9The longleaf pine (Pinus palustris) ecosystem of the North American Coastal Plain (NACP) is a global 10 biodiversity hotspot. Disturbances such as tropical storms play an integral role in ecosystem maintenance in 11 these systems. However, altered disturbance regimes as a result of climate change may be outside the historical 12 threshold of tolerance. Hurricane Michael impacted the Florida panhandle as a Category 5 storm on October 13 10th, 2018. In this study, we estimate the extent of Florida longleaf habitat that was directly impacted by 14 Hurricane Michael. We then quantify the impact of Hurricane Michael on tree density and size structure using 15 a Before-After study design at four sites (two wet flatwood and two upland pine communities). Finally, we 16 identify the most common type of tree damage at each site and community type. We found that 39% of the 17 total remaining extent of longleaf pine habitat was affected by the storm in Florida alone. Tree mortality 18 ranged from 1.3% at the site furthest from the storm center to 88.7% at the site closest. Most of this mortality 19 was in mature sized trees (92% mortality), upon which much of the biodiversity in this habitat depends. As the 20 frequency and intensity of extreme events increases, management plans that mitigate for climate change 21 impacts need to account for large-scale stochastic mortality events in order to effectively preserve critical 22 habitats. 26 27 28 2 30 1. Introduction
31Disturbance plays an integral role in maintaining ecosystem structure and functioning (1,2). However, many 32 ecological disturbances are expected to change as the climate changes (3), altering the frequency, intensity, duration, 33 and timing of events (4). Shifting disturbance regimes due to climate change pose a threat to the conservation of 34 biodiversity as species experience conditions outside their historical norms (5-7). In forest and savanna ecosystems,
35disturbances can include fire, hurricanes, extreme wind events, insect outbreaks, exotic plant invasions, or drought, 36 among many others (1).
37Longleaf pine (Pinus palustris Mill.) forests and savannas provide critical habitat for numerous endangered 38 species of animals such as the red-cockaded woodpecker (Picoides borealis), gopher tortoise (Gopherus 39 polyphemus), and the indigo snake (Drymarchon corais couperi) as well as many endangered plants such as the 40 American chaffseed (Schwalbea americana), Florida skullcap (Scutellaria floridana), and Harper's beauty 41 (Harperocallis flava) (8)(9)(10)(11). About 30% of all plant species associated with longleaf pine habitat are endemic to the 42 region (12). Yet, the range of longleaf pine has been reduced to <3% of its historical extent (13). Florida, and more 43 specifically the Florida Panhandle, is one of the most important strongholds of endangered longleaf pine habitat 44 (14,15) containing 51% and 31%, respectively, of all the remaining longleaf pine ecosystem (16,17).
45Longleaf pine habitats in the Panhandle of Florida are located within...