Abstract
On the Savannah River Site, South Carolina, USA, large areas of floodplain swamp forest of baldcypress (Taxodium distichum) and water tupelo (Nyssa aquatica) were destroyed by the cumulative impacts of cooling-water discharges over a 35-year period of nuclear reactor operations. In one floodplain area, four years after thermal discharges ended, we analyzed the pattern of forest recovery across a disturbance gradient spanning from a site of chronic thermal impact and extensive sediment deposition to sites of intermittent thermal impact and little substrate change. Across this spatial gradient, we measured density and size structure of cypress and tupelo and assessed regeneration success in relation to density of surviving canopy trees and to substrate changes. Compared with undisturbed forest, canopy tree density was lower in all disturbed sites and decreased progressively with greater site disturbance. Density of trees regeneration decreased in parallel with declining canopy tree density; however, regeneration was particularly low in the site of chronic impact, where very few canopy trees had survived and where substrate had been modified by sedimentation. Size structures suggested that tree recruitment had occured synchronously during a 5-year period of regional drought and minimal river flooding. Thus, cypress-tupelo recovery was influenced both by availability of seed sources and by site conditions, but floodplain hydrology also affected regeneration. The pattern of differential recovery across the disturbance gradient has allowed the use of natural regeneration potential in efforts to restore the pre-disturbance forest, and it also illustrates several key factors in wetlands design.
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Literature Cited
Brinson, M. M. and L. C. Lee. 1989. In-kind mitigation for wetland loss: statement of ecological issues and evaluation of examples. p. 1069–85.In R. R. Sharitz and J. W. Gibbons (eds.) Freshwater Wetlands and Wildlife. U.S. Dept. of Energy Office of Scientific and Technical Information, Oak Ridge, TN, USA. DOE Symposium Ser. No. 61 (CONF-8603101).
Burns, R. M. and B. H. Honkala (tech. coords.). 1990. Silvics of North America. Agriculture Handbook 654. U.S. Department of Agriculture, Forest Service, Washington, DC, USA.
Busch, D. E. and S. D. Smith. 1995. Mechanisms associated with decline of woody species in riparian ecosystems of the southwestern U.S. Ecological Monographs 65:347–70.
Christensen, E. J., M. E. Hodgson, J. R. Jensen, H. E. Mackey, Jr., and R. R. Sharitz. 1984. Pen Branch delta expansion. Savannah River Laboratory, E.I. DuPont de Nemours and Company, Aiken, SC, USA. DPST-83-1087.
Clewell, A. F. and R. Lea. 1990. Creation and restoration of forested wetland vegetation in the southeastern United States. p. 195–231.In J. A. Kusler and M. E. Kentula (eds.) Wetland Creation and Restoration: the Status of the Science. Island Press, Covelo, CA, USA.
Conner, W. H. and J. W. Day, Jr. 1988. Rising water levels in coastal Louisiana: implications for two coastal forested wetlands in Louisiana. Journal of Coastal Research 4:589–96.
Dulohery, N. J., C. S. Bunton, C. C. Trettin, and W. H. McKee, Jr. 1995. Reforestation, monitoring, and research at Pen Branch: Restoring a thermally-impacted wetland forest. U. S. Forest Service Center for Forested Wetlands Research, Charleston, SC, USA. FS-6200-7.
Dunn, C. P. and R. R. Sharitz. 1987. Revegetation of aTaxodium-Nyssa forested wetland following complete vegetation destruction. Vegetatio 72:151–57.
Huenneke, L. F. and R. R. Sharitz. 1986. Microsite abundance and distribution of woody seedlings in a South Carolina cypress-tupelo swamp. American Midlands Naturalist 115:328–35.
Jensen, J. R., E. J. Christensen, and R. R. Sharitz. 1984. SRP swamp vegetation map. Report Savannah River Laboratory, E.I. DuPont de Nemours and Company, Aiken, SC, USA. DPST-84-372.
