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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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.

Title pages, table of contents, abstract

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Conclusions and literature cited

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