Baldcypress-tupelogum swamp forests 

 are characterized by poorly drained 

 soils and lengthy inundations. Taxodium 

 distichum (baldcypress) and Nyssa 

 aquatica (tupelogum) are the dominant 

 trees. On very poorly drained sites, 

 baldcypress tends to dominate. On 

 slightly raised drier sites within the 

 swamp, tupelogum increases in abundance, 

 and some black willow (Salix nigra ) , 

 pumpkin ash ( Fraxinus caroliniana ) , and 

 Drummond red maple ( Acer rub rum var. 

 drummondii ) occupy part of the canopy. 



The presence of standing water al- 

 lows the growth of floating vegetation. 

 Duckweed ( Lemna minor and Spirodela 

 polyrrhiza ) , Riccia , and American frog- 

 bit ( Limnobium spongia ) are common 

 (Conner and Day 1976). Herbs such as 

 amaryllises, ferns, pennyworts, and 

 grasses are found growing on rotting 

 stumps and logs and other dry substrates 

 (Conner and Day 1976). 



Consumer species in the swamp are 

 numerous and varied. Of the many insect 

 species present, the forest tent cater- 

 pillar ( Malacosoma disstria) is one of 

 the more obvious; it often defoliates 

 large areas of tupelogum trees in the 

 MDPR and apparently speeds the passage 

 of nutrients from the canopy to the 

 forest floor in the process (Pollock and 

 Bahr, in preparation). Omnipresent mos- 

 quito larvae are eaten by fish, and 

 adult mosquitoes by birds, spiders, 

 dragonflies, and water beetles. Adult 

 mosquitoes and the microparasites they 

 host are regulators of vertebrate popu- 

 lations. Important decomposers in the 

 swamp include fungi, microbiota, and 

 termites. Crawfish ( Procambarus clar - 

 kii ) , harvested commercially from the 

 swamp, are an important food item for 

 many higher order consumers, and craw- 

 fish biomass exceeds that of all other 

 invertebrates that live on the swamp 

 forest floor (Sklar and Conner 1979). 

 Large carnivores include snakes, alli- 

 gators, raptorial birds (owls and 

 hawks), wading birds, and mammals. The 

 swamp hosts a wide variety of bird 

 species, mainly on a seasonal basis. 

 Amphibians and reptiles are represented 

 by 18 and 32 species, respectively 

 (Gosselink et al. 1979). 



The information on swamp function 

 presented below is based on measurements 

 from the Lac des Allemands swamp in the 

 Barataria hydrologic unit. This river- 

 ine swamp is generally characteristic of 

 swamps in the MDPR, and it has been the 

 site of numerous biological and hydro- 

 logical studies. 



Unaltered portions of the des Alle- 

 mands swamp flood for about 11 months of 

 the year. Spring high water occurs in 

 April and May, followed by a dry summer 

 period in July and August, when the 

 swamp's surface water drains off com- 

 pletely. Inundation generally resumes 

 in late August or September with de- 

 creasing evapotranspiration and in- 

 creasing rainfall. 



Water flows into the des Allemands 

 swamp from surrounding wooded natural 

 levee ridge lands, agricultural fields, 

 and urban areas. Little standing water 

 on the swamp floor infiltrates the soil, 

 which is clayey and saturated. Most 

 water evaporates, or runs off to down- 

 stream habitats, which are primarily 

 swamp bayous and freshwater lakes. 



During the period when the soil is 

 flooded, surface water flows control the 

 transport of nitrogen, phosphorus, total 

 organic matter (TOM) , and sediment in 

 and out of the swamp. If nutrients 

 entering the surface waters are not 

 taken up by aquatic plants (primarily 

 duckweed) , they settle out and contri- 

 bute to soil fertility. Some nutrients 

 that wash into the swamp via water from 

 agricultural fields are removed. Nitro- 

 gen is put into the atmosphere through 

 denitrification, and some phosphorus is 

 buried beneath sediments. Plant nutri- 

 ent requirements are small relative to 

 the large total quantities of nutrients 

 present (Kemp and Day 1981). Rainfall 

 contributes a small portion of nutrient 

 input to the swamp surface water. 



Total primary production by swamp 

 plants was estimated at 2,038 g dry or- 

 ganic matter/m 2 /yr (18,186 lb/ac/yr) 

 (Conner and Day 1976.) Calculations of 

 primary production, along with a de- 

 tailed matter and energy flow diagram 

 and input-output table, are included in 

 the companion technical report. 



50 



