(2009) Barr, J.G., Fuentes, J.D., Engel, V. and Zieman, J.C. Physiological responses of red mangroves to the climate in the Florida Everglades. Journal of Geophysical Research-Biogeosciences 114(

Abstract
This manuscript reports the findings of physiological studies of red mangrove (Rhizophora mangle L.) conducted from June to August 2001 and from May to June 2003 in the Florida Everglades. In situ physiological measurements were made using environmentally controlled gas exchange systems. The field investigations were carried out to define how regional climate constrains mangrove physiology and ecosystem carbon assimilation. In addition, maximum carboxylation and photosynthetic active radiation (PAR) limited carbon assimilation capacities were investigated during the summer season to evaluate whether ecophysiological models developed for mesophyte plant species can be applied to mangroves. Under summertime conditions in the Florida Everglades, maximum foliar carbon dioxide (CO2) assimilation rates reached 18 mmol CO2 m(-2) s(-1). Peak molar stomatal conductance to water vapor (H2O) diffusion reached 300 mmol H2O m(-2) s(-1). Maximum carboxylation and PAR-limited carbon assimilation rates at the foliage temperature of 30 degrees C attained 76.1 +/- 23.4 mu mol CO2 m(-2) s(-1) and 128.1 +/- 32.9 mmol (e(-)) m(-2) s(-1), respectively. Environmental stressors such as the presence of hypersaline conditions and high solar irradiance loading (> 500 W m(-2) or > 1000 mu moles of photons m(-2) s(-1) of PAR) imposed sharp reductions in carbon assimilation rates and suppressed stomatal conductance. On the basis of both field observations and model analyses, it is also concluded that existing ecophysiological models need to be modified to consider the influences of hypersaline and high radiational loadings on the physiological responses of red mangroves.

(2009) Belmont, M.A., White, J.R. and Reddy, K.R. Phosphorus Sorption and Potential Phosphorus Storage in Sediments of Lake Istokpoga and the Upper Chain of Lakes, Florida, USA. Journal of Environmental Quality 38(3), 987-996.

Abstract
Phosphorus (P) can be an important nutrient in regulating primary productivity in lakes. The ability of lake sediments to retain P from external sources depends on the physiochemical characteristics of the sediment. To assess the P dynamics in Lake Istokpoga and the upper chain of lakes that drain into Lake Okeechobee, Florida, USA, sorption properties of batch sediment samples for Lakes Tohopekaliga, Cypress, Hatchineha, Kissimmee, and Istokpoga were characterized under aerobic and anaerobic conditions. Langmuir model parameters fit the experimental data well (in general, r(2) > 0.70). There were strong correlations between P sorption and total C, total P, Ca, Mg, Fe, and Al (r = 0.83-0.97). Equilibrium P concentration values ranged between 0.001 and 0.192 mg L-1 for aerobic conditions. A single-point isotherm (initial concentration, 5 mg L-1) was found for a wide range of sediment types, which allows estimation of the maximum potential sorption (S) as 1.7 times the sorption (S-max = 1.7 S-s). Results suggest that although these sediments have high P sorption capacities, the lake sediments may release P into the water column by desorption under aerobic conditions if water-column P concentrations are low enough (<0.036 mg L-1 for Lake Tohopekaliga and <0.003-0.027 mg L-1 for the other four lakes). Current watershed management strategies must balance efforts to reduce P inputs into the lakes from point and nonpoint sources against lowering the water-column P concentration to such a low level that the lake sediments become a source of P to downstream Lake Okeechobee.

(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.

(2009) Herbert, D.A. and Fourqurean, J.W. Phosphorus Availability and Salinity Control Productivity and Demography of the Seagrass Thalassia testudinum in Florida Bay. Estuaries and Coasts 32(1), 188-201.

Abstract
Biomass, net primary productivity (NPP), foliar elemental content, and demography of Thalassia testudinum were monitored in populations from five sites across Florida Bay beginning in January 2001. Sites were selected to take advantage of the spatial variability in phosphorus (P) availability and salinity climates across the bay. Aboveground biomass and NPP of T. testudinum were determined five to six times annually. Short-shoot demography, belowground biomass, and belowground NPP were assessed from a single destructive harvest at each site and short-shoot cohorts were estimated from leaf scar counts multiplied by site-specific leaf production rates. Biomass, relative growth rate (RGR), and overall NPP were positively correlated with P availability. Additionally, a positive correlation between P availability and the ratio of photosynthetic to non-photosynthetic biomass suggests that T. testudinum increases allocation to aboveground biomass as P availability increases. Population turnover increased with P availability, evident in positive correlations of recruitment and mortality rates with P availability. Departures from seasonally modeled estimates of RGR were found to be influenced by salinity, which depressed RGR when below 20 psu or above 40 psu. Freshwater management in the headwaters of Florida Bay will alter salinity and nutrient climates. It is becoming clear that such changes will affect T. testudinum, with likely feedbacks on ecosystem structure, function, and habitat quality.

