Ceratiola Research Articles

Mapping spatially explicit vegetation gaps in Florida rosemary scrub using unmanned aerial vehicles

AbstractAdvances 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.

Fine-scale spatial variation in fitness is comparable to disturbance-induced fluctuations in a fire-adapted species.

The spatial scale at which demographic performance (e.g., net reproductive output) varies can profoundly influence landscape-level population growth and persistence, and many demographically pertinent processes such as species interactions and resource acquisition vary at fine scales. We compared the magnitude of demographic variation associated with fine-scale heterogeneity (<10m), with variation due to larger-scale (>1ha) fluctuations associated with fire disturbance. We used a spatially explicit model within an IPM modeling framework to evaluate the demographic importance of fine-scale variation. We used a measure of expected lifetime fruit production, EF , that is assumed to be proportional to lifetime fitness. Demographic differences and their effects on EF were assessed in a population of the herbaceous perennial Hypericum cumulicola (~2,600 individuals), within a patch of Florida rosemary scrub (400×80m). We compared demographic variation over fine spatial scales to demographic variation between years across 6 yr after a fire. Values of EF changed by orders of magnitude over<10m. This variation in fitness over fine spatial scales (<10m) is commensurate to postfire changes in fitness for this fire-adapted perennial. A life table response experiment indicated that fine-scale spatial variation in vital rates, especially survival, explains as much change in EF as demographic changes caused by time-since-fire, a key driver in this system. Our findings show that environmental changes over a few tens of meters can have ecologically meaningful implications for population growth and extinction.

Do plant-microbe interactions support the Stress Gradient Hypothesis?

The Stress Gradient Hypothesis (SGH), which predicts increasing ratios of facilitative:competitive interactions with increasing stress, has long been a guiding framework for conceptualizing plant-plant interactions. Recently, there has been a growing recognition of the roles of microbes in mitigating or exacerbating environmental stress for their plant hosts. As such, we might predict, based on the SGH, that beneficial microbial effects on plant performance should be positively associated with stress. Specifically, we hypothesized that support for the SGH would depend on the host plant's habitat specialization such that species that specialize in high stress habitats and thus likely coevolved with the resident microbes would exhibit stronger support for the SGH than non-specialist plant species. We further hypothesized that support for the SGH would vary with germination frequency, since boosting germination of low-frequency germinators is one effective means by which microbes can benefit plant species performance. Here, we explore whether plant-microbial interactions support the SGH using 12 plant species native to the Florida rosemary scrub. We conducted factorial experiments that manipulated the presence of microbes in nine soils collected along an elevational stress gradient, and recorded germination frequency and biomass. Microbes increased the germination frequency of four species, all of which had relatively low germination rates. Furthermore, we found support for the SGH in nearly one-half of the species examined, with soil microbes facilitating germination with increasing stress for 5 of the 12 species tested, and none of the species exhibiting the opposite trend. Support for the SGH was not predicted by either the plant hosts' habitat specialization or germination frequency. In contrast to germination, biomass results showed little support for the SGH, with four of 12 species refuting and one species supporting SGH predictions. Taken together, our study documents that interactions between the soil microbial community and plant species along a stress gradient can support the SGH, but emphasizes that these effects are life-history-stage dependent. This work also identifies a common mechanism (germination facilitation) by which microbes can benefit plant species in stressful habitats.

Assessing the roles of seed bank, seed dispersal and historical disturbances for metapopulation persistence of a pyrogenic herb

