Reassessment of revegetation strategies for Kaho'olawe Island, Hawai'i

Abstract

This work investigates 2 US Army Construction Engineering Research Laboratory revegetation experiment sites (Phase I and II) on Kaho'olawe Island, Hawai'i (USA) to determine the long-term success of several revegetation strategies and to identify species that are best suited for future restoration activities in the highly eroded central plateau region of the island. Only the Phase I treatments receiving the highest rates of phosphorus and nitrogen fertilizer and the Phase II strategy (moderately high fertilization and landscaping) produced enough cover to begin providing protection from erosion processes. Buffelgrass (Cenchrus ciliaris L.), glycine (Neonotonia wightii (Wight Arnott) Verdc.), Natal redtop (Rhynchelytrum repens (Willd.) Hubb.), and siratro (Macroptilium atropurpureum (DC) Urb.) appear to be resilient to the harsh island conditions, which include strong winds, low annual rainfall, acute erosion, and a nutrient-depleted soil profile. Although all 4 species offer some protection against erosional processes, none are particularly desirable for long-term restoration of the island. Glycine and siratro, both of which volunteer readily in planting sites, are considered invasive in that they may smother other more desirable species, particularly less competitive natives. Finally, native woody species are shown to have difficulty in surviving on the island without special attention to planting and maintenance.