Some books says the dominant plant form in tropical rainforest biome is broad leaved evergreen trees. Other books say it is broad leaved evergreen trees and deciduous trees. What is the most accepted way (or the truth)? Also how do you explain the deciduousness adaptation in tropical rainforest (e.g., when do they shed leaves)?
Deciduous trees are those which shed their leaves once a year at the time of winter season and later grow new leaves, plants those keep their foliage throughout the year are called evergreens. Deciduous trees usually have broad leaves e.g., ash, beech, birch, maple and oak. There is a confusion exists over the dominance of trees in rain forest, but most of the resources suggests broad leaf evergreen trees as the most dominant. But deciduous trees are equally important because the difference may be negligible.
Deciduous trees shed their leaves usually as an adaptation to a cold or dry season. Evergreen trees do lose leaves, but each tree loses its leaves gradually and not all at once. Most tropical rainforest plants are considered to be evergreens, replacing their leaves gradually throughout the year as the leaves age and fall, whereas species growing in seasonally arid climates may be either evergreen or deciduous.Reference
The dominant plants in the tropical rain forest are broadleaf evergreen trees. Unlike evergreens that grow in colder parts of the United States, those of the tropical rain forest have no protection against cold weather or droughts.Reference
Adaptations of Deciduous trees
- Broad green leaves capture sunlight needed to make food through photosynthesis.
- They cuts off the supply of water to the leaves and seals off the area between the leaf stem and the tree trunk, as sunlight and water become scarce, the leaves are unable to continue producing chlorophyll and this produce vibrant colors in the leaves.
- In winter, they simply loose their leaves and seal up the places where the leaves attach to the branch. Losing their leaves helps trees to conserve water loss through transpiration.
- In spring the trees grows back their leaves and start the cycle once more.
In the spring, deciduous trees begin producing thin, broad, light-weight leaves. This type of leaf structure easily captures the sunlight needed for food production (photosynthesis). The broad leaves are great when temperatures are warm and there is plenty of sunlight. However, when temperatures are cold, the broad leaves expose too much surface area to water loss and tissue damage. To help prevent this damage from occurring, deciduous trees make internal and physical adaptations that are triggered by changes in the climate.
Cooler temperatures and limited sunlight are two climatic conditions that tell the tree to begin adapting. In the Fall, when these conditions occur, the tree cuts off the supply of water to the leaves and seals off the area between the leaf stem and the tree trunk. With limited sunlight and water, the leaf is unable to continue producing chlorophyll, the "green" stuff in the leaves, and as the chlorophyll decreases the leaves change color. The beautiful display of brilliant red, yellow, and gold leaves, associated with deciduous forests in the fall, is a result of this process. Most deciduous trees shed their leaves, once the leaves are brown and dry. Reference