Document: SHA-3-32-45

Water-use patterns of the invasive exotic Schinus terebinthifolius contrasted with native plant species in Everglades National Park.

EWE, S.M.L.* and L.S.L.DA STERNBERG

University of Miami, Coral Gables, 33124 FL ¹

Abstract:
Schinus terebinthifolius, Raddi (Schinus), is a widely dispersed invasive exotic which has been observed growing from upland pinelands into the mangrove communities of south Florida. Schinus success could be in part due to its tolerance for a wide range of hydrologic conditions; Schinus is hypothesized to behave like native species during the wet season but be more drought-tolerant during the dry season. This study examined the seasonal water-use patterns of Schinus compared to that of native species. In the Everglades National Park, Schinus is the dominant species in a post-farmed area known as the Hole-in-the-Donut (HID); Schinus is also observed growing in its adjacent pinelands. Water potential, stable isotope and gas exchange methods were used to examine Schinus and representative native species in-situ, both in the short hydroperiod HID and a rocky pineland. In both the HID and pineland sites, seasonal predawn water potentials of Schinus remained the same although water potentials of all native species decreased during the wet season. We hypothesized that during the wet season flooded soils in both sites could have caused anaerobic conditions which resulted in root death of native species, leading to lower water potentials. For both seasons sampled, instantaneous water-use efficiency (WUE) was significantly higher during the wet season compared to the dry season in all species due to lower transpiration rates. Schinus had consistently higher WUE than most of the native species over both seasons. We conclude that Schinus physiological function is less affected by seasonal hydrological functions compared to that of native species at these sites. Contrary to expectations, we found that it was the wet season and not the dry, that distinguished Schinus physiologically from the native species.

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This abstract is being presented at: 11:30 AM in session:
Oral Session #45: Water Relations in Shrubs and Annuals.