THE RAIN FOREST



The characteristic structure of the rain forest is many "layers" or levels of growth: starting with the tallest trees emerging from the canopy, many levels of shorter trees below that, tall shrubs, short shrubs, vines that grow up into the canopy, epiphytes (plants that grow on other plants, usually trees, which are not parasitic to the tree, but simply use it to "perch" on it) abound at every level, and lastly, small ferns and herbaceous (non-woody) plants at the ground level.

Native Plants




Acacia koa is an important rain forest tree. Epiphytes, plants growing on other plants or trees, are common in rain forests.


Santalum freycinetianum, 'iliahi


Along with koa and 'ohi'a lehua, Santalum freycinetianum, or 'iliahi, commonly called sandalwood, is found in the rain forest. The two photos above, by Priscilla Millen, are of sandalwood, which is probably the rarest of the three trees since it was extensively logged in the 1800. Large trees of this genus are unusual in Hawaii today.


Fern
Dubatia laxa, or na'ena'e


Ferns and na'ena'e occupy the shrub, or lower mid level, in the rain forest. Both plants are endemic, as is typical of rain forest plants.


Freycinetia arborea 'ie'ie
Smilax melastomifolia, or pi'oi


Vines are prevalent in the rain forest and are represented here by the indigenousFreycinetia arborea, or 'ie'ie, and the endemic Smilax melastomifolia, called pi' oi or hoi kuahiwi in Hawaiian.

The lowest level of the rain forest is covered with mosses and herbaceous plants like this Peperomia, called 'ala'ala wai nui.


Introductions




Clidemia hirta Koster's Curse
Psidium cattleianum Strawbery guava

Rain forest environments are important watershed areas for the Hawaiian Islands. Introduced plants like Eucalyptus, Silk Oak, Strawberry guava, and ground -covering plants like Clidemia are thought to reduce the absorption of water in rain forests. Some use more water themselves. Eucalyptus trees use about 40% more water than native trees. Others destroy the many layers of intercepting leaves of native plants. For example, Strawberry guava tends to create pure stands, allowing little plant growth around them.


Photo by Lorin Gill
Another introduction which has affected rain forest environments is the feral, or wild, pig. The first introduction was the small pig the Polynesians brought with them. It is not thought to have ranged to more than 3,000 feet and is not thought to have caused great damage. However, when the larger domestic pig ran wild after its introduction by Europeans, the two hybridized, and the resulting larger feral pig ranges higher and does much more damage. Below, a tree fern has been destroyed by pigs, which eat the starchy core. The resulting shell fills with water and becomes a breeding place for mosquitoes. Mosquitoes can carry avian malaria, a disease threatening the native honeycreepers.