Ecology | ||||||||||||||||||||||||||||||
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Vegetation
is varied and made up of seasonally flooding grassland and various
types of tropical
forest. The wetland is bounded to the east, south and west by
dense humid evergreen forest with Hills
supporting semi-evergreen and deciduous forest. A substantial part
of Nam Cat Tien floods which significantly
affects the flora and fauna found the area. Vietnamese scientists
have identified a number of major vegetation zones in Cat
Tien National Park: 5. Besides forest,
the Park contains: De-forested
land may become infested with alien invasive
species. The
pictures above show boulder pathways, made to help visitors traverse
some of the wetter areas during the rainy season - the significance
of which may not be apparent during the dry season (right) This
picture also shows rattan,
a vine-like palm [Arecaeae], trailing on the forest floor (to left
of the picture). Recycling
nutrients: termites and fungi Tropical
soils are often poor in plant nutrients and frequently acidic. The
spectacular growth in a rain forest is largely supported by the
efficiency of nutrient recycling after plants die and decay. Three
groups of organisms: bacteria, fungi and arthropods are primarily
responsible for this recycling, of which the latter two are most
obvious. A
nasute termite
band. This
photograph was taken during the rainy season, but termites often
form characteristic galleries in which give them protection from
predators and dry air. Their
nests are frequently arboreal appearing as earth covered 'swellings'
on tree trunks. Species in the genus Nasutitermes have "nasute"
soldiers, with a head drawn to a point - from which they squirt
a noxious sticky liquid if enemies attack. Unlike many other termite
groups that have large jaws (mandibles), those of nasute termites
are fused to the head capsule. The majority of this genus are associated
with hardwoods, and may be timber pests in buildings. Identification
from soldier caste with assistance from worker, nest habit and region
of occurrence (species often having a strong geographical distribution). See
more insects (Isoptera) Millipedes
are important recyclers of leaf litter They
can be distinguished from centipedes (which are usually carnivorous)
by apparently having 2 pairs of legs per segment. Unlike centipedes
they do not normally bite, but they may use a very unpleasant stink
gland! Fungi are perhaps ultimately the most important decomposers of wood, leaves and other dead matter and many species are microscopic. They include mushrooms (implying that they are edible) and toadstools (some of which are deadly poisonous). The attractive red cup-shaped fungus is Cookeina sp. (order: Pezizales), which belongs to the Ascomycete phylum of fungi, is commonly found on forest paths during the rainy season. Many of the larger toadstool species belong to the Basidiomycetes; an Amanita sp. is shown here (top right) and the ubiquitous bracket fungi (Ganodermataceae), such as the Amauroderma sp. (below right), can be seen growing out of dead branches. A forest
such as Cat Tien almost certainly contains many thousands of
species that are new to science - some of which might be economically
useful. Examples include the entomopathogenic
fungi, which can be used for pest control. This
picture shows Homopteran
insects - probably whitefly nymphs (related to important agricultural
pests) that have been killed with what is probably Hypocrella
raciborski (ananmorph: Aschersonia placenta) - showing
white/yellow fungal growth. There is also a more cryptic, unidentified
pathogen forming chocolate-brown stromata (courtesy
H. Evans). Dead
animals
don't escape the attention of ants for long! This
recently dead krait
(Bungarus
sp.), that was possibly killed by a mongoose has already attracted
a trail of ants (detail bottom right) and a necrophagous fly (top
centre). See
also: conservation, forest |
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updated: 25 June 2012 |
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