Southern Research Station Headquarters - Asheville, NC
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Issue 13
The Harrison
Longleaf genetics come of age
Located in the lower Coastal Plain in southeastern Mississippi, the Harrison Experimental Forest (Harrison) was established on the Desoto National Forest in 1934. By that time, vast stands of southern pines, mostly longleaf pine, had been cut from the estimated 31 million acres that made up the southern Coastal Plain forest. Located just north of Gulfport, MS, the 4,111-acre experimental forest has provided critical information about the genetics of longleaf pine for over half a century.
In 1955, the SRS Southern Institute of Forest Genetics (SIFG) was located on the Harrison, with research studies focused on forest genetics and pathology. SIFG research on the genetics of growth, form, and pest resistance of forest trees has guided tree improvement programs across the South. Studies on longleaf pine were prominent from the very beginning. Early selection studies by longleaf pine research pioneer Philip Wakeley were followed by a multigenerational longleaf pine breeding program based on his selections. Geographic seed source research and resin yield studies in relation to southern pine beetle resistance followed, involving emeritus scientists Ron Schmidtling and Jim Roberds, respectively.
Molecular biology and genetic mapping techniques have ushered in a whole new era of research on the Harrison. The location of SIFG on the experimental forest provides the unique capacity to combine these new tools with experimental plots and data that span decades to address issues that affect longleaf pine growth.
The fungus Scirrhia acicola, better known as brown spot needle blight, attacks 28 species of pines, but it inflicts the most damage on the longleaf pine, killing seedlings in the earliest stage of their development. Through work on the Harrison, SIFG researchers led by project leader Dana Nelson combine the latest in genetic mapping tools with classic genetic breeding to give longleaf seedlings a better shot at surviving the blight.
SIFG research geneticist Tom Kubisiak contributes expertise in genetic mapping, using statistical analysis to locate sites on the pine genome that affect traits like early height growth and blight resistance. Nurul Faridi, SIFG research cytogeneticist located at College Station, TX, uses fluorescent in situ hybridization, or FISH—a molecular biology tool that allows scientists to mark specific pieces of genetic code with fluorescent tags—to locate genes in the longleaf pine genome that might affect resistance to blight.
Hurricanes and Climate Change
Experimental plots were installed on the Harrison in 1961 to test the responses of three different pine species—longleaf, loblolly, and slash—to fertilization. Along with a surprisingly strong response to onetime fertilization in all three species, the experiments showed that after about 25 years longleaf pine catches up with loblolly pine. In 1999, at mean age 39, mean timber volume per acre was actually greatest in the longleaf pine plots.
When Hurricane Katrina hit the Harrison in 2005, the experimental plots took a beating. In 2006, researchers measured the damage, comparing their data to 1999 records. They found that the damage from Katrina was over 30 percent greater in the loblolly pine plots than in the longleaf pine and slash pine plots. Findings from the damaged plots have provided important information for land managers trying to decide how to replant hurricane-damaged areas along the Gulf Coast while taking into account the increased storm activity predicted under global climate change.
During the same period, SRS research physiologist Kurt Johnsen and his Southern Institute of Forest Ecosystems Biology team based in North Carolina started studying the Harrison plots as part of their research on carbon sequestration and tree species adaptation to climate change. In spring 2008, Johnsen, research biological scientist Chris Maier, and plant physiologist John Butnor drove out to the Harrison to map tree roots and measure soil respiration for research on the differences in carbon storage among the three pine species.
Johnsen and his team also started designing and preparing a companion study in collaboration with SIFG researchers. (All are part of the larger SRS Forest Genetics and Ecosystem Biology unit led by Nelson.) Seedlings for the new study will be grown from seeds harvested from the 1961 study and from genetically improved seeds. Various fertilization and prescribed fire treatments will be applied, and instruments to measure carbon efflux installed on the site so that scientists can study the interplay among genetics, silviculture treatments, and carbon sequestration. Together, the old and new studies will provide land managers the science-based knowledge they will need to manage and adapt Coastal Plain forests as the climate changes over the next century.
Collaborators:
Auburn University, Clemson University, University of Florida, Cornell University, Oklahoma State University, Mississippi State University, Louisiana State University, International Paper Company, North Carolina State University, Texas A&M University, University of Georgia
For more information:
Dana Nelson at 228–832–2742, x201 or dananelson@fs.fed.us
