Ligustrum sinense (Chinese privet) is an introduced species in the United States. Dense stands of L. sinense are found in the understory in many bottomland forests in western Tennessee. The widespread abundance of this species is problematic because of the potential loss of valuable native bottomland species due to competition. Flooding has been proposed as a potential means of eradicating this species. Therefore, the objectives of this experiment were to examine survival, growth, and physiological responses of L. sinense under various flooding and shading regimes. An experiment consisting of three levels of flooding (control, shallow flooding, and deep flooding) and three levels of shading (full sun, 30–35% full sun (photosynthetic active radiation), and 10–15% sun) was performed in a greenhouse. Plant gas exchange was adversely affected in all flooded plants. Likewise, growth (height and diameter) was lower in those plants that were flooded as compared to non-flooded plants. However, morphological adaptations (i.e., lenticels and adventitious roots) were observed by the third week of the experiment. Plant survival in flooded treatments was 75% by the conclusion of the experiment, with an equal rate of survival seen in the shaded treatments compared to non-shaded. Although flooding alone did have significant effects on physiological function and growth, shading and shading × flooding interaction were not significant. Our data support the hypothesis that L. sinense is capable of withstanding both short-term flooding and shading; thus, short-term flooding is unlikely to irradicate this species from the infested bottomland stands.

Developing an understanding of wetland hydrology that is free from site-specific constraints is difficult. Many hydrologic studies are focused upon a single site and the development of water-budget components. Our previous research (Cole et al. 1997) examined the hydrology of several wetlands based upon monthly sampling during the growing season. Those data did not provide adequate information on moisture regimes and did not tell us enough about year-round hydrodynamics. Our new objective was to expand hydrologic analyses to a larger proportion of our reference wetlands and extend them over a longer period of time. We continued to organize our wetlands and our analyses around hydrogeomorphic (HGM) principles. We found ground-water-dominated wetlands (riparian depressions and slopes) to be the wettest sites. Surface-water systems (headwater and mainstem floodplain wetlands) were drier. We found little difference between slopes and the floodplain wetlands in the amount of time water was within the root zone. Riparian depressions were wetter longer, as the average duration of water within the root zone was almost a year for riparian depressions and much less for all other wetland types. Disturbance seemed to play a large role in hydrologic behavior, even more than did HGM classification. We believe that knowledge of HGM subclass might serve as a useful surrogate for actual knowledge of site-specific hydrology. The level of uncertainty increases with surface-water systems, but we have shown a large degree of predictability by HGM subclass. Our data likely have applicability within the entire Ridge and Valley province of the Appalachian Mountains in the United States, although our conclusions have not been tested over that wide latitudinal range.

The poorly drained pine flatwoods of the Lower Coastal Plain of the Southern United States, including Florida, contain many pond cypress (Taxodium ascendens) wetlands, which cover about one-third of the area. Management of the resource includes pine silviculture and cypress harvesting for lumber, plywood, paper, and mulch. Concern about the ecological impacts and hydrologic effects prompted a cooperative study of cypress wetlands integrating several disciplines. This paper reports results of clear-cut harvesting on the wetland hydrology. Three wetlands of about 0.5 ha were selected and instrumented to measure the climatic and hydrologic variables before and after treatments from January 1993 to January 1997. Silvicultural treatments were wetland-only clear-cut harvesting, wetland plus surrounding upland clear-cut harvesting, and an undisturbed control. The absence of observable soil surface runoff (high infiltration rate) and slow ground-water movement in the upland pine flatwoods suggested that normally the precipitation and evapotranspiration balanced each other and that the wetlands generated most of the runoff from the landscape mosaic as a whole. However, the results showed that open-water evaporation after wetland harvesting exceeded evapotranspiration of the control, explaining in part a decrease in outflow after wetland-only harvesting. Increased runoff from the pine upland, generated by reduced evapotranspiration and expanded saturated areas after clear-cut harvesting, apparently was buffered to some extent by increased evaporation from the embedded clear-cut cypress wetland. The average open-water area was about fifty percent larger than the wetland area as defined by the vegetation. However, excess wetland water balance data suggested the presence of a rain-catchment area that was 2–3 times larger than the vegetative wetland area because of semi-saturated soil in the low slopes. Therefore, the actual catchment area of a cypress wetland in the pine flatwoods may be variable in time, space, and silviculture depending on the topography, the extent of open water, and saturated soil. The application of this information in water management is for better control of first-year runoff from the pine-cypress landscape as a whole. Furthermore, silvicultural Best Management Practices for cypress wetland water management need to consider a variable source area for surface-water pollution that is larger than the wetland area as defined by the vegetation.

