Definition of forest
Forest is an assemblage of trees growing close to each other, these trees form a layer of foliage that largely covers the ground and shows stratification with more than one layer. Forests provide home for different plants and animals, they provide ecosystem services to humans and serve as tourist attraction to man and they also beautify his environment. The word forest is therefore defined as the presence of dense vegetation, however, an area that is completely lacking trees may still be seen as a forest, if there were trees presence in the past and there is hope of growing trees in the future in the case where there are no trees.
For a forest to grow and stand out among other bushes it requires a relatively high amount of annual precipitation. The trees do not really need to be uniformly distributed throughout the year; the stems and the leaves of the trees have a way of storing or reserving water for a long period, although it may be depleted during the dry season. This type of vegetation extends over a wide range of climate and latitude.
Types of forests
There are three major types of forest such as:
- Tropical rainforests
- Temperate deciduous forests
- Coniferous forests
1. Tropical rainforests
Tropical rainforest location
The rainforest biome is located in the tropics and principally within the equatorial climate belt. The rainforest includes the amazon and Zaire basins and the coastal lands of Ecuador, West Africa and extreme South East Asia.
Tropical rainforests climate
The temperatures are high and constant throughout the year because the sun is always high in the sky, which means that the mean monthly temperatures range from 260C- 280C and a slightly higher temperature may occur during any drier season. Insolation is evenly distributed throughout the year with each day having approximately 12 hours of daylight, and 12 hours of darkness. Evening temperatures rarely fall below 220C, while due to the presence of afternoon cloud, daylight temperatures rarely rise above 320C and relative humidity is high. Annual rainfall usually exceeds 2000mm and most afternoons have heavy showers. Evapotranspiration is also rapid and most rainstorms are violent accompanied by thunder and lightning.
Tropical forest plants
The tropical rainforest dominant vegetation consists of trees of many different species (e.g. mahogany, ebony, rubber, palm, green heart and rosewood) which are mainly hardwoods and they have an evergreen appearance, although deciduous plants can shed their leaves at any time during the continuous growing season. The tallest tree called the Emergent may reach up to 50m in height and form the habitat for numerous birds and insects. Below the emergent are three layers and all competing for light and space.
The top layer is called the Canopy and it forms an almost continuous cover, which absorbs over 70% of the light and intercepts 80% of the rainfall. The crowns of these trees emerge 30m above ground level. They shade the underlying species, protect the soil from erosion and provide a habitat for most of the birds, animals and insects of the forest.
The second layer called Under-canopy consists of trees growing up to 20m and the lowest layer, shrub layer, consists of shrubs and smaller trees which are adapted to living in the shade of their taller neighbours.
The climate in the forest vegetation is at the optimum for photosynthesis. The trees grow tall and almost reaching the sunlight, and the tallest trees have buttress roots which emerge over 3m above ground level to give support. The trunks of the tress are usually slender and branchless, some have flowers growing on them and their barks are thin as there is no need for protection against adverse climatic conditions. The tree trunks also provide support for lianas, vines-like or creeping plants that can grow up to 200m in length. The leaves of trees are dark green, smooth and often have drip tips to shed excess water. Less than 5% of insolation reaches the forest floor with the result that undergrowth is thin except I areas where tress may have been felled by cultivators or where a giant emergent has fallen, dragging with it several of the top canopy trees.
Epiphytes, plants that do not have their roots in the soil grow on trees trunks, branches and even on the leaves of trees and shrubs. They simply hang on to the tree; they derive no nourishment from the host and are not parasitic. The productivity of this vegetation type upon which the world depends to replace much of its used oxygen is due largely to the rapid and unbroken recycling of nutrients. Man on his own way contributes in breaking this system by falling of trees and this has consequences on the cycle.
Tropical rainforest animals
Vegetation here is dense and although ground animals are relatively few in number, the rainforests of Brazil alone are habitats for 2000 speci
2. Temperate deciduous forests
Temperate deciduous forests location
These forests are located on the west of continents, North West Europe and the British Isle, North West USA, British Columbia, South Chile, Tasmania and South, New Zealand.
Climate of temperate deciduous forests
Summers are cool with the warmest month between 150C and 170C. This is as a result of the relatively low angle of the sun in the sky, coupled with the frequent cloud cover and the cooling influence of the sea, winters are mild, mean monthly temperatures remain a few degrees above freezing point due to the warming effect of the sea. Precipitation is usually more than 2000mm annually and it falls throughout the year, but with a winter maximum when depressions are more frequent and intense. Although snow is common in the mountains, it rarely lies for long as sea level and fog is more common in autumn.
The temperate deciduous forest falls well short of the figure for tropical rainforest mainly because of the dormant winter season when the deciduous trees in temperate latitudes shed their leaves. Leaf fall has the effect of reducing evapotranspiration when colder weather reduces the effectiveness of photosynthesis, and when roots find it harder to take up water and nutrients.
