Herbaceous Marsh Research Articles

Freshwater Fish Assemblages in Isolated South Florida Wetlands

Abstract We sampled fish communities in 19 isolated cypress pond and herbaceous marsh wetlands at locations in southwest, south-central, and southeast Florida. Breder fish traps were more effective at sampling fish communities at these sites than either seine or dip nets. We collected 23 total species, but species richness varied from 1–16 among sites. The availability of deepwater refugia and the extent to which periodic flooding connected these wetland habitats to other aquatic environments appeared to be principal factors influencing composition of fish assemblages. Models of fish distribution in response to hydrological changes in the Everglades have proposed size-structured, fish functional groups of ≤ or > 7 cm, but our data suggested size and ecology of fish functional groups in isolated wetlands may be better described as small, omnivorous species (≤15 cm) and larger predatory species (> 15 cm). We suggest incorporating fish functional groups in programs to monitor ecological health of isolated we...

Subtroprical wetland fish assemblages and changing salinity regimes: Implications for everglades restoration

During the 1960s, water management practices resulted in the conversion of the wetlands that fringe northeastern Florida Bay (USA) from freshwater/oligohaline herbaceous marshes to dwarf red mangrove forests. Coincident with this conversion were several ecological changes to Florida Bay’s fauna, including reductions in the abundances of top trophic-level consumers: piscivorous fishes, alligators, crocodiles, and wading birds. Because these taxa rely on a common forage base of small demersal fishes, food stress has been implicated as playing a role in their respective declines. In the present study, we monitored the demersal fishes seasonally at six sites over an 8-year time period. During monitoring, extremely high rainfall conditions occurred over a 3.5-year period leading to salinity regimes that can be viewed as “windows” to the area’s natural past and future restored states. In this paper, we: (1) examine the changes in fish communities over the 8-year study period and relate them to measured changes in salinity; (2) make comparisons among marine, brackish and freshwater demersal fish communities in terms of species composition, density, and biomass; and (3) discuss several implications of our findings in light of the intended and unintended water management changes that are planned or underway as part of Everglades restoration. Results suggest the reduction in freshwater flow to Florida Bay over the last several decades has reduced demersal fish populations, and thus prey availability for apex consumers in the coastal wetlands compared to the pre-drainage inferred standard. Furthermore, greater discharge of freshwater toward Florida Bay may result in the re-establishment of pre-1960s fauna, including a more robust demersal-fish community that should prompt increases in populations of several important predatory species.

Energy-Based Land Use Predictors of Proximal Factors and Benthic Diatom Composition in Florida Freshwater Marshes

The Landscape Development Intensity index (LDI), which is based on non-renewable energy use and integrates diverse land use activities, was compared to other measures of LU (e.g., %agriculture, %urban) to determine its ability for predicting benthic diatom composition in freshwater marshes of peninsular Florida. In this study, 70 small, isolated herbaceous marshes located along a human disturbance gradient (generally agricultural) throughout peninsular Florida were sampled for benthic diatoms and soil and water physical/chemical parameters (i.e., TP, TKN, pH, specific conductance, etc.). Landscape measures of percent agriculture, percent urban, percent natural, and LDI index values were calculated for a 100 m buffer around each site. The strongest relationships using Mantel's r statistic, which ranges from -1 to 1, were found between benthic diatom composition, the combined soil and water variables, and LDI scores (r=0.51, P<0.0001). Although similar, soil and water variables alone (r=0.45, P<0.0001) or with percent agriculture or percent natural were not as strongly correlated (both Mantel's r=0.46, P<0.0001). Little urban land use was found in the areas surrounding the study wetlands. Diatom data were clustered using flexible beta into 2 groups, and stepwise discriminant analysis identified specific conductance, followed by LDI score, soil pH, water total phosphorus, and ammonia, as cluster-separating variables. The LDI explained slightly more of the variation in species composition than either percent agriculture or percent natural, perhaps because the LDI can combine disparate land uses into a single quantitative value. However, the ecological significance of the difference between land use metrics and diatom composition is controvertible, and additional tests including more varied land uses appear warranted.

Early Pliocene vegetation changes forced by eccentricity-precession. Example from Southwestern Romania

Repetitive changes in Early Pliocene marine and continental sediments were forced by astronomical cycles (eccentricity, precession) and related to low amplitude climatic fluctuations as demonstrated at Capo Rossello and Monte San Nicola (Sicily). This work aims to establish if such climatic fluctuations have also controlled changes in the vegetation during the warm Early Pliocene. High-resolution pollen analysis of the Lupoaia section (SW Romania) provides evidence of a clear response owing to its location within a delta system which constitutes a reliable area for pollen deposition near the Carpathians (i.e. capable of registering all the vegetation ecosystems from edaphic coastal associations up to the highest altitudinal belts), and owing to its Southeastern European longitude probably where warm–humid air masses arrived regularly, making the region a highly favourable refuge for thermophilous plants. Eccentricity appears to have controlled fluctuations in temperature (development of thermophilous elements during eccentricity minima, and descent of altitudinal trees during eccentricity maxima) while precession appears to have forced changes in humidity (expansion of cypress swamps related to precession maxima, and spread of herbaceous marshes requiring more humidity related to precession minima) with respect to increased precipitation and run-off.

