Javascript DHTML Drop Down Menu Powered by dhtml-menu-builder.com
Go to Everglades-HUB homepage

Abstracts-Wetlands'09

Literature
     Search Site:

EvergladesHUB Home > Science Literature > Wetlands-ABSTRACTS'09

 
  ABSTRACTS
abs     TEXT (2010) Naja, G.M., Rivero, R., Davis, S.E., Van Lent, T. Hydrochemical Impacts of Limestone Rock Mining. Water, Air and Soil Pollution (online, August 2010: http://www.springerlink.com/content/0t440560178m2k30/)
 
ABSTRACT
Hydrochemical impacts of shallow rock industrial-scale mining activities close to sensitive constructed and natural wetlands were investigated. The shallow surficial groundwater and surface water in the Everglades Agricultural Area (EAA) were characterized. The chemical composition of sulfate and chloride in groundwater increased with depth. The average concentration of chloride averaged 182 mg/L at 6 m deep and increased gradually to 1,010 mg/L at 15 m deep, 1,550 mg/L at 30 m deep to reach 7,800 mg/L at 60 m deep. Comparatively, the surface water chemical composition in the surrounding areas showed much lower cationic and anionic charge. The specific conductivity and total dissolved solids of surface water in canals (close to the mining operations) are <900 μS/cm and <600 mg/L, respectively, which should be compared to groundwater quality in wells from the EAA area (>2,000 μS/cm and >1,000 mg/L, respectively). A steady-state groundwater fluid flow and transient solute transport modeling exercise was conducted to estimate surface/groundwater interactions. The modeled solute in surface water was transported downgradient through groundwaters, migrated approximately 30 m from the source area (after 5 years of operation), and needed more than 116 years to dissipate. An upward transport was also identified whereby chloride and sulfate, naturally present in deeper groundwaters, migrated approximately 200 m (after 1 year of mining) into the pristine shallower aquifer and reached the surface water with a concentration equaling 80% of that in the rock mining pit.
top     TEXT

(2009) Chang, C.C.Y., McCormick, P.V., Newman, S. and Elliott, E.M. Isotopic indicators of environmental change in a subtropical wetland. Ecological Indicators 9(5), 825-836.

  ABSTRACT
The delta N-15 and delta C-13 signatures of major organic matter (OM) pools were measured across chemical and hydrologic gradients in a large (58,800 ha) subtropical wetland to evaluate whether stable isotopes were useful indicators of environmental change. Once a rainfall-driven wetland, the Loxahatchee National Wildlife Refuge in the Florida Everglades now receives agricultural and urban drainage that has increased phosphorus (P) and mineral loads around the wetland perimeter. Additionally, water impoundment at the southern end has produced a latitudinal hydrologic gradient, with extended hydroperiods in the south and overdrained conditions in the north. Detritus (-4.8 parts per thousand to 8.6 parts per thousand), floc (-1.4 parts per thousand to 3.6 parts per thousand), and metaphyton (-6.6 parts per thousand to +7.4 parts per thousand) delta N-15 declined southward with changes in hydrology as indicated by water depth. This pattern was attributed to higher mineralization rates under shorter hydroperiods. These signatures were also strongly correlated with increased nutrient and mineral loading. Rooted macrophyte delta N-15, by contrast, appeared more responsive to soil nutrient pools. Cattail (-8.9 parts per thousand to +7.7 parts per thousand) was restricted to the wetland perimeter and had the widest delta N-15 range, which was positively correlated with soil P. Sawgrass (-5.3 parts per thousand to +7.7 parts per thousand) occurred across most of the wetland, but its ON was not strongly correlated to any gradient. Patterns for delta C-13 were more strongly related to chemical gradients caused by canal intrusion than to latitude or hydrology. Again, metaphyton and detrital signatures were more sensitive to water chemistry changes than macrophytes. This pattern is consistent with their locations at the soil-water (detritus-floc), and air-water (metaphyton) interface. Metaphyton delta C-13 (-36.1 parts per thousand to -21.5 parts per thousand) which had the broadest range, was affected by DIC source and pool size. In contrast, cattail delta C-13 (-28.7 parts per thousand to -26.4 parts per thousand) was more closely related to soil P and sawgrass delta C-13 (-30.1 parts per thousand to -24.5 parts per thousand) was not related to any environmental gradient except latitude. There was no correlation between the two isotopes for any OM pool except cattail. These results indicate that isotopic signatures of microbial (metaphyton and detrital) pools are more responsive to changes in wetland hydrology and water chemistry while those of rooted macrophytes respond only to the extent that soil chemistry is altered. Rooted macrophytes also differ in the sensitivity of their isotopic signatures to environmental change. The selection of OM pools for isotopic analysis will, therefore, affect the sensitivity of the analysis and the resulting patterns. Furthermore, delta N-15 may be more robust and interpretable than delta C-13 as an indicator of ecosystem change in wetlands exposed to multiple or complex anthropogenic gradients.
top     TEXT

