Evaluation of the success of rare plant introductions requires analysis of demographic success. We analyze the success of 10 wild and 8 introduced populations of Florida goldenaster (Chrysopsis floridana), a federally endangered forb endemic to west‐central Florida, using demographic and stage‐class data collected from 2017 to 2019. We also collected microhabitat data to characterize factors associated with this species' success. Introductions had higher annual survival rates and fecundity than wild populations; plants in scrub plots had higher survival than roadside plants, although fecundity was higher in roadside plants. Seedling recruitment was only higher for scrub plots in 1 year. Chrysopsis floridana occupancy was better predicted by lower soil nutrients and pH, but introduction success did not consistently vary according to soil conditions. Occupied plots had higher cover of bare sand, lichens, and forbs while unoccupied plots had higher cover of litter, shrub, and subcanopy. The presence of higher litter levels (>60%) appeared to significantly lower survival in 2018. Z‐score site ranking suggested a slight disadvantage for wild populations overall, with the two highest ranked sites both being introductions. Conversely, stage‐class data revealed that both wild and introduced populations had high counts across 3 years of sampling. Most of the healthiest populations had received recent fire, suggesting this may be crucial in providing conditions that promote recruitment and occupancy. More information is needed on aspects of fire and fire surrogates that are likely to affect the demography and distribution of this rare species.
Advances in remote sensing technologies offer new means to monitor habitats of importance on large scales. Florida rosemary scrub is one such threatened habitat, found in patches across the landscape in relatively elevated areas, and is often characterized by shrub‐less areas (gaps) among the dominant shrubs, which provide favorable microhabitats for many endemic and endangered plants and animals. However, gaps are difficult and time‐consuming to characterize, especially across large areas, using traditional ground‐based field methods. We developed and tested a method for rapidly classifying gaps using an unmanned aerial vehicle (UAV or drone). Aerial data were collected by a UAV‐mounted camera in April 2018, and stratified, random ground surveys to verify UAV data were conducted March through April 2018 at Archbold Biological Station in south‐central Florida, USA. We used mosaicked and georeferenced digital surface and terrain models to calculate vegetation height across 33 rosemary scrub sites (~230,000 m2 at 0.064 m2 pixel resolution). Gaps were defined as >1 m2 areas where vegetation height was <10 cm. We found that gap areas from UAV models and field surveys were significantly correlated across varying gap sizes, times‐since‐fire, and relative elevations. We also observed a significant decrease in mean gap area and percent gap space with increasing time‐since‐fire, a pattern consistent with smaller‐scale, ground‐based sampling, and a marginally significant increase in gap area with relative elevation. This remote sensing method lends itself to better exploration of how gap areas, their spatiotemporal patterns, and associated fire history, elevation, soil, and other geographic data affect structural vegetation dynamics across the landscape. This study illustrates the success of UAV modeling of gap space in Florida rosemary scrub, a result of regional consequence for the southeastern United States, but more broadly, it encourages the use of UAV technology as a tool to enhance traditional field‐based methods in systems globally. As habitat fragmentation and loss become increasingly problematic for the conservation of threatened habitats, understanding these complex spatial dynamics is crucial to the conservation and management of vegetation communities and their biodiversity.
Savanna plant communities are highly diverse, characterized by an open-canopy structure with a rich herbaceous understory, and maintained by frequent low-intensity re and grazing. Due to habitat loss and fragmentation, savannas are globally threatened, with less than 1% of former oak savanna land cover found in the Midwestern United States remaining. In remnant oak savannas, loss of re and grazing has led to woody encroachment and canopy closure over the past century with cascading consequences for the taxonomic composition of the understory community. Whether these taxonomic changes can be broadly predicted using species functional traits (morpho-physio-phenological characteristics that impact the tness of a species) is a key question. We ask whether the impacts of woody encroachment on understory changes can be predicted from species' abilities to persist (avoid extinction) and disperse (colonize new areas). Speci cally, we pair persistence traits (e.g., clonality, belowground storage) and dispersal traits (e.g., seed mass, dispersal mode) with a rare 60 year dataset from oak savanna understories in Wisconsin, USA to understand how the representation of these traits has changed in the understory community over time. Over 60 years, savanna understory change was explained less by species persistence than dispersal abilities; small-seeded species reliant on unassisted dispersal and moderately clonal species experienced the greatest losses. These changes in functional composition are likely due to increased woody encroachment, which may impede propagule production and movement.Restoration efforts need to prioritize species that are dispersal limited and those that create ne fuels, which help maintain open re-maintained open habitat savannas.
Savanna plant communities are highly diverse, characterized by an open-canopy structure with a rich herbaceous understory, and maintained by frequent low-intensity fire and grazing. Due to habitat loss and fragmentation, savannas are globally threatened, with less than 1% of former oak savanna land cover found in the Midwestern United States remaining. In remnant oak savannas, loss of fire and grazing has led to woody encroachment and canopy closure over the past century with cascading consequences for the taxonomic composition of the understory community. Whether these taxonomic changes can be broadly predicted using species functional traits (morpho-physio-phenological characteristics that impact the fitness of a species) is a key question. We ask whether the impacts of woody encroachment on understory changes can be predicted from species’ abilities to persist (avoid extinction) and disperse (colonize new areas). Specifically, we pair persistence traits (e.g., clonality, belowground storage) and dispersal traits (e.g., seed mass, dispersal mode) with a rare 60 year dataset from oak savanna understories in Wisconsin, USA to understand how the representation of these traits has changed in the understory community over time. Over 60 years, savanna understory change was explained less by species persistence than dispersal abilities; small-seeded species reliant on unassisted dispersal and moderately clonal species experienced the greatest losses. These changes in functional composition are likely due to increased woody encroachment, which may impede propagule production and movement. Restoration efforts need to prioritize species that are dispersal limited and those that create fine fuels, which help maintain open fire-maintained open habitat savannas.
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