Ka'uhako Crater botanical resource and threat monitoring, Kalaupapa National Historical Park, Island of Moloka'i, Hawai'i

Abstract

Botanical monitoring of the remnant dryland forest of Ka'uhako Crater on July 11 - July 14, 1995 grew out of a desire to provide baseline data on the vegetation components of the crater prior to fencing and removal of feral ungulates, primarily axis deer (Axis axis) and feral pigs (Sus scrofa). The exclusion of ungulates, identified as damaging to the crater's native flora in the Kalaupapa National Historical Park Resource Management Plan (NHPRMP) (1994), was proposed in a Draft Environmental Assessment prepared by Larry Katahira (1995) through the construction of two miles of feral animal proof fence outside the crater's rim. Ka'uhako Crater, designated as a Special Ecological Area in the Kalaupapa NHPRMP (1994), contains one of the finest examples of low elevation windward dryland forest remaining on the island of Moloka'i and the entire state of Hawai'i. Although previous botanical surveys have examined the flora of Ka'uhako Crater (Linney 1987; Asherman et al. 1990), none had established any permanent monitoring plots to document the inevitable changes which will follow the removal of browsing herbivores. This system of permanent monitoring was established in 1995 by utilizing the three key native trees of Ka'uhako Crater, Wiliwili (Erythrina), 'Ohe makai (Reynoldsia), and Hala pepe (Pleomele), as the centers of circular cover plots that document every plant taxa on both the ground and in the canopy. Future monitoring and data acquisition in these plots will not only record the transitions in cover composition, but will also help identify potentially damaging alien plants that threaten the recovery of the native components. In addition, vital statistics recorded for a representative sample of each of the three key native trees will provide an overall picture of the health and status of the remnant dryland forest and will help steer management decisions necessary in implementing future restoration processes for these trees and the associated native flora. As part of the monitoring protocol, other threats and potential problems in the preservation of the crater's native flora, from the detrimental effects of the two-spotted leafhopper (Sophonia rufofascia) on native taxa to the lack of seedling recruitment for many of the native species, have been identified, and their implications to the long term survival of the dryland ecosystem have been addressed. Furthermore, future management concerns, such as the increased threat of wildland fire associated with an accumulation in fuel biomass following exclusion of feral ungulates, are predicted to become a greater priority with the passage of time, and, depending upon the future establishment and spread of certain alien grasses, may supersede all other management considerations. Early identification of these and other problems may help managers to address the situations at a stage when response efforts are still practical and feasible.