(2009) Doyle, T.W., Krauss, K.W. and Wells, C.J. Landscape Analysis and Pattern of Hurricane Impact and Circulation on Mangrove Forests of the Everglades. Wetlands 29(1), 44-53.

  ABSTRACT
The Everglades ecosystem contains the largest contiguous tract of mangrove forest Outside the tropics that were also coincidentally intersected by a major Category 5 hurricane. Airborne videography was flown to Capture the landscape patient and process of forest damage in relation to storm trajectory and circulation. TWO aerial video transects, representing different topographic positions, were used to quantify forest damage from video frame analysis in relation to prevailing wind force, treefall direction, and forest height. A hurricane simulation model wits applied to reconstruct wind fields corresponding to the ground location of each video frame and to correlate observed treefall and destruction patterns with wind speed and direction. Mangrove forests within the storm's eyepath and ill the right-side (forewind) quadrants suffered whole or partial blowdowns, while left-side (backwind) sites South of the eyewall zone incurred moderate canopy reduction and defoliation. Sites along file coastal transect sustained substantially more storm damage than sites along the inland transect which may be attributed to differences in stand exposure and/or Mature. Observed treefall directions were shown to be non-random and associated with hurricane trajectory and simulated forewind azimuths. Wide-area sampling using airborne videography provided an efficient adjunct to limited ground observations and improved our spatial understanding of how hurricanes imprint landscape-scale patterns of disturbance.
top     TEXT

(2009) Dray, F.A., Hale, R.E., Madeira, P.T., Bennett, B.C. and Center, T.D. Concordance between life history traits, invasion history, and allozyme diversity of the Everglades invader Melaleuca quinquenervia. Aquatic Botany 90(4), 296-302.

  ABSTRACT
During the century following its initial introduction in 1886, the Australian tree Melaleuca quinquenervia (Myrtaceae) dispersed from a few introduction points to occupy over 200,000 ha, primarily in historic Everglades wetlands of southern Florida. Cellulose acetate gel electrophoresis (CAGE) was used to investigate the allozyme diversity and population genetic structure of 208 individuals in a dozen populations resulting from this invasion. The analyses showed that these populations have a high (82%) rate of polymorphic loci and an average of 2 alleles/locus. There was substantial heterozygosity (mean H-e = 0.356), which concords well with recent studies reporting a greater number of introduction events and sources than generally recognized. The introduction history and distributional patterns within Florida have led to geographic structuring (G(ST) = 0.419) in which the Gulf Coast metapopulation has a greater effective number of alleles and greater heterozygosity than the Atlantic Coast metapopulation. The gene diversity in M. quinquenervia was comparable to other tropical woody species. Its strong population divergence was reminiscent of pioneer species and consistent with its status as a plant invader in Florida.
top     TEXT

(2009) Gandiaga, S., Volin, J.C., Kruger, E.L. and Kitajima, K. Effects of hydrology on the growth and physiology of an invasive exotic, Lygodium microphyllum (Old World climbing fern). Weed Research 49(3), 283-290.