Abstract Seed bank, seed dispersal and historical disturbance are critical factors affecting plant population persistence. However, because of difficulties collecting data on these factors they are often ignored. We evaluated the roles of seed bank, seed dispersal and historical disturbance on metapopulation persistence of Hypericum cumulicola, a Florida endemic. We took advantage of long‐term demographic data of multiple populations (22 years; ~11 K individuals; 15 populations) and a wealth of information on burn history (1962–present), and habitat attributes (patch specific location, elevation, area and aggregation) of a system of 92 patches of Florida rosemary scrub. We used previously developed integral projection models to assess the relative ability of simulations with different levels of seed dormancy for recently produced and older seeds and different dispersal kernels (including no dispersal) to predict regional observed occupancy and plant abundance in patches in 2016–2018. We compared a simulation with this model using historical burn history to 500 model simulations with the same average fire regime (using a Weibull distribution to determine the probability of ignition) but with random ignition years. The most likely model had limited dispersal (mean = 0.5 m) and the highest dormancy (field estimates × 1.2 %) and its predictions were associated with observed occurrences (67% correct) and densities (20% of variance explained). Historical burn synchrony among neighbouring patches (skewness in the number of patches burned by year = 1.79) probably explains the higher densities predicted by the simulation with the historical fire regime compared with predicted abundances after simulations using random ignition years (skewness = 0.20 + SE = 0.01). Synthesis. Our findings demonstrate the pivotal role of seed dormancy, dispersal and fire history on population dynamics, distribution and abundance. Because of the prevalence of metapopulation dynamics, we should be aware of the significance of changes in the availability and configuration of suitable habitat associated with human or non‐human landscape changes. Decisions on prescribed fires (or other disturbances) will benefit from our knowledge of consequences of fire frequency, but also of location of ignition and the probability of fire spread.

Condylops (Neocondylops) Obrieni Wittmer (Coleoptera: Melyridae): Distribution, Plant Associations, Seasonality, and Mating Behavior

Condylops (Neocondylops) obrieni Wittmer is a small (1.8 mm long), shiny blue melyrid of the subfamily Malachiinae. It is the only Nearctic member of an otherwise Old World genus. Described from Florida in the late 1980s, it has been collected in southeastern Alabama and is newly reported from Georgia, with additional records from Alabama and Florida. Seasonality and mating behavior were observed in the Ohoopee Dunes system of southeastern Georgia from 2011 to 2016 and in 2018. Adults were found from early February to early May in ultra-xeric communities, especially on Florida rosemary (Ceratiola ericoides Michx.; Ericaceae) and saw palmetto (Serenoa repens [W. Bartram] Small; Arecaceae). The wider leaf blades of saw palmetto facilitated behavioral observations, in contrast to the needlelike leaves of Florida rosemary. Males typically appeared a few days before females, whereas females began to predominate by early April. Early in the season, solitary adults (mainly females) fed on pine pollen adhering to leaves of saw palmetto. Sexual interaction began by late February, with males running up and down leaves behind females. Periodically, a pair would stop, the male circling the female, before the pair initiated antennal interplay; after separating, some pairs resumed head-to-head contact. Of the approximately 75 pairs that were observed, courtship resulted in only two copulations. In pairs already found in copula, males remained immobile, slightly above the substrate ventral surface up, as the female walked up and down leaves. Males remained unresponsive when approached by other males.

Florida Rosemary, Ceratiola ericoides

Florida rosemary is important in maintaining back dune structures and is found inland in scrub communities. This plant is found throughout scrub plant communities in Florida, and more broadly is found west to Mississippi and east to South Carolina in xeric soils and in communities with fire return intervals of 20 to 40 years. Plants are killed by fire and storm surge events, but seeds germinate readily post-disturbance. Its fruit is an important food source for wildlife but is not produced until plants are at least 12 years old.https://edis.ifas.ufl.edu/sg164 &#x0D; Note: This fact sheet is also available as a chapter in a comprehensive manual titled Dune Restoration and Enhancement for the Florida Panhandle, Please see the manual for more information about other useful and attractive native plants for dunes and for further information about restoration and preservation techniques.

