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Introduction to what a rain forest really is.
A RainForest is different from other forest types because of the unique structures, and weather found in the RainForest that are not found in other types of forests.
These features include layers that are inhabited by unique plants and animals that do not necessarily live in other parts of the forest. Light and water levels also allow certain plants and animals to exist in the rain forest where they might not be able to otherwise.
A tropical rainforest has four distinct layers, we will explore each layer together!
There are features in a rain forest that help make the forest unique. Some of these features are:
As we begin our exploration of the rain forest layers we are starting at the top. Literally emerging from the forest are the tallest trees. These ancient giants have fought their way to the top. The forest floor is darkened by the shadows of these giants, making it difficult for new trees to find enough sun, water and room to grow.
By making it all the way to the top the giant trees get the benefit of unlimited tropical sun. No need for sun tan lotion with these trees, they soak up all the UV rays the sun has to offer.
Because most plants need the sun to produce energy, the most successful trees often produce the most flowers and fruit. The largest of these giants can reach almost 200 feet into the sky! Some of the largest trees are estimated to be over 2,000 years old.
Try to picture a dense layer of thick green leaves, branches and tropical flowers. Much of the forest life can be found living high above the ground. You might normally think of birds and other flying creatures living up here, but did you know that many mammals also call the canopy layer home? We are just beginning to discover how complex this layer of the rain forest really is.
Many species of insects and reptiles also dwell in the canopy. Due to the fact that many plants produce flowers and fruit at this level a high concentration of pollinating creatures are busy making sure the plants can produce flowers. Much of the canopy is home to plants like bromeliads which actually capture the falling rain water and hold it in "cups or vases" that provide drinking water to a host of creatures living way up in the air.
New research is being conducted to determine how many types of plants and animals live in the canopy. Some biologists believe that as much as 70% of the living organisms in the rainforest live in the canopy.
The Under Story
The under story is a relatively dark place. Light has a very hard time penetrating the dense canopy layer above. Because of this lack of suitable sun light many of the plants that live in the under story are low light plants such as ferns and mosses. The humidity is generally high in the under story since the sun does not penetrate to dry off the rain that falls from the canopy.
While there are some creatures that live in the under story of the rain forest it is more difficult to find birds and mammals at this level. The under story is really the domain of the invertebrates!
The Forest Floor
Descending further down in our journey we encounter the forest floor. If you and I were to take a walk in the jungle we would spend most of our time on the forest floor. Large mammals such as tapirs call the forest floor home, give the dense vegetation many parts of the forest floor are nearly impenetrable. This fact often limits the size of the mammals that live here, even though most of the life is found here, the majority of it is small, such as insects and other invertebrates.
The floor is a dark place, the sun from above has been all but blocked out by the dense layers of the canopy and the emergent layer. Even the middle of the day seems like nothing more than a moonlit night on the forest floor.
The base of the giant trees that form the canopy, and the emergent layer can be seen on the forest floor. These giants are often held up by something known as a "buttress root system" Seen here, the buttress of a tree actually forms pyramid shapes to help stabilize the towering giants. The buttresses of the trees are utilized by many creatures as homes! Be careful where you walk, the giant Bushmaster may be hiding in the buttress of that tree you are standing next to!
Over time the leaves and branches from the trees above have fallen and formed a mat of rotting organic matter. In spite of what you may think the soil down here is actually very poor. There are literally millions of organisms per acre that breakdown the fallen vegetation and literally consume it! The trees consume all of the nitrogen and other elements produced by the decomposition of the fallen plant matter. Nothing goes to waste in the jungle!
Every rain forest has it's rivers. From the mighty Amazon to the tiniest tributary, rivers make up the life blood of a rain forest. Home to creatures great and small, the river system of each forest literally drains off the vast amounts of rain that fall annually. In some cases the rivers are permanent, in other cases they form after heavy seasonal rains.
Many species of fish, mammals (fresh water dolphins), reptiles and amphibians call the rivers home. Some creatures rely on the river for only parts of the year, others rely on the river for their very existence.
Considering the amount of annual rain fall as well as the presence of lakes and rivers the rain forest generally has a high humidity level. This high level of moisture in the air allows certain plants and animals to survive.
The temperature of the rain forest varies little by season. In fact the difference between the annual highs and lows can be as little as 15 degrees Fahrenheit.
By definition a rain forest should receive at least 80 inches of rain per year. There are certain regions of the rain forest belt that receive the rain more consistently than others.
Unlike the temperate zones of the United States and Europe, the rain forests of the world have only two primary seasons, the wet season and the dry season.
Types of Rain Forests
Let's explore the rain forests closest to home first!
Temperate Rain Forests
Here in the United States we have temperate rainforests. The Pacific northwest of the United States is home to some of the most breath taking temperate rain forests on earth.