  ABSTRACT
We conducted a glasshouse study to examine effects of hydrology on the growth and physiology of Lygodium microphyllum (Old World climbing fern), an invasive exotic that is rapidly colonising forested wetlands in Florida, USA. We assessed the fern's growth and physiological responses to three hydrological treatments - flood, drought and field capacity. To further explore the physiology of the treatment responses of L. microphyllum, we also sprayed each plant with gibberellic acid, paclobutrazol (gibberellin inhibitor) or a water control solution (at a rate of 5 mL three times per week) using a 3 x 3 factorial design. Flooding reduced relative growth rate by 55%, whereas periodic exposure of ferns to a soil water potential of -1 MPa did not affect growth or physiology. Flooding led to substantial decreases in specific leaf area and area-based rates of pinna photosynthesis, resulting in a 64% lower rate of photosynthesis per unit pinna mass. Application of growth regulators had no effect on fern growth, morphology or physiology. Even though flooding substantially reduced growth, L. microphyllum still showed a positive relative growth rate after > 2 months of inundated soils. This apparent hydrological plasticity is likely a contributing factor to the introduced fern's widespread establishment across a range of plant communities within the Florida Everglades ecosystem. Short-term manipulation of site hydrology does not appear to be an effective management option. Consequently, this has considerable implications for the Everglades, which is undergoing a 30-year system-wide hydrological restoration.
top     TEXT

(2009) Harvey, J.W. and McCormick, P.V. Groundwater's significance to changing hydrology, water chemistry, and biological communities of a floodplain ecosystem, Everglades, South Florida, USA. Hydrogeology Journal 17(1), 185-201.

  ABSTRACT
The Everglades ( Florida, USA) is one of the world's larger subtropical peatlands with biological communities adapted to waters low in total dissolved solids and nutrients. Detecting how the pre-drainage hydrological system has been altered is crucial to preserving its functional attributes. However, reliable tools for hindcasting historic conditions in the Everglades are limited. A recent synthesis demonstrates that the proportion of surface-water inflows has increased relative to precipitation, accounting for 33% of total inputs compared with 18% historically. The largest new source of water is canal drainage from areas of former wetlands converted to agriculture. Interactions between groundwater and surface water have also increased, due to increasing vertical hydraulic gradients resulting from topographic and water-level alterations on the otherwise extremely flat landscape. Environmental solute tracer data were used to determine groundwater's changing role, from a freshwater storage reservoir that sustained the Everglades ecosystem during dry periods to a reservoir of increasingly degraded water quality. Although some of this degradation is attributable to increased discharge of deep saline groundwater, other mineral sources such as fertilizer additives and peat oxidation have made a greater contribution to water-quality changes that are altering mineral-sensitive biological communities.
top     TEXT

(2009) Inglett, P.W., D'Angelo, E.M., Reddy, K.R., McCormick, P.V. and Hagerthey, S.E. Periphyton nitrogenase activity as an indicator of wetland eutrophication: spatial patterns and response to phosphorus dosing in a northern Everglades ecosystem. Wetlands Ecology and Management 17(2), 131-144.

  ABSTRACT
The use of periphyton nitrogenase activity (biological N-2 fixation) as an indicator of wetland P impact was assessed using patterns of nutrient content (C, N, P, Ca, Mg, K, Fe, and Mn) and acetylene reduction (AR) in floating cyanobacterial periphyton mat (metaphyton) communities of a P-enriched portion of the Florida Everglades, USA (Water Conservation Area-2A, WCA-2A). Spatial patterns of nutrients indicate the enrichment of floating mat periphyton N, P, Fe, and K, and the reduction of Mn and TN:TP in enriched marsh areas. In highly enriched areas, floating mat periphyton AR was approximately threefold greater than that in less enriched, interior marsh zones. Multiple regression models indicated AR dependence on P in eutrophicWCA-2A areas while the AR of more interior marsh periphyton mats was more closely related to tissue levels of Ca and Fe. Nitrogenase activity of floating mat periphyton from P-loaded mesocosms revealed a significant enhancement of N-2 fixation in samples receiving approximately 2-3 mg P m(-2) of cumulative P dosing or with biomass TP content of 100-300 mg kg(-1). At P contents above the optimum, mat periphyton AR was suppressed possibly as a result of changes in species composition or increased levels of NH4+. After 3 years of dosing, consistently high AR occurred only at low rates of P enrichment (0.4-0.8 g P m(-2) yr(-1)), and the patterns appeared to be seasonal. These findings agree with the hypothesis that P availability is a key determinant of nitrogenase activity in aquatic systems, and thus, may support the use of periphyton nitrogenase to indicate P impacts in P-limited systems. These results also demonstrate the potential existence of a P threshhold for biogeochemical alteration of periphyton mat function in the Everglades, and that cumulative loading of limiting nutrients (i.e., P), rather than instantaneous concentrations, should be considered when evaluating nutrient criteria.
top     TEXT

