The forest ecosystem is a complex assemblage of different types of biotic communities. Forest communities are formed in the presence of optimum conditions of temperature and soil moisture. The vegetation of the forest is determined by the nature of the soil, local topography, and climate. These factors affect the distribution of trees and their abundance.
The forest ecosystems are classified into three major types viz., tropical forest, temperate forest, and coniferous forest. These forests are distributed around the earth generally on a gradient, from latitudes north to south, or from low altitudes to high altitudes. Forests can also be evergreen and deciduous based on the season in which the trees shed their leaves. On the basis of types of leaves, they can be distinguished into broad-leafed or needle-leafed forests.
Tropical Rain Forests
- These are found close to the equator where the temperature and humidity remain high throughout the year.
- They are found in areas where the annual rainfall exceeds 200 cm and is distributed throughout the year.
- Tropical rainforests are among the richest ecosystems in terms of biodiversity. They have very high floral and faunal diversity
- An important feature of the flora here is that it is vertically stratified. The forests have very tall trees with a dense canopy at the top. The trees are often covered with vines, creepers, lianas, epiphytic orchids, and bromeliads. The layer below it consists of shrub variety trees like ferns and palm.
- The soils in tropical rainforests are known as red latosols or lateritic soils. They are very thick. They have undergone high rates of leaching which makes them unsuited for agriculture. However, if left undisturbed without high precipitation, they experience fast recycling of nutrients from the decomposing litter and can regain their lost nutrient value.
- These forests do not have a dense undergrowth due to lack of adequate sunlight at the bottom. The dense canopy of these forests blocks most of the sunlight from reaching the bottom layer.
Subtropical Rain Forests
- These are broad-leaf evergreen forests found in the regions of high rainfall with a low annual range of temperatures.
- The biodiversity in these forests is similar to that found in the tropical rainforests. Epiphytes are common here.
Tropical Seasonal Forests
- Also known as the monsoon forests, they are found in regions where the annual rainfall is high but is concentrated in a few months of the year and there are distinct wet and dry seasons.
- These forests are found in India, South-east Asia, northern Australia, central and South America, western Africa, and the tropical islands of the western Pacific.
Temperate Rain Forests
- These are found in temperate latitudes which exhibit a marked seasonality with respect to rainfall and temperature.
- These forests experience dense fog and high rainfall. Fog is considered to be a more important water source than rainfall.
- Biodiversity of these forests is higher than other temperate forests but not as high as tropical rainforests.
Temperate Evergreen Forests
- These forests are found in regions with a Mediterranean type of climate. The summers are warm and dry, and the winters are cool and moist.
- The region supports the growth of short, broad-leaved evergreen trees.
- Dry summers make this region prone to forest fires. However, the plants here have adapted themselves to forest fires which enables them to regenerate quickly even after getting burnt.
Temperate Deciduous Forests
- These are found in regions with a moderate climate. The trees are broad-leaved which shed their leaves in autumn in order to save water during the dry season by reducing transpiration losses. The forest appears bare in winters but new foliage starts to appear in the spring.
- The rainfall is uniformly distributed throughout the year.
- These forests contain podzolic soils and are sufficiently deep.
- These are also known as boreal forests.
- These are found in regions with long and cold winters and short and cool summers. They are found in the northern latitudes close to the Arctic circle.
- The trees are of evergreen variety with prominent plant species such as pine, spruce, fir etc.
- They harbour unique faunal species such as red fox, lynx, arctic wolf, squirrel, amphibians such as Hyla, Rana (both are frogs) etc.
- The soils of coniferous forests are thin podzols which are rather poor in nutrient content. This is because the weathering of rocks and the decomposition of ground litter proceeds slowly in the cold climate. Microbial activity on the dead organic matter is slow under cold conditions.
- The soils are also acidic in nature. This is because of the movement of water through the soil in large quantities without any significant counter-movement upwards due to slow evaporation. Essential soluble nutrients such as calcium, nitrogen, potassium are leached from the soil even beyond the reach of the roots. Since there are no alkaline cations which can neutralize the accumulating organic acids from the litter, the soils become acidic. They are also mineral deficient.
- The productivity of a coniferous forest is much less than a tropical or a temperate forest due to insufficient solar radiation. These forests have a low level of community stability as against other forest types due to lower biodiversity.