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Compass issue 13
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Compass is a quarterly publication of the USDA Forest Service's Southern Research Station (SRS). As part of the Nation's largest forestry research organization -- USDA Forest Service Research and Development -- SRS serves 13 Southern States and beyond. The Station's 130 scienists work in more than 20 units located across the region at Federal laboratories, universites, and experimental forests.



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Issue 13

Longleaf Pine Seed Problems

Do the Math

In 1963, from his work on the Escambia, SRS researcher Bill Boyer developed the guide to longleaf pine seed dispersal that became one of the foundations for the natural regeneration of the species. Natural regeneration—literally allowing seedlings to sprout wherever seeds fall—seems the intuitive choice for replanting longleaf pine, but compared to other pines, longleaf ranks very low when it comes to producing seed. It takes 3 years for seed to develop after the tree flowers. Seed crops adequate enough to regenerate a stand may come once every 5 or 7 years.

In 1997, after more than 40 years of working with longleaf, Boyer wrote: “Longleaf cone crops are highly variable from year-to-year, and also from place to place. Given a receptive seedbed, 360 cones per acre are needed, on average, just to obtain the first seedling. A minimum of 750 cones per acre is usually needed for acceptable regeneration. Given 25 residual seed trees per acre in a shelterwood stand, it takes an average of 30 cones per tree to reach this minimum. Cone crops of this size or larger are uncommon throughout much of the longleaf region, and are erratic in their occurrence …. In most years, cone crops will average less than 10 cones per mature seed tree.” For marginal stands, this means little or no regeneration.

 

(More...)

In 1966, Boyer helped set up a regionwide study that continues to monitor flowering and count cones and seeds from mature longleaf pine trees on sites ranging from North Carolina to Louisiana, as well as on the Escambia. Analyzing data from the extensive database developed for this project, scientists found something intriguing: over the last two decades (1986 to 2008), cone production on the Escambia has more than doubled when compared to that of the preceding 20 years. Researchers are not yet sure why, whether it has to do with tree age or changes in climate.

 

 





Compared to other pines, longleaf ranks very low when it comes to producing seed. (Forest Service photo)
Compared to other pines, longleaf ranks very low when it comes to producing seed. (Forest Service photo)