Earth Restoration Project

 

 

This is a popular term for the wet evergreen forests of the tropics, but scientists define 13 major categories of tropical rainforest, and there are many lesser and local variations beyond those.  These types are expanded on

This is the richest of all forests ecosystems and is the classic rainforest, with a high canopy through which emergent trees reach to the light.  Buttresses on the trees and lianas are common, and it occurs in those areas with high rainfall which is evenly distributed throughout the year.  This is the predominant rainforest type in Malesia and it is also found in the Neotropics.

 

This rainforest type occurs in areas which have an uneven annual rainfall, usually with a dry season of one or two months.  Some of the trees are decidious and the species diversity is slightly less than in the evergreen rainforest.  This is perhaps the most extensive of all the rainforest formations, particularly in the Neotropics and in Africa.

 

Also known as lower montane rainforest, this type is found on the middle elevationsof tropical mountains, and is usually demarcated from the lowland rainforest at an altitude of about 1000 M.  The trees are still tall but not as tall as in the lowlands, and buttressing is rare, although epiphytes and tree ferns are common.  This type is somewhat akin to subtropical rainforests.

 

Sometimes referred to as upper montane rainforest , this formation occurs on higher elevations, typically from 2000 to 3000 M or higher.  The trees are small and often gnarled, and epiphytes and moss cover them and the ground.  Most of the moisture comes from clouds, giving rise to their common name of cloud forest, and in composition and appearance they are similar to temperate rainforests.

 

 

A cloud forest is an evergreen, montane forest that can be found in the tropical and sub tropical regions of the earth. It is named after, and characterised by, the low level clouds that form in the canopy of the forest on a daily basis.

 

On the highest tropical mountains, subalpine forest occurs above the cloud forest up to the tree line.  It consists of stunted trees and shrubs which usually have very small leaves.

 

This is dwarf forest growing on exposed ridge tops, usually at high elevations, where the trees are miniature in size (2-5 M high) due to constant effects of wind and fog.

 

This is a community of trees and shrubs which grows in the tidal zones on sheltered coasts in the tropics.  The trees have evolved many unique features to withstand the difficulties of their habitat, including stilt roots, pneumatophores (upward growing roots which enable them to breathe in the mud), and salt-excreting leaves.

 

Also known as riparian forest, this is narrow strip of trees along watercourses in tropical savannas and other largely open spaces.  The presence of the water in rivers and streams allows vegetation more typically found in rainforests to grow in these areas which often have prolonged dry seasons. 

 

 

In areas where the land is constantly flooded in the tropics, the rainforest takes the form of swamp forest.  Scientists distinguish between two main types, freshwater swamp forest, which is inundated with fresh water and is often dominated by palms, and peat swamp forest, which grows over areas of peat - this type is particularly common in west Malesia in Malaya and on the islands of Sumatra and Borneo.  In the lower reaches of the Amazon basin in Brazil, the nutrient-poor black water rivers such as the Rio Negro support a freshwater swamp forest known as igapo which is flooded for 6-12 months of the year.

 

Although many tropical rainforests grow on very poor soil, heath forest occurs where the soil is so deficient in nutrients that the physiognomy of the forest is markedly different.  In Borneo the heath forest is known as kerangas, and the trees are pole like and much shorter than in the rainforest.  In South America the heath forest is known as wallaba in Guyana, and as catingas do Rio Negro in Brazil.

 

Limestone outcrops occur to soils in various forms, sometimes as upraised coral platforms in coastal areas, or most spectacularly as the 30 M high pinnacles on the slopes of Gunung Api in Sarawak, Borneo.  The rainforest which grows over limestone is often quite distinctive and contains a large number of endemic species.

 

 

Ultrabasic rocks give rise to soils which are deficient in most major plant nutrients and which can contain high elements of toxic elements such as nickel and chromium.  Consequently, the rainforest which grows over these rocksis often very different from the surrounding forests, with the trees being much shorter in height and of a few specialised species.

 

This type of forest occurs in the tropics where there is a longer dry season, typically of several months.  In southeast Asia, this type of forest is predominately over large areas, with teak being the principal trees.  Where the dry season is even longer, of six months or more, the forest is known as dry tropical forest or tropical decidous forest.  In Central America this latter type has been reduced to just 2 percent of its original extent, and in northeast Brazil the catingaa, a mosaic of decidious and xerophytic vegetation, is also highly threatened.

