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Introduction:Plant zones are distinctive groupings of native plants those existence primarily on enviromental factors. Two important ones are elevation and rainfall. As elevation increases, average temeratures decreases. Plants which grow best at cooler temeratures and found at higher elevations. Rainfall, especially in Hawaii, is greatly influenced by elevation, but also by land forms, such as mountains and also by wind patterns, likethe trades.
I. Strand Vegetation Zone CLICK on vegetation zone title to see plant examples.
A. The area is defined by salt spray and the presence of dunes and rocky sites.
B. It is dominated by low shrubs and perennial herbs (non-woody plants that live a long time).
C. Native plants found here are Naupaka (Scaevola sericea), 'Ilima(Sida fallax) and Pa'u o hi'iaka
D. There are more coastal non-endemic plants (indigenous) than found in other zones, probably because they are easily dispersed by floating or by birds and thereby arrive relatively frequently.
E. This region has been greatly reduced due to development of the shoreline for tourism.
F. A number of introduced plants have become common such as the tropical almond (Terminalia catatappa) and mangrove (Rhizophora mangle).
A. The Arid coastal zone is found mostly on leeward side.
1. Rainfall is 15-40 inches per year, falling mostly in winter Kona storms. Elevation is 0-300 meters (about 900 ft.).
2. Only strand and coastal vegetation zones are found on northwestern Hawaiian Island chain (from Kaua'i to Kure Atoll).
3. It is one of most completely altered zones, being a primary location of urban and resort areas.
4. Native trees and shrubs are wiliwili (Erythrina sandwicensis), coastal sandalwood (Santalum ellipticum), naio (Myoporum sandwicense), also called false sandalwood, and ma'o (Gossypium sandvicense).
5. Presently introduced plants dominate: haole koa (Leucaena leucocephala), mesquite or kiawe (Prosopis pallida), ironwood (Casuarina equisetifolia) and introduced grasses such as swollen finger grass (Chloris inflata) and bermuda grass (Cynodon dactylon).
B. The MESIC coastal zone area is found on windward side which was once dominated by forests which have become virtually extinct in the last 2,000 years.
1. Native plants include hala (Pandanus tectorius) and loulu or the native fan palm (Pritchardia spp).
2. Also there are naturalized Polynesian plant species such as hau (Hibiscus tiliaceus), milo
3. Introduced species include the Passion flowers (Passiflora sp.) and common guava (Psidium guajava).
A. Dryland forest covers more area on the leeward sides of the larger islands.
B. This area is most impacted by the burning and agriculture of the Hawaiians and also has been prime agricultural and ranch land since contact times.
C. It has probably suffered the greatest loss and extinction of species of any zone. Many of the unique trees and shrubs are gone or very rare. Wiliwili, naio and the small koa, koa koai'a
D. Presently, it is dominated by introduced grasses, such as African fountain grass (Pennisetum setaceum) and molasses grass (Melinus minutiflora) which burn in hot fires that native plants cannot withstand. Also lantana (Lantana camara), koa haole, mesquite, and prickly pear cactus (Opuntia) are present.
A. Most species rich of any zone.
B. Occurs best at Koke'e Plateau on Kaua'i but it is greatly altered by human activity. Generally, it was best developed on the two oldest islands, O'ahu and Kaua'i.
C. Rainfall is less than in rain forests but does not have extended dry periods. The zone had an open canopy (shade not continuous) with a mixture of trees and shrubs.
D. Native plants are representing by some of the largest genera (those with largest number of species) such as Alani, Mokihana (Pelea which is the largest flowering genera), Haha (Cyanea the largest tree lobelioid genus) and Schiedea. Many species of these genera are endemic to the islands.
E. Koa (Acacia koa) and 'ohi'a lehua (Metrosideros polymorpha) are the common trees here along with shrubs such as ho'awa (Pittosporum sp.), endemic and rare Koki'o (Kokia) and Hau kuahiwi (Hibiscadelphus), and more the common Maile (Alyxia oliviformis) and 'uki'uki (Dianella sandwicensis).
F. It is found in some places relatively untouched; however, serious degradation has occurred, especially in the last 100 years, when the zone was converted into pastures, as in the Waimea area on the Big Island.
G. The introduced plants that dominate are listed below.
1. Kikuyu grass (Pennisetum clandestinum) is so ground-covering and aggressive that native plants cannot reseed. Also, it burns and the grass recovers, but not the native plants.
2. Banana poka (Passiflora mollissima) has escaped from garden cultivation and covers and smothers the native plants.
3. Also Christmas berry (Schinus terebinhifolius), lantana, silk oak tree (Grevillea robusta), and firetree (Myrica faya) invade and take over from the native plants.
A. The zone is characterized by high rainfall, 150 to 300 inches per year. Lyon Arboretum in Manoa Valley is in this zone.
B. The typical daily pattern is clear in the mornings and rain in afternoons and evenings.
C. This represents about the only natural vegetation visitors to Hawai'i may encounter because it can be seen from the road at Volcanoes National Park on the Big Island and somewhat on O'ahu at the high passes of the Pali and Likelike.
D. Dominant plants are 'ohi'a lehua, and usually koa, both trees, and at one time, 'iliahi, the sandalwood.
1. Other characteristic plants are hapu'u (CIBOTIUM sp. or native tree fern), and two vines; maile, and ie'ie (FREYCINETIA ARBOREA), related to hala.
