Wet 'Ohi''a Lehua-Koa Forest - Code: Ne4F

Wet ʻŌhiʻa lehua-Koa Forest is an extremely moist, montane, broadleaf forest found at elevations between 2400 and 7800 feet (750-2400 m) on the windward slopes of the high islands. These forests are characteristically steep and muddy, shrouded in clouds with a low tree canopy, and an abundance of epiphytes. The area receives huge amounts of rainfall, anywhere between 60 and 350 inches (1500 – 8900mm) per year. Mount Waiʻaleʻale on Kaua’i is one of the wettest places on earth and in 1982 recorded an astonishing 683 inches (17,300 mm) of precipitation. Fog drip also makes a significant contribution to the total annual precipitation and is responsible for as much as 40 inches (1000 mm). The Wet ʻŌhiʻa lehua -Koa Forest is generally cool and annual temperatures vary little. Typical wintertime temperatures range from 50-75°F (10-24°C) and summer temperatures increase slightly to an average of 60-82°F (15-28°C). Near the upper elevational limits ʻohiʻa lehua-koa forest can be quite cold and most species at this altitude are frost resistant. The forest here naturally experiences little disturbance except for occasional openings caused by large storms. In areas with recent volcanic activity, ʻohiʻa lehua-koa forest occurs in isolated islands or hammocks called kipuka, generally surrounded by unvegetated lava flows.
As the name implies, ʻŌhiʻa lehua (Metrosideros polymorpha) and koa (Acacia koa) are the dominant trees in this habitat. However, the structure and relative abundance varies with elevation. At lower elevations koa is the dominant species with a well stratified understory of ʻŌhiʻa lehua and other trees and a moderately open canopy.  These forests are typically of intermediate height, with a canopy typically reaching 50-80 ft (15–25 m). As the elevation increases, ʻŌhiʻa lehua becomes more common, the canopy grows denser and decreases in stature. By the time you reach the treeline this habitat is entirely dominated by moss and epiphyte laden ʻŌhiʻa lehua only about 10 ft (3m) in height. Other common tree species here include kāwaʻu (Ilex anomala), ʻalani (Melicope clusiifolia), olomea (Perrottetia sandwicensis), ʻōhiʻa ha (Syzygium sandwicensis), ʻōlapa (Cheirodendron sp), and ʻohe (Tetraplasandra sp.) as well as hāpuʻu tree ferns (Cibotium sp.).
Naturally the understory is moderate to dense and full of a wide variety of ferns, mosses, woody plants and forbs. In many areas the understory is choked with thick stands of invasive kahili ginger (Hedychium gardnerianum). Common native shrubs include ʻApeʻape (Gunnera petaloidea), ʻoha wai (Clermontia sp.), olopua (Nestegis sandwicensis), hame (Antidesma platyphyllum), hāhā (Cyanea spp.), kāmakahala (Labordia hirtella), kanawao (Broussaisia arguta), ʻākala (Rubus hawaiensis), kāmanamana (Adenostemma lavenia), hōʻawa (Pittosporum spp.), and olonā (Touchardia latifolia). Interestingly, many of the plants here have lost defenses against herbivory. The ʻākala (Hawaiian Raspberry) has no thorns and the honohono (Hawaiian mint) lacks the minty scent and taste of other mints.