Hawai'i conservation alliance

2011 Runner Up Best Student Poster Presentation

Understory forest cultivation of three native plants under different light conditions

Cynthia Nazario-Leary, Travis Idol
University of Hawaii at Manoa, Honolulu, HI, United States

Understory cultivation within a forest farming system is a promising approach to increase abundance of desired plant material while reducing collection pressures on wild plants. We assessed the impact of cleared forest understory and resulting light availability on the establishment and growth of three culturally valued native plants: palapalai (Microlepia strigosa), māmaki (Pipturus albidus) and maile (Alyxia stellata). Species were outplanted within a wet-mesic non-native forest on O‘ahu in 2006. Survival and species-specific plant measurements were monitored for two years; percent light transmittance and canopy cover measured once in 2007. Palapalai had the highest survival; maile and māmaki only survived in the cleared understory treatments. Growth of surviving plants for all three species was greatest in plots cleared of understory species and under a non-continuous overstory. Thus, palapalai can survive in low light levels (1-5%) of an intact forest understory, but higher light levels associated with understory clearing (15-20%) maybe necessary to support harvesting. Maile and māmaki did not establish well in the intact understory and growth rates, even with understory clearing, were insufficient for harvesting after two years. Our study suggests that within lowland wet mesic forests dominated by non-native species, light availability is the most critical resource limiting establishment and growth of understory native species. Successful and sustainable cultivation will require some level of canopy opening or manipulation to ensure adequate light levels.