The Forest Biome

The forest biome consists of close growing trees with leaf canopies that generally overlap. The overlapping canopy prevents much light from hitting the forest floor. The shaded conditions keeps forest soils relatively moist. Forest require ample amounts of annual precipitation to support their growth. Forests are found over a wide range of temperature regimes , from the hot equatorial regions to the cold subarctic. Forests occupy approximately one third of land surface though this value is shrinking as humans cut the forest for material needs and economic gain.

The Tropical Rain forest

The Tropical Rain forest contains trees standing 30 to 55 meters in height, creating a continuous canopy of foliage. The enclosed canopy shades the forest floor inhibiting the development of much undergrowth, creating an open forest formation. Few pure stands of trees exist, instead individuals are widely dispersed throughout the forest. Mahogany, teak and other tropical hardwoods are harvested for creating fine furniture. The lush vegetation and great animal diversity should be expected in the tropical rain forest climate.

rainforest_Congo_FAO.jpg (10790 bytes)

Figure 12.15 The multistory canopy of the tropical rain forest (Congo) (Image courtesy FAO)

Peering into the canopy reveals a multi-story appearance of broad leaf, evergreen vegetation called "selva". The typical three-tiered zonation includes an emergent layer of solitary, giant trees reaching heights of 55 meters (180 ft) for the sunlight they require. Beneath is an intermediate zone (canopy) of continuous foliage 9 to 18 meters (30 to 60 ft) high. The forest floor is relatively open as the shade of the closed canopy inhibits plant growth. It is a damp and dim world as one walks through the aroma of decaying vegetation. Giant woody vines called "lianas" snake their way up the trunks of trees. Epiphytes ("air plants"), like the brilliantly colored bromeliad, grow in the hollows of trees or the upper surfaces of horizontally-growing branches capturing nutrients and moisture from the air. Imagine That! -- "Rainforest Canopy" : NSF/Finger Lakes Productions International

Bromeliads

Figure 12.16 Bromeliads clinging to a rain forest tree (Image courtesy FAO)

A cloud forest exists on extremely moist mountain slopes above the elevation of the true rain forest. The cloud forest differs from the rain forest found at lower elevations in that trees are much shorter and the forest floor is virtually impenetrable.

Plants have adapted to this environment in unique ways:

“ The canopy itself, the ceiling of the jungle, is a dense continuous layer of greenery some 6 or 7 meters deep. Each leaf is accurately angled to ensure that it will collect the maximum amount of light. Many have a special joint at the base of the stalk that enables them to twist and follow the sun as it swings over head from east to west each day. All except the topmost layer is screened from the wind, so the around them is warm and humid.”

The Living Planet
D. Attenborough

The rain forest is a treasure trove of different animal and plant species. The numerous species that inhabit the rain forests are not well documented. The intense precipitation of the tropical rain forest climate heavily leaches the soil. Oxisol soil common to the rain forest are relatively infertile due to intense weathering and a lack of available nutrients. Deforestation and habitat destruction is severely crippling the rain forest ecosystem.

Examine of the Amazon river and flooded forest ecoregion
from the National Geographic Society (Commercial interruptions).

Tropical Monsoon/Seasonal Forest and Shrub

The Tropical Monsoon/Seasonal Forest and Shrub, contains trees of smaller stature than those found in the rain forest. The Monsoon forest may include deciduous trees, as well as, broadleaf evergreen trees reflecting the seasonal precipitation of the monsoon climate. The trees of the Monsoon Forest have a more open canopy than the rain forest, creating a dense, closed forest at the floor, or what we think of as a "tropical jungle" beneath. The thick surface undergrowth makes it difficult to navigate through the forest. Jungle growth is also found along streams, and in openings created by humans.

BE.17 Monsoon forest of India monsoon_monkey_FAO.jpg (16449 bytes)
(Image courtesy FAO)

Like the tropical rain forest, the monsoon forest supports a diversity of plant and animal species. And like the rain forest, it's biotic system is being stressed by human activities.

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