Seasonal gas exchange characteristics of Schinus terebinthifolius in a native and disturbed upland community in Everglades National Park, Florida

Schinus terebinthifolius Raddi (Schinus) is an invasive exotic plant widely found in Florida and Hawaii. This species is found from the upland pinelands to the mangrove forests of Florida. Dense Schinus infestations have the capacity to displace native species, reduce species diversity and been shown to reduce faunal use of the community. The purpose of this study was to determine if gas exchange patterns of Schinus were significantly different from native species. This work was part of a larger study to determine if the exotic's physiology contributed to its presence in two upland communities of South Florida. The first was an endemic rock pineland community and the second, a disturbed previously farmed area where Schinus was the canopy dominant. Schinus gas exchange, leaf nitrogen and carbon stable isotope contents were contrasted with four native species for one wet and dry season. Schinus tended to have higher assimilation (A), mesophyll conductance (g(m)), intrinsic water-use efficiency (WUE) and photosynthetic nitrogen-use efficiency (PNUE) than native species in the pineland site during the wet season but these differences were not statistically significant. There were also no significant differences in conspecific plant responses between the two communities. Seasonal differences were, however, significant for most of the gas exchange parameters at either one or both of the study sites. Wet season A, g(m), nitrogen concentration ([N]), intrinsic WUE, PNUE and carbon stable isotope signatures (delta(13)C) were higher than the dry season, most likely a consequence of greater water availability within the substrate. Although differences in gas exchange could contribute to the invasiveness of Schinus into native pineland and disturbed upland areas, other aspects of its autoecology also play an important role. (C) 2002 Elsevier Science B.V. All rights reserved.