The highest elevations in the Smoky Mountains in east Tennessee are considered by some to be temperate rainforests as well.
Generally the trees do not grow as high, the quantity of species is not as great and the size of the forests are almost always smaller.
When you think of a temperate rain forest you should think of moss shrouded branches and rocks. The constant cool temperatures combined with high annual rain fall couple to produce extremely wet conditions most of the year. In fact a temperate rain forest is often wetter on a consistent basis than the seasonal heavy rains experienced by the tropical forest.
Another feature of the temperate rain forest is the presence of conifers or pine like trees. Tropical forests do not have the needle like leaves found on many of the trees in the temperate forests. Tropical rain forests are often home to extremely broad leafed plants such as bananas and elephant ears.
A temperate rain forest is generally found along a coastal region such as the pacific northwest of the United States. While the rain fall may be similar to the tropical rain forest the temperatures can be quite different. Temperate rain forests almost never experience the searing heat of an equatorial rain forest. Move a few miles inland from the coast and the forest looses the warming effect of the ocean waters, winters are much harsher and unable to support the great bio diversity found near the coast in a temperate rain forest.
Tropical Rain Forests
This is the rain forest most of us think of when we think of a jungle! Wet, hot, and dense, the tropical rain forests of our planet are found in a belt around the equator.
More species of plants and animals are found in the tropical rain forests of the world than in any other eco-system, including temperate rain forests!
Some estimates place up to 50% of all species in the rain forests of the world. That is an astounding fact considering rain forests cover less than 6% of our earth.
Sadly the tropical rain forests are under an intense assault. Loss of habitat for agriculture, timber, and other reasons are resulting in significant destruction.
Lowland rainforests have generally consistent weather throughout the year. This means that the rainfall and the humidity are usually the same from day to day.
This also means that they provide a perfect environment for plants and animals and so contain a great diversity of life. There may be 15 000 different animal and plant species in a single acre of lowland rainforest. Lowland rainforests contain the tallest trees and the largest variety of species.
Flooded forests are divided into two categories, forests that flood for short periods, and forests that flood for long periods of the year, sometimes up to eleven months of the year.
The Portuguese names varzea and igapo are often used to refer to these forests. Varzea means 'white water' and is a forest flooded for a short time after heavy rains, which sometimes raises the water level by as much as 33 feet. Igapo means 'black water' and refers to a forest which may be under as much as 40 feet of water for up to eleven months of the year. These rising waters replenish nutrients in flood plain areas (low land that is regularly flooded) and regenerate flood plain lakes and other seasonal habitats.
This has resulted in adaptations of both trees and fish. Trees take on strange shapes and strategies to survive in conditions that would kill most temperate species. Freshwater fish move into these flooded forests and often feed on the fruits that drop from the trees.
These flooded forests in the Amazon region are the most extensive of this habitat type in the entire world. The entire Amazon basin contains the largest number of freshwater fish species in the world, estimated at more than 3000 species. Every year the Amazon River rises more than nine metres (30 feet) and floods surrounding forests.
Montane rainforests include the 'cloud forests'. This is where the forest is at a height where it sits among the clouds. A cloud forest exists on extremely moist mountain slopes above the elevation of the true rainforest.
Altitudes of between 1,000 to 3,000 feet are known as lower montane regions, and between 3,000 to10, 000 feet are known as upper montane regions. At these altitudes, these forests are often cooler than lowland rainforests and are almost constantly dripping with moisture from the swirling clouds which engulf them. The trees grow shorter in cloud forests due to the cooler temperatures but there are more ferns and epiphytic plants (a plant that grows on top of another) than in lowland rainforest as there is more moisture.
Mangrove forests, as their name would suggest, are forests of mangroves. They are found on river banks and coasts. Mangroves are wetland plants that filter the water that flows through them. Found in coastal areas, mangrove forests favor salty environments and can tolerate periods of drought in the dry season. Mangrove trees can reach heights of 80 feet and are supported by stilt-like roots which raise the main tree from the water. Mangroves need to keep their trunk and leaves above the waterline, but they also need to be firmly attached to the ground so they are not moved by the waves. Any part of a root that appears above the waterline channels oxygen to the plant below the waterline. Over time, as soil begins to build up, these roots produce additional roots that become embedded in the soil. Mangrove forests provide shelter for the wildlife which live in coastal waters and river systems and help to aerate (add air to) and cleanse the water
Location: Where are the rainforests?
Most of the world's rainforests are in South America (57 percent), South-East Asia (25 percent) and Africa (18 percent). There are also smaller areas of rainforest in Central America, Madagascar, India and Australia. Rainforests cover approximately 6 percent of the Earth's land. This does not include areas of water such as the oceans, rivers and lakes of the world.
