The forest of Mauna Kea, Hawaii, was studied from 1973 through 1975 in order to define composition and phenology patterns of the two dominant tree species, and to determine the influence of man and feral mammals upon the ecosystem. There was a significant change in tree species composition across a 150 m elevational gradient; soil characteristics, drainage conditions, past disturbances by man, and browsing pressure by feral mammals are suggested as possible reasons. Although species composition varied with elevation, the tree density did not change. The phenological patterns of Sophora chrysophylla were found more closely tied to the weather pattern than were those of Myoporum sandwicense. Methods of pollination and seed dispersal were different between Sophora and Myoporum, and the spread of the latter is thought to be related to increased seed dispersal by recently introduced avian species, in conjunction with the limitation of Sophora reproduction due to browsing pressure by feral sheep. Because of the changes that are affecting the ecological organization of this community, the forest and its associated fauna need to be carefully examined in terms of present management policies. ONE OF THE LAST REMAINING NATIVE DRYFOREST ECOSYSTEMS in Hawaii is composed of 12,000 hectares of high mountain savanna on the southwestern slope of Mauna Kea. Sophora chrysophylla (Leguminosae) and Myoporum sandwicense (Myoporaceae) are the most abundant trees, with scattered stands of Euphorbia olowaluana (Euphorbiaceae), Santalum ellipticum (Santalaceae), Dubautia arborea (Compositae), and two small plantings of introduced pine, eucalyptus, and cedar. Shrub and ground-cover species are considered elsewhere. No one has described the phenology of this forest although Hartt and Neal (1940) gave a species account of the vegetation on the eastern slope of Mauna Kea. This ecosystem has been greatly influenced by the activities of man and introduced animals for the last 100 years (Warner 1960). Until the 1950's Parker Ranch grazed horses and cut Sophora for fence posts. Since the 1820's herds of feral sheep have roamed these volcanic slopes eliminating much of the Sophora reproduction by destroying the younger trees (Giffin 1976). Because of these perturbations, information was desperately needed on the present condition of the forest. This study was undertaken from April 1973 through August 1975 to compare forest composition and reproductive strategies of the two primary tree species (Sophora and Myoporum) in an effort to understand ecological interactions and influences on the forest as it exists today. METHODS Study sites were selected on the southwestern slope of Mauna Kea at elevations of 1980, 2130, and 2290 m along the jeep road from Kilohana to Puu Laau (fig. 1). The 1980 and 2130 m sites were open to grazing by feral sheep, while the 2290 m study site was fenced on all sides. Five contiguous 30 x 30 m releves, arranged in the shape of a T, were arbitrarily established near the center of each study site. All trees taller than 2 m (the height when Sophora and Myoporum first flower) were numbered, tagged, and, with the aid of a grid system, recorded on a map. Circumference at breast height (CBH) measured 1.4 m above the ground, was determined with a tape measure, and total tree height was measured with a clinometer. Canopy density, flowering, and fruiting were measured monthly (see Lamoureux 1973, Frankie et al. 1974). Canopy density was determined by standing under each tree and recording the percentage of open sky observed. Flowering and fruiting were measured by estimating the number of available terminal branches on each tree, and recording the percentage of those that possessed fully opened flowers or mature ripe fruit. To offset the phenomenon of trees in one area being in heavy flower while 500 m away others lacked blossoms, every month I systematically walked across each study area outside the releve's, measuring the nearest tree each 30 m until 50 trees had been considered. These data were then added to those obtained from the releves. With the density of trees and intensity of flowering known, it was possible to extrapolate the yearly lPresent address: Department of Zoology and C.P.S.U., University of California, Davis, California 95616, U.S.A. 282 BIOTROPICA 12(4): 282-291 1980 This content downloaded from 207.46.13.127 on Fri, 14 Oct 2016 04:07:05 UTC All use subject to http://about.jstor.org/terms Mauna Kea Game Management Area