Dynamics of gaps, vegetation, and plant species with and without fire

Areas lacking dominant plants, or gaps, can support high diversity and specialist species. Previous chronosequence research in Florida rosemary scrub showed indistinct gap area patterns with fire and the dependence of certain species on gaps. We hypothesized that fire and gap size would affect extinction, colonization, diversity, and vegetation composition. In 2011-12, we revisited gaps first sampled in 2003, recording vascular plant and ground lichen occurrence by species, gap area, and burn history. We analyzed gap, vegetation, and species dynamics using linear mixed models, with Florida rosemary scrub patch as a random factor. Gap areas declined quickly during the first 10 yr postfire and then stabilized. Between 2003 and 2011-12, unburned gaps usually remained extant or split, whereas burned gaps usually merged. Unburned gaps tended to shrink, whereas burned gaps became larger. Species richness was positively related to gap area, fire, and their interaction. Over time, richness declined in unburned gaps and increased in burned gaps. Local extinction and colonization of individual species were related to fire between 2003 and 2011-12. In burned gaps, ground lichens disappeared, but many herbaceous species, including those killed by fire, increased occupancy. Colonization of most species was favored by burning, large gaps, or both. In Florida rosemary scrub, fire and increasing gap size increased species richness and many individual species occurrences, reduced local extinctions, and increased colonizations. Therefore, land management activities that encourage the creation and maintenance of large gaps will promote biodiversity in this system.

Neopamera bilobata (Say) and Ozophora trinotata Barber (Hemiptera: Lygaeoidea: Rhyparochromidae) as Frugivores on Florida Rosemary (Ceratiola ericoides; Ericaceae)

Abstract. Neopamera bilobata (Say) is a wide-ranging, generalist seed predator that lives in the litter layer, but unlike many other species of Rhyparochromidae, it also ascends plants to feed on seeds. In Florida scrubs and other xeric plant communities in the southeastern United States, N. bilobata was found frequently, but irregularly, on female plants of Florida rosemary, Ceratiola ericoides (Ericaceae), from 2007 to 2016. This dioecious shrub flowers mainly in autumn and produces fleshy fruits and smaller, dry fruits that have been attributed to lack of pollination. Nymphs and adults of N. bilobata were collected from rosemary (31 sites) in Alabama, Florida, Georgia, Mississippi, and South Carolina. All nymphal instars were observed from mid-October to late April, suggesting that nymphs develop on the plant. The bug's seasonality on rosemary in the coastal plain of Georgia and peninsular scrubs of Florida varied from year to year and between nearby sites sampled the same day. A second rhyparochromid,...

Hurricane Impacts on Florida Rosemary Across the Northeastern Region of the Gulf Coast

Hurricanes represent a major source of stochastic disturbance to coastal plant communities, with the potential to temporarily alter both species composition and environmental characteristics. Ceratiola ericoides Michx. (Florida rosemary) is a dominant member of an association of xeric species known collectively as rosemary scrub, which occur on barrier islands along the Gulf Coast and in inland peninsular Florida scrub. Unlike interior populations of Florida rosemary, which are periodically reduced by fire, coastal populations of rosemary are likely to be influenced by hurricanes more than by fire, with resultant differences in the frequency of damage to adults. We quantified the impact of major hurricanes on coastal populations of Florida rosemary and examined the impact of storm surge, elevation, and time-since-hurricane on rosemary survival and resprouting in five populations on the Mississippi and Florida coasts. Ratio of living-to-dead rosemary shrubs was higher in two coastal populations not recently struck by a major hurricane than on three barrier islands affected in 2004 – 2005 by Hurricanes Ivan and Katrina. There was also a trend toward greater mortality from Hurricanes Ivan and Katrina on islands with lower elevation, but the difference was not statistically significant, perhaps reflecting similar impacts of these hurricanes and their occurrence in consecutive years. In contrast to previous observations of infrequently disturbed inland populations of Florida rosemary, which exhibited an obligate seeder strategy, coastal populations showed a significant capacity for resprouting following hurricane damage. Given a two-year or more delay in seedling establishment following severe damage to adults, resprouting could expedite post-hurricane recovery of these populations.

