Vegetation-environment relationships in forest ecosystems of the Cordillera Central, Dominican Republic.
We examined forest vegetation-environment relationships in the central mountain range of Hispaniola to improve general understanding of tropical montane forests. Forest inventory data were collected in 1999 and 2000 from 245 plots established in the Armando Bermúdez and Carmen Ramírez National Parks, Dominican Republic, over an elevation range of 1,100-3,075 m. Average tree density (≥10 cm dbh), basal area, and dbh were highly variable across the elevation gradient; species richness declined significantly with elevation; and the canopy height of broadleaved stands declined whereas the height of stands dominated by the endemic pine, Pinus occidentalis Sw., was relatively constant across the elevation gradient. Four major forest associations were identified using TWINSPAN: a low elevation broadleaved forest; a pine-broadleaved mixed forest; a mid-elevation cloud forest; and a largely monospecific pine forest that extends from the cloud forests to the summits of the highest peaks and dominates the leeward slopes of the mountains. Species composition varied continuously along the elevation gradient up to 2,250 m; however, above 2,250 m there was an abrupt shift from cloud forest to monospecific pine forests. Temperature, humidity, and fire history appear to regulate the position of this boundary, probably reflecting the position of the trade wind inversion. Ordination and logistic regression indicated that disturbance history and topo-edaphic factors influenced individual species distributions.