dedicated to residential, commercial, or 

 industrial use. Grand Isle is an impor- 

 tant recreational area as well as the 

 site of activity by the petroleum and 

 sulfur industries. The Mississippi Sound 

 islands are largely a part of the Gulf 

 Islands National Seashore, and the main- 

 land beaches are primarily developed for 

 recreation. 



The greater part of the Chandeleur 

 Islands are within the Breton National 

 Wildlife Refuge (which also includes 

 Breton Islands) . Other islands of the 

 Chandeleur chain (Curlew, Grand Gosier, 

 and North and New Harbor) are owned by 

 the State of Louisiana. 



Although the beach and dune habitat 

 is not large in area, it is an important 

 habitat ecologically and economically. 

 Further study of the ecological rela- 

 tionships and methods for slowing ero- 

 sion of these areas is warranted 

 (Mendelssohn 1982). 



BOTTOMLAND HARDWOODS (3) 



The forested wetlands of the MDPR 

 (Figure 20) contain two types of plant 

 communities: bottomland hardwoods and 

 baldcypress-tupelogum. Bottomland hard- 

 woods (BLH) covered 46,128 ha (113,933 

 acres), or 1.34% of the MDPR in 1978 

 (Table 5). BLH forests occur in areas 

 that are better drained than those in 

 which cypress-tupelo are found. BLH 

 areas typically have moist soil and 

 short annual floodings. 



Most information available on BLH 

 in the MDPR has been collected from a 

 site in the des Allemands area of the 

 Barataria hydrologic unit. This site is 

 presumably fairly representative of BLH 

 habitat throughout the MDPR, and the 

 following description of the des Alle- 

 mands site should generally apply. 



In the upper Barataria basin, the 

 entire swamp forest (baldcypress-tupelo 

 and BLH) is less than 1.5 m in elevation 

 (Conner and Day 1976). Small changes in 

 elevation in the swamp can have major 

 effects on vegetative composition. 



Brown (1972) observed that a 15-cm or 

 6-inch) change in the swamp is as im- 

 portant as a 30-m change in mountainous 

 regions. This sensitivity to elevation 

 stems from the fact that the character 

 of BLH forests (like all wetland habi- 

 tats) is determined by hydrologic condi- 

 tions. Amount of water input, season- 

 ality, and average current speed through 

 the habitat are all important in deter- 

 mining community structure, composition, 

 and chemical cycling (Day et al. 1981). 



BLH sites are flooded each year for 

 several weeks to a few months. During 

 the remainder of the year the water 

 table is near or just below the soil 

 surface (Conner and Day 1982). The des 

 Allemands BLH site has been flooded 

 15-30 cm (6-12 inches) for a period of 2 

 to 3 months during the time of its exam- 

 ination (Conner and Day 1976). 



The BLH plant community is more 

 species-rich than the deep swamp 

 (cypress-tupelo). Conner and Day (1976) 

 reported 23 tree species in the des 

 Allemands BLH swamp, compared with 9 

 species in a nearby cypress-tupelo swamp 

 site. Bell (1974) found that species 

 richness in floodplain forests is in- 

 versely proportional to flooding fre- 

 quency. 



Undisturbed BLH sites also appear 

 to be slightly more productive than un- 

 disturbed cypress-tupelo sites. Produc- 

 tion in the des Allemands BLH community 

 is 1,574 g dry wt/m 2 /yr (14,045 lb/ 

 ac/yr) compared with 1,140 g/m z /yr for a 

 nearby undisturbed baldcypress-tupelogum 

 community (Conner and Day 1976). 



BLH habitat hosts a variety of 

 woody plant species. The red maple ( Acer 

 rub rum var. drummondii ) , is the most 

 abundant tree, but maples at the des 

 Allemands BLH site were generally small 

 (average diameter at breast height was 

 5.8 cm or 2.3 inches). Oak ( Quercus 

 spp.), willow ( salix nigra ) , elm ( Ulmus 

 americana ) , boxelder ( Acer negundo ) , 

 Cottonwood ( Populus spp.), dogwood ( Cor- 

 nus drummondii ) , pe rs immon ( Diospyros 

 virginiana ) , hackberry ( Celtis laevi- 

 gata ) , ash ( Fraxinus spp.), and privet 



43 



