Moist Tropical Forests

Distribution of rain forests

Actually, many types of forests.

In lowland areas, range from tropical rain forests with abundant rain in every month to tropical deciduous forests, with a dry season long enough that most of the trees lose their leaves for several months.

In river basins, there are several types of forest types. In Amazonia, varzea forest borders whitewater rivers with high sediment loads (Amazon itself). Ipago forests border low-sediment, blackwater rivers like Rio Negro. May be submerged for several months.

Varzea

Flooded ipago

At higher elevations, there are tropical montane forests, with the epitome being the cloud forests.

Cloud forest

May also classified as primary or secondary. Primary forest is free from signs of disturbance. Secondary forests are recovering from something.

Takes 60 to 80 years for full recovery.

Primary

Secondary

Moist tropical forests cover about 23% of the land area of the tropics. NW, Africa, Southeast Asia. NW Tropics is largest. 80% of the moist tropical forest area is found in only nine countries. Brazil has 31% by itself. Huge political significance.

Characteristics:• high productivity.• tremendous diversity (100-250 species

per hectare)• Very tall. May reach 70-80 meters.

Many layers – canopy, several understory layers, lianas, epiphytes

Liana

Epiphytes

Keystone mutualists.Some figs and other fruiting trees are of great significance to a wide variety of rain forest animals.

Mobile links.Some animals, like certain pollen- and nectar-feeding birds, carry pollen from individual to individual or deposit seeds.

Bulk of net primary production enters detritus food chains. Rapidly recycled. Litter biomass small.

Most rain forest soils are not very fertile.

Very old, highly weathered.

Productivity depends on biotic mechanisms ofnutrient retention and recycling.

Particularly important are the mycorhizzal rootsof trees.

 Biggest problem? Deforestation.

Over 142,000 square kilometers are being destroyed annually. About 1.5% of the remaining forest. Total loss least in NW and greatest in Africa, continuing annual rate of loss greatest in Asia.

Satellite image showing deforestation in Brazil

Greatest impact of deforestation – extinction.

Between 5% and 15% of tropical forestspecies will be lost in the next twenty years.Forest primates particulary heavily impacted.May also lead to drier climatic conditions.

Mountain gorilla

Asian elephant

African forest elephant

Deforestation may interact with other climatic and environmental factors to create a variety of global impacts.

Conservation of Tropical Forest Diversity

In Amazonia, a plan has been developed for a system of 48 in eight biogeographic regions of the basin.

Half to be larger than 5000 square kilometers. This is thought to be large enough to reduce the extinction rate. Reserves centered on areas of high diversity. Investigate Biodiversity

Rapid Assessment Program – uses experts on taxonomy of different groups. Can evaluate an areas potential.

Conservation International Rapid Assessment Program

Unfortunately, weak economies in many tropical nations may favor the rapid and poorly regulated exploitation of resources in rain forests.

Deforestation and Development in Amazonia

Problem – illegal exploitation.  

 

Sustained Management Efforts Have to have a long range plan. Can’t rely simply on preserves.

Brazil is working on extractive reserves, in which tree products like rubber, nuts, etc. can be harvested. First approved in 1989.

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Agroforestry: development, of multi-species communities of trees that yeidl timber, fuelwood, food, and industrial products.

Mimic structure and function of natural forest.

Several schemes have been suggested for sustained-yield timber harvest:

1. contour strip-harvesting – like shifting

cultivation.

In 1990, the International Tropical Timber Organization adopted the year 2000 as a target date for attaining sustainable yields of timber.

“Most conservation experts believe that if effective plans for production and sustained use are not implemented by this date, the world’s moist tropical forests will be irreparably damaged.”

Cox 1997

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