Skip to main content

Regeneration as an indicator of tree genetic degradation risk

Genetic diversity provides a basis for adaptation and resilience to environmental stress and change. Which native tree species may be at risk of losing genetic variation? Researchers from the USDA Forest Service and North Carolina State University explored this issue by combining national forest inventory data with genetic seed transfer zones.

Longleaf pine, here in the Bankhead National Forest in Alabama, is one of 46 U.S. tree species that may be at risk of losing genetic variation. USDA Forest Service photo by Kevin Potter.

In its periodic sustainability assessments, the USDA Forest Service monitors forest species at risk of losing genetic variation. This has been a challenge because of the large number of trees native to the U.S. and the difficulty of measuring the genetic diversity in species found across wide areas.

To address this challenge, researchers from the Southern Research Station and North Carolina State University identified tree species that may not have adequate regeneration to maintain existing levels of genetic variation. They combined information from two large datasets: provisional seed zones and tree occurrence data from national Forest Inventory and Analysis plots. The team calculated the proportion of small trees (seedlings and saplings) relative to all trees for each species and within seed zone sub-populations, assuming that insufficient regeneration could lead to the loss of genetic variation.

The research suggests that 46 of 280 forest tree species, or 16.4%, are at risk. The Southeast and California had the most at-risk species. The results are useful for sustainability reporting. They can also help focus management activities to conserve adaptive genetic variation within tree species.