Hydrology and history: land use changes and ecological responses in an urban wetland

The impacts of changing land use on hydrology and dominant plant species from 1850–1990 were investigated in a palustrine wetland in southern Wisconsin, USA. Aerial photographs, historic maps and water levels of the area were used to determine changes in land use, wetland vegetation, and groundwater and surface flows over time. Piezometers and water table wells were monitored weekly for two years. Vegetation was quantified in four one-square meter quadrats at each water level measurement site. Linear regression models and multivariate ordinations were used to relate wetland plant species to hydrologic, chemical and spatial variables. The current hydrