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Only on
the younger islands of Maui and Hawai`i do the volcanoes reach
a height allowing the development of subalpine vegetation. This
high-elevation zone (above 6,000 feet) occurs on both the windward
and leeward slopes of Haleakala, Mauna Kea, Mauna Loa and Hualalai,
and is essentially a band encircling the tall mountains. Plants
that grow here are adapted to dry conditions and periodic cold
temperatures. Rainfall ranges from approximately 20-50 inches
per year, and the mean monthly temperature is less than 50°F.
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The dominant
tree of the subalpine zone is the mamane, a shrubby tree with
bright yellow flowers, in the pea family. Another common shrub
is the naio, or false sandalwood, which is a widespread species
occurring in communities from the coast to the subalpine zone.
Subalpine shrub communities extend well above the treeline to
above 10,000 feet, but with increasing elevation, shrubs become
sparser and lower to the ground. The unique Hawaiian silverswords
are found in the upper subalpine region; their silver color is
associated with reflective hairs, an adaptation to extremes of
temperature and exposure to strong sunlight. |
 Silverswords were once
one of the more common plants of the subalpine zone, but feral animals
caused a serious decline in their numbers from browsing and trampling.
Attracted by the silvery ball of the silverswords, humans used to
pull up the plants and roll them downhill...a practice that contributed
to a drop in silversword populations. |
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 The
palila, a native finch-billed honeycreeper, is found in the subalpine
mamane/naio forests. The palila is an active bird that feeds upon
immature seeds in pods of the mamane tress. It will also eat insects,
naio berries, and mamane buds, flowers, and young leaves. Formerly
found on the slopes of Mauna Loa and Hualalai, the palila now
lives only on Mauna Kea, and is an endangered species.
The yellow-faced
bee is found in the subalpine forest, though its range can extend
all the way down to the coast. There are over 60 species of native
yellow-faced bees, and they are important pollinators of native
plants. |
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 The
mamane forests of Maui and Hawai`i have been seriously damaged
by feral goats and sheep. These animals eat the native plant seedlings,
and trample the ground, making it difficult for the trees to grow.
Without the forest habitat, the populations of native birds, insects,
and snails that were dependent on the mamane and naio, were also
reduced.
Haleakala National Park is a
protected area for the silversword and other species found in
the subalpine zone. The park was fenced to keep out feral ungulates,
and the silverswords were protected by law from damage by humans.
These actions have resulted in the comeback of many native species. |
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