(2009) Knickerbocker, C.M., Leitholf, S., Stephens, E.L., Keellings, D.J., Laird, H., Anderson, C.J.R., Fauth, J.E. and Quintana-Ascencio, P.F. Tree Encroachment of A Sawgrass (Cladlum jamaicense) Marsh within an Increasingly Urbanized Ecosystem. Natural Areas Journal 29(1), 15-26.

  ABSTRACT
Fire suppression and altered water drainage often change community structure and species composition in human-dominated ecosystems. We describe the decline of sawgrass marshes between 1940 and 2002, and assess the current condition of remnant marshes within the MacKay Tract, an isolated wetland embedded within rapidly developing eastern Orlando, Florida. We tested the correlation between live sawgrass and presence of adult hardwood trees and seedlings (primarily red maple, Acer rubrum) and describe vegetation in plots with different levels of tree encroachment. Total area occupied by open sawgrass in the MacKay Tract has declined dramatically the last 60 years, in 2006, open sawgrass comprised only 12% of the area covered in 1940. Tree basal cover was negatively associated with live sawgrass and positively related to red maple seedling density, but not associated with dead sawgrass tussocks. Sawgrass was positively correlated with the second axis of a non-metric multidimensional scaling ordination on understory plant assemblage, while red maple seedlings and several species associated with disturbed areas were significantly negatively cot-related with this axis. Another nine plant species were positively correlated with the first axis, while Osmunda cinnamomea (cinnamon fern) was negatively associated with it. We suggest that woody species are continuing to colonize what is left of the sawgrass marsh. Without intervention (e.g., restoring hydrologic flow and fire), the sawgrass (Cladium jamaicense Crantz) area within the marsh will continue being replaced by woody and exotic species.
top     TEXT

(2009) Lai, D.Y. and Lam, K.C. Phosphorus sorption by sediments in a subtropical constructed wetland receiving stormwater runoff. Ecological Engineering 35(5), 735-743.

  ABSTRACT
This study investigated the potential of using a mixture of fishpond bund material, completely decomposed granite and river sand as substrate in a constructed wetland for phosphorus removal. Core samples were collected from the newly constructed Hong Kong Wetland Park (HKWP) receiving influent stormwater from a nearby new town, and batch incubation experiments were conducted to determine the P sorption characteristics of sediments. The HKWP sediments adsorbed the majority of available P in the initial 20 min of incubation, with a first-order rate constant of 1.01-2.11 h(-1). Sediments in the reedbeds and freshwater marshes possessed a great capacity for P adsorption with the high Langmuir sorption maxima (478-858 mg kg(-1)) and Freundlich adsorption constants (417-672 L kg(-1)) obtained, attributable to the high amorphous iron and aluminium concentrations compared to other constructed wetlands. Moreover, sediment equilibrium P concentrations were generally low (4.6-23.6 mu g L-1), facilitating a net P adsorption by sediments under moderate P loadings. Yet, the amount of P adsorbed by the HKWP sediments was limited by the low ambient porewater P concentrations and there was even a risk of P desorption when sediments in the freshwater marshes were resuspended into the water column. While substrates in the HKWP demonstrated a great potential for P adsorption, consideration should also be given to P loadings in influent water to fully utilize the P sorption capacity of sediments and enhance the P removal efficiency of constructed wetlands.
top     TEXT

(2009a) Larsen, L.G., Harvey, J.W. and Crimaldi, J.P. Morphologic and transport properties of natural organic floc. Water Resources Research 45, Art.No.W01410