(2009) Hoang, T.C., Schuler, L.J., Rogevich, E.C., Bachman, P.M., Rand, G.M. and Frakes, R.A. Copper Release, Speciation, and Toxicity Following Multiple Floodings of Copper Enriched Agriculture Soils: Implications in Everglades Restoration. Water Air and Soil Pollution 199(1-4), 79-93.

Abstract
This study characterizes the effects of water-soil flooding volume ratio and flooding time on copper (Cu) desorption and toxicity following multiple floodings of field-collected soils from agricultural sites acquired under the Comprehensive Everglades Restoration Plan (CERP) in south Florida. Soils from four field sites were flooded with three water-soil ratios (2, 4, and 6 [water] to 1 [soil]) and held for 14 days to characterize the effects of volume ratio and flooding duration on Cu desorption (volume ratio and flooding duration study). Desorption of Cu was also characterized by flooding soils four times from seven field sites with a volume ratio of 2 (water) to 1 (soil) (multiple flooding study). Acute toxicity tests were also conducted using overlying waters from the first flooding event to characterize the effects of Cu on the survival of fathead minnows (Pimephales promelas), cladocerans (Daphnia magna), amphipods (Hyalella azteca), midges (Chironomus tentans), duckweed (Lemna minor), and Florida apple snails (Pomacea paludosa). Acute tests were also conducted with D. magna exposed to overlying water from the second and third flooding events. Results indicate that dissolved Cu concentrations in overlying water increased with flooding duration and decreased with volume ratio. In the multiple flooding study, initial Cu concentrations in soils ranged from 5 to 223 mg/kg (dw) and were similar to Cu concentration after four flooding events, indicating retention of Cu in soils. Copper desorption was dependent on soil Cu content and soil characteristics. Total Cu concentration in overlying water (Cu-w) was a function of dissolved organic carbon (DOC), alkalinity, and soil Cu concentration (Cu-s): log(Cu-w) = 1.2909 + 0.0279 (DOC) + 0.0026 (Cu-s) -aEuro parts per thousand 0.0038 (alkalinity). The model was validated and highly predictive. Most of the desorbed Cu in the water column complexed with organic matter in the soils and accounted for 99% of the total dissolved Cu. Although total dissolved Cu concentrations in overlying water did not significantly decrease with number of flooding events, concentrations of free Cu2+ increased with the number of flooding events, due to a decrease in DOC concentrations. The fraction of bioavailable Cu species (Cu2+, CuOH+, CuCO3) was also less than 1% of the total Cu. Overlying water from the first flooding event was only acutely toxic to the Florida apple snail from one site. However, overlying water from the third flooding of six out of seven soils was acutely toxic to D. magna. The decrease in DOC concentrations and increase in bioavailable Cu2+ species may explain the changes in acute toxicity to D. magna. Results of this study reveal potential for high Cu bioavailability (Cu2+) and toxicity to aquatic biota overtime in inundated agricultural lands acquired under the CERP.

(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.

(2009) 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(

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.

(2009) Liu, Y. and Labuschagne, M.T. The influence of environment and season on stalk yield in kenaf. Industrial Crops and Products 29(2-3), 377-380.

Abstract
Kenaf is an important fiber crop worldwide. it was recently introduced to South Africa as a commercial fiber crop. The aim of this study was to deter-mine how different environments and seasons influence stalk yield. Nine kenaf cultivars from various countries were analysed in two environments, over two consecutive seasons, where one location was irrigated and the other not. Data were recorded for total fresh yield, defoliated stalk yield and dry stalk yield. Yield stability was analysed with four different statistical models. The dry stalk yield varied from 15.33 to 17.78 ton/ha. El Salvador and Tainung 2 had high dry stalk yields in the favourable environments, but Tainung 2 did not have stable yield across all trials. Everglades 41 and El Salvador were the most stable of the varieties across both environments and seasons. El Salvador was the cultivar that had the highest and most stable dry stalk yield in the two seasons and two locations in South Africa, and should perform well in commercial production.

(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.

(2009) Miao, S.L., Zou, C.B. and Breshears, D.D. Vegetation Responses to Extreme Hydrological Events: Sequence Matters. American Naturalist 173(1), 113-118.

Abstract
Extreme hydrological events such as flood and drought drive vegetation dynamics and are projected to increase in frequency in association with climate change, which could result in sequences of extreme events. However, experimental studies of vegetation responses to climate have largely focused on responses to a trend in climate or to a single extreme event but have largely overlooked the potential for complex responses to specific sequences of extreme events. Here we document, on the basis of an experiment with seedlings of three types of subtropical wetland tree species, that mortality can be amplified and growth can even be stimulated, depending on event sequence. Our findings indicate that the impacts of multiple extreme events cannot be modeled by simply summing the projected effects of individual extreme events but, rather, that models should take into account event sequences.

(2009) Min, J.H. and Wise, W.R. Simulating short-circuiting flow in a constructed wetland: the implications of bathymetry and vegetation effects. Hydrological Processes 23(6), 830-841.

