A tropical rainforest evokes images of thick, lush green vegetation. Learn more about the plant life that inhabit these forests.
Tropical rainforests have the kind of climate that can be described as hot and wet – it rains throughout the year, and the temperature almost never drops below 15oC. The season never changes; well, almost never. This is conducive for plant growth. Rainforests usually have enormous biodiversity. It is said that two-third of all the flowering plants in the world can be found in the world’s rainforests. Along with that, it is also claimed that many of the medicinal plants we know of were first discovered in rainforests.
The collection of plant you get to see in a rainforest is quite unique. This is owing to the fact that the set of climatic conditions that persist in tropical rainforests are extremely unusual; known also as equatorial climate. the three key feature of equatorial climate are –
- The temperature is always warm
- There is always a high amount of annual rainfall
- The forests experience alternate wet and dry seasons, as the amount of rainfall varies through the year
Out of these, the temperature is more or less constant. Hence, it is the amount of annual rainfall that controls and affects the flora and fauna the most.
Understanding the Climate of Tropical Rainforests
The sunlight that hits rainforests is not angular but mostly perpendicular (owing to the equatorial location of the forests). This means that the incident sunlight covers less surface area. This makes trees compete with each other for sunlight, making them grow unusually tall. Due to this trend, very little (or almost no) sunlight reaches the forest floor. This give rise to a huge variety in the vegetation of rainforests. The rainforest floor may be populated with shade loving shrubs, bushes, while evergreen trees dominate most of the forest area.
However, this pattern of vegetation has another important consequence – a lot of heat gets trapped under the tall, thick, dense forest cover. The heat causes water to vaporize. Hence rainforests are high on moisture as well. All the trapped heat and moisture in turn causes dead plants and leaf litter to rapidly decay. Hence what happens at a slow rate in other ecological settings is accelerated in the rainforests. The decaying plant material is recycled as nutrient to the other plants. This ensures the plants are constantly fertilized ‘naturally’.
Finally, due to a high degree of moisture, the climate in rainforests is usually humid. There is a constant moisture cover over the forests. This ensures precipitation when the temperatures drop.
Common Types of Tropical Rainforest Plants
Looking at the climatic conditions persisting in a rainforest might have helped you to predict the kind of vegetation that occurs in a rainforest. The diversity of the rainforest biome is huge, so that almost all kinds of plants are represented in rainforests. Here is more information on the tropical rainforest plant types.
General Vegetation Pattern
The general vegetation types (or vegetation trend) in a rainforest is as follows –
- Emergent trees are 100 to 120 feet tall. They form umbrella-shaped canopies that grow above the canopy of the forest. They have small pointed leaves.
- A closed canopy of 80-foot tall trees. Light is available at the top and greatly diminished below it.
- A closed canopy of 60-foot tall trees. There is high humidity and restricted air movement.
- Shrub layer. Very little light is available.
- There are litter and wet leaves at the bottom of the forest layer.
Types of Plants
1. Broad-leaf trees – these are the most common form of vegetation in a tropical rainforest. The size of the leaves is a kind of adaptation shown by the trees. As very little sunlight reaches the forest, the trees have adapted to maximize the surface area of the leave to absorb as much of sunlight as possible.
2. Vines and Lianas – Lianas are woody creepers. It is claimed that the rainforests are home to more than 2500 species of creepers. The vines and creepers found here are often dubbed ‘strangler’. They use a strong and tall tree as the host plant and ascend up the tree. However, in the process, they strangle the host tree to death as they get stronger and bigger.
3. Epiphytes – Epiphytes also grow on host trees. However, the major difference between a strangler and an epiphyte is that a strangler is still rooted to the forest floor and derives nutrition from the soil. An epiphyte, on the other hand, is a parasitic plant that sends its roots into the host plant to derive nutrients.
4. Saprophytes – Saprophytes are those species that survive on dead decaying matter by deriving nutrition from it. Since the persistent heat and moisture in the rainforests accelerates the decay of dead plant matter, a number of saprophytic plants species are also seen in rainforests.
Adaptations in Tropical Rainforest Plants
There are certain attributes of tropical vegetation that are different from those of other kinds of vegetation. These are considered as adaptation. One of the most common adaptation is seen in the leaves of tropical plants. As mentioned before, the leaves are broad, with extensive surface area, to maximize photosynthesis. The other significant adaptation is the waxy coating present on the leaves. It helps the leaves shed off excess of water from their surfaces. The leaves also have structures called drip tips; they also help in getting rid of excess water and improve transpiration.
With respect to the roots, most tropical plants have buttress roots. These kind of roots spread wide like a network instead of penetrating deep into the surface. This adaptation is mainly seen because the forest floor is scarce in nutrients. Most of the plant nutrients are concentrated in the top-most soil layer, which is not very thick. The roots, hence, develop horizontally to form a dense network, rather than growing deep under the ground.
Tropical rainforest plants usually have large, fleshy fruits that are sweet and quite juicy. Flowers of these plants usually grow directly from the bark. They may have very thin barks having thorns or spines.
Common Examples of Tropical Rainforest Plants
Some of the tropical rainforest plants are pineapple, pepper, palm tree, orchid, fern, peanut, orange, lemon, coffee, banana and avocado. Also present are Saw palm, Cat’s-foot, Lichen Moss, Twisty grass, Teak, Cypress, Live Oak, Parasol Plant, Sargasso, Sesame, Cedar, Palmetto.
Tropical rainforests are the lungs of the earth. They are a major source of oxygen. Most of the plant species grow there. Many plants and trees have medicinal uses. For example Quinine is used for the treatment of malaria. Vincristine, extracted from the rainforest plant periwinkle (Vinca rosea) is used for the treatment of Cancer. Trees prevent soil erosion. They prevent flooding. Tropical rainforests are a gift to mankind. It is important to conserve them for posterity.