Impoundment and Baldcypress Swamp Management

Open-File Report 2006-1270

U.S. Department of the Interior

U.S. Geological Survey
Impoundment and Baldcypress Swamp Management 

By Beth A. Middleton 

Open-File Report 2006–1270 

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

P. Patrick Leahy, Acting Director 

U.S. Geological Survey, Reston, Virginia 2006 

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Suggested citation: 

Middleton, B.A., 2006, Impoundment and baldcypress swamp management: U.S. Geological 

Survey Open-File Report 2006-1270, 4 p. 

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government. 
Impoundment and Baldcypress Swamp Management 

By Beth A. Middleton1

Baldcypress swamps (Taxodium distichum) are impounded for many reasons, but this 

practice results in the demise of the swamp. The permanent impoundment of baldcypress 

swamps first lowers primary production and eventually results in death of the trees (Fig. 1; 

Penfound, 1949; Eggler and Moore, 1961; Harms and others, 1980; Conner and Day, 1988, 

1992; Heitmeyer and others, 1989; Loftus, 1994; Osment-DeLoach and Moore, 1996). 

Individuals of most species die if they are flooded continuously above the root collar for 1 to 6 

years (Yeager, 1949). The most likely cause of death and low production in impounded 

conditions is the low available oxygen levels in the tree roots, where the carbohydrate reserves 

are stored (Harms and others, 1980). Trees begin to show decline when the major growth 

regions of the trees are near the trunk and not near the branch tips (Klimas, 1987). Managers 

should avoid impounding baldcypress swamps for long periods of time because of the 

relationship of tree death to long-term flooding. 

Figure 1. The detrimental effects of permanent impoundment are evident in this swamp, known locally as Henderson 

Swamp, in the Atchafalaya Basin Floodway of southern Louisiana. 

 

1

 U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Boulevard, Lafayette, LA 70506 
 Another reason that managers should avoid the permanent flooding of these forests is that 

production levels are lower in impounded situations than they are in natural swamps with flood 

pulsing (Broadfoot and Williston, 1973; Conner and others, 1981; Mitsch and others, 1991; 

Conner and Day, 1992; Megonigal and others, 1997; Conner and Buford, 1998; Watt and 

Golladay, 1999; Middleton and McKee, 2005). As primary production declines, the amount of 

material available to wildlife species also becomes lower, and a decline in the fishery or wildlife 

population may be detected about 10 years after impoundment (Young and Crew, 1982). During 

a study of impoundment in Illinois, production was reduced from 1992 to 1998 in the 

permanently flooded parts of Buttonland Swamp (a National Natural Landmark) by about onehalf, although it is not known what the minimum level of production is before trees begin to die 

(Middleton and McKee, 2005). The regeneration of trees was limited to the margins of the 

swamp because trees can only germinate and establish in drawn down conditions (Middleton 

1999, 2000). 

Wildlife production is also reduced by swamp impoundment. For example, a dam was 

constructed to improve sport fishing in Dead Lake along the Chipola River in Florida. Fishing 

increased for a time after the construction of the impoundment, but then fish populations began 

to decrease after 10 years (Young and Crew, 1982). Consequently, the dam was removed and 

the fishing and water quality improved (Hill and Hardin, 1993). 

From a management perspective, any impoundment developed for for fisheries or 

wildlife purposes needs a drawdown for periods of time during the summer growing season. In 

cases where drawdown is reestablished after 1 year (but not more than 5 years), species such as 

baldcypress trees recover rapidly (Duever and McCollom, 1986). Tree regeneration of 

baldcypress also may occur (Keeland and Conner, 1999) in the presence of a seed bank 

(Middleton, 2003). The effects of impoundment seem particularly severe in the South 

(Middleton and McKee, 2005), so managers should take care to include at least a short period of 

drawdown during the summer growing season, especially in southern swamps. Managers should 

create impoundments in baldcypress swamps judiciously and recognize that swamps can not 

tolerate permanent inundation. 

References Cited 

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Forestry, v. 71, p. 584 - 587. 

Conner, W.H., Gosselink, J.G., and Parrondo, R.T., 1981, Comparison of the vegetation of three 

Louisiana swamp sites with different flooding regimes: American Journal of Botany, v. 

68, p. 320 - 331. 

Conner, W.H., and Day, J.W., Jr., 1989, Response of coastal wetland forest to human and natural 

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Conner, W.H., and Day, J.W., Jr., 1992, Water level variability and litterfall productivity of 

forested freshwater wetlands in Louisiana: American Midland Naturalist, v. 128, p. 237 - 

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Conner, W.H., and Buford, M.A., 1998, Southern deepwater swamps, in Messina, M.G., and 

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Eggler, W.A., and Moore, W.C., 1961, The vegetation of Lake Chicot, Louisiana, after eighteen 

years of impoundment: Southwestern Naturalist, v. 6, p. 175 - 183. 

Harms, W.R., Schreuder, H.T., Hook, D.D., Brown, C.L., and Shropshire, F.W., 1990. The 

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370-384. 

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farming: Journal of Applied Ecology, v. 40, p. 1025-1034. 

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Middleton, B.A., 2003, Soil seed banks and the potential restoration of forested wetlands after 

farming: Journal of Applied Ecology, v. 40, p. 1025 - 1034. 

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production to examine physiological controls on biotic boundaries and potential 

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