Fire and forest in the highlands of the Cordillera Central, Dominican Republic: Modern dynamics and long-term history.

摘要

This dissertation investigates past and present environments of the highlands of the Dominican Republic using paleoecological and modern ecological techniques. The relatively unstudied highlands (>2000 m) of the Cordillera Central are blanketed by a mosaic of pine forests, open pine woodlands, and grasslands, with broadleaf trees joining the canopy in sheltered locations. My research on modern vegetation and fire ecology, and on long-term fire and vegetation history, helps fill gaps in the knowledge of Caribbean environments, and may assist land managers in conservation efforts in the Dominican highlands.; A study of the relationship between modern pollen rain and vegetation cover in the highlands provided a basis for interpreting pollen assemblages in sediment profiles. As expected, pine pollen dominated most samples. Detrended Correspondence Analysis indicated that the modern pollen spectra of forested uplands and open wetland sites are clearly distinct, while a variety of other site types that are intermediate in terms of vegetation are also intermediate in terms of modern pollen spectra. The lack of pine stomata was an excellent indicator of treelessness. The distinction between forested and non-forested sites may be useful in interpreting highland fossil records that may reach back into the last glacial period.; Analysis of a 126.5 cm sediment core from a bog in Valle de Bao on the windward slope of the Cordillera Central indicated that disturbance by fire, tropical storms, and climatic fluctuations has been part of the highland ecosystem for millennia. The bog formed during a relatively moist period around 4000 yr BP. The record includes strong signals of dry periods during the late Holocene.; A study of postfire regeneration of pines and shrubs at five recently burned sites provided evidence that the woody vegetation of the pine-forested highlands is well adapted to fire. Most shrubs at all sites resprouted from their bases, and in one site, shrubs regained prefire stem heights within seven years. Recovery of shrub stem diameters lagged behind. Large pines can survive fire, but in this study no trees 13 cm in diameter survived. Repeated fires may create and maintain a shrub-dominated landscape.