Decadal changes in tree range stability across forests of the eastern U.S.

The monitoring of tree range dynamics has emerged as an important component of adaptive responses of forest management to global change scenarios such as extreme precipitation events and/or invasive species. Comparisons between the locations of adults versus seedlings of individual tree species using contemporary forest inventories is one tool widely used to assess the status of tree ranges in light of these changing conditions. With the consistent remeasurement of standard forest inventory plots across the entire eastern US occurring since the 2000s, the opportunity exists to evaluate the stability of tree ranges of focal species across a decade. Using said inventory, the northern range margins of tree distributions were examined by comparing differences (Holm-Sidak adjusted p-value = 0.2) in the 95th percentile locations of seedlings to adults (i.e., trees) by 0.5 degree longitudinal bands over nearly 10 years and by categories of canopy disturbance (i.e., canopy gap formation) for 20 study species. Our results suggest that range margins are stable for 85% of study species at both time one and at remeasurement regardless of canopy disturbance. For the very few species that had a significant difference in seedlings and adults at their range margins, there was nearly a 0.4 degree difference in latitude with seedlings being farther south irrespective of disturbance. Our findings of tree range stability across forests of the eastern US indicate a general propensity towards range contraction, especially for study species forecasted to lose range and located on disturbed sites, which may present substantial hurdles for adaptive management strategies focused on maintaining and enhancing forest ecosystem resilience in the context of global change and associated rapid climate change.