Trees and plants in tropical rainforests
A tropical rainforest has more types of trees than anywhere else in the world; as many as 100-300 species have been found in a 2 1/2 acre site by scientists in South America. The top layer of a rainforest is called the emergent layer.Trees are spaced far apart and are 100 to 240 feet high with umbrella-like upper branches that grow above the rest of the forest. The trees have small pointed leaves, straight, smooth trunks with very few branches. To support their size, they developed wide bases or buttresses.
The canopy layer is characterized by 60 to 130 feet trees. Branches are packed tightly together, creating a ‘ceiling’ of foliage, or canopy. Sunlight is abundant at the top of the canopy, but quickly turns to shade. Leaves have developed "drip spouts" that allows rain to run off, to keep them dry and avoid mold or mildew. It's here that the majority of gases are exchanged and CO2 and H2O are converted into oxygen. As scientists have discovered, by removing carbon from the atomsphere and storing it, the canopy layer effects both the local and global climate. The understory, or lower canopy, has 60 foot trees. This layer is made up of the trunks of canopy trees, shrubs, plants and small trees. There is little air movement, less then 3% sunlight and very high humidity.
Various plants can be found at different layers in the rainforest. Bromeliads and orchids, or epiphytes, grow on tree branches in the upper levels of trees, grabing onto the branches for support and taking their moisture from the air. Over 2,500 species of vines grow in the rainforest. Woody vines, or lianas, grow up tree trunks to the upper canopy to flower and provide fruit. Green stemmed plants like philodendron stay in the shaded understory -- roughly 25 to 60 feet above the forest floor. Other climbers in the understory include wild yams and sweet potatoes.In between the understorey and the forest floor, about 25 feet high live most of the ferns and small shrubs. Many of the plants have various healing properties, and over 1,400 species of tropical plants may provide cures for cancer.