Ecological and Physiological Aspects of Caribbean Shrublands

Shrubland vegetation has not received as much scientific attention in the Carib- bean as forest vegetation has. However, shrublands constitute ~25% of the woody vegetation classification units in the Caribbean, and in 10 islands that we analyzed, the average cover of shrublands was 16% of the land area and 27% of the vegetation area. Caribbean vegetation is subject to strong environmental gradients, and many tree species change habit from arbo- real to shrubby along those gradients. Shrublands usually occur at the extremes of edaphic and climatic gradients, which explains why many studies of forests in the Caribbean are actually studies of shrublands or include shrublands. Shrubland vegetation is of scientific interest because it possesses adaptations for dealing with extreme conditions of drought, oli- gotrophy, salinity, inundation, fire, temperature, and wind. These conditions have floristic, ecological, and ecophysiological consequences. Caribbean shrublands, particularly those on ultramafic or serpentine soils, have a high level of endemism and high species diversity. Shrublands exhibit a high level of leaf sclerophylly, high root-to-shoot ratios, and high re- silience. We generalize the development of shrublands with a stress model that emphasizes environmental gradients and duration (chronic or acute) of limiting conditions. Human activity is creating shrubland habitat, a trend that is bound to intensify in the Anthropocene Epoch. These changes in environmental conditions are leading to novel shrublands where introduced species mix with native ones forming new species assemblages.