Forest ThreatNet

Genetic diversity is essential because it provides a basis for adaptation and resilience to environmental stress and change. Researchers from the USDA Forest Service and North Carolina State University assessed which native tree species may be at risk of losing genetic variation because of inadequate regeneration by combining data from a national forest inventory with genetic seed transfer zones. The results are useful both for sustainability reporting and conservation decision-making.

In its periodic forest sustainability assessments, the USDA Forest Service monitors the number and geographic distribution of forest-associated species at risk of losing genetic variation. This has been a challenge because of the large number of trees native to the United States and because of the difficulty of measuring the genetic diversity of species found across wide areas. To address this challenge, researchers from the Southern Research Station and North Carolina State University determined which tree species may not have adequate regeneration to maintain existing levels of genetic variation. They combined information from two large datasets: (1) tree occurrence data from the national Forest Inventory and Analysis (FIA) plot network and (2) provisional seed zones defined in terms of climate and soils. They 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. They found that 46 of 280 U.S. forest tree species (16.4%) may be at risk. The Southeast and California encompassed the most at-risk species. These findings can help focus conservation and management activities to prevent the loss of adaptive genetic variation within tree species.