Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Montane mesic koa/‘ōhi‘a forest
Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
The habitat between 4,500-5,800 ft is defined as a montane mesic koa/„ōhi„a forest. It is primarily
composed of mixed age trees of both species. The midcanopy is dominated by a mix of flowering
and fruiting trees such as Clermontia sp., pilo, pūkiawe, „ōhelo, kōlea, kāwa„u. Tree ferns, mixed
ferns, and epiphytes also occur in the understory.
The mesic koa/„ōhi„a forest is potential habitat for several endangered species, such as the „alalā,
„ōpe„ape„a, picture-wing flies, and various plants. It also provides foraging and nesting areas for
native forest birds.
Wildfires are a serious threat to the mesic forests above 5,000 ft in elevation due to nonnative grass
fuel. The montane mesic koa/„ōhi„a forest is threatened by ungulates. Sheep, which do not exist in
the wet „ōhi„a forest, exist in the montane mesic koa/„ōhi„a forest above 5,000 ft. A lack of native
pollinators also threatens this habitat.
Native dry koa/‘ōhi‘a/māmane forest
This native dry koa/„ōhi„a/māmane forest is located at the upper elevation of the KFU between
5,800-6,100 ft. Abandoned pastures, skid trails, and mill sites are present in this zone.
The upper canopy of this forest is composed of koa, „ōhi„a, and māmane, while the understory
consists of iliahi, kukainene, naio, pilo, pūkiawe, „ōhelo, and mixed ferns.
The dry koa/„ōhi„a/māmane forest is potential habitat for the „alalā, „ōpe„ape„a, endangered plants,
and endangered invertebrates. Native forest birds (such as „akiapōlā„au, Hawai„i „ākepa, and Hawai„i
creeper) are also found in this habitat.
This forest shares similar threats as other habitats within the Refuge, such as invasive species and
lack of native pollinators.
Lava tube and lave tube skylight
Lava tubes are subterranean channels that were created by flowing molten lava, particularly
pahoehoe lava. This type of basaltic lava is warmer, faster moving and less viscous than „a„ā lava
(Howarth 1973). Because pahoehoe lava does not fuse with the existing surface, extensive horizontal
spaces and vesicle-like channels develop. When the surface crust of a lava flow cools, the underlying
flow is insulated, allowing it to travel for many miles without losing its heat energy. As the volcanic
eruption ceases, the molten lava drains from the channel, leaving an empty passage or lava tube. In
Hawai„i, tubes formed in pahoehoe lava can reach up to 40.7 ft in length (Howarth 1983, Kauahikaua
et al. 2004).
Sections of lava tube roofs often collapse naturally creating skylights, which are vertical-walled
openings. Typically, skylights form on sloped terrain shortly after lava tube formation (Kauahikaua
et al. 2004). Skylights are exposed to the surface environment of rainfall, sunlight, and temperature
fluctuations. Due to the steep walls, skylights also serve as natural refugia where endangered or rare
plants can persist without being damaged by herbivores (USFWS, unpubl.).
Chapter 4. Refuge Biology and Habitats 4-13