The existence of different growth forms (tall and short) in various species of the genus Spartina has, on occasion, been attributed to differences in the availability of nutrients. In the present work, macronutrient (N, P, K, Mg, Ca, S) and micronutrient (Fe, Mn, Zn, Cu) contents of the soils and tissues (leaves and stems) of three populations of S. maritima from the NW Iberian Peninsula were studied. The results obtained showed that although there were differences in the physicochemical properties of the soils and in the concentration of nutrients in soils and plants at the different locations, these do not explain the different growth forms of S. maritima. Since other authors have found that the growth forms displayed by different species of the same genus are in part due to genotypic differences, ecotypic differentiation, along with other environmental factors that were not assessed in this research, may control the differences in height and biomass of S. maritima. However, more detailed studies of this species are required in order to assess the importance of environmental (e.g., fertilization experiments) and genetic factors (e.g., RAPD analysis) that influence the growth form of natural populations of Spartina maritima.

The Missouri River floodplain historically contained numerous wetlands; however, alterations to the corridor have resulted in the loss of flood-pulse processes. The annual contributions of small wetlands (<15 ha) perched on the Missouri River floodplain have not been viewed as important; however, consequences of draining or filling perched wetlands in the upper Missouri River basin remain unclear. The objective of this study was to survey aquatic fauna and basic habitat characteristics in a small perched wetland before, during, and after a connection period within a naturally functioning section of the Missouri River. Fishes, macroinvertebrates, zooplankton, and habitat parameters were sampled during May, July, and September 1997. No significant differences (P > 0.05; F < 4.2; df = 2,9) in densities or catch-per-unit-effort among sample periods were detected for macroinvertebrates. Copepoda nauplii, calanoid Copepoda, and Bosmina spp. densities showed significant changes (P < 0.03; F > 6.1; df = 2,9) and collectively surpassed 3,200 organisms/L. These densities exceeded other regional means by as much as 900%. Twenty-four fish species were documented in the wetland; however, the black bullhead, Ameiurus melas Rafinesque, dominated the fish community. Wetland depth and surface area increased during the connection period and inundated terrestrial grasses and woody debris. Decay of submerged organic matter, combined with the lack of rooted macrophytes, loss of algal productivity to flushing, and higher turbidity, may have all contributed to reduced summer dissolved oxygen levels. Avian feeding activity suggested that fishes were using the upper water column when nearly anoxic lower water column conditions existed. Although the wetland habitat may be harsh, presence of juvenile fishes and dense zooplankton populations establishes the potential importance of these water bodies to the Missouri River ecosystem.

The purpose of this research was to determine if slope and exposure are important determinants of plant communities emerging on reservoir shorelines. We sampled 30 sites on the previously inundated shoreline of Cave Run Lake, a U.S. Army Corps of Engineers flood-control reservoir in east-central Kentucky, USA. These sites were categorized as either flats, riparian forests, exposed banks, or sheltered banks. Two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis were used with presence/absence data to group sites of similar community composition. There were 167 species of plants identified in the study plots, of which 29% were annuals, 2% were biennials, 69% were perennials, 11% were non-indigenous, and 63% met the criterion for inclusion in community analysis. A distinct assemblage of plant species was associated with all riparian forests, with six of eight flats, and with five of twelve exposed banks. Six sheltered banks were not obviously associated with a single community type. The TWINSPAN group including riparian forests had the highest percentage of wetland species; the TWINSPAN group including most flats had the highest species richness; the TWINSPAN group comprised entirely of exposed banks had low species richness and low representation of wetland species. Our results suggest that plant communities of high conservation value can emerge on relatively flat sites under a human-controlled flooding regimen as long as the soil remains intact. However, steep exposed banks are susceptible to soil loss, and the resulting rock substrates support a depauperate flora of low conservation value.

