Planting longleaf pine is widely promoted as a means of restoring and connecting the fragmented forest of the southeastern coastal plain, yet planted stands may be vulnerable to lacerating winds from tornados and tropical cyclones. Longleaf pine is among the most wind resistant southern trees, yet little is known about wind risk in young stands. We hypothesized that the likelihood of damage would be greater for trees that were tall, had low taper (diameter-to-height ratio), and few neighboring trees. We measured structure in 80 stands in Florida and southwest Georgia that were in the path of Hurricane Michael, which made landfall in October 2018 storm as a Class 4 storm. Stands were up to 30 years old. Covariates measured included depth to a soil’s B horizon; stand density; and management actions such as thinning. Covariates estimated included maximum wind gust extrapolated with a landscape hurricane model. Survival was estimated as proportion of intact trees per ha, based on 0.04 ha plots.
Results/Conclusions
Estimated maximum wind gusts varied from 30 to 80 m s-1, and proportion of intact stems varied from 0% to 100%. A multivariate linear modeled captured 63% of variance. Survival was strongly correlated with estimated peak wind speed; there was a 17% decrease in survival with each 10 m s-1 increase in estimated peak wind speed. Other variables such as height, taper, and depth to B horizon did not explain a significant amount of survival. In contrast, there was a protective effect of stand density, with significantly increased survival at higher stand density. Our results suggest that even for the highly wind-firm longleaf pine there is unavoidable risk of loss of significant portions of stands due to hurricane winds, and that the risk increases with proximity to the coast. The positive effect of stand density on survival – an Allee effect – suggests a role for carefully calibrated thinning strategies as stands are managed over time. For example, thinning of large stands may be staggered in time to diminish hurricane risk. Innovative, variable-density thinning approaches in which single trees are interspersed with blocks of un-thinned trees may also help to mitigate risk. Ultimately, better understanding of wind-throw risk will increase knowledge of costs and benefits of longleaf pine ecosystem restoration.