Hobbies And Interests
Sunlight Maximization
Rain forests, especially those in the tropics, are characterized by multiple layers of vegetation, ranging from tall emergent and canopy trees down to shrubs and small trees. While sunlight at the top is plentiful, successive layers of vegetation are adapted to maximize the small amounts of sunlight that penetrate upper layers. The tall canopy trees of the rain forest tend to grow straight up without branching until they reach the sunlight. The trees do not waste energy on leaves and branches at lower forest levels that will not receive as much light. Plants in the understory of rain forests often have very large leaves to capture as much sunlight as possible. Other plant types, such as lianas, and epiphytes, catch a ride to the top on taller trees. Lianas are tropical vines that climb up larger trees so their leaves can reach sunlight. Epiphytes, which include orchids, some ferns and bromileads, grow directly on the trunks or branches of trees. Epiphytes, such as mosses and ferns, are also common in temperate rain forests.
Water Shedding
Water is plentiful in a rain forest, especially at the lower levels of the forest that receive rainwater dripped through upper levels without the strong sunlight to help evaporate water. Rain forest vegetation must shed water so the extra weight does not break leaves and limbs, so leaf pores can allow gas exchange and to prevent the growth of mildew and mold. Some types of rain forest plants have pointed drip tips on their leaves that channel and drip water off the leaves. Some plants' leaves also have a waxy coating that helps shed water. In temperate rain forests, evergreen conifers are better adapted than broadleaved plants to shed snow in the winter and to allow photosynthesis in cold seasons.
Gas Exchange
All plants exchange gasses to survive and grow. During photosynthesis, plants take in carbon dioxide and release oxygen. Pores in the plants' leaves called stomata allow for the exchange of gasses. In most conditions, plants must balance opening their stomata to allow gas exchange and closing them to prevent water loss through transpiration. Since water loss is usually not a problem in a rain forest, rain forest plants can keep their stomata open for longer periods. The resulting increased gas exchange means rain forests, especially those in the tropics, produce 40 percent of the Earth's oxygen.
Trunk Support
In tropical rain forests, lower layers of soil are generally poor in nutrients, so trees have shallow root systems. Large trees often employ buttress roots that provide extra support to make up for the lack of deep roots. The buttress roots start as high as 15 feet up the trunk and fan out away from the tree. The roots also help increase the area able to absorb nutrients from the top layer of soil. Trees such as mangroves that grow in flood-prone areas grow stilt roots that form a web of stilts to help provide support, maintain gas exchange and keep the plants from drowning.