Global biodiversity hotspots (GBHs) are increasingly vulnerable to human stressors such as anthropogenic climate change, which will alter the ecology of these habitats, even where protected. the longleaf pine (Pinus palustris) ecosystem (Lpe) of the north American coastal plain is a GBH where disturbances are integral for ecosystem maintenance. However, stronger storms due to climate change may be outside their historical norm. in this study, we estimate the extent of florida Lpe that was directly affected by Hurricane Michael in 2018, an unprecedented Category 5 storm. We then leveraged a unique data set in a Before-After study of four sites within this region. We used variable-area transects and generalized linear mixed-effects models to estimate tree densities and logistic regression to estimate mortality by size class. We found at least 28% of the global total remaining extent of LPE was affected in Florida alone. Mortality was highest in medium sized trees (30-45 cm dbh) and ranged from 4.6-15.4% at sites further from the storm center, but increased to 87.8% near the storm center. As the frequency and intensity of extreme events increases, management plans to mitigate climate change need to account for large-scale stochastic mortality events to preserve critical habitats. Ecological disturbances play an integral role in maintaining ecosystem structure and functioning 1-3. Many ecological disturbances are expected to change with anthropogenic climate change 4 , altering the frequency, intensity, duration, and timing of events 5. Shifting disturbance regimes due to climate change pose a threat to the conservation of biodiversity as species experience conditions outside their historical norms 6-8. In savanna systems, which are characterized by a grassy or herbaceous understory and low tree densities, changing disturbance regimes can trigger demographic transitions altering the density of trees 9-11 , upon which biodiversity depends. Longleaf pine (Pinus palustris Mill.) habitats located within the North American Coastal Plain (NACP) are a global biodiversity hotspot 12,13. These savanna-type systems provide critical habitat for numerous endangered plant and animal species, which are dependent on the presence of sparse but critically important mature longleaf pine trees 14-17. The canopy of longleaf pine habitats is generally monotypic, with a range of tree densities (from <100 to 300+ tree/ha), a largely open canopy, and an herbaceous, grass dominated understory 18-20. Frequent seasonal fire is an integral part of this ecosystem and is the most important process for maintaining ecosystem structure and function 12,21-24. The highest quality stands are dominated by mature trees with a sufficiently frequent fire interval (1-5 year return) to promote regeneration and maintain a highly biodiverse understory-containing as many as >40 species per m 2,17,25-28. Canopy gaps are critical in promoting this biodiverse understory 29 and allow for recruitment and regeneration of longleaf pine 30,31. Gaps allow for greater li...

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...

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The longleaf pine ( Pinus palustris Mill.) and related ecosystem is an icon of the southeastern United States (US). Once covering an estimated 37 million ha from Texas to Florida to Virginia, the near-extirpation of, and subsequent restoration efforts for, the species has been well-documented over the past ca. 100 years. Although longleaf pine is one of the longest-lived tree species in the southeastern US—with documented ages of over 400 years—its use has not been reviewed in the field of dendrochronology. In this paper, we review the utility of longleaf pine tree-ring data within the applications of four primary, topical research areas: climatology and paleoclimate reconstruction, fire history, ecology, and archeology/cultural studies. Further, we highlight knowledge gaps in these topical areas, for which we introduce the Longleaf Tree-Ring Network (LTRN). The overarching purpose of the LTRN is to coalesce partners and data to expand the scientific use of longleaf pine tree-ring data across the southeastern US. As a first example of LTRN analytics, we show that the development of seasonwood chronologies (earlywood width, latewood width, and total width) enhances the utility of longleaf pine tree-ring data, indicating the value of these seasonwood metrics for future studies. We find that at 21 sites distributed across the species’ range, latewood width chronologies outperform both their earlywood and total width counterparts in mean correlation coefficient (RBAR = 0.55, 0.46, 0.52, respectively). Strategic plans for increasing the utility of longleaf pine dendrochronology in the southeastern US include [1] saving remnant material ( e.g., stumps, logs, and building construction timbers) from decay, extraction, and fire consumption to help extend tree-ring records, and [2] developing new chronologies in LTRN spatial gaps to facilitate broad-scale analyses of longleaf pine ecosystems within the context of the topical groups presented.

Questions: Global climate change is predicted to cause widespread shifts in the distribution and composition of forests, particularly in mountain environments where climate exerts strong controls on tree community arrangement. The upslope movement of vegetation has been observed in association with warming temperatures and is especially evident in ecotones-the transition zones between vegetation types. We explored the role of drought and tree mortality on recent changes in high-elevation forests.