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41.
Posthurricane Seedling Structure in a Multi‐aged Tropical Dry Forest: Implications for Community Succession
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Hurricane‐caused tree mortality in tropical dry forests occurs predominantly in early successional species. Consequently, hurricanes may accelerate succession in these forests. Forest regeneration, however, must be measured over an extended posthurricane time period to demonstrate this pattern. In this study, we recorded tree seedlings in 19 Florida Keys forests during May–August 1995, 3 years after Hurricane Andrew. For these forests—spanning a chronosequence from 14 to over 100 years since the most recent clearing—we used weighted averaging regression on relative abundances of pre‐hurricane trees to calculate a successional age optimum for each species; and used weighted averaging calibration to calculate inferred successional ages for stands based on pre‐hurricane trees and on posthurricane seedlings. To test the hypothesis that successional stage of seedlings exceeded successional stage of pre‐hurricane trees, we compared inferred stand ages based on posthurricane seedlings with those based on pre‐hurricane trees. Across the study area, inferred stand ages based on posthurricane seedlings were greater than those based on pre‐hurricane trees (P < 0.005); however, more seedlings in the youngest stands were early successional than in older stands. Of 29 species present both as pre‐hurricane trees and posthurricane seedlings, 23 had animal‐dispersed seeds. These results provide evidence that: (1) hurricanes do not ‘reset’ succession, and may accelerate succession; and (2) a strong legacy of stand successional age influences seedling assemblages in these forests. 相似文献
42.
Thomas P Freeman John A Goolsby Sebahat K Ozman Dennis R Nelson 《Australian Journal of Entomology》2005,44(1):57-61
Abstract The ultrastructure of the mite Floracarus perrepae was investigated in relation to its host, Lygodium microphyllum , the Old World climbing fern. Floracarus perrepae has been suggested as a means of biological control for the fern, which is an aggressive weed in tropical areas. Feeding by the mite induces a change in the size of epidermal cells, and cell division is stimulated by mite feeding, causing the leaf margin to curl over into a roll with two to three windings. The enlarged epidermal layer greatly increases its cytoplasmic contents, which become a nutritive tissue for the mite and its progeny. Damage by the mite ultimately debilitates the fern. The structure and depth of stylet penetration by the mite, and the thickness of the epidermal cell wall of L. microphyllum , do not appear to account for the mite's differential ability to induce leaf rolling in its co-adapted host from south-east Queensland but not in the invasive genotype of the fern in Florida. 相似文献
43.
Functional groups based on leaf physiology: are they spatially and temporally robust? 总被引:6,自引:0,他引:6
The functional grouping concept, which suggests that complexity in ecosystem function can be simplified by grouping species
with similar responses, was tested in the Florida scrub habitat. Functional groups were identified based on how species regulate
exchange of carbon and water with the atmosphere as indicated by both instantaneous gas exchange measurements and integrated
measures of function (%N, δ13C, δ15N, C:N ratio) in fire-maintained Florida scrub, which was considered the natural state for scrub habitat. Using cluster analysis,
five distinct physiologically based functional groups were identified in the fire-maintained scrub and were determined to
be distinct clusters and not just arbitrary divisions in a continuous distribution by the non-parametric multivariate analysis
of similarities (ANOSIM; R=0.649, P=0.005). These functional groups were tested for robustness spatially, temporally, and with management regime using ANOSIM.
The physiological functional groups remained distinct clusters in this broader array of sites (R=0.794, P=0.001) and were not altered by plot differences, primarily, water table depth (R=−0.115, P=0.893) or by the three different management regimes: prescribed burn, mechanically treated and burned, and fire-suppressed
(R=0.018, P=0.349). The physiological groupings also remained robust between the two climatically different years, with 1999 being a
much wetter year than 2000 (R=−0.027, P=0.725). Easy-to-measure morphological characteristics, if they indicate the same functional groups, would be more practical
for scaling and modeling ecosystem processes than detailed gas exchange measurements; therefore, we tested a variety of morphological
characteristics as functional indicators. A combination of non-parametric multivariate techniques were used to compare the
ability of life form, leaf thickness (LT), and specific leaf area (SLA) classifications to identify the physiologically based
functional groups. Life form classifications (ANOSIM; R=0.629, P=0.001) were able to depict the physiological groupings more adequately than either SLA (ANOSIM; R=0.426, P=0.001) or LT (ANOSIM; R=0.344, P=0.001). The ability of life forms to depict the physiological groupings was improved by separating the parasitic Ximenia americana from the shrub category (ANOSIM; R=0.794, P=0.001). Therefore, a life form classification including parasites was determined to be a good indicator of the physiological
processes of scrub species and would be a useful method of grouping species for scaling physiological processes to the ecosystem
level. 相似文献
44.