 

Savannas are tropical grasslands which have scattered trees and small pockets of forest, which are usually well adapted to fire.  In Africa the savanna forest is typified by spreading, flat-topped Acacia trees, while in Brazil the savanna vegetation is known cerrado and is characterised by small, twisted or gnarled trees.

 

Where continuous rainfall patterns extend outside the tropics, subtropical rainforest flourishes.  Although not as rich and diverse as the true tropical rainforest, the formation is still profuse and lush in its vegetation.  Examples of subtropical rainforest are often isolated, such as in the foothills of the Himalayas or on the east coast of South Africa, while it also occurs in southern Brazil and northern Argentina, and on the east coast of Australia.

 

 

These are dry forests outside the tropics in areas where the summers are hot and dry and the winters warm and wet.  They are typifiedby the forests around the Mediterranean basin, in central and southern California, in central Chile, in South Africa and in the southwestern tip of Australia.  As they grow in areas which have a climate considered ideal by many humans, the sclerophyllous forests have all been greatly reduced in extent.

 

These forests occur mainly on the eastern seaboards of the continents, where they receive plentyful rain throughout the year from the trade winds.  They are found in China, Korea, southern Japan, eastern Australia, New Zealand and in the southeast of the USA, where characteristics trees include evergreen oaks and bald cypress.

 

 

On the western seaboards of the continent in temperate regions where there is plentiful year-round rainfall, temperate rainforest flourish.  Similar in appearance to the cloud forests of the tropics, they are characterised by an abundance of mosses, lichens and ferns.  Surviving (but threatened) temperate rainforests include those of the Pacific northwest of North America, the valdivian rainforest in Chile, those in Tasmania and the southeast of Victoria in Australia and the southwest of the south Island in New Zealand.  The west coasts of Scotland and Ireland also contained temperate rainforests before they were deforested by humans.

 

This is the type of forest which covered much if western Europe in former times, and which is still extensive in Eastern North America, in northern Japan and in nearby mainland Asia.  The most obvious feature of the trees in this formation is the shedding of their leaves for winter as an adaptation to withstand cold (whereas in tropical deciduous forests it is an adaptation to withstand drought).  This is preceded by the spectacular colour change of their leaves, a phenomenon which is almost exclusive to the northern hemisphere as temperate deciduous forests are only found in the south in Patagonia and Tierra del Fuego, and in Tasmania, where there is one species of deciduous beech.

In central Europe and western North America the deciduous forests give way to conifers, particularly at higher elevationsm where this formation resembles the boreal coniferous forest. Conifers are mostly absent from the southern hemisphere, although the Araucaria or monkey puzzle forests of Chile come into this category.

 

In northern latitudes up to 70 degrees N the boreal coniferous forests covers vast areas in Scandinavia, Russia, Alaska, Canada, and also formerly in the highlands of Scotland.  The trees, which are mostly spruces, firs and, pines and larches, are well adapted to the extreme cold of winter and grow above a ground-cover of dwarf shrubs. At its northermost limits the boreal forest opens out and becomes intespersed with tundra, and in Russia this is known as Taiga. This formation does not occur in the southern hemisphere because there is no land mass at the equivalent latitude.

 

This is not a forest formation as such, but rather is the state of maximum development of a given forest type.  When a forest begins to grow in a natural situation it begins with the pioneer trees, which grow quickly and have a short life-span.  They provide shade and shelter for the slower-growing species and, as these take over, the forest eventually reaches a stable state with a maximum number of species.  The composition of such a climax forest will not change if the soil and climate do not change, and it is also known as primary forest or in North America, as old growth forest.  In areas where this forest is removed, the forest which replaces it, especially in tropical climates, is poor in species and fast growing and is called secondary forest.  If there is primary forest nearby it will eventually grow up through the secondary forest, but with present-day large-scale clearfelling operations this is becoming increasingly unlikely.

 

 

The above information is taken with kind permission from the Calendar and Engagement Diary of Trees for Life