Temperate deciduous forests plants
Oak which can reach the height of 30-40m are the dominant species. Others are elm, beach, sycamore, ash, and chestnut. These grow a little less than the oaks and they developed large crowns and have broad leaves. Unlike the rain forests, the temperate deciduous forests contain relatively few species. The maximum number of species per square km in the Southern Britain is eight and some woodland such as beech may only have a single dominant. The trees have a growing season of 6-8 months in which they bud
Leaves bring out flowers and fruits and may only grow by about 50cm a year. Most woodland that shows some stratification beneath the canopy is the lower shrub layers varying between 5m (holly, hazel and hawthorn) 20m (ash, and birch). This layer can be quite dense because of the open mosaic of branches of the taller trees that allows brighter light to penetrate than in the rainforest. The forest floor if the shrubs layers are not too dense, the floor is often covered with thick undergrowth of grasses, brackens and ferns. Many flowering plants like blue bells bloom early in the year before the taller trees have developed their full foliage. Epiphytes, which include mosses lichens, and algae often, grow on tree trunks.
Most of the Britain natural primary deciduous woodlands have been cleared for farming purpose, used for fuel and in building and for urban development. The Deciduous trees give rise to coniferous towards the polar latitudes and where there is an increase in altitude or steepness of slope.
Temperate deciduous forests animals
There are different animals in temperate forest biomes including insects; such animals include white- tailed deer, opossums, porcupines, red foxes, racoons, snowy owl, broad-wing hawks, cardinals, pileated woodpeckers. Some other lives found in these biomes are spider turtle, frog, spider and salamanders.
3. Coniferous forests (Taiga Biomes)
The coniferous forest or taiga biome occurs in cold climates to the pole towards the side of Eurasia and North America, as well as at high latitudes in latitudes that are more temperate and in southern Chile, winters are long and cold and minimum mean temperature may be as low as -300C. There is a little moderating influence from the sea and no insolation, as at this time of the year, the sun never rises in places of Artic Circle. Strong winds mean that there is a high wind chill factor (frostbites is a hazards). However, the summers are short, but the long hours of daylight and clear skies mean that they are relatively warm. Precipitation is light throughout the year because the air can hold only limited amounts of moisture and most places are far from the sea.
Coniferous forests animals
The cold climates and soils discourage earthworms and bacteria. Needles therefore decompose very slowly rapidly than being accumulate to give an acid more humus. Although precipitation is limited, evapotranspiration rates are low. Animal life is not in abundant because of the limited food supply. The dark woods are not favoured by the presence of birds, although deer, wolves, brown bears, moose, elk and beavers are found in certain areas. Cold and heavy snowfall make life difficult for animals in the coniferous forest; however, few animals have spread-out toes that enable them to move rapidly over deep snow without sinking, while others develop heavy winter coats for coverage. Animals found in the coniferous forests include deer, reindeer, moose, mice and squirrels. Some predators include wolves, lynxes, wolverines, bears and foxes
Coniferous forests plants
The coniferous trees have distinctive adaptations which enable them to tolerate long cold winter, cool summers with short growing season; limited precipitation, and podsolic soils. The trees are soft woods and are rarely number more than two or three species per square kilometre. There are always extensive stands of a single species of spruce, fir or pine. In colder areas like Siberia, the larch tends to dominate. Although larches are cone bearing, the European larch is deciduous and sheds its leaves in winter. All trees in the taiga, some of which attain a height of 40m are adapted to living in a harsh environment.
The conditions for photosynthesis become favourable in spring as in coming radiation increases and water becomes available through snowmelt (winter days are longer and dark and soil moisture becomes frozen). The needle-like leaves are small and the cuticles help to reduce transpiration during times of strong winds and during winter when moisture is unavailable for absorption by trees roots. Cones shield the seeds and thick, resinous bark protects the trunk from the extreme cold of winter and the threat of summer forest fires. The conical shape of the trees and its downward sloping springy branches allow the winter snows to slide off without breaking the branches. The conical shapes also give some stability against winds, as the tree roots are usually shallow. This is usually one layer of vegetation in the coniferous forest. The amount of ground cover is limited, partly due to the lack of sunlight reaching the forest floor, and partly to the deep acidic layer of non-decomposed needles. Plants that survive on the forest floor include mosses, lichens and wood sorrel.
Importance/uses of forests
Forest is an important part of the ecosystem; they provide man with many benefits in the following ways-
- Leaf fall serves as soil covering; there by prevention soil erosion and leaching of top soil, the leaves that fall from plants also add nutrients to the soil when they decay.
- Forests provide trees for construction of houses, tools, furniture and roads
- Ropes, canes, fibre, bamboo, and paper are also gotten from forest trees
- Forests herbs are important for medicinal purpose and they provide many raw materials for making of rubbers, fruit drinks, gum, essential oil and beverages.
- Forests serve as habitats for both plants and animals
- They provide fuels in form of firewood and charcoals
- They create job opportunities for many people and also serve as tourist attraction for educational purpose and relaxation
- Wild games provide food for man in form of meat, which is a source protein, and fat, they provide hides for clothing and for musical instruments.
- Forest could serve as a source of revenue to the government.
- Forests assist in purifying the atmosphere by eliminating carbon dioxide and proving clean air.
- Forests provide oxygen we need for a living
- Tall trees serve as windbreak, especially in places that experience strong wind.
- Forests influence weather pattern and they help to stabilize the atmosphere in different ways.