The Chassahowitzka, Homosassa and Crystal rivers along the central Gulf coast of Florida were studied from 1998 to 2000 to identify factors controlling the abundance and distribution of submersed aquatic vegetation (SAV). Each of these three low-lying coastal rivers are spring-fed and exhibit low to moderate absolute flow rates (flows in either direction because of tidal influences, 0.06–0.46ms–1) with only 14 of the stations sampled for SAV having flow rates in excess of 0.25ms–1. At those stations where flow rates exceeded 0.25ms–1, the substrate was generally comprised of exposed limestone outcroppings and did not provide a favorable habitat for either submersed macrophytes or macroalgae. The remaining sampling stations, where flow rates were less than 0.25ms–1, had suitable substrates (e.g. mud, mud/sand, and sand) for the colonization and subsequent growth of SAV. Light availability and salinity were determined to be major factors affecting the distribution and abundance of SAV. Sampling stations, where the percent of incident light at the surface reaching the substrate was less than 10, had little or no SAV biomass. Low SAV biomass was also linked to sites where annual average salinities exceeded 3.5. Nutrient loads and nutrient concentrations accounted for little variance in SAV biomass after accounting for flow and related substrate type, light and salinity. These latter factors control the distribution and abundance of SAV in these three Florida coastal rivers. 相似文献
45.
Andrew P Collins Chenan Andy Huang Megan Ann Bernier Naser Mubarak Sami Hemaidan Hadi Hemaidan Ammar Hemaidan 《Bioinformation》2021,17(1):1
Our knowledge of the disease burden and symptoms with age in COVID-19 patients is limited. Therefore, it is of interest to document the clinical aspect of this association with respect to the disease. We used the data of 3363 patients enrolled with an urgent care clinic in Volusia county, Florida for this study. Data shows difference in age among COVID-19 antibody (Ab) - positive patients (48.3 years, 95% CI = 46.9,49.7 years) and Ab-negative patients (46.1 years, 95% CI = 45.4, 46.8 years). However, disease burden by age is not significant on average. Nonetheless, COVID-19 positive patients between 40-69-years of age experienced the highest burden of disease and highest average number of symptoms. Thus, COVID-19 disease burden and number of symptoms experienced were highest among the 40-69-year-old patients. Those above the populations mean age of 46.4 years old were more likely to test positive for COVID-19. 相似文献
46.
The genetic rescue of the Florida panther 总被引:8,自引:5,他引:3
We examine the consequences of panthers introduced from Texas into south Florida, an area housing a small, isolated, inbred and distinct subspecies ( Puma concolor coryi ). Once part of a continuous, widespread population, panthers became isolated in south Florida more than a century ago. Numbers declined and the occurrence of genetic defects increased. Hoping to reverse the genetic damage, managers introduced eight female panthers from Texas into south Florida in the mid-1990s. This action was highly controversial and we explain the arguments for and against the intervention. We synthesized data systematically collected on the Florida panthers from before, during and after this management intervention. These data include information on movements, breeding, mortality, survivorship and range. There is no evidence that purebred Florida females produce fewer kittens at a later age or less often than do hybrid cats (i.e. those with a Texas ancestor). Hybrid kittens have about a three times higher chance of becoming adults as do purebred ones. Hybrid adult females survive better than purebred females; there is no obvious difference between the males. Males die younger than females, are more often killed by other males and are more likely to disperse longer distances into habitats that are dangerous to them. Hybrids are expanding the known range of habitats panthers occupy and use. 相似文献
47.
Tree island ecosystems are important and distinct features of Florida Everglades wetlands. We described the inter-relationships
among abiotic factors describing seasonally flooded tree islands and characterized plant–soil relationships in tree islands
occurring in a relatively unimpacted area of the Everglades. We used Principal Components Analysis (PCA) to reduce our multi-factor
dataset, quantified forest structure and vegetation nutrient dynamics, and related these vegetation parameters to PCA summary
variables using linear regression analyses. We found that, of the 21 abiotic parameters used to characterize the ecosystem
structure of seasonally flooded tree islands, 13 parameters were significantly correlated with four principal components,
and they described 78% of the variance among the study islands. Most variation was described by factors related to soil oxidation
and hydrology, exemplifying the sensitivity of tree island structure to hydrologic conditions. PCA summary variables describing
tree island structure were related to variability in Chrysobalanus icaco (L.) canopy cover, Ilex cassine (L.) and Salix caroliniana (Michx.) canopy cover, Myrica cerifera (L.) plot frequency, litter turnover, % phosphorus resorption of co-dominant species, and nitrogen nutrient-use efficiency.
This study supported findings that vegetation characteristics can be sensitive indicators of variability in tree island ecosystem
structure. This study produced valuable, information which was used to recommend ecological targets (i.e. restoration performance
measures) for seasonally flooded tree islands in more impacted regions of the Everglades landscape. 相似文献
48.
