Southern Research Station Headquarters - Asheville, NC
![[Images] Five photos of different landscape](/images/imstr1.jpg "[Images] Five photos of different landscape")
Issue 13
The Delta
From bottomland hardwood restoration to food for the “lord god” bird
This 2,600-acre bottomland forest is owned and managed by Mississippi State University (MSU). The SRS Center for Bottomland Hardwoods Research conducts research there under a long-term cooperative agreement. Located in Washington County, the site was established in 1945 by the Forest Service as an experimental forest through a cooperative agreement with the State of Mississippi. Until the 1970s, the Delta Experimental Forest (Delta) was a working forest; timber receipts paid for a crew of technicians to establish and maintain research studies conducted by Center scientists.
Research during the first 30 years involved thinning studies, developing methods for growing quality southern hardwoods, evaluating results of efforts to improve eastern cottonwood clones, and studying the progression of heartrot diseases and the life cycles and impacts of insect borers. Later studies included determining the causes of oak decline and investigating red oak-sweetgum stand dynamics.
These studies provided much of what is now known about growing different tree species in the poorly drained but fertile soils deposited by the Mississippi River. In addition, several eastern cottonwood clones selected during the 1960s and 1970s by SRS geneticists and tested in the Delta are still used by forest industry throughout the South, by government agencies, and in many foreign countries around the world.
The 1970s brought changes in State priorities that resulted in a decline in both forest operations and new studies on the Delta. By the mid-1990s, heartrot had degraded many of the older trees on the site, and ice storms had damaged the crowns of most canopy trees. Most of the Delta forest was cut in the late 1990s to regenerate degraded forest stands. Oak seedlings were planted to supplement natural oak regeneration.
A Multifaceted Resource
In the last decade, the Delta has become home for a new round of experiments that combine the expertise of SRS scientists in the bottomland hardwoods unit on subjects ranging from wood-destroying insects and fungi to food for ivorybilled woodpeckers.
Research entomologist Nathan Schiff and research plant pathologist Dan Wilson have joined forces to better understand the symbiotic interaction between woodwasps and wood decay fungi. Like other woodboring insects, woodwasps are unable to break down cellulose themselves. The insects carry wood decay fungi in special glands; when they lay their eggs under tree bark, they also inject the fungi. When the larvae hatch, they feed off wood rotted by the fungi, boring further in until they emerge 1 to 3 years later. Schiff and Wilson conduct studies on the Delta to identify the fungus species used by woodwasps, measure damage to trees and wood, and explore novel ways to control the wasps and fungi. Woodwasps are of particular concern because their larvae are often transported in lumber to areas where they become nonnative invasive pests, wreaking havoc on native tree species.
The Delta also hosts a site for the study set up by Schiff and wildlife biologist Paul Hamel in 2006 to look at food availability for the ivory-billed woodpeckers rumored to still inhabit the Big Woods areas of Arkansas and Mississippi. Previous researchers had concluded that the disappearance of the “lord god” bird might be linked to declines in the insects the species preferred. Hamel started his investigations with a list of insects James Tanner had identified in the 1940s by looking at stomach contents and nest leavings of the few ivory-billed woodpeckers remaining. When Schiff looked at Hamel’s list, he immediately noticed that all the insects on it were borers. These insects would not have been available to the birds by just stripping the bark; the woodpeckers may have relied on the periodic emergences of adults from injured trees for their meals.
Hamel and Schiff started a study that involves subjecting trees from species that had been identified as primary ivory-billed woodpecker forage trees to four different levels of wounding, allowing insects a growing season to lay eggs, then using isolation chambers to measure the numbers of emerging insects in relation to the level of wounding. The study, a unique ecological assessment of the types and numbers of insects infesting dead and dying trees, will also yield broader information about insect predation and tree condition useful to forest managers.
In the Future, Wood for Energy
A future project brings research at the Delta full circle, back to the question of how to most efficiently grow hardwoods on the more difficult soils of the region. In cooperation with MSU, SRS researchers are planning to establish a bioenergy plantation study on the experimental forest as early as 2009. Experimental plots will be set up to test the potential of fastgrowing hardwood tree species that can survive the area’s heavy clays— such as sycamore, black willow, and red maple—as alternative sources of energy. The study will be one of the first to test red maple as a possible bioenergy source.
To read more about SRS bottomland hardwoods science, see Issue 6 of Compass online at www.srs.fs.fed.us/ compass/issue6/.