  The morphology, entrainment, and settling of suspended aggregates ("floc'') significantly impact fluxes of organic carbon, nutrients, and contaminants in aquatic environments. However, transport properties of highly organic floc remain poorly understood. In this study detrital floc was collected in the Florida Everglades from two sites with different abundances of periphyton for use in a settling column and in racetrack flume entrainment experiments. Although Everglades flocs are similar to other organic aggregates in terms of morphology and settling rates, they tend to be larger and more porous than typical mineral flocs because of biostabilization processes and relatively low prevailing shear stresses typical of wetlands. Flume experiments documented that Everglades floc was entrained at a low bed shear stress of 1.0 x 10(-2) Pa, which is considerably smaller than the typical entrainment threshold of mineral floc. Because of similarities between Everglades floc and other organic floc populations, floc transport characteristics in the Everglades typify the behavior of floc in other organic-rich shallow-water environments. Highly organic floc is more mobile than less organic floc, but because bed shear stresses in wetlands are commonly near the entrainment threshold, wetland floc dynamics are often transport-limited rather than supply limited. Organic floc transport in these environments is therefore governed by the balance between entrainment and settling fluxes, which has implications for ecosystem metabolism, materials cycling, and even landscape evolution.
top     TEXT

(2009b) Larsen, L.G., Harvey, J.W., Noe, G.B. and Crimaldi, J.P. Predicting organic floc transport dynamics in shallow aquatic ecosystems: Insights from the field, the laboratory, and numerical modeling. Water Resources Research 45, Art.No. W01411.

  ABSTRACT
Transport of particulate organic material can impact watershed sediment and nutrient budgets and can alter the geomorphologic evolution of shallow aquatic environments. Prediction of organic aggregate ("floc'') transport in these environments requires knowledge of how hydraulics and biota affect the entrainment, settling, and aggregation of particles. This study evaluated the aggregation and field transport dynamics of organic floc from a low-gradient floodplain wetland with flow-parallel ridges and sloughs in the Florida Everglades. Floc dynamics were evaluated in a rotating annular flume and in situ in the field. Under present managed conditions in the Everglades, floc is not entrained by mean flows but is suspended via biological production in the water column and bioturbation. Aggregation was a significant process affecting Everglades floc at high flume flow velocities (7.0 cm s(-1)) and during recovery from high flow; disaggregation was not significant for the tested flows. During moderate flows when floc dynamics are hydrodynamically controlled, it is possible to model floc transport using a single "operative floc diameter'' that accurately predicts fluxes downstream and to the bed. In contrast, during high flows and recovery from high flows, aggregation dynamics should be simulated. When entrained by flow in open-water sloughs, Everglades floc will be transported downstream in multiple deposition and reentrainment events but will undergo net settling when transported onto ridges of emergent vegetation. We hypothesize that net transport of material from open to vegetated areas during high flows is critical for forming and maintaining distinctive topographic patterning in the Everglades and other low-gradient floodplains.
top     TEXT

(2009) Marshall, F.E., Wingard, G.L. and Pitts, P. A Simulation of Historic Hydrology and Salinity in Everglades National Park: Coupling Paleoecologic Assemblage Data with Regression Models. Estuaries and Coasts 32(1), 37-53.

  ABSTRACT
Restoration of Florida's Everglades requires scientifically supportable hydrologic targets. This study establishes a restoration baseline by developing a method to simulate hydrologic and salinity conditions prior to anthropogenic changes. The method couples paleoecologic data on long-term historic ecosystem conditions with statistical models derived from observed meteorologic and hydrologic data that provide seasonal and annual variation. Results indicate that pre-drainage freshwater levels and hydroperiods in major sloughs of the Everglades were about 0.15 m higher and two to four times greater, respectively, on average compared to today's values. Pre-drainage freshwater delivered to the wetlands and estuaries is estimated to be 2.5 to four times greater than the modern-day flow, and the largest deficit is during the dry season. In Florida Bay, salinity has increased between 5.3 and 20.1 with the largest differences in the areas near freshwater outflow points. These results suggest that additional freshwater flows to the Everglades are needed for restoration of the freshwater marshes of the Everglades and estuarine environment of Florida Bay, particularly near the end of the dry season.
top     TEXT

(2009) McCormick, P., Newman, S. and Vilchek, L. Landscape responses to wetland eutrophication: loss of slough habitat in the Florida Everglades, USA. Hydrobiologia 621(105-114.

