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

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Species Common Name(s)
Hakalau
Forest
Kona
Forest
HPWRA
Score
Holcus lanatus velvetgrass X
Paspalum dilatatum dallis grass X 12
Pennisetum clandestinum Kikuyu grass X 18
Polygonaceae Buckwheat family
Rumex acetosella common sheep sorrel X
Proteaceae Protea family
Grevillea robusta silky oak X 5
Ranunculaceae Buttercup family
Anemone hupehensis
Roseaceae
Japanese anemone X
Photinia davidiana photinia X -2
Rubus argutus Florida blackberry X X 21.5
Rubus rosifolius Thimbleberry X X
Zingiberaceae Ginger family
Hedychium gardnerianum Kahili ginger X X 16
Source: Jacobi and Price (2007), Barnett and Simonson (2008).
Hakalau Forest Unit
Numerous invasive plant surveys have been conducted at HFU (Stone et al. 1991, Jacobi and Price
2007, Barnett and Simonson 2008), where approximately 45 nonnative plant species have been
recorded. Although similar nonnative species occur at all elevations, the highest concentration of
nonnatives are found at the higher elevations from 5,000-5,500 ft compared to the lower elevation
forest (Barnett and Simonson 2008). This trend has also been observed in other Hawaiian forests
(D‟Antonio et al. 2000); in comparison to high-elevation sites, middle elevations have steeper
topography and greater precipitation, resulting in denser forests that are less accessible to humans,
ungulates, and nonnative plant species (Pejchar and Press 2006).
At the HFU, historical anthropogenic impacts that occurred at higher elevations, such as cattle
ranching, logging, and fire, removed the native forest and allowed for the invasion of nonnative plant
species (Scowcroft and Jeffrey 1999, Barnett and Simonson 2008). Adjacent land uses also increase
the continued problem of invasive species. Invasive plants are abundant at the adjacent Pīhā Game
Management Area due to the presence of pigs that act as vectors (Jeffrey, pers. comm.).
Jacobi and Price (2007) focused on 25 invasive plant species that pose a serious threat by displacing
native plants and disrupting native ecosystems. Three species (Ehrharta stipoides, Juncus effuses,
and Rubus argutus) showed an increase in frequency from 1987-2007. Barnett and Simonson (2008)
found a negative relationship between nonnative species cover and native canopy cover suggesting
that disturbances that reduce canopy cover increase the ability of invasion. Pattison et al. (1998)
found a similar trend and suggested that invasive species have a higher ability to capture and utilize
light resources, particularly in high-light, disturbed areas.
Invasive plants such as gorse, Florida blackberry, English holly, Photinea, and banana poka are being
controlled at the HFU using a combination of mechanical and chemical removal. Additional invasive
plant control techniques include removal of ungulates and reforestation with native species.
Chapter 4. Refuge Biology and Habitats 4-99