The influence of feral goats on the lowland vegetation in Hawai`i Volcanoes National Park

Mueller-Dombois, Dieter; Spatz, Gunter

The c o a s t a l lowland of Hawaii Volcanoes National Park, p a r t i c u l a r l y its western part, is a concentration c e n t e r of f e r a l goats. Here, i n a t r o p i c a l seasonal climate, a widespread vegetation is an annual E r a ~ r o s t i s t e n e l l a grassland t h a t occurs on lava rock substrates with t h i n layers of ash. Localized within t h i s area occurs a l s o a small area of deep-ash deposit (Puu Kaone) t h a t is occupied by perennial introduced grass with scrub. Experimental goat displacenent i n form of exclosures on these two grasslands ' has shown t h a t both are e n t i r e l y goat-derived vegetations. The response t o displacement of goats was immediate i n both areas. In the annual grassland, bunch- ) grasses, woody chamaephytes and an endemic legume vine ( ~ a n a v a l i a kauensis) became established within l e s s than two years, while the annuals a r e f a s t disappearing. In the perennial grassland, Melinis minutiflora enlarged its grass mat, woody plants became more abundant and exposed s o i l was p a r t i a l l y covered within a year a f t e r exclosure construction. The remarkable recovery of the endemic vine i n the annual grassland shows that gaat removal still holds hopes for a t l e a s t a p a r t i a l return of native vegetation. The e f f e c t s of goats apart of t h e i r physical degradation of the lowland ecosystem has been primarily i n the form of exhausting the seed supply of native glants by feeding on seedlings wherever they occurred i n t h i s t e r r i t o r y . T o t a l elimination of goats from t h i s area can be expected t o yield a p a r t i a l return of native plants on these rockland surfaces.