Big Hammock: Land of Surprising Contrasts


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Big Hammock: Land of Surprising Contrasts

 

 Public Lands Profile

By Lisa Kruse

Across its 800 acres, Big Hammock Natural Area showcases a fascinating diversity of natural communities of the lower Atlantic Coastal Plain. For this reason, the property near Glennville was secured by the state in 1973 and designated a National Natural Landmark in 1976. Despite past harvest of the native longleaf pine and extensive livestock grazing, significant habitat for rare plant and animal species remains intact.

A hammock is a rise in elevation of an otherwise flat landscape. Big Hammock Natural Area is dominated by an ancient sand dune that rises from the Altamaha River floodplain to 100 feet above sea level. Between 16,000 to 45,000 years ago, water levels of the Altamaha fluctuated more than they do now. The river was composed of many smaller braided channels in a sandy bed. During times of drought, the sands would be exposed

and transported by dominant winds to the northeast side of the river, forming the dunes that remain today. Similar riverine dunes are found throughout Georgia’s Atlantic Coastal Plain on other rivers, such as the Ohoopee and the Ocmulgee, and form a unique part of Georgia’s landscape.

The sand dune at Big Hammock underlies the area's natural diversity. The ancient topography causes extreme environmental conditions that morph the vegetation into dramatic contrasts.

Evergreen hardwood forest dominates the deep sands of the hammock. Natural fire is suppressed by the Altamaha River on the south side, encouraging the persistence of this fire-intolerant forest type. A canopy of live oak (Quercus virginiana) and darlington oak (Q. hemisphaerica) is interspersed with southern magnolia (Magnolia grandiflora).

Beneath the canopy is the largest known population of Georgia plume (Elliottia racemosa), a small tree that puts on a show in June with sprays of beautiful whi

te flowers. Georgia plume (pictured at right) is state-protected, and Georgia is the only place it occurs in the world. Overall, Georgia plume has more than 50 documented occurrences; however, most are in decline and only nine are on protected lands. Seedlings of this species have not been observed in the wild. This may be due to some combination of low population genetic diversity and habitat fragmentation. Clonal reproduction is common.

Also of interest is the most extensive inland population of the shrubby myrtle oak (Quercus myrtifolia) in Georgia. This oak thrives on the hammock, even though it is most typical of sand dunes on the coast. Shrubby myrtle oak shares space with thickets of farkleberry (Vaccinium arboreum), holly (Ilex opaca), devilwood (Osmanthus americanus), red bay (Persea borbonia), horsesugar (Symplocos tinctoria), deerberry (Vaccinium stamineum) and witchha

zel (Hamamelis virginiana). In this closed forest, listen for evidence of songbirds, gray squirrels, deer and armadillo seeking shelter and food.

Xeric longleaf pine/oak sandhill scrub forest is represented on the portions of the hammock that are adjacent to pine flatwoods. Historically, naturally occurring fire would sweep across the extensive flatwoods landscape and from there burn onto Big Hammock, which is favorable for this fire-adapted community. Old-growth longleaf pine forms the sparse canopy; a few of the pines are likely 200 years old. There is a diverse suite of oaks in the shrub layers: Sand post oak (Quercus margarettae), myrtle oak (Q. myrtifolia), turkey oak (Q. laevis) and sand live oak (Q. geminata) are characteristic. Despite the lack of a tall hardwood canopy, Georgia plume is still abundant in the oak scrub community. select

Butterfly on dicerandra mintThe extremely dry conditions of this community cause wide swaths of open sands to persist among the scrub oaks. These microhabitats are essential to maintaining the biodiversity of Big Hammock. Here, herbaceous plants are able to germinate and persist. In autumn, you can catch glimpses of the tansy-colored woody goldenrod flowers (Chrysoma paucifloculosa) –against a backdrop of golden grasses and pink dicerandra mints. The woody goldenrod is a plant typical of the Florida coast.

Several representatives of Georgia’s rare herpetofauna depend on these open patches. The state reptile, the gopher tortoise, burrows here and needs the herbaceous plants for food. The gopher tortoise is a large terrestrial turtle that digs deep shelters in sandy soils. These burrows are used by many other species of wildlife, including the federally threatened eastern indigo snake, which also is found at Big Hammock. Other unusual reptiles documented from Big Hammock that depend on open woodlands are the southern hognose snake, eastern coral snake and the eastern diamondback rattlesnake.

Longleaf harvest and fire suppression have changed the ecology of the hammock. Because longleaf pine depends on fire for regeneration, few young longleaf are found at Big Hammock and the scrub oak is becoming denser. With increasing habitat homogeneity, species that depend on unique microsites will decline. Therefore, the primary focus of

management at Big Hammock is restoring the natural fire ecology. Controlled burns are an essential tool for conserving and enhancing the biodiversity of this site.

For visitors, a nature trail traverses the high hammock and gives an opportunity to experience the diversity of Big Hammock. Walk through gnarled evergreen forests dwarfed by the xeric, or dry, infertile sands. In open areas, old-growth longleaf pine radiates the sun. Descend the hammock into low pine flatwoods, which edge deep cypress-tupelo swamps fed by tributaries of the powerful Altamaha River, less than two miles away. See the fresh spring green of lichens and turkey oak, early-summer blooms of Georgia plume, or the brilliant show of golden grasses and wildflowers in autumn.

Visiting Big Hammock Natural Area is a magical experience.

Getting there

From Glennville: Take Ga. 144 south 10 m

iles. Before reaching the Altamaha River, turn left (east) onto Mack Phillips Road (County Road 441). Continue two miles. The area’s entrance is a gravel driveway on the right.

A kiosk with maps and information is available in the parking lot. Big Hammock Natural Area is open to the public during the day year-round. Camping is not allowed. Foot travel only is allowed within the Natural Area. No motorized vehicles are permitted. Hunting is available; deer season is archery only. See current Georgia DNR hunting regulations for more information about hunting.

Lisa Kruse is a botanist with the Nongame Conservation Section of Georgia DNR’s Wildlife Resources Division.

Natural communities map




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