps from the wet forest. The
lower canopy can range from 23 to 75 ft (7-23 m) in height. The understory of
these forests is rich in lianas. Sri Lanka has a large remnant of evergreen forests that
are important habitat for the Asian elephant.
The seasonal forests of the Asian-Pacific region are relatively poor in climbing
species apart from palms and dipterocarps. However, some climbing species in the
dogbane, milkweed, morning glory, legume, and squash families are present. Spiny
rattan palms are the most diverse group.
Seasonal forests of the East Malesian subregion contain a mix of species from
Australia and Asia, but only fragments of seasonal forests in this subregion still
