Regeneration as an indicator of tree genetic degradation risk

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.