© 2006 Heron Publishing—Victoria, Canada
Leaf gas exchange characteristics of three neotropical mangrove species in response to varying hydroperiod
Ken W. Krauss (1, 2, 5), Robert R. Twilley (3), Thomas W. Doyle (1) and Emile S. Gardiner (4)
1. U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, LA 70506, USA / 2. University of Louisiana at Lafayette, Center for Ecology and Environmental Technology, P.O. Box 42451, Lafayette, LA 70504,
USA / 3. Louisiana State University, Wetland Biogeochemistry Institute, Baton Rouge, LA 70803, USA / 4. USDA Forest Service, Center for Bottomland Hardwoods Research, P.O. Box 227, Stoneville, MS 38776, USA / 5. Corresponding author (kkrauss@usgs.gov) / Received May 25, 2005; accepted November 11, 2005; published online April 3, 2006
Summary
We determined how different hydroperiods affected leaf gas exchange characteristics of greenhouse-grown seedlings (2002) and
saplings (2003) of the mangrove species Avicennia germinans (L.) Stearn., Laguncularia racemosa (L.) Gaertn. f., and Rhizophora mangle L. Hydroperiod treatments included no flooding (unflooded), intermittent flooding (intermittent), and permanent flooding
(flooded). Plants in the intermittent treatment were measured under both flooded and drained states and compared separately.
In the greenhouse study, plants of all species maintained different leaf areas in the contrasting hydroperiods during both
years. Assimilation–light response curves indicated that the different hydroperiods had little effect on leaf gas exchange
characteristics in either seedlings or saplings. However, short-term intermittent flooding for between 6 and 22 days caused
a 20% reduction in maximum leaf-level carbon assimilation rate, a 51% lower light requirement to attain 50% of maximum assimilation,
and a 38% higher demand from dark respiration. Although interspecific differences were evident for nearly all measured parameters
in both years, there was little consistency in ranking of the interspecific responses. Species by hydroperiod interactions
were significant only for sapling leaf area. In a field study, R. mangle saplings along the Shark River in the Everglades National Park either demonstrated no significant effect or slight enhancement
of carbon assimilation and water-use efficiency while flooded. We obtained little evidence that contrasting hydroperiods affect
leaf gas exchange characteristics of mangrove seedlings or saplings over long time intervals; however, intermittent flooding
may cause short-term depressions in leaf gas exchange. The resilience of mangrove systems to flooding, as demonstrated in
the permanently flooded treatments, will likely promote photosynthetic and morphological adjustment to slight hydroperiod
shifts in many settings.
Keywords:
Avicennia germinans, carbon assimilation, flooding, Laguncularia racemosa, photosynthesis, Rhizophora mangle, stress physiology, water-use efficiency.