Variable responses within epiphytic and benthic microalgal communities to nutrient enrichment 总被引:3,自引:3,他引:0
We evaluated how changes in nutrient supply altered the composition of epiphytic and benthic microalgal communities in a Thalassia testudinum (turtle grass) bed in Florida Bay. We established study plots at four sites in the bay and added nitrogen (N) and phosphorus
(P) to the sediments in a factorial design. After 18, 24, and 30 months of fertilization we measured the pigment concentrations
in the epiphytic and benthic microalgal assemblages using high performance liquid chromatography. Overall, the epiphytic assemblage
was P-limited in the eastern portion of the bay, but each phototrophic group displayed unique spatial and temporal responses
to N and P addition. Epiphytic chlorophyll a, an indicator of total microalgal load, and epiphytic fucoxanthin, an indicator of diatoms, increased in response to P addition
at one eastern bay site, decreased at another eastern bay site, and were not affected by P or N addition at two western bay
sites. Epiphytic zeaxanthin, an indicator of the cyanobacterial/coralline red algae complex, and epiphytic chlorophyll b, an indicator of green algae, generally increased in response to P addition at both eastern bay sites but did not respond
to P or N addition in the western bay. Benthic chlorophyll a, chlorophyll b, fucoxanthin, and zeaxanthin showed complex responses to N and P addition in the eastern bay, suggesting that the benthic
assemblage is limited by both N and P. Benthic assemblages in the western bay were variable over time and displayed few responses
to N or P addition. The contrasting nutrient limitation patterns between the epiphytic and benthic communities in the eastern
bay suggest that altering nutrient input to the bay, as might occur during Everglades restoration, can shift microalgal community
structure, which may subsequently alter food web support for upper trophic levels. 相似文献
49.
To determine relationships between soil nutrient status and known gradients in primary production, we collected and analyzed
soils from 17 LTER sampling sites along two transects through south Florida wetland ecosystems. Through upstream freshwater
marsh, a middle reach including the oligohaline marsh/mangrove ecotone, and downstream estuarine habitats, we observed systematic
variation in soil bulk density, organic content, and pools of phosphorus (P), inorganic sulfur, and extractable iron. Consistent
with observed differences in wetland productivity known to be limited by P availability, total P averaged ~200 μg g dw−1 in soils from the eastern Taylor Slough/Panhandle and was on average three times higher in soils from the western Shark River
Slough. Along both transects, the largest pool of phosphorus was the inorganic, carbonate-bound fraction, comprising 35–44%
of total P. Greater than 90% of the total inorganic sulfur pool in these south Florida wetland soils was extracted as pyrite.
Freshwater marsh sites typically were lower in pyrite sulfur (0.2–0.8 mg g dw−1) relative to marsh/mangrove ecotone and downstream estuary sites (0.5–2.9 mg g dw−1). Extractable iron in freshwater marsh soils was significantly higher from the Taylor Slough/Panhandle transect (3.2 mg g dw−1) relative to the western Shark River Slough transect (1.1 mg g dw−1), suggesting spatial variation in sources and/or depositional environments for iron. Further, these soil characteristics
represent the collective, integrated signal of ecosystem structure, so any long-term changes in factors like water flow or
water quality may be reflected in changes in bulk soil properties. Since the objective of current Everglades restoration initiatives
is the enhancement and re-distribution of freshwater flows through the south Florida landscape, the antecedent soil conditions
reported here provide a baseline against which future, post-restoration measurements can be compared. 相似文献
50.
CRISTINA DOCKX 《Biological journal of the Linnean Society. Linnean Society of London》2012,106(4):717-736
The eastern North American population of the monarch butterfly (Danaus plexippus plexippus) has different migratory routes. The majority fly to overwintering colonies in Mexico and others take an eastern route through Florida and Cuba. Monarchs migrating through Florida–Cuba do not overwinter and are mostly found nectaring and flying close to vegetation. This present study explores whether Florida–Cuba versus Mexican migrants differ in (1) phenotypic traits important for migration (e.g. wing size and condition, lipid and lean mass content, and reproductive status) and (2) migratory strategies. The monarch natal grounds (e.g. migrants versus residents) were determined through thin‐layer chromatography cardenolide fingerprint and stable isotopes (hydrogen δ2H and carbon δ13C). In addition, wing size and condition, lipid and lean mass, and reproductive status were determined. The results suggest that Mexican migrants are better suited for longer sustained flights and successful overwinter periods as a result of larger wings in better condition, reproductive diapause, and significant fat content. By contrast, Florida–Cuba migrants are more suited for shorter flights and opportunistic migratory strategies, given that their wings were in poor condition, as well as the active reproductive status of > 50% of these butterflies and their significantly low fat content. Eastern monarch migration is more complex and diverse than previously assumed. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??. 相似文献