Abstract
Short-circuiting flow, commonly experienced in many constructed wetlands, reduces hydraulic retention times in unit wetland cells and decreases the treatment efficiency. A two-dimensional (2-D), physically based, distributed modelling approach was used to systematically address the effects of bathymetry and vegetation on short-circuiting flow, which previously have been neglected or lumped in one-dimensional wetland flow models. In this study, a 2-D transient hydrodynamics with advection-dispersion model was developed using MIKE 21 and calibrated with bromide tracer data collected at the Orlando Easterly Wetland Cell 7. The estimated topographic difference between short-circuiting flow zone and adjacent area ranged from 0.3 to 0.8 m. A range of the Manning roughness coefficient at the short-circuiting flow zone was estimated (0.022-0.045 s m(-1/3)). Sensitivity analysis of topographical and vegetative heterogeneity deduced during model calibration shows that relic ditches or other ditch-shaped landforms and the associated sparse vegetation along the main flow direction intensify the short-circuiting pattern, considerably affecting 2-D solute transport simulation. In terms of hydraulic efficiency, this study indicates that the bathymetry effect on short-circuiting flow is more important than the vegetation effect.

(2009) Regalado, C.M. and Ritter, A. A Soil Water Repellency Empirical Model. Vadose Zone Journal 8(1), 136-141.

Abstract
The contact angle (alpha) varies nonlinearly with the soil water content (theta(g)) in water-repellent soils; however, a quantitative description of such a theta(g) dependence of alpha is still lacking. Using a dimensionality reduction technique such as dynamic factor analysis (DFA), we managed to identify two common patterns within a scattered data set of a vs. theta(g) measurements performed with the molarity of an ethanol droplet test in 16 soil samples. These two common patterns, derived from the DFA, provided the basis for calibrating a proposed empirical, three-parameter, linear model that described satisfactorily (R-2 > 0.89) an additional alpha-theta(g) data set used for model validation, from 40 soil samples with organic matter contents spanning from 110 to 650 g kg(-1). This offered both scaling and a flexible quantitative description of the soil water content dependence of water repellency.

(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.

(2009) Ruehlmann, J. and Korschens, M. Calculating the Effect of Soil Organic Matter Concentration on Soil Bulk Density. Soil Science Society of America Journal 73(3), 876-885.

Abstract
Soil bulk density (rho(b)) is required to estimate, evaluate, and calculate many physical soil properties and processes and is essential to convert data from weight-based to volume- and area-related data. One of the dominating factors changing rho(b) is the soil's organic matter (SOM) concentration that alters the soil's compressibility; rho(b) is an important soil structure attribute. Currently, no parameter for characterizing soil compactness giving directly comparable values for all soils is available. Therefore, our aim was to develop a general approach to calculate the effect of SOM concentration on rho(b) that would be universally valid for soils different in their genesis, compaction, and type of land use. To describe the effect of SOM on rho(b) mathematically, we used a nonlinear regression model that was parameterized and validated using published data from experiments where SOM concentration was the main rho(b)-affecting factor (long-term fertilization and proctor experiments, wetlands, reclaimed soils, and volcanic soils). To obtain a standardized parameter describing the present compaction status of a site, we introduced the standardized bulk density s rho(b). Mathematically, s rho(b) is the intercept parameter of the used nonlinear regression model, and ranged between 0.7 and 2.1 Mg m(-3) and was very simple to estimate. Another distinct advantage of this novel concept is that only one representative pair of rho(b) and SOM has to be known to calculate s rho(b) as well as the bulk densities corresponding to other SOM concentrations measured on the site. This concept might also be helpful for identifying similar universal approaches to standardize the effect of other rho(b) affecting parameters (e.g., texture, soil depth, tillage regime), however, reassessed from the SOM effect.

(2009) Wang, H.Q., Walclon, M.G., Meselhe, E.A., Arceneaux, J.C., Chen, C.F. and Harwell, M.C. Surface Water Sulfate Dynamics in the Northern Florida Everglades. Journal of Environmental Quality 38(2), 734-741.

Abstract
Sulfate contamination has been identified as a serious environmental issue in the Everglades ecosystem. However, it has received less attention compared to P enrichment. Sulfate enters the Arthur R. Marshall Loxahatchee National Wildlife Refuge (Refuge), a remnant of the historic Everglades, in pumped stormwater discharges with a mean concentration of approximately 50 mg L-1, and marsh interior concentrations at times fall below a detection limit of 0.1 mg L-1. In this research, we developed a sulfate mass balance model to examine the response of surface water sulfate in the Refuge to changes in sulfate loading and hydrological processes. Meanwhile, sulfate removal resulting from microbial sulfate reduction in the underlying sediments of the marsh was estimated from the apparent settling coefficients incorporated in the model. The model has been calibrated and validated using long-term monitoring data (1995-2006). Statistical analysis indicated that our model is capable of capturing the spatial and temporal variations in surface water sulfate concentrations across the Refuge. This modeling work emphasizes the fact that sulfate from canal discharge is impacting even the interior portions of the Refuge, supporting work by other researchers. In addition, model simulations suggest a condition of sulfate in excess of requirement for microbial sulfate reduction in the Refuge.

(2008) Cade, B.S. and Dong, Q. A quantile count model of water depth constraints on Cape Sable seaside sparrows. Journal of Animal Ecology 77(1), 47-56.