Due to the fact of being located between
the savanna to the south and the low-lying Amazonian forest to the north,
the Meridional Amazon Forest, at somewhat higher elevation, is considered
to be among the richest areas of the whole Amazon basin, presenting an
astonishing diversity of flora and fauna, and some of the highest rainforest
canopies in the world. The states of Mato Grosso, Rondônia and Acre
are part of the Meridional Amazon.
In Alta Floresta region there is a great
amount of endemism related to birds. "The geographic location of
the Alta Floresta area in the headwaters of the Tapajós contributes
greatly to its ornithological importance because the river separates different
populations of many forest birds" (Bret Whitney : Cotinga Magazine-
April 1997). A list of birds known to occur in the Alta Floresta region
up to 1996 was published by Zimmer et al. (Ornithological Monographs of
the A.O.U. No. 48. 1997. pages 887-918.
The mammals found in the this region of the
Amazon include Brazilian Tapir (usually seen along river banks), Capybara
(the largest rodent in the world), anteaters and opossums, river otters,
Giant Otter, brocket deer, agoutis and Paca, and others. The agoutis and
Pacas, with their powerful teeth, are the only mammals capable of opening
the Brazil Nut shell. Many nuts are eaten, but some are buried, saving
food for later, and some of these germinate to start new Brazil nut trees
growing. Large macaws, with massive bills, are purely predatory on these
and the seeds of other canopy trees. There is a remarkable diversity of
monkey species in this region of Amazonia, including Night Monkey, Dusky
Titi Monkey, Brown Capuchin Monkey , Red-handed Howler Monkey, White-bellied
Spider Monkey, and the handsome and endemic White-nosed Bearded Saki Monkey.
The butterflies are starting to be researched
by Dr. Keith Brown, who classified an amazing 450 species in just four
days on the Rio Cristalino, during his first visit in the rainy season
(February/2000) .
The Cristalino State Park in Mato Grosso
State is formed by primary growth forest, where visitors can admire the
singular beauty of undisturbed Amazonian rainforest.
A closed forest canopy blocks 90 to 95% of
the sun from penetrating to the forest floor. Thus, it is relatively easy
to walk in this type of forest because the understory is sparse and trails
are not closed with vegetation. Those viewing the forest from the river,
where the edge presents a wall of trees and vines, often imagine that
the forest interior is much denser than it really is. It is in the treetops
where most life can be found, much of the time beyond our sight. The forest
mid- and understory is relatively shady and humid, and promoting an abundant
growth of epiphytes, which are plants growing on other plants. Epiphytes
are not parasites, but grow on trees or rocks after their seeds are deposited
on these surfaces by birds, bats, and other organisms. Ferns, orchids,
philodendrons, and bromeliads are examples of epiphytes. In general, the
greater the annual rainfall, the greater the abundance and diversity of
epiphytes. Vines of different sizes and shapes are also common in the
forest and they can be dozens of meters long. Most of the time, vines
do not have leaves or flowers in the lower level of the forest, but when
reaching the canopy they have large ones to catch the sun.
Due to high annual rainfall in these forests, nutrients in the soil are
washed away almost constantly. Soil nutrients are generaly poor and concentrated
very near the surface. Consequently, tree root systems are quite shallow
relative to most temperate regions. Tall rainforest trees have evolved
two major strategies to support their great girth and weight: buttresses,
some of which are enormously high and long; and stilt roots, which characterize
many species of palms, perhaps especially those in frequently flooded
places. Forests keep the rivers clean and flowing regularly all year long.
When the river-edge forest is cut down, erosion sets in and the river
becomes muddy and narrow due to the deposit of sediments. Flooding can
become disastrous.
Tropical forests harbor an unparalleled wealth of plant species and diversity.
The high temperature and the humidity inside the forest favor the existence
of funguses which, together with termites and ants, play a vital role
in the decaying process of fallen trees, leaves, and fruits. Vegetative
rot can be completed within six weeks, while in temperate regions it would
take about one year. In the boreal and coniferous forests, the same process
may take about seven years. In the tropical forests, we find a great number
of animal species, but the number of individuals in the species is small,
due to the flora diversity, where the plants from which they feed are
kept too far away from each other.
Tropical forests play a very important role
in global climate regulation. In the Amazon rainforest, 50% of the circulating
humidity is kept inside the forests. When the forest is cut down, the
vegetation does not retain the humidity, affecting the atmosphere and
climate of the region by making it dryer. When large areas of forests
are destroyed, the alteration in the climate extends to surrounding areas,
because clear ground reflects solar radiation, changing the wind currents
and the rainfall, not only locally, but also in areas distant from the
tropics.