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

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Table 4-7. Total Native Seedlings Outplanted at the HFU 1987 - 2007.
4.10.1 Koa (Acacia koa)
Native Species
Total Seedlings
Planted (1987-2007)
Acacia koa 328,827
Metrosideros polymorpha 30,232
Myrsine sp. 3,150
Cheirodendron trigynum 2,268
Sophora chrysophylla 1,997
Coprosma ochracea 1,911
Coprosma montana 1,856
Coprosma rhynchocarpa 1,699
Myoporum sandwicense 1,687
Rubus sp. 1,304
Ilex anomala 920
Leptecophylla tameiameiae 698
Vaccinium calycinum 665
Chenopodium oahuensis 397
Ranunculus hawaiiensis 395
Phyllostegia brevidens 304
Coprosma sp. 280
Vaccinium reticulatum 278
Vaccinium sp. 188
Stenogyne calaminthoides
Source: USFWS, unpubl.
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Koa (Acacia koa) is endemic to the islands of Hawai„i, Moloka„i, Maui, Lāna„i, O„ahu, and Kaua„i.
Although it can be found between 200-6,760 ft, its current distribution is mainly restricted to areas
above 2,000 ft due to introduced pests and diseases (Wagner et al. 1999, Elevitch et al. 2006). It
tolerates a wide array of rainfall regimes and can withstand drought periods up to 5 months. The
optimal temperature range of koa is between 48-70°F (Elevitch et al. 2006). Seedlings cannot endure
frost, although protective techniques enhance survival (Scowcroft et al. 2000).
Koa is the largest native tree in the archipelago, reaching 50-80 ft in height (Elevitch et al. 2006).
Mature trees, which can live for over 100 years, have a diameter at breast height (dbh) often
measuring more than 3.27 ft (Leary et al. 2004). While koa seedlings have true leaves, mature koa
trees have only phyllodes, or expanded petioles. The flattened seed pods contain 6-12 seeds. The
seeds are typically gravity-dispersed and require scarification in order to germinate (USFWS 1996b).
Koa seeds appear to remain viable for about 15 years (USFWS 1996b). At Hakalau, koa trees flower
December - February and seeds ripen November-January (USFWS 1996b). Koa flowers are
primarily insect-pollinated, but birds and wind are also possible pollinators.
Acacia koa is an important species for several reasons, providing habitat as well as food for native
birds, insects, and plants. Banko and Peck (2008) collected over 78,000 arthropods from the branch
tips of 160 koa trees. Pysllids (Homoptera) comprised over 90 percent of all individuals collected.
4-76 Chapter 4. Refuge Biology and Habitats