  ABSTRACT
Much of the historical Everglades has been either lost or degraded as a result of human activities. Among the aquatic habitats that comprise the Everglades landscape mosaic, open-water sloughs support critical ecological functions and appear especially sensitive to both hydrologic and water-quality perturbations. We used a combination of remote sensing and on-the-ground sampling to document spatial changes in the extent and vegetative composition of sloughs along a phosphorus (P) gradient in the northern Everglades. Increasing levels of water and soil P were associated with a decline in slough coverage, loss of the abundant native periphyton community, and a shift in dominant macrophyte species. The characteristic slough macrophyte species Eleocharis cellulosa and Nymphaea odorata exhibited different sensitivities to P enrichment, but both species declined with enrichment as slough habitats were invaded by Typha domingensis, a species that is known to expand aggressively in response to enrichment. A limited amount of open-water habitat occurred in highly enriched areas, but these habitats were maintained largely as a result of airboat disturbance and did not contain characteristic slough vegetation. Many changes in slough coverage and composition occurred in areas where water and soil P concentrations were only marginally higher than background levels. Our findings support the need for Everglades hydrologic restoration efforts to adhere to strict water-quality standards for P to avoid further degradation of this key landscape feature.
top     TEXT

(2009) Miao, S.L. and Zou, C.B. Seasonal variation in seed bank composition and its interaction with nutrient enrichment in the Everglades wetlands. Aquatic Botany 90(2), 157-164.

  ABSTRACT
In the Florida Everglades, nutrient enrichment from agricultural outflow and the change in hydrology have collectively contributed to the expansion of cattails (Typha spp.). To assess the effectiveness of prescribed fire in controlling cattails and to predict vegetation dynamics after the fire, it is important to understand the seasonal variation of the soil seed bank and how the seed bank is affected by nutrient enrichment and fire. This paper investigates the effects of season, nutrient enrichment, and fire on soil seed bank species composition, richness, and density along a nutrient gradient in Water Conservation Area 2A (WCA 2A) of the Florida Everglades. Species richness was significantly affected by nutrient enrichment and season but not their interaction. Total seed density, however, was significantly affected by the interaction between nutrient enrichment and season. Yet, at species level, the relationship between seed density, nutrient enrichment and season varied. The highest seed density of cattail occurred in summer at highly enriched sites, but that of sawgrass occurred in fall regardless of enrichment; the seed density of water lily was very low regardless of season and nutrient enrichment, and the highest Amarathus seed density occurred at highly enriched sites year round. Moreover, germination timing differed greatly among species. While cattail seeds had a short incubation period and started to germinate 2-3 days after initiation of the germination assay, sawgrass seeds generally started to germinate 4 weeks later. Further, both the prescribed summer fire at the highly enriched site and the natural winter fire at the moderately enriched site reduced the seed density of cattail but not of sawgrass. Our results suggest that fire application for vegetation recovery in WCA 2A would benefit from explicitly considering seasonal dynamics of the seed bank.
top     TEXT

(2009) Richardson, T.C., Robison, C.P., Neubauer, C.P. and Hall, G.B. Hydrologic Signature Analysis of Select Organic Hydric Soil Indicators in Northeastern Florida. Soil Science Society of America Journal 73(3), 831-840.

  ABSTRACT
The magnitude, duration, and return intervals of surface water flooding and dewatering of the landward extent of the hydric soil indicators muck (LM), histic epipedon (LHE), and Histosol (LH) were quantitatively defined, providing a better understanding of the hydrologic conditions maintaining these hydric soil indicators. Land surface elevations were determined for the LM, LHE, and LH at 16 lakes with long-term (30-60-yr) modeled or gauged hydrologic data. The probability of flooding and dewatering of the elevations of the LM, LHE, and LH were determined from frequency analysis of hydrologic data from each lake. The resulting hydrologic signatures for the LM, LHE, and LH are composed of magnitude and return interval of 1, 30, 90, 183, 274, and 365-d duration flooding and dewatering events. As an example, the LM, LHE, and LH were flooded for 30 continuous days with average annual probabilities of 42, 65, and 77%, respectively. As a second example, the LM, LHE, and LH were dewatered for 365 continuous days with average annual probabilities of 49, 24, and 16%, respectively. Probabilities of flooding and dewatering for the LM, LHE, and LH are presented for 1, 30, 90, 183, 274, and 365-d durations. Mean hydrologic signatures reduce variability and may be considered representative of each soil characteristic. Quantitatively defining the hydrology associated with the presence of the LM, LHE, and LH as well as other soil characteristics is essential for environmental protection, assessment of hydrologic impacts, wetlands restoration, wetlands creation, and other environmental management applications.
top     TEXT