The Okefenokee Swamp is a 160,000 ha freshwater wetland in Southeast Georgia, USA that developed in a landscape basin. Hydrologic variability across the swamp suggests that water-surface elevations are not uniform across the swamp. The topographic surface map discussed herein was developed to describe the swamp topography at local to landscape scales and relate the swamp peat- and sand-surface elevations to elevation above mean sea level. These data were then used to relate water-surface elevations across the swamp so that the swamp hydrologic environment could be described spatially and temporally with a spatial hydrology model. The swamp was divided into 5 sub-basins that reflect similar seasonal hydrodynamics but also indicate local conditions unique to the basins. Topographic gradient influences water-level dynamics in the western swamp (2 sub-basins), which is dominated by the Suwannee River floodplain. The eastern swamp (3 sub-basins) is terraced, and the regional hydrology is driven less by topographic gradient and more by precipitation and evapotranspiration volumes. The relatively steep gradient and berm and lake features in the western swamp's Suwannee River floodplain limit the spatial extent of the Suwannee River sill's effects, whereas system sensitivities to evapotranspiration rates are more important drivers of hydrology in the eastern swamp.

Developing a more thorough understanding of water and chemical budgets in wetlands depends in part on our ability to quantify time-varying interactions between ground water and surface water. We used a combined water and solute mass balance approach to estimate time-varying ground-water discharge and recharge in the Everglades Nutrient Removal project (ENR), a relatively large constructed wetland (1544 hectare) built for removing nutrients from agricultural drainage in the northern Everglades in South Florida, USA. Over a 4-year period (1994 through 1998), ground-water recharge averaged 13.4 hectare-meter per day (ha-m/day) or 0.9 cm/day, which is approximately 31% of surface water pumped into the ENR for treatment. In contrast, ground-water discharge was much smaller (1.4 ha-m/day, or 0.09 cm/day, or 2.8% of water input to ENR for treatment). Using a water-balance approach alone only allowed net ground-water exchange (discharge − recharge) to be estimated (−12 ± 2.4 ha-m/day). Discharge and recharge were individually determined by combining a chloride mass balance with the water balance. For a variety of reasons, the ground-water discharge estimated by the combined mass balance approach was not reliable (1.4 ± 37 ha-m/day). As a result, ground-water interactions could only be reliably estimated by comparing the mass-balance results with other independent approaches, including direct seepage-meter measurements and previous estimates using ground-water modeling. All three independent approaches provided similar estimates of average ground-water recharge, ranging from 13 to 14 ha-m/day. There was also relatively good agreement between ground-water discharge estimates for the mass balance and seepage meter methods, 1.4 and 0.9 ha-m/day, respectively. However, ground-water-flow modeling provided an average discharge estimate that was approximately a factor of four higher (5.4 ha-m/day) than the other two methods. Our study developed an initial understanding of how the design and operation of the ENR increases interactions between ground water and surface water. A considerable portion of recharged ground water (73%) was collected and returned to the ENR by a seepage canal. Additional recharge that was not captured by the seepage canal only occurred when pumped inflow rates to ENR (and ENR water levels) were relatively high. Management of surface water in the northern Everglades therefore clearly has the potential to increase interactions with ground water.

Fixed-width belt transects employed in surveys of irregular shaped regions will differ in length and, therefore, in area. When estimating density from such a sample, the unequal transect areas must be taken into account.A density estimator dividing the mean number of objects (e.g., plants or animals) per transect by the mean transect area is recommended. An alternative estimator, the mean density per transect, is applicable for equal-area transects but often has undesirable properties for unequal-area transects. The recommended density estimator is identified as a ratio estimator, and its standard error is derived from ratio estimation theory.