Tropical rainforests are located around the equator, which is an imaginary line that cuts the world into north and south. Tropical rainforests lie between the Tropic of Cancer in the north and the Tropic of Capricorn in the south. The largest areas of rainforest are found in Brazil, which is in South America. The Democratic Republic of Congo, which is in Africa, has the second-largest area of rainforest. The third-largest area of rainforest is found in Indonesia, a group of islands to the north of Australia. Others are found in Asia, Hawaii and the Caribbean Islands.
Latitude: Between 15-25o north and 15-25o south latitude.
Temperate rainforests are found along coasts. The largest temperate rainforests are in North America on the Pacific Coast, from Alaska to Oregon. Temperate rainforests are also found in the United Kingdom, Norway, Japan and New Zealand. In Australia they are found in New South Wales, Victoria and Tasmania. Small pockets of rainforest also occur in the Kimberley's and northern areas of the Northern Territory. Tasmania contains Australia's largest tracts (areas) of cool temperate rainforest, covering around ten percent of the State.
Latitude: Between 30o north and 30o south latitude
The largest of the rainforests is the Amazon, which covers an area of seven million square kilometres. The Amazon Rainforest is in the Amazon Basin in South America. 62 percent of the Amazon is in Brazil. The Amazon Rainforest partially covers Bolivia, Peru, Ecuador, Colombia, Venezuela, French Guyana, Suriname and Guyana.
Topography: What do rainforests look like?
Topography is the word used to describe the features of the land. Mountains, hills, rivers, canyons and valleys are examples of these features.
One thing that all rainforests have in common is that many rivers and streams run through them. This is because of the large quantity of water that is involved in the natural rainforest cycle. Rivers and streams develop as a way of removing excess water, and act as drainage systems.
The Amazon Rainforest has an enormous river running through it. The Amazon River is over 3,000 miles long. This river begins in the Andes mountain ranges in Peru and flows all the way to the Atlantic Ocean. An interesting fact about this river is that a large area of it is so deep that an ocean liner could travel over half its length.
Meteorologists, scientists who study the atmosphere, define climate as the condition of the atmosphere over a long period of time. In describing climate, they consider air temperature and rainfall conditions and how these conditions remain the same or change from one season to the next. Tropical rainforests are located near the equator where the climate is consistent. They have hot temperatures, daily rainfall and high humidity. Temperate rainforests are located further from the equator, and have a different climate, but they still receive a lot of rain. The climate is therefore labeled 'wet', but because of the distance from the equator, temperate rainforests are much cooler than tropical rainforests. The climate of a temperate rainforest is cool and wet.
Both tropical and temperate rainforests are lush and wet. Both types of rainforest receive regular rainfall.
Rainforests are very important to us because they help to maintain global weather patterns.
The name 'rainforest' could not be better suited to these unique forests. A rainforest is created by the rain, and without it a rainforest could never survive. To be tropical, a rainforest must receive between 90cm and 130cm of rainfall a year, with some having a yearly rainfall of up to 1000cm. In the Amazon, there are up to 120 days of rain each year. Rain is not the only important climatic feature of a tropical rainforest. It must also have a constant high temperature, with an average temperature of 27oC all year round. The humidity of a rainforest like the Amazon does not usually fall below 80 percent. The temperature does not change much from day to night.
Tropical rainforests are one of the most productive areas on earth. They contain a diverse range of animals and plants. The warm temperatures and daily rain mean that nutrients are produced and used at a fast rate. Plant growth is rapid, and, because there is no winter, the growing season lasts all year. There are flowers and fruit all year round.
The consistency of a tropical rainforest's temperature and humidity means that a rainforest does not have the four seasons of spring, summer, autumn and winter. Rainforests have their own seasons; they have a wet season and a dry season.
Rain: The water in a rainforest is
constantly being recycled. The atmosphere of moisture, the damp earth and the
rainfall are all part of this cycle. This cycle is described in Topic 3.
A temperate rainforest is one that receives more than
125cm-150cm of rain each year. Some temperate rainforests receive up to 500cm a
year. Moisture also comes from the coastal fog. This fog provides 18cm-30cm of
rain a year.
Temperate rainforests have two separate seasons. They have a long, very wet winter, and they have a much shorter summer, which is drier. Temperate rainforests are cooler than tropical rainforests, but the temperature is still mild. The mild summers help to protect a temperate rainforest from drought.
Temperate rainforests have a less complex ecology compared with tropical rainforests. Cool winters limit the numbers and types of life forms that live in temperate rainforests. Temperate forests have nutrient-rich soil because there is a lot of dead organic matter on the ground. This dead material is slowly digested by the fungi, insects, and bacteria that live here. In tropical forests, the trees have to spend some of their energy drawing up water and losing heat, whereas in this milder climate the trees can use more of their energy to grow. Most of the animals in this forest live on or near the ground where there is lots of food. The trees provide shelter from the sun, wind, and rain