Understanding the structure and function of longleaf pine savanna affected by Hurricane Michael

Title: Understanding the structure and function of longleaf pine savanna affected by Hurricane Michael

1. G. R. Kenney ¹, C. L. Staudhammer ¹, S. Brantley ², S. Bigelow ², S. Wiesner ^1,3, G. Starr ¹

February 20^th, 2020

¹: Department of Biological Sciences, The University of Alabama

²: The Jones Center at Ichauway, Newton GA

³: Biological Systems Engineering, University of Wisconsin, Madison

Background/Question/Methods

On October 10^th, 2018, Hurricane Michael made landfall in Florida with wind speeds up to 160 mph (~257 km/h). The storm created a destructive path across the southeastern US, directly impacting the longleaf pine savanna at the Jones Center at Ichauway in southwestern Georgia. The storm caused considerable damage to the canopy through removal of leaves, crown and uprooting. This disturbance caused significant alterations in the system’s structure and function. Using eddy covariance, long-term forest monitoring plots and aerial LiDAR, we analyzed tree damage, changes in ecosystem physiological activity, and subsequent post-storm recovery at two study sites located at ends of an edaphic moisture gradient.

Results/Conclusions

Ground-based surveys showed a 9% and 3% loss in tree density at the mesic and xeric site respectively. Tree basal area at the mesic site decreased by 10%, but the xeric site showed no change in basal area from the storm. Preliminary results comparing net ecosystem exchange to photosynthetically active radiation also showed a reduction in ecosystem maximum photosynthetic capacity (A_max). From 2018 to 2019, A_max at the mesic site decreased by ~50% in the spring and by ~25% in the summer. Meanwhile, A_max at the xeric site decreased by ~25% in the spring and by ~15% in the summer. These results appear to show that while both sites were damaged, they are rapidly recovering. Based on our initial results, the xeric site, which had lower initial basal area, stem density, and stand density, was less damaged by the hurricane than the mesic site. A number of factors may explain this result including shorter tree heights, more deeply rooted trees, or that the ecosystem at the xeric site has developed other adaptations to promote faster disturbance recovery and higher ecological resistance due to lower soil water availability at the site.