Mitsch, W. J. and J. G. Gosselink. 1993. Wetlands. Chapter 17: Wetland Creation and Restoration. Van Nostrand Reinhold. New York, NY, USA.
Pickett, S. T. A. and P. S. White. 1985. The Ecology of Natural Disturbance and Patch Dynamics. Academic Press, New York, NY, USA.
Rejmánek, M., C. E. Sasser, and J. G. Gosselink. 1987. Modeling of vegetation dynamics in the Mississippi River deltaic plain. Vegetatio 69:133–40.
Repaske, W. A. 1981. Effects of heat water effluents on the swamp forest at the Savannah River Plant, South Carolina. M.S. Thesis. University of Georgia, Athens, GA, USA.
Rogers, V. 1990. Soil survey of Savannah River Plant area, parts of Aiken, Barnwell, and Allendale Countries, South Carolina. United States Department of Agriculture, Washington, DC, USA.
Schneider, R. L., N. E. Martin, and R. R. Sharitz. 1989. Impact of dam operations on hydrology and associated floodplain forests of Southeastern rivers. p. 1113–22.In R. R. Sharitz and J. W. Gibbons (eds.) Freshwater Wetlands and Wildlife. U.S. Department of Energy Office of Scientific and Technical Information, Oak Ridge, TN, USA. DOE Symposium Ser. No. 61 (CONF-8603101).
Schneider, R. L. and R. R. Sharitz. 1986. Seed bank cynamics in a southeastern riverine swamp. American Journal of Botany 73:1022–30.
Schneider, R. L. and R. R. Sharitz. 1988. Hydrochory and regeneration in a bald cypress-water tupelo swamp forest. Ecology 69:1055–63.
Scott, M. L., R. R. Sharitz, and L. C. Lee. 1985. Disturbance in a cypress-tupelo wetland: an interaction between thermal loading and hydrology. Wetlands 5:53–68.
Sharitz, R. R., J. E. Irwin, and E. J. Christy. 1974. Vegetation of swamps receiving reactor effluents. Oikos 25:7–13.
Sharitz, R. R., R. L. Schneider, and L. C. Lee. 1990. Composition and regeneration of a disturbed river floodplain forest in South Carolina. p. 195–218.In J. G. Gosselink, L. C. Lee, and T. A. Muir (eds.) Ecological Processes and Cumulative Impacts: Illustrated by Bottomland Hardwood Wetland Ecosystems. Lewis Publishers, Inc, Chelsea, MI, USA.
Shines, J. E. and E. L. Doak. 1982. A study of thermal plumes at the Savannah River Plant, Aiken, South Carolina. EG&G. Las Vegas, NV, USA. EGG-1183-1827.
Streng, D. R., J. S. Glitzenstein, and P. A. Harcombe. 1989. Woody seedling dynamics in an East Texas floodplain forest. Ecological Monographs 59:177–204.
U.S. Department of Energy. 1991. Record of decision: continued operation of K, L, and P reactors, Savannah River Site, Aiken, SC. Federal Register 56(28):5584–87.
Wike, L. D., R. W. Shipley, J. A. Bowers, A. L. Bryan, C. L. Cummins, B. R. del Carmen, G. P. Friday, J. E. Irwin, H. E. Mackey, Jr., J. J. Mayer, E. A. Nelson, M. H. Paller, V. A. Rogers, W. L. Specht, and E. W. Wilde. 1994. SRS Ecology: Environmental Information Document. Chapter 5: SRS Savannah River Swamp, and Chapter 6: Pen Branch Wetland Changes, 1987–1992. Westinghouse Savannah River Company, Savannah River Site, Aiken, SC, USA.
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De Steven, D., Sharitz, R.R. Differential recovery of a deepwater swamp forest across a gradient of disturbance intensity. Wetlands 17, 476–484 (1997). https://doi.org/10.1007/BF03161513
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DOI: https://doi.org/10.1007/BF03161513