Summer 2005

CSI--Longleaf Pine!

In Virginia, Verifying the Tree's Original Range

by Tom Eberhardt and Phil Sheridan

Crime scene investigation shows are all the rage on TV these days. To determine the original range of longleaf pine in Virginia, we return to multiple "ecoscenes" to investigate the "remains" of very old southern yellow pine stumps. We use chemical and physical analyses in an effort to determine whether the wood samples collected from the stumps are actually longleaf pine. Jolie Mahfouz, biological technician with the Southern Research Station (SRS) Bark Beetles and Invasive Insects unit in Pineville, LA, adds another level of analysis with her expertise in gas chromatography and mass spectrometry.

Straight growth, coupled with strength and density, make longleaf pine highly desirable for poles, construction lumber, and flooring. Longleaf pine has a wellestablished history in naval stores production, from early turpentine operations to the subsequent processing of residual stumps, especially those from trees harvested in the late 19th and early 20th centuries.

The range for longleaf pine spans from southeastern Virginia to eastern Texas. In Virginia, harvesting practices and changes in land use since colonial settlement have dramatically reduced the presence of longleaf pine. Of the original 1.5 million acres of longleaf forest estimated to exist in Virginia before colonial settlement, only 800 acres remain. Longleaf pine restoration efforts include studies designed to verify its range by determining the species of very old pine stump remnants. Since wood structure cannot be used to differentiate between the southern yellow pines, the objective was to assess whether chemical and physical differences could be used for species identification.

We collected highly weathered fragments from stump remnants located in Caroline, Southampton, and Sussex Counties in eastern Virginia. Wood shavings were obtained using an electric drill to put holes into retrieved stump fragments. Mahfouz then analyzed sample extracts using gas chromatography coupled with mass spectrometry. This technique separates an extract into its components, allowing the collection of mass spectra that, like fingerprints, can be compared to a database for identification. We also used small wood blocks cut from the samples to determine wood densities. The greatest obstacle to the investigation was the lack of well-characterized stump samples for comparison. Only recently has the study of old stumps become important.

We think the stumps we have sampled are longleaf or loblolly pine, based on species identification signatures. Despite their age, the stumps have retained their resinous quality. Examining the gummy wood shavings revealed significant amounts of monoterpenes, the substances found in the oleoresins of conifers used to make solvents and other products. The most abundant monoterpene in both longleaf and loblolly pines is pinene. Turpentine has a minimum pinene content of 40 percent by weight. Distilled from pine oleoresin or pine wood, turpentine can be used as a solvent to thin oil paints and make varnishes.

The stump sample from Sussex County was particularly interesting because it showed an even greater degree of monoterpene oxidation. This could be the result of high temperatures from forest fires. In fact, burn scars on the Sussex County sample indicate the exposure to fires that one would expect in a longleaf pine ecosystem. Since pond pine has a very low concentration of pinene, lower than that found in the stumps, we excluded it from consideration. The tree stumps could not be the remains of slash pines because that species' range does not extend as far north as Virginia.

Finally, consider the evidence of specific gravity, a measure of the amount of wood substance per unit volume, essentially meaning wood density. Specific gravity values for loblolly pine are lower than those for longleaf pine. The specific gravity values for the samples we took were significantly higher than those reported in the literature and reflect the very resinous nature of the samples. These results show that specific gravity, which can be easily measured in the field by determining the size and weight of a specimen, could be an alternative to extractions requiring solvents and laboratory facilities.

Since longleaf, not loblolly, pine has an established history of use in naval stores production, highly resinous samples would seemingly have a greater likelihood of being longleaf pine. The high specifi c gravity values of the stumps also point toward longleaf being the trees that towered over the still resinous stumps. New leads on the case are also being pursued to provide the best possible evidence to reach a proper verdict on the historical range of longleaf pine. These fi ndings will be used to guide further restoration efforts.

For more information:

Tom Eberhardt at 318-473-7274 or
teberhardt@fs.fed.us

Phil Sheridan at 804-633-4336 or
meadowview@pitcherplant.org

---

Tom Eberhardt is a research scientist with the SRS Utilization of Southern Forest Resources unit in Pineville, LA. Phil Sheridan is director of Meadowview Biological Research Station in Woodford, VA

Back to the top