Effects of habitat and time-since-fire on recruitment, survival, and reproduction of Paronychia chartacea ssp. chartacea, a short-lived Florida scrub endemic herb1

Conservation of a threatened species requires knowledge of the factors that affect its recruitment, survival, and reproduction. We conducted a long-term study on the demography of Paronychia chartacea ssp. chartacea, a short-lived, gynodioecious Florida rosemary scrub endemic. Specifically, we assessed the effects of habitat (rosemary scrub vs. roadsides), time-since-fire, microhabitat, and rainfall on recruitment, survival, flowering, and seed production. In addition, in a shorter-term study, we assessed the effects of habitat, time-since-fire, and gender on flower and seed production. Overall, approximately one-third of individuals survived more than one year and individuals most often flowered twice indicating that P. chartacea ssp. chartacea is an iteroparous, short-lived perennial, which is in contrast to its disjunct conspecific, the annual P. chartacea ssp. minima. Recruitment was higher in roadsides, but seed production was higher in rosemary scrub. Within rosemary scrub, recruitment was highest at intermediate times-since-fire and in the center of large gaps, the microhabitat with the greatest amount of bare sand. Median lifespan was longest in long unburned sites, suggesting that P. chartacea ssp. chartacea is able to persist despite litter accumulation and competition from shrubs. Rainfall had a positive effect on annual survival, but did not affect seedling recruitment. Females produced more seeds than hermaphrodites, indicating that females contribute more to population persistence. Our study suggests P. chartacea ssp. chartacea populations will persist under the 15–40 year fire return interval characteristic of regularly burned Florida rosemary scrub, but may not persist in roadsides if greater recruitment does not balance shorter lifespans.

Spatial pattern and composition of the Florida scrub seed bank and vegetation along an anthropogenic disturbance gradient

AbstractQuestionHow does spatial pattern and composition of the seed bank and its relationship to above‐ground cover vary across an anthropogenic disturbance gradient of intact Florida rosemary scrub, degraded scrub and improved pasture?LocationFlorida rosemary scrub, Lake Wales Ridge, Highlands County, FL, USA (27° 11′N, 81° 21′W).MethodsIn nine grid plots located in intact Florida rosemary scrub, degraded scrub and improved pasture, we assessed percentage vegetation cover and seed bank composition.ResultsThe vegetation was dominated by long‐lived perennials, while the seed bank was dominated by short‐lived species. Shrubs were the dominant above‐ground cover in rosemary scrub, sub‐shrubs and the spike moss Selaginella arenicola in degraded scrub and non‐native grasses in pastures. Scrub forbs were dominant in the seed bank of rosemary scrub, similar amounts of sedges, ruderal forbs and scrub forbs in degraded scrub, and ruderal species and sedges in pastures. Species absent from the vegetation were randomly distributed in the seed bank, while species present above‐ground had an aggregated spatial distribution. In rosemary scrub, scrub forb seed banks were spatially aggregated and were positively associated with conspecific species above‐ground and with litter cover. These patterns were not observed in degraded scrub, perhaps due to reduced shrub and increased bare ground.ConclusionOur results suggest that reduced shrub cover and increased bare ground in the degraded scrub may explain why there is less spatial aggregation of scrub forbs in the seed bank. Restoration of Florida rosemary scrub in pasture sites will require species reintroduction of appropriate scrub species; restoration of degraded scrub should emphasize increasing shrub cover to restore habitat spatial structure.

