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Technical Report #175.
McDaniel, S., R. Loh, S. Dale, and C. Yanger. 2011. Experimental
restoration of mesic and wet forests in former pastureland, Kahuku
Unit, Hawaii Volcanoes National Park
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ABSTRACT:
The Kahuku unit of Hawaii Volcanoes National Park (HAVO) contains seven
thousand acres of former forest that was converted to pasture for
grazing cattle. There
were several phases of forest clearing and pasture development (Parker
Ranch 1912-
1947, James Glover 1947-1958, and Damon Estate 1958-2000) creating an
open
pasture with scattered native trees and small remnant stands of native
species. In 2005,
methods to facilitate forest recovery were tested in four ungulate-proof
exclosures (four
hectares each). Within the exclosures, three temporary grass removal
treatments
(herbicide, soil turnover, and herbicide/soil turnover) were tested with
the objective of
finding a method that best promoted native forest recovery in
conjunction with ungulate
exclusion. In addition to monitoring plant recruitment from the natural
seed bank in the
soil, establishment by direct seeding and planting of native species in
the different
treatments was evaluated. By year one, rapid re-establishment of alien
grasses
occurred in all removal treatments, but was slowest in plots that
received a combination
of soil turnover and herbicide. Natural native plant recovery was
evident in all grass
removal treatments with a limited number of seedlings in the untreated
grass control.
Plant establishment from direct seeding for koa and pilo was highest in
the combination
soil turnover and herbicide treatment. No seedlings of Pipturus
albidus (māmaki),
Cheirodendron trigynum (‘ōlapa), Coprosma pubens (pilo),
Myoporum sandwicense
(naio) and very few Acacia koa (koa) and Metrosideros polymorpha
(‘ōhi‘a) were
observed outside of ungulate-proof exclosures. Planted seedling survival
was moderate
to high with no significant differences among sites and treatments
(57-70%). Based on
these results, temporary suppression of alien grasses in conjunction
with ungulate
exclusion can facilitate recovery of native species once abundant in the
Kahuku region.
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