Vegetation dynamics in a coastal grassland of Hawaii

Abstract

Vegetation development following goat removal in a tropical grassland with a Mediterranean rainfall seasonality on leeward Hawaii is reported from two permanent monitoring sites. The two sites are equipped with experimental exclosures against feral goats. The sites were monitored annually for a decade (1971–80) for changes in cover by species. The vegetation changes reported relate to both inside- and outside-exclosure developments.

Four dynamic categories were recognized among the grassland species following goat removal. These are the decreasers, the increasers and the persistent species. The latter were divided into stable and oscillating persisters. Attention was drawn to the oscillating persisters, as exemplified by the endemic vine Canavalia kauensis, and to the absence of any correlation of its oscillation pattern to the variation in year-to-year rainfall. It was concluded that the oscillation pattern resides in the population it self and can be attributed to its life-cycle phases. It is suggested that synchronized life-cycle dependent death in local populations is an important dynamic phenomenon in certain plant communities. This phenomenon may be considered as separate from phenology and succession, but of similar significance in understanding the processes of vegetation dynamics.