Metacommunity Dynamics Over 16 Years in a Pyrogenic Shrubland

Metacommunity theory allows predictions about the dynamics of potentially interacting species' assemblages that are linked by dispersal, but strong empirical tests of the theory are rare. We analyzed the metacommunity dynamics of Florida rosemary scrub, a patchily distributed pyrogenic community, to test predictions about turnover rates, community nestedness, and responses to patch size, arrangement, and quality. We collected occurrence data for 45 plant species from 88 rosemary scrub patches in 1989 and 2005 and used growth form, mechanism of regeneration after fire, and degree of habitat specialization to categorize species by life history. We tested whether patch size, fire history, and structural connectivity (a measure of proximity and size of surrounding patches) could be used to predict apparent extinctions and colonizations. In addition, we tested the accuracy of incidence-function models built with the patch survey data from 1989. After fire local extinction rates were higher for herbs than woody plants, higher for species that regenerated only from seed than species able to resprout, and higher for generalist than specialist species. Fewer rosemary specialists and a higher proportion of habitat generalists were extirpated on recently burned patches than on patches not burned between 1989 and 2005. Nestedness was highest for specialists among all life-history groups. Estimated model parameters from 1989 predicted the observed (1989-2005) extinction rates and the number of patches with persistent populations of individual species. These results indicate that species with different life-history strategies within the same metacommunity can have substantially different responses to patch configuration and quality. Real metacommunities may not conform to certain assumptions of simple models, but incidence-function models that consider only patch size, configuration, and quality can have significant predictive accuracy.

Effects of Fire History on Amphibian and Reptile Assemblages in Rosemary Scrub

Abstract Florida scrub is a fire-maintained ecosystem with a high concentration of endemic and imperiled species. To assist in the conservation of these taxa, we evaluated how communities and populations of amphibians and reptiles varied with fire history in rosemary (Ceratiola ericoides) scrub. We calculated species richness, evenness, total abundance, and individual species abundance for all amphibians and reptiles captured from May through August 2003 and May 2004 at 12 rosemary scrub sites in Highlands County, Florida, that differed in fire history (time since last fire, TSF). Vegetation structure (bare ground and canopy cover) varied polynomially with TSF, with intermediate TSF sites most open and long-unburned sites least open. Species richness, evenness, and total abundance did not vary with fire history. At the species level, only two species, Plestiodon reynoldsi and Aspidoscelis sexlineata, showed significant relationships with TSF: P. reynoldsi was most common in least open, longest-unburned ar...

Seed Bank Changes with Time-since-Fire in Florida Rosemary Scrub

The soil seed bank plays a central role in the regeneration of obligate seeding species in fire-prone habitats. We evaluated how seed density and species composition changed with time-since-fire in the Florida, USA, rosemary scrub community. Because fire affects habitat availability and plant demographic variation, we predicted that soil seed density would be low in recently burned and long-unburned stands and high at intermediate time-since-fire. Seed bank soil samples were collected from a chronosequence of time-since-fire composited from two trials conducted in 1992–1993 and 2008–2009: two sites each of 3, 6, 10, and 24 years post-fire, and 3 long-unburned (~67 years) sites. The seedling emergence method was used to determine species composition of the seed bank. Across all time-since-fire age classes, herbaceous species dominated the seed bank, while long-lived subshrubs and shrubs were present in low densities. Seed banks from sites three years post-fire were distinct from the other sites. When species were sorted as functional groups, seed density was related with time-since-fire for subshrubs and ruderal herbs, but not for scrub herbs and graminoids. Subshrubs and ruderal herbs had highest seed densities in recently burned stands. Seed densities of Florida rosemary (Ceratiola ericoides Michx.) (the major obligate seeding shrub in this community) were associated with time-since-fire and showed highest densities at recently burned and long-unburned sites. The seed banks of two scrub herb species, paper nailwort (Paronychia chartacea Fernald) and nodding pinweed (Lechea cernua Small), were associated with time-since-fire. They reached peaks in density in the first ten years post-fire, corresponding with similar changes in their aboveground abundances with time-since-fire. Soil seed densities of several species and functional groups were associated with time-since-fire, but timing of peak seed density varied depending on species’ life span and age of reproductive maturity.

