american samoa - University of Hawaii at Manoa

poIvon/l~os, Dtrvulliu solidu (which occurs all the way
down lo sea level), Humata heterophylla, Ctenopteris
hlcchnoides, and Ctenopteris contigua. Mosses and
liverworts are also common.
Many different epiphytic orchids are found in this
forest, but probably the most abundant one is
llcribobium sludei. Other common species include
Dcndrobium biflorum, Flickingeria comata, Liparis
con~ylobulbon, Phreatia micrantha, Phreatia matthewsir,
Bulbophyllum polypodioides, Bulbophyllum
longiscapum, Glomera montana, Diplocaulobium
fililohum, and Coelogyne lycastoides.
Vines are also common in the montane forest. There
are few lianas in the forest in the park, mainly because
of the absence of a canopy. The most common
species present are Faradaya amicorum (mamalupe)
and Alyxiu hracteolosa (lau maile). Less common
and snialler species include Medinilla samoensis,
IMscorca hulbifcra, and Hoya vitiensis (fue selela).
The most common trunk climbers are Freycinetia
reineckei and Freycinetia storckii (both called 'ie'ie).
Less common species include Piper graeffei ('ava'ava
aitu). One fern, Lomagramma cordipinna, also
becomes a trunk climber when it encounters a tree
while growing across the forest floor (see Fig. 24).
D. Summit Vegetation
'The summit vegetation category comprises a single
plant community on Tutuila, montane scrub, first
described in Samoa by Whistler (1980). Another type
of summit vegetation, "summit scrub" was described
from Ta'u (Whistler 1992b); although this has a
somewhat similar structure, it differs in origin and
floristic composition.
7. Montane Scrub
'l'his is the scrubby vegetation in which trees are
dwarfed and secondary in importance (biomass) to the
dcnse tangle of ground cover of species-mostly ferns
and climbers. In Samoa this community appears to be
unique to Tutuila, where it is restricted to ancient
"trachyte plugs" scattered around the islands. As
noted in the earlier section on geology, trachyte plugs
are the remains of old volcanic cores. Their unique
white clayey soil is characterized by a deficiency of
calcium, magnesium, and phosphorus. The white soil
is noticeable from a distance on the cliffs that are
often found in areas of montane scrub (see Fig. 5).
There are several areas of trachyte with their
associated montane scrub vegetation on Tutuila,
the most significant of which are Mt. Matafao and
Mt. Pioa. These two peaks, which reach 650 m
(2142) and 520 m (17 18 ft) respectively, can
easily be seen from Pago Pago Harbor, but are not
within the boundaries of the park. The trees
present are scattered and mostly shrublike, and
most belong to species different from those found
in the surrounding lowland forest. In an earlier
survey of these vegetation types (Whistler 1980),
the dominant trees recorded from montane scrub
on Matafao, Pioa, and another area called Mt. Tau
(near the airport) were Pandanus reineckei,
Rapanea myricifolia, Syzygium brevifolium,
Astronidium pickeringii, Metrosideros collina, and
Alstonia paczjlca. The ground cover, or perhaps
more aptly described, the vegetation between the
scattered trees, was dominated by Dicranopteris
linearis (false-staghorn fern, asaua), Dipteris
conjugata (a fern reported in Samoa only from
Matafao and Pioa), Duvallia epiphylla, and
Freycinetia storckii ('ie'ie).
Only a single trachyte plug is found within the
park boundaries-Mt. Mauga-o-Tula behind the
village of Vatia (Fig. 25). Its steep summit (a ridge
with high points on either end) is reached only
with difficulty via an ill-defined trail ascending the
east-facing slope. This trachyte ridge is only half
the elevation of Pioa and Matafao (less than 300
m), yet it has some of the same species that
characterize montane scrub. In a cursory sample
on Mauga-o-Tula during the present survey, the
dominant trees recorded were Metrosideros
collina, Intsia bijuga (ifilele), Alstonia pacifica,
Eurya pickeringii, Psychotria insularum
(matalafi), and Erythrospermum acuminatis-
simum. This is a mixture of lowland ridge forest
species and montane scrub species. However, the
dominant ground cover species is Dicranopteris
linearis, which is characteristic of, although not
entirely restricted to, montane scrub (Fig. 26).
Also present, but of lesser importance, are Scleria
polycarpa, Oplismenus hirtellus, and Lindsaea
ens folia.