Long-term tree ring chronologies from sympatric tropical dry-forest trees: individualistic responses to climatic variation

The influence of local precipitation and temperature on long-term growth dynamics in two species of seasonally dry tropical forest trees were investigated. Growth records were extracted from tree rings in Guanacaste province, Costs Rica. These chronologies provide a long-term (c. 85-y) record of tree growth for two species with contrasting phenologies. Annual growth, in both species, was dependent on annual and/or monthly variation in local precipitation but less so on temperature. For each species, however, patterns of growth reflected unique degrees of sensitivity to monthly rainfall and rainfall during previous years. It is hypothesized that such differences were due to the rooting depth of these species. A review of the literature also indicated similar diverse cambial growth responses by tropical trees to variation in annual and monthly climate. Lastly, it was shown that variation in longer term fluctuations in the Pacific and Atlantic oceans, as measured by the El Nino Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO), significantly influenced local precipitation in Guanacaste only during the wettest portion of the wet season. Such temporal sensitivity may have differentially influenced the longer-term growth of some tropical tree species but not others. Together, these results support the hypothesis that tropical tree species respond individualistically to variation in local and regional climate and that some tropical assemblages may in fact be structured by species-specific differences in soil water-use.