© 2007 Heron Publishing—Victoria, Canada
Sap flow characteristics of neotropical mangroves in flooded and drained soils
Ken W. Krauss (1–3), P. Joy Young (4), Jim L. Chambers (4), Thomas W. Doyle (1) and Robert R. Twilley (5)
1. U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Boulevard, Lafayette, LA 70506, USA / 2. Center for Ecology and Environmental Technology, Department of Biology, University of Louisiana at Lafayette, Lafayette, LA
70504, USA / 3. Corresponding author (kkrauss@usgs.gov) / 4. School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA / 5. Department of Oceanography and Coastal Sciences, Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge,
LA 70803, USA / Received April 28, 2006; accepted July 27, 2006; published online February 1, 2007
Summary
Effects of flooding on water transport in mangroves have previously been investigated in a few studies, most of which were
conducted on seedlings in controlled settings. In this study, we used heat-dissipation sap probes to determine if sap flow
(Js) attenuates with radial depth into the xylem of mature trees of three south Florida mangrove species growing in Rookery Bay.
This was accomplished by inserting sap probes at multiple depths and monitoring diurnal flow. For most species and diameter
size class combinations tested, Js decreased dramatically beyond a radial depth of 2 or 4 cm, with little sap flow beyond a depth of 6 cm. Mean Js was reduced on average by 20% in Avicennia germinans (L.) Stearn, Laguncularia racemosa (L.) Gaertn. f. and Rhizophora mangle L. trees when soils were flooded. Species differences were highly significant, with L. racemosa having the greatest midday Js of about 26 g H2O m–2 s–1 at a radial depth of 2 cm compared with a mean for the other two species of about 15 g H2O m–2 s–1. Sap flow at a depth of 2 cm in mangroves was commensurate with rates reported for other forested wetland tree species. We
conclude that: (1) early spring flooding of basin mangrove forests causes reductions in sap flow in mature mangrove trees;
(2) the sharp attenuations in Js along the radial profile have implications for understanding whole-tree water use strategies by mangrove forests; and (3)
regardless of flood state, individual mangrove tree water use follows leaf-level mechanisms in being conservative.
Keywords:
Avicennia germinans, basin mangroves, flood stress, individual tree water use, Laguncularia racemosa, radial xylem depth, Rhizophora mangle, south Florida.