2. The characteristic structure of the rain forest is many "layers" of growth: starting with the tallest trees emerging from the canopy, many levels of 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) abound at every level, and lastly, small ferns and herbaceous (non-woody) plants at the lowest level.
E. Watershed: An extremely important function of the native plants found in the rain forests of Hawaii is to provide the watershed area.
1. Because of condensation from clouds and mists on the plant leaves and interception of rainfall by the leaves at the many levels of growth, this zone plays a major role in providing maximum absorption of rainfall.
2. Rain is absorbed into the porous, underlying volcanic rock, and travels down to the lens of fresh water at the base of the islands: the source of fresh water on which we depend.
F. It has been shown that introduced plant species, such as EUCALYPTUS trees, Silk oak trees, Strawberry guava trees, and ground covering plants, such as Clidemia (Koster's Curse), interfere significantly and reduce this absorption of water in two WAYS:
1. By using more the water themselves (Eucalyptus uses about 40% more water than native trees)
2. Destroying the many levels of intercepting leaves of native plants, like Strawberry guava which grows in pure stands which prevent any other plant growth around them.
G. The rain forest has the greatest diversity of plants (numbers of different kinds) and numbers of unique species (endemics). A number of plant endemic genera (one level above species) are found here, such as endemic genera of mints and tree lobelioids. The only three native orchids are found here.
H. Alterations of the rainforest.
1. Perhaps this zone is less altered than any other, partly due to its relative inaccessibility and laws that protect designated watershed areas, much of which falls within this zone.
2. However, it is under attack by feral animals (domesticated stock now gone wild), especially PIGS. They root up plants and destroy them, and the disturbance they cause allows aggressive weed-type plants to come in and replace the native plants. Erosion from pig activity washes down into streams and then deposits on to the coral reefs, damaging them. Hapu's hollow stems become breeding places for mosquitoes, and mosquitoes, in turn, carry bird malaria to which native birds are very susceptible.
These occur in the Rain Forest Zone
. CLICK on zone title for plant examples.A. Most Hawaiian bogs occur on top of mountains where old caldera form a bowl-like depression that has underlying rock that is relatively impervious to water. When rainfall, which is usually quite high in this areas, exceeds drainage, giant "puddles" develop that rarely dry up. In these soggy places, plants grow that are adapted to water logging and acid soils (due to poor decomposition).
B. The growth form here is usually hummocks, or bunches of plants clumped together on "bumps," or raised areas of soil.
C. The dominant plant life here is grasses and sedges. Some trees and shrubs can grow in this environment, but they are slower-growing in the bog as compared to other places. Often they are dwarfed by the relatively adverse conditions.
D. Other non-grass plants are 'Ohi'a trees, Vaccinium shrubs like 'Ohelo (related to cranberries), endemic tree-like violets, the bog SILVERSWORD and Dubautia, an endemic genus closely related to the silversword.
E. This zone, relatively recently pristine, is also coming under attack. More hikers damage bogs just walking through them. The bog on top of Mount KA'ALA of the Wai'anae on O'ahu has a boardwalk which helps to alleviate this problem. Damage by feral pig activity is reduced by fencing. (See p. 13 in Sohmer and Gustafson)
A. This zone occurs above the temperature inversion zone, at 1850 meters (6,000 feet) and higher.
B. It is found only on the highest mountains of the islands, HALEAKALA on Maui and Mauna Kea and Mauna Loa on the Big Island.
C. Open woodland/shrubland is found at the lower elevations of this zone, because it receives more rain than higher up and supports more trees and shrubs. It is dominated by mamane, (Sophora), a native legume tree with yellow pea-like flowers, and naio (Myoporum), a large shrub with glossy green leaves and small white flowers. A'ali'i (Dodonaea) is common, as are tussock-forming grasses.
D. This area has been damaged by overgrazing, especially by feral goats.
A. On the windward side, there are azonal (without distinct regions), wet fluted basalt cliffs, extremely vertical, up to 1,000 meters (3,000 feet) in elevation. The Pali on the windward side of O'ahu is a good example.
B. Plants found are dwarf 'ohi'a, 'ohelo (Vaccinium) and Brighamia, often called "cabbage on a stick" because of its unusual life form.
A.CLICK on title for plant examples.Is an introduced landscape, found in most of our urban and suburban areas. A. These are the human-planted areas that most tourists and many local residents assume are filled with the natural plants of the islands. They dominate the coastal and lowland areas.
B. Plants that are found here are Ironwood (Casuarina) at the beaches (and all the way up the Pali), Formosa koa (Acacia confusa), kiawe (Prosopis), many introduced grasses, bright colored Bougainvillea, Gingers, shower trees, and plumerias to name just a few.
C. For example, Kapio'lani park is filled with these non-natives.
A large desert area is the Ka'u desert on the Big Island.
A. On recent lava flows native plants include 'ohi'a, ama'u, a type of tree fern (Sadleria cyatheoides), the low-growing fern, 'ae
B. Ka'u Desert and Acid Rain: CLICK on zone title for plant examples.
Ka'u desert is in the rain shadow of Kilauea volcano and receives very little rain. Its barrenness also has very much to do with sulfur dioxide escaping the vents in the crater and blowing downwind. Sulfer dioxide combines with water to form sulfuric acid which falls as acid rain.
C. A kipuka is an "island" of older vegetation surrounded by a new lava flow. Vegetation types depend on which vegetation zone is being invaded by lava, but generally the vegetation OUTSIDE and surrounding the kipuka are the first lava flows colonists; later dryland or coastal types of plants can invade.
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