(2009) Smith, T.J., Anderson, G.H., Balentine, K., Tiling, G., Ward, G.A. and Whelan, K.R.T. Cumulative Impacts of Hurricanes on Florida Mangrove Ecosystems: Sediment Deposition, Storm Surges and Vegetation. Wetlands 29(1), 24-34.

  ABSTRACT
Hurricanes have shaped the structure of mangrove forests ill the Everglades via wind damage, storm Surges and sediment deposition. Immediate effects include changes to stern size-frequency distributions and to species relative abundance and density. Long-term impacts to mangroves are poorly Understood at present. We examine impacts of Hurricane Wilma oil mangroves and compare the results to findings from three previous storms (Labor Day, Donna, Andrew). Surges during Wilma destroyed 1,250 ha of mangroves and set back recovery that started following Andrew. Data from permanent plots affected by Andrew and Wilma showed no differences among species or between hurricanes for % stern mortality or % basal area lost. Hurricane damage was related to hydro-geomorphic type of forest. Basin mangroves suffered significantly more damage than riverine or island mangroves. The hurricane by forest type interaction was highly significant. Andrew did slightly more damage to island mangroves. Wilma did significantly more damage to basin forests. This is most likely a result of the larger and more spatially extensive storm surge produced by Wilma. Forest damage was not related to amount. of sediment deposited. Analyses of reports from Donna and the Labor Day storm indicate that sonic sites have recovered following catastrophic disturbance. Other sites have been permanently converted into a different ecosystem, namely intertidal mudflats. Our results indicate that mangroves are not in a steady state as has been recently claimed.
top     TEXT

(2009) Utescher, T., Ivanov, D., Harzhauser, M., Bozukov, V., Ashraf, A.R., Rolf, C., Urbat, M. and Mosbrugger, V. Cyclic climate and vegetation change in the late Miocene of Western Bulgaria. Palaeogeography Palaeoclimatology Palaeoecology 272(1-2), 99-114.

  ABSTRACT
A late Miocene paludal to lacustrine sequence from a carbonate basin in NW Bulgaria (Staniantsi Basin) is analysed displaying up to 27 rhythmically bedded sedimentary cycles. In the lower part of the sequence, the cycles consist of alternating autochthonous brown coal and marls containing diverse mollusc assemblages. The upper part of the sequence is characterized by alternating dark to light grey clays and calcareous silts. A palynomorph record comprising 163 samples is analysed by statistical means to reconstruct vegetation changes. The Coexistence Approach is used to calculate quantitative palaeoclimate records for 6 parameters. The studied section displays hierarchical cyclicity patterns. Longer-term cycles possibly related to eccentricity (period similar to 100 kyr) are present in the palynomorph record and show climate changes of warmer/wetter and cooler/drier periods in combination with frequency oscillations of thermophilous elements. Short-term cycles most probably related to precession (period similar to 21.7 kyr) are expressed by alternations of brown coal and marl/shell beds and show cyclic change in peat-forming vegetation related to oscillations of the groundwater level. As a triggering mechanism, wetter/warmer and drier/cooler climate phases related to orbital precession are probable. In addition, sections sampled at high resolution display small scale climate and vegetational variability. As is shown by the analysis ferns were an important component of the peat-forming vegetation, while outside the mire, a wetland vegetation consisting of pioneers and a mixed mesophytic forest with evergreen shrubs existed. An oligo- to mesotrophic slightly alkaline lake became repeatedly established with a diverse mollusc fauna and a dense hydrophytic vegetation with characean meadows. In the upper part of the section, a spreading of herbaceous vegetation is observed, also known from other contemporaneaous palynomorph records in Bulgaria and surrounding areas. The increase of Asteraceae in the upper part of the section, combined with a marked decrease in woody taxa, points to an opening of habitats and a decrease in mean annual precipitation. This trend is paralleled by the mollusc fauna which yields several terrestrial, partly xerophilous taxa.
top     TEXT

