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

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Outplanting of „ōhi„a throughout Hawai„i Island has not been as extensive as koa, due to failed
restoration efforts (Scowcroft and Jeffrey 1999). Since 1997 over 30,000 „ōhi„a trees were planted on
the HFU (USFWS, unpubl.). These trees were planted in the understory of the previously planted koa
corridors, which increases survival. Experimental plantings in open pastures resulted in nearly
100 percent mortality, possibly due to grass competition. Planting on downed logs in open areas and
under canopy also increased survival but is not efficient because of the lack of substrate logs.
4.10.3 Māmane (Sophora chrysophylla)
The ecological characteristics of māmane have not been as extensively studied as koa or „ōhi„a.
Māmane is an important component of certain native forests and a valuable food source for native
birds, particularly the listed palila. Māmane is a polymorphic species and can be found throughout
Hawai„i as a shrub or tree in both dry and wet conditions. On the eastern slope of Mauna Kea at the
drier, upper portions of the Refuge (above 6,000 ft), māmane is codominant with koa. As the
elevation continues to increase, koa drops out and māmane becomes more abundant. Koa-māmane
forest type is transitional between the taller, mesic koa-„ōhi„a stand type and the drier, lower stature
subalpine māmane forest. Understory species for this forest type include naio, pūkiawe, „a„ali„i,
„ōhelo, and native ferns and grasses. Ecologically, māmane has much in common with koa. It is
pollinated by insects and birds and is also a leguminous, nitrogen-fixing species whose seeds are
primarily gravity dispersed. It is also able to spread through root sprouting and by seed. Growth rates
are likely to be faster at the lower elevation koa-māmane communities at the Refuge.
4.11 Cave Resources
According to the Federal Cave Resources Protection and Management Act of 1988, as amended, a
cave is a naturally occurring void, cavity, recess, or system of interconnected passages that occurs
beneath the Earth‟s surface or within a cliff or ledge. Cave resources are any material or substance
occurring naturally in caves, including animals, plants, paleontological deposits, sediments, minerals,
and relief features (16 U.S.C. §§ 4301-4310). In Hawai„i, caves can occur in limestone or basaltic
lava (Howarth 1983) and are generally more extensive in pahoehoe lava flows (Howarth et al. 2007).
These dark ecosystems are typically wet, with high levels of CO2 and low levels of O2. The
temperature inside the cave typically reflects the annual temperature at the surface of the cave;
however, caves that extend downslope from the entrance often have cooler temperatures (Howarth
1983).
Caves, including lava tubes, have historically been considered inhospitable habitats not favorable to
fauna (Howarth 1979, 1983). In reality, these habitats provide refuge for rare and highly specialized
invertebrates, such as insects, spiders, and other arthropods. Cave animals can be divided into four
categories. Obligate cave species, or troglobites, are unable to survive outside of cave ecosystems
and typically exist within deep, damp cave areas that are protected from surface air. Obligate cave
species known to occur on the Island of Hawai„i include the endemic moths and spiders (Sinella
yoshiia, Schrankia sp., Littorophiloscia sp.). Facultative species, or troglophiles, have the ability to
live and reproduce in caves but are also capable of surviving in other similar environments. The third
cave type of cave species are the trogloxenes. These species regularly inhabit caves, but return to the
surface to feed. Finally, accidental visitors are fauna that inadvertently enter caves and are unable to
survive in the habitat (Howarth 1973, 1983, Howarth et al. 2007). In general, cave species can occur
4-80 Chapter 4. Refuge Biology and Habitats