Acclimation or stress symptom? An integrated study of intraspecific variation in the clonal plant Aechmea bromeliifolia, a widespread CAM tank-bromeliad

The clonal tank-bromeliad Aechmea bromeliifolia (Rudge) Baker was found in four different habitats in a restinga (vegetation mosaic on sandy coastal plains), of south-eastern Brazil. These habitats (swamp forest, dry forest, dry shrubland and herbaceous marsh) lie within a few hundred metres of each other along a gradient extending inland from the coast, and differ markedly in terms of light and flood regime. We compared ramet morphology, leaf anatomy and physiology, and population parameters to examine the amplitude of trait variation of this widespread species in the studied restinga. This integrated approach allowed us to examine which variation conferred acclimation and which was merely a stress symptom. A. bromeliifolia showed site-specific differences in abundance, distribution, rosette size and shape, leaf anatomical arrangement and photochemical efficiency (potential quantum yield; Fv/Fm) during the day. Most of the variation found seemed to be related to the interaction of light and flooding. The lowest number and size of ramets at the exposed, dry shrubland was matched by a marked leaf photoinhibition, which suggested poor acclimation to local levels of light intensity and limited water supply. In the other habitats, the morpho-physiological parameters measured suggested adequate foraging behaviour and site acclimation. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 140, 391-401.

Sediment and nutrient accumulation in floodplain and depressional freshwater wetlands of Georgia, USA

Abstract Soil accretion, sediment deposition, and nutrient (N, P, organic C) accumulation were compared in floodplain and depressional freshwater wetlands of southwestern Georgia, USA to evaluate the role of riverine (2600 km2 catchment) versus depressional (<10 km2 catchment) wetlands as sinks for sediment and nutrients. Soil cores were collected from three floodplain (cypress-gum) and nine depressional (three each from cypress-gum forest, cypress-savannah, and herbaceous marsh) wetlands and analyzed for radionuclides (137Cs, 210Pb), bulk density, N, P, and organic C to quantify recent (30-year) and long-term (100-year) rates of sediment and nutrient accumulation. There was no significant difference in organic C, N, or sediment accumulation between depressional and floodplain wetlands. However, P accumulation was 1.5 to three times higher in the floodplain (0.12–0.75 g/m2/yr) than in the depressional wetlands (0.08–0.25 g/m2/yr). Sediment and nutrient accumulations were highly variable among depressional...

The combined effects of scale and productivity on species richness

Summary 1 Although species–area curves are well documented, we know little about how they vary along productivity gradients, nor do we have a firm understanding of whether the richness–productivity relationship is independent of scale. In order to investigate these relationships, 10 species–area curves were constructed for 10 sets of nested quadrats (from 0.25 m2 to 150 m2) in herbaceous marshes where biomass ranged from 128 g m–2 to 1050 g m–2. 2 Slopes (z) of the species–area curves (logS = logc + zlogA) were positively correlated with production (whether measured as biomass or soil organic content). A possible cause of increased slope was larger potential species pools at high biomass. The constants (c) were negatively associated with production, which concurs with the general richness–productivity relationship. 4 Linear models were used to predict both c and z using biomass and soil organic content. Biomass explained about 38% of the variation in both z and logc. Soil organic content was a better predictor. It explained 60% of the variation in z and 41% of the variation in c. 5 The slopes (z) and constants (c) of the species–area curves were negatively correlated. Because c is the expected species richness at 1 m2 and z strongly affects larger‐scale richness, the results suggest that small‐scale richness is not a good indicator of larger‐scale richness. There was no significant relationship between species richness in small‐scale (0.25 m2) quadrats and large‐scale quadrats (150 m2). 6 These results suggest that the conflicting data that have led to recent debate over the richness–productivity relationship may reflect both the effects of scale and the natural history peculiarities of the systems studied.