(2009) Webb, J., Miao, S.L. and Zhang, X.H. Factors and mechanisms influencing seed germination in a wetland plant sawgrass. Plant Growth Regulation 57(3), 243-250.

  ABSTRACT
Sawgrass (Cladium jamaicense) is the predominant plant and vegetation community in the Florida Everglades. Germination of sawgrass seeds in the laboratory or nursery has been difficult and problematic, yet little is known about the physiological mechanistic regulation of the sawgrass seed germination process. In the present study, we examined the factors and mechanisms that influence sawgrass seed germination. We found that removal of seed husk and bracts, pre-soaking with bleach (hypochlorite), breaking the seed coat, or combinations of these treatments promoted the rate and success of germination, whereas presence of seed-encasing structures or treatment with husk/bract extract inhibited germination. We further detected the presence of abscisic acid (ABA) in the husk and bract. Experiments with ABA and gibberellin biosynthesis inhibitors fluridone and tetcyclacis suggested that ABA already presented in the pre-imbibed seeds, and not derived through post-dormancy de novo synthesis, contributed to the inhibition of seed germination. Examination of bleach and mechanical treatments indicated the physical barrier presented by the seed-encasing structures provided additional mechanism for the long-term delay of seed germination. Based on the results of this study and others, we discussed the implications of sawgrass seed dormancy and germination in relation to its natural habitat and proposed a hypothesis that the protracted seed dormancy in sawgrass offered an adaptive advantage in the pre-anthropogenic Everglades environment, but may become a liability in the current man-managed Everglades water system.
top     TEXT (2009) Whelan, K.R.T., Smith, T.J., Anderson, G.H. and Ouellette, M.L. Hurricane Wilma's Impact on Overall Soil Elevation and Zones within the Soil Profile in a Mangrove Forest. Wetlands 29(1), 16-23.
  ABSTRACT
Soil elevation affects tidal inundation period, inundation frequency, and overall hydroperiod, all of which are important ecological factors affecting species recruitment composition, and survival in wetlands. Hurricanes can dramatically affect a site's soil elevation. We assessed the impact of Hurricane Wilma (2005) on soil elevation at a mangrove forest location along the Shark River in Everglades National Park, Florida, USA. Using multiple depth surface elevation tables (SETs) and marker horizons we measured soil accretion, erosion, and soil elevation. We partitioned the effect of Hurricane Wilma's storm deposit into four constituent soil zones: surface accretion) zone, shallow zone (0-0.35 m). middle zone (0.35-4 m), and deep zone (4-6 m). We report expansion and contraction of each soil zone. Hurricane Wilma deposited 37.0 (+/- 3.0 SE) mm of material: however, the absolute soil elevation change was + 42.8 mm due to expansion in the shallow soil zone. One year post-hurricane, the soil profile had lost 10.0 mm in soil elevation, with 8.5 mm of the loss due to erosion. The remaining soil elevation loss was due to compaction from shallow subsidence. We found prolific growth of new fine rootlets (209 +/- 34 SE g m(-2)) in the storm deposited material suggesting that deposits may become more stable in the near future (i.e., erosion rate will decrease). Surficial erosion and belowground processes both played an important role ill determining the overall soil elevation. Expansion and contraction ill the shallow soil zone may be due to hydrology. and in the middle and bottom soil zones due 10 shallow subsidence. Findings thus far indicate that soil elevation has made substantial gains compared to site specific relative sea-level rise, but data trends suggest that below-round processes, which differ by soil zone. may come to dominate the long term ecological impact of storm deposit.
top   

ABSTRACT

   

2009-2014, Boya Volesky
E-mail: evergladeshub@gmail.com