Bayou-Diversity (22 April 2018) LOWLAND OAKS Oaks were once a major component of Louisiana landscapes. From the highest hills to just one step above cypress brakes, oaks were found in a variety of habitats. Today we’ll consider those that grow in lowlands, such as are found in the parishes east of Monroe to the Mississippi River.
Oaks can be divided into two major groups consisting of red oaks and white oaks. The white oak group usually has leaves with rounded edges and their acorns mature in a single season. Examples of white oaks that grow in lowlands include overcup oak, delta post oak, and swamp chestnut oak, also known as cow oak.
The leaves of red oaks are usually bristle-tipped and their acorns take two years to mature. Lowland species include willow oak, water oak, cherrybark oak and nuttall oak. Willow oak and water oak are commonly called pin oaks in this area, but true pin oaks are not found in Louisiana and generally grow from central Arkansas northward.
In natural settings oak trees are very site specific by species. Lowland oaks are tied closely to land elevation and soil type. For example, beginning in the lowest swamps, one will normally find overcup oaks. As you move upwards in elevation in the swamp, perhaps only a few inches, the oak component will change to willow oak and nuttall oak. These in turn will be replaced by water oak and cherrybark oak as one progresses upwards to the subtle ridges along our bayous and rivers.
Over thousands of years each species has adapted to grow best in specific conditions. Changes in these conditions, either natural or man-made, can prove devastating to a species. A good example can be found on the D'Arbonne National Wildlife Refuge where hundreds of acres of willow oak died several years ago. The die-off was likely tied to the development of the Ouachita River Navigation Project which raised water tables in the affected area. The trees, being unable to adapt to the new wetter site, were severely stressed making them more susceptible to natural diseases and insects.
More than seven million acres of bottomland hardwood forests have been cleared and converted to agriculture in the lower Mississippi River Valley in the last century. Oaks were a primary component of this ecosystem and anchored the rich biodiversity there. Every animal from bears to songbirds was tied directly or indirectly to oaks.
In recent years, government and private conservation agencies began an effort to reforest some of the cleared areas, which proved to be marginal farmland. Since then, several thousand acres in northeast Louisiana have been replanted to oaks and other native species. At the beginning of the program, the science of reestablishing an oak forest was in its infancy, and much work was by trial and error. Although setbacks occurred, successes are now obvious as there are more forested acreage in the northeast Louisiana delta than forty years ago. (photo of overcup oak acorns by USDA)