Field mapping and monitoring of vegetation, sedimentation patterns, substrate characteristics, and geomorphology in the Bush River tributary to upper Chesapeake Bay has been conducted since 1991 to ascertain the process-morphology dynamics in a tidal freshwater marsh. Nine plant associations from 5 distinct marsh habitats were identified by clustering species abundance measurements from 115 quadrats throughout an 84-hectare area. High spatial variability in physical habitat conditions such as summer-average sediment deposition, summer-average organic content, and surface-sediment grain size distributions were explainable using combinations of independent variables, including elevation, plant distributions, and distances to the tidal inlet and an adjacent stream. Sedimentation and vegetation were both observed to show a predictable response to disturbance by animal activity.

Global climate-change models (GCMs) predict that the midwest USA will be drier and warmer as a result of global climate change. Other studies suggest that climate change has already started in the Lake Michigan region. This study uses climate predictions from GCMs and projections of historical climate-change trends to examine the potential effects of climate change on riparian vegetation along the Pere Marquette River in west central Michigan. A model of stream discharge as a function of temperature and precipitation was used to estimate the percent of time that each of 25 plots would be inundated at a field site in the riparian corridor on the river. Four vegetation classes were identified at the field site (Alnus, Open-Viburnum, Fraxinus-Carpinus, and Acer-Tsuga). The stream discharge model was used to calculate the percent of time each plot was inundated at the field site under the different climate scenarios and to predict the distribution of vegetation classes that would be present under climate-change conditions. The results suggest that the areal extent of vegetation classes at the field site may change by up to 27%.

Revegetation under wetland rather than dryland conditions provides an alternative to traditional methods of rehabilitation of metal mine tailings. The wetland plant Glyceria fluitans (floating sweetgrass) was found growing in a lead/zinc mine-tailings pond. The potential of this species for revegetation of mine tailings under wetland conditions had not previously been investigated. In two outdoor experiments, G. fluitans of non-contaminated origin grew successfully on alkaline tailings containing elevated metal concentrations (230 μmol g⁻¹ Zn, 11 μmol g⁻¹ Pb). Growth of G. fluitans was significantly enhanced on tailings treated with NPK fertilizer (700 kg ha⁻¹), but the plants grew well even without fertilizer, indicating a low nutrient requirement. Glyceria fluitans did not survive on saline (MgSO₄) tailings originating from another mine that contained much higher lead (34 μmol g⁻¹) and iron (2584 μmol g⁻¹) concentrations. The ability of G. fluitans to tolerate many of the adverse conditions associated with mine tailings favors its use for revegetation purposes.

Mountain fens are uncommon and unique wetlands in the southern Appalachian Highlands. We selected four mountain fens in North Carolina to compare soil particle-size distribution, organic carbon, pH, cation exchange capacity (CEC), and exchangeable Mg ², Ca ², and K . Three of the sites are depressional areas on alluvial floodplains at elevations between 700 and 1130 m above sea level, while the fourth site is located on a slope intersecting ground-water seepage at an elevation of 950 m. Peat accumulation amounted to a shallow surface Sphagnum layer (usually <5 cm) at three sites, and the organic carbon content of the surface soil horizon ranged from 4 to 21%. Three of the soils would be classified as Cumulic Humaquepts, and the other is a Terric Haplohemist. The pH of the surface horizon of the four soils ranged from 4.3 to 4.9. The alluvial fens had higher silt concentrations than the seepage fen, and two of the alluvial fens had a subsurface, fine-textured deposit. The seepage fen showed little textural variation with depth. Exchangeable Ca ² concentrations were higher for the seepage fen. The CEC ranged from 15 to 62 cmol_c kg⁻¹ in the surface horizon, and base saturation (Ca ², Mg ², and K ) was <12% for the three alluvial fens and 20% for the seepage fen. Base saturation increased to 40% in the lower horizons of the seepage fen but remained <10% for the alluvial fens. The differences in soil characteristics suggest that geomorphic location should be considered when comparing mountain fens.