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

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Montane wet ‘ōhi‘a/uluhe forest, including Carex bogs
This habitat type is found between 2,500-4,000 ft in elevation. The topography of the montane wet
„ōhi„a/uluhe forest is gently sloping; however, numerous steep-sided streams bisect the surface. The
volcanic soils are aged, eroded, and typically poorly drained (USFWS, unpubl.).
The upper canopy of this habitat type is composed of scattered mature „ōhi„a (over 100 years old), as
well as medium stature „ōhi„a approximately 30 ft in height. The midcanopy zone, between 10-15 ft,
is dominated by hāpu„u. The ground cover is composed mostly of dense mats of uluhe that make
access difficult. Numerous native Carex bogs can be found scattered throughout the lower elevations
of this habitat. These bogs occur naturally in flat areas where a limited amount of open water is
retained in a clay-layered depression. Sphagnum moss also exists in these bogs. The bogs at the HFU
range from 8-12 ft deep (Tomonari-Tuggle 1996).
The steep topography of the montane wet „ōhi„a/uluhe forest provides protection for native and
endangered plants from grazing ungulates. For example, the bogs are used by rare invertebrates and
possibly the koloa maoli (USFWS, unpubl.).
Although endangered flora and fauna do occur in this habitat type, the montane wet „ōhi„a/ uluhe
forest in the HFU is the most exposed to invasive species from lower elevations. Limiting factors in
the montane wet „ōhi„a/uluhe forest include invasive species such as ungulates, rats, mice, slugs,
mosquitoes, and nonnative plants. In particular, native bird densities are curbed by avian diseases,
which are transmitted by mosquitoes that are able to breed up to 4,500 ft in elevation. Native plant
and invertebrate diversity is also assumed to be low and native pollinators are lacking. Eutrophication
and elimination of Carex bogs is occurring due to pig activity. As a result, the bogs are primarily
invaded by nonnative rushes. Limited historical and current anthropogenic disturbance occurs within
the montane wet „ōhi„a/uluhe forest (USFWS, unpubl.).
Montane wet ‘ōhi‘a forest
This habitat type is found upslope of the montane wet „ōhi„a/uluhe forest, between 4,000-5,000 ft.
The montane wet „ōhi„a forest within the HFU maintains a more diverse plant and native bird
community than the lower elevation habitat due to the location above the mosquito zone (USFWS,
unpubl.).
The upper canopy of the wet „ōhi„a forest is dominated by a mature closed canopy of „ōhi„a that
reach 60-90 ft. Midcanopy species include „ōhi„a, „ōlapa, pilo, kōlea, epiphytes, and tree ferns
reaching up to 15 ft. The ground cover is dominated by mixed ferns, Astelia lilies, „ōhelo, kanawao,
pūkiawe, and kāwa„u. Downed timber and sphagnum moss are also dominant in this habitat at the
ground level. Slopes are moderate (USFWS, unpubl.).
Rare native forest birds, such as the „akiapōlā„au, Hawai„i creeper, and Hawai„i „ākepa, are found in
montane wet „ōhi„a forest at the HFU. The area also provides potential habitat for Clermontia
peleana subsp. peleana and other rare native plants.
Similar to the montane wet „ōhi„a/uluhe forest, invasive species and lack of native pollinators are
also a problem within the montane wet „ōhi„a forest (USFWS, unpubl.).
4-6 Chapter 4. Refuge Biology and Habitats