The Mississippi Sound and the Gulf of Mexico are separated by a chain of barrier islands. The easternmost of these, Dauphin Island, lies at the mouth of Mobile Bay in Mobile County, Alabama. It is situated between Fort Morgan to the east and Petit Bois Island to the west. The island is approximately six miles south of the mainland coast. The elevation of the island ranges from sea level to approximately 50 feet on the back dunes of the south-facing beach.
In the 1960's I undertook a floristic survey, photographing many of the plants occurring on the island at that time---this website is devoted to those photographs, showing habitats as well as individual plants and flower close-ups.
The beaches are of white sand and are gently sloping. Plants there include Ipomoea stolonifera, Ipomoea sagittata, Hydrocotyle bonariensis, Heterotheca subaxillaris, Croton punctatus, Paronychia erecta, and others.
Inland from the beach is the dune region, with taller plants such as Uniola paniculata, Iva frutescens, Iva imbricata, Andropogon maritimus, Cynodon dactylon, Spartina patens, and several species of Panicum. Upon the higher, more inland and older dunes adjacent to the pine forest grow shrubs such as Solidago pauciflosculosa and Ceratiola ericoides. Between these grow herbs such as Cnidoscolus stimulosus, Opuntia compressa, Helianthemum arenicola and Polygonella gracilis.
The leeward slopes of the dunes are more mesic and support such woody species as Quercus myrtifolia, Quercus virginiana var. maritima, Ilex vomitoria, Sassafras albidum, Magnolia grandiflora and Asimina parviflora.
The high dunes toward the east end of the island are relatively stable and support a fairly dense vegetation. Toward the western end, plant cover is sparse and sand encroachment upon the forest appears to be rapid. Adjacent to the north-facing beach bordering the sound is a narrow, low dune area. Common species are grasses such as Spartina patens, Distichlis spicata, Panicum repens, and Andropogon maritimus.
FOREST
The forested portion occupies a band on the eastern end of the island and is dominated by slash pine, Pinus elliottii. This canopy of pines attains a height which approximates that of the dunes. Within the drier southeast portion of the forest, common understory plants include Quercus virginiana, Serenoa repens, Conradina canescens and several species of Vaccinium. Common herbs include Eupatorium rotundifolium, Solidago microcephala, Vernonia angustifolia, Balduina uniflora, Helianthus radula, and several species of Polygala and Rhexia.
There are fresh water swamps in depressions within the pine forest. The dominant canopy species is water gum, Nyssa sylvatica var. biflora. At the periphery of these swamps are found shrubs such as Cephalanthus occidentalis and Sapium sebiferum as well as herbs such as Carex glaucescens, Saururus cernuus, Utricularia inflata and several species of Panicum, Osmunda and Woodwardia.
The western and northern portions of the forest are more mesic. In some of the areas the pine canopy is quite open and sweet gum, Liquidambar styraciflua, becomes the dominant understory tree. Common shrubs are Rhus copallina, Myrica cerifera and several species of Ilex. Less common species include Magnolia virginiana and Persea palustris.
MARSH
Along the narrow west end of the island, between the north and south facing beaches is the marsh vegetation, predominantly grasses, sedges, and rushes. There is a marked zonation of these marshes, influenced by elevation, tidal submergence and salinity of the soil solution. The lower zone has graminoids such as Juncus roemerianus, Sparitna alterniflora, and several species of Fimbristylis, and Scirpus. In slightly higher areas one finds Salicornia bigelovii, Suaeda linearis, Scirpus americanus, Cyperus lecontei, Sabatia stellaris, Cynanchum palustre, and Borrichia frutescens.
DISTURBED AREAS
The greatest number and diversity of species is found in the disturbed areas such as mowed roadsides and drainage ditches. In the latter one finds herbs such as Callitriche heterophylla, Centella asiatica, Rhynchospora corniculata; Sagittaria graminea, Polygonum punctatum and several species of Hydrocotyle, Ludwigia and Proserpinaca. On the moist slopes of these ditches are Bacopa monnieri, Cyperus surinamensis, Dichromena colorata, Drosera leucantha, Tradescantia virginiana, Utricularia subulata and several species of Eleocharis, Hypericum, Juncus and Xyris. On drier sunny roadsides are herbs such as bulbous Allium canadense, spreading Asclepias humistrata, Daucus pusillus, Helenium amarum, and Plantago virginiana. The lawns and other open grassy areas are similar in species composition to the roadside areas. Weedy species there include Portulaca pilosa, Geranium carolanianum, dichondra carolinensis, Cerastium glomeratum Cenchrus echinatus and Poa annua.