Vegetation Monitoring of Created Dune Swale Wetlands, Vandenberg Air Force Base, California

AbstractA monitoring program was established on San Antonio Terrace at Vandenberg Air Force Base to compare vegetation development at two created wetland sites and six nearby natural wetlands. The reference wetlands were chosen to represent a range of habitats in dune swale wetlands on the Terrace. Vegetation in the reference wetland plant communities varies from low‐growing herbaceous marsh species with open canopies to closed canopies dominated by shrub or tree species. Transects and plots for long‐term vegetation monitoring were established in all the wetlands, stratified by plant communities in the reference wetlands and by geomorphic location in the newly created wetlands. Quantitative vegetation and environmental data were collected at all the sites; measures included species distributions, species cover, and topographical elevations. Over the first three years of monitoring, variations in groundwater depth at different geomorphic locations in the created wetlands resulted in a variety of physical conditions for plant growth. In the first year, more than 100 plant species were observed, the majority being natives. During the next two years, species richness at the created wetland sites remained relatively stable and was higher than at the reference sites. Statistical comparisons of vegetation parameters by analysis of variance and hierarchical clustering exhibited patterns of increasing similarity between the created and reference wetlands. Long‐term monitoring will be continued to track the progress of vegetation at the created sites, and to assess their development relative to the reference wetlands.

Hydroseral development in southern Ontario: patterns and controls

Palaeoecological data from a range of wetland types were synthesized in order to study the development of wetland ecosystems in southern Ontario. The present‐day nature of the wetland system occurring in a topographically defined basin was shown to be controlled in part by basin morphology. Stratigraphic and vegetational (pollen and macrofossil analysis) data were used to compare the sequence of communities occupying basins during the postglacial. In systems where terrestrial peat overlies lake sediment, the broad stages of development were relatively uniform (from a lake to a shallow open water wetland to a herbaceous marsh or fen to a woody plant‐dominated community), although the exact nature of each stage varied widely between basins. The accumulation rate of sediment within such basins varied by up to two orders of magnitude during the postglacial. Allogenic and autogenic factors have been acting on these systems throughout the postglacial, and the sensitivity of individual sites to changes in these environmental conditions will also have varied. Even the widespread land clearance associated with European settlement in the area in recent centuries has not affected some wetland systems detectably, while others have either been destroyed or profoundly changed. The patterns of hydroseral development, both timing and direction, were compared with known regional environmental changes.

Organic-clastic Facies Relationships and Chronostratigraphy of the Barataria Interlobe Basin, Mississippi Delta Plain

ABSTRACT The lithofacies of Barataria Basin, an interlobe basin of the Mississippi Delta Plain, were established from analyses of 115 boreholes. Five organic lithofacies are distinguished by organic matter content, botanical origin and degree of decomposition. Organic-rich facies accumulated in three stages (A, B, and C) during two depositional events. Stage A developed locally, but stages B and C developed as blankets over abandoned delta lobes, protected from marine influx by a shoreline. Stage B lasted from 2,300-1,000 yr BP and ended when clastic sediments from renewed deltaic sedimentation blanketed the peats, expanding the basin about 50 km seaward. Peat accumulation of stage C lasted from 900 yr BP to the present and is currently being terminated by subsidence-induced transgression. High-quality stage B peats accumulated beneath herbaceous, freshwater-floating and emergent marshes, mainly above the footwall of a strike-oriented, reactivated growth fault. Above the footwall, the basin was shallower than on the hanging wall, where the deeper basin invited more overbank sedimentation, which increased ash content and diluted peats. Thus, both tectonic and sedimentary factors influenced organic facies. The quality and quantity of Barataria Basin peats differ from those of many deltaic coals. However, these peats accumulated in only 2,300 yr immediately after a rapid sea-level rise. Frequent delta-lobe switching increased organic matter preservation potential but did not provide sufficient time for the accumulation of thick, low ash peats. The geometries of organic and clastic facies are similar to those of some coal-bearing strata.

Origine et évolution du marais tourbeux de Keswick, Ontario, par l'analyse pollinique et macrofossile

The objectives of the present study were to explain the origin and to reconstitute the different phases of the paleovegetation of the Keswick marsh, Ontario. Palynological evidence was used to key out the regional and extra-local paleovegetation, and macrofossils analysis served to establish the history of the vegetation at the field site. The data showed that in the vicinity of Lake Simcoe the origin of the marsh was closely associated with the changes in the climatic conditions that favored the development of an environment suitable for peat-forming plant communities; 2.4 m of peat accumulated in the last 4000 years on a washed silty clay. The macrofossils of hardwood species, seeds of Aralia racemosa, and sporangia of Polypodiaceae at the base of the deposit indicated that a mixed forest, composed mainly of deciduous species surrounded by tamaracks, prevailed prior to the initiation of peat accumulation. Furthermore, additional vegetation changes occurred, notably the replacement of an arboreal swamp vegetation by an herbaceous marsh, followed by a shrub–herb marsh and then an herbaceous marsh, recently drained and cultivated.