Subalpine Vegetation Change 14 Years after Feral Animal Removal on Windward East Maui, Hawai‘i

Considerable time and effort has been spent removing nonnative ungulates from sensitive subalpine and forest areas in Hawai‘i, with less effort dedicated to documenting changes in plant community structure after feral animal removal. Abundance of native and nonnative vegetation was quantified in a study comparing plots both before (1994) and 14 yr after (2008) removal of feral animals from windward East Maui subalpine and forest habitat in Waikamoi Preserve. An analysis of changes in abundance in two vegetation layers documented increases in relative cover of native subalpine vegetation: bryophytes tripled and lichens increased over nine times in the subalpine shrubland habitat within the ground cover (0 to 1 m) layer, and alien grass cover was halved. In the understory (1 to 2 m) layer, native ferns increased significantly, and native shrub cover tripled. In the forest habitat, bryophytes increased in both layers, and lichens increased in the understory layer. Higher-elevation plots in 2008 more closely resembled the species composition and abundance of plots about 100 m lower in elevation sampled in 1994. Rainfall declined and temperatures increased during the study period; however, vegetation responses were more likely a result of release from ungulate damage than a response to climate. We conclude that goat and pig removal programs conducted in the late 1980s and early 1990s likely contributed to an overall increase in native vegetation cover in spite of a relatively dry 14-yr period since ungulate removal.