Antifeedant effect of commercial chemicals and plant extracts againstSchistocerca americana(Orthoptera: Acrididae) andDiaprepes abbreviatus(Coleoptera: Curculionidae)

The deterrent effect of seven commercial compounds against Schistocerca americana (Drury) nymphs and Diaprepes abbreviatus L. adults, two important citrus pests, was investigated. Extracts of three Florida local plants were also tested as deterrents. Antifeedant activity was assayed using a leaf-disk bioassay in choice and no-choice tests. The residual activity of the commercial compounds that significantly deterred the insects was assayed by applying them to foliage of citrus plants exposed to three time intervals of sunlight. Sabadilla, azadirachtin and ryanodine effectively deterred S. americana, whereas rotenone, sabadilla and ryanodine reduced the feeding activity of D. abbreviatus. Methanol and methylene chloride extracts of Ceratiola ericoides Michaux deterred D. abbreviatus, but only methylene chloride extract dissuaded S. americana. Methanol extract of Ardisia crenata Sims functioned as a feeding deterrent against both S. americana and D. abbreviatus, but only the latter species was deterred by methylene chloride extract of A. crenata. Extracts of Illicium parviflorum Michaux ex Ventetat only dissuaded the insects in choice bioassays. Rapid loss of effectiveness was observed under field conditions. Sabadilla was the only compound that maintained its antifeedant properties in the field, but only against S. americana. Based on their deterrency, some of the commercial products and plant extracts have potential for use as substitute crop protectants against the pest species tested.

Effects of Time-Since-Fire and Microhabitat on the Occurrence and Density of the Endemic Paronychia chartacea ssp. chartacea in Florida Scrub and Along Roadsides

Conservation of an imperiled plant species requires an understanding of its local occurrence and density in relation to habitat variation. Paronychia chartacea ssp. chartacea is a federally threatened species restricted to gaps in fire-maintained Florida rosemary scrub and to roadside sites that mimic scrub gaps. To assess the effects of time-since-fire and microhabitat on the occurrence and density of Paronychia populations, we conducted surveys of 119 scrub gaps and 16 roadside macroplots. In rosemary scrub, we found that the frequency of gap occupancy decreased with time-since-fire and that Paronychia occurrence and density were greater in the centers of large gaps than in small gaps or large gap edges. In roadside sites, the distance from adjacent rosemary scrub did not affect the presence of Paronychia, but density increased with distance from rosemary scrub vegetation. Paronychia densities in roadside sites were most similar to densities in recently burned rosemary scrub. Time-since-fire and microhabitat quality affect the occurrence and density of Paronychia and should be considered in management of Paronychia populations.

Keltonia balli (Knight) (Hemiptera: Miridae: Phylinae): A Rarely Collected Specialist on Staminate Flowers of the Dioecious Shrub Florida Rosemary (Ceratiola Ericoides Michx.; Ericaceae)

Abstract Described in 1926 from Florida and Mississippi, the phyline plant bug Keltonia balli (Knight) has been known in the literature only from 10 specimens; six additional specimens, reported herein, have been found in museum collections. The mirid's host-plant relationships have remained unknown. From 2002 to 2008, I collected 359 adults and 78 nymphs (instars II–V) on Florida rosemary (Ceratiola ericoides Michx.; Ericaceae), a dioecious evergreen shrub endemic to the southeastern United States. Nymphs and all but four adults were on male plants with flower buds or flowers in October, November, or December; the mirid was not found during sampling in January, February, March, April, June, or August. Keltonia balli was found only in the Lake Wales Ridge and other sand scrubs of peninsular Florida from Clay County south to Highlands County. The plant bug is a rosemary specialist whose nymphs develop on reproductive structures of male plants. Aspects of this herbivore-plant system needing elucidation, suc...

Germination Ecology ofLiatris ohlingerae(S.F. Blake) B.L. Rob. (Asteraceae), an Endangered Herb Endemic to Florida Scrub

Seed source, absence of favorable microhabitat conditions, and presence of competitors, predators or allelochemicals are among the many factors that may limit the germination of viable seeds. We conducted six field, growth chamber, and veranda experiments to investigate the effects of seed source, physical or chemical presence of co-occurring species, and litter presence on germination percentages of the Florida scrub endemic Liatris ohlingerae. This perennial herb produces many seeds but recruits few seedlings. Germination percentages were similar when seeds from scrub and roadside habitats were sown into their own and the contrasting habitat. We found no evidence of chemical inhibition from a co-occurring terrestrial lichen or from the allelopathic Florida rosemary (Ceratiola ericoides), the dominant shrub in the habitat preferred by L. ohlingerae. However, germination was higher in shallow than in deep litter, and was suppressed by litter from oaks and pines compared to litter from Florida rosemary. In one experiment, higher levels of post-sowing seed predation closer to Florida rosemary shrubs limited germination. Germination of intact L. ohlingerae seeds generally exceeded 60% under a range of field and lab conditions. High field germination percentages within a few weeks of sowing suggest that L. ohlingerae does not maintain a sizeable persistent seed bank. Low seedling recruitment in this endangered plant is not likely caused by poor seed germination.

Distance from the Gulf Influences Survival and Growth of Three Barrier Island Dune Plants

Abstract After hurricane overwash, restoration of dune ecosystems requires information on when, where, and how to replace plants removed by storms. Survival and subsequent growth of Schizachyrium maritimum (Chapman) Nash, Morella cerifera (L. Small), and Ceratiola ericoides Michx., transplanted at increasing distances from the Gulf of Mexico (92, 124, 179, and 200 m landward of the Gulf) with increasing protection from salt spray and desiccating winds by developing dunes, were evaluated. Survival and growth was followed for 15 months. Schizachyrium maritimum survival and growth was high regardless of distance from the Gulf. Ceratiola ericoides and M. cerifera did not survive when planted 92 m from the Gulf behind embryo dunes approximately 0.5–1 m tall. Foliage loss was noted at all distances but survival and regrowth were higher at 170 and 200 m behind two to three ridges of embryo dunes 0.5–1 m tall.

Linking the patterns in soil moisture to leaf water potential, stomatal conductance, growth, and mortality of dominant shrubs in the Florida scrub ecosystem

Patterns in soil moisture availability affect plant survival, growth and fecundity. Here we link patterns in soil moisture to physiological and demographic consequences in Florida scrub plants. We use data on different temporal scales to (1) determine critical soil moisture content that leads to loss of turgor in leaves during predawn measurements of leaf water status (Ψ crit), (2) describe the temporal patterns in the distribution of Ψ crit, (3) analyze the strength of relationship between rainfall and soil moisture content based on 8 years of data, (4) predict soil moisture content for 75 years of rainfall data, and (5) evaluate morphological, physiological and demographic consequences of spring 2006 drought on dominant shrubs in Florida scrub ecosystem in the light of water-uptake depth as determined by stable isotope analysis (δ18O). Based on 1998–2006 data, the soil moisture content at 50 cm depth explained significant variation in predawn leaf water potential of two dominant shrubs, Quercus chapmanii and Ceratiola ericoides (r 2 = 0.69). During 8 years of data collection, leaves attained Ψ crit only during the peak drought of 2000 when the soil moisture fell below 1% by volume at 50 and 90 cm depth. Precipitation explained a significant variation in soil moisture content (r 2 = 0.62). The patterns in predicted soil moisture for 75 year period, suggested that the frequency of drought occurrence has not increased in time. In spring 2006, the soil reached critical soil moisture levels, with consequences for plant growth and physiological responses. Overall, 24% of plants showed no drought-induced damage, 51% showed damage up to 50%, 21% had intense leaf shedding and 2% of all plants died. Over the drought and recovery period (May–October 2006), relative height growth was significantly lower in plants with greater die-back. All species showed a significant depression in stomatal conductance, while all but deep-rooted palms Sabal etonia and Serenoa repens showed significantly lower predawn (Ψ pd) and mid-day (Ψ md) leaf water potential in dry compared to wet season. Plants experiencing less severe die-back exhibited greater stomatal conductance, suggesting a strong relationship between physiology and morphology. Based on results we suggest that the restoration efforts in Florida scrub should consider the soil moisture requirements of key species.