Seasonal water-use by the invasive exotic, Schinus terebinthifolius, in native and disturbed communities

Abstract.

Schinus terebinthifolius Raddi (Anacardiaceae) is an aggressive invader found in both disturbed and native habitats of Florida. The purpose of this study was to compare Schinus water uptake patterns to those of four native species in a disturbed previously farmed area versus a native pineland community. Although neither of the study sites was flooded, soils in both sites were saturated with water at the end of the wet season. Isotopic analysis of stem water showed that almost all the native species in both sites showed a seasonal change in plant water uptake; plants utilized mainly groundwater during the dry season but shifted to a high proportion of soil water during the wet season. In the pineland community, Schinus showed no seasonal shift in water uptake source. In the disturbed community, however, Schinus was not isotopically distinct from the native species with regard to water source. Despite greater soil water availability in the wet season, predawn water potentials were significantly lower in the wet than in the dry season for native species at both sites. The counterintuitive decrease in water potentials during the wet season in both study sites could be the response of native plants to root flooding. Predawn water potentials of Schinus in both study areas however, remained constant across seasons. Predawn and noontime water potential differences were smaller in Schinus than in the native species at both sites during the wet season, but this pattern was found only in the disturbed area during the dry season. Schinus was most likely less affected by seasonality and more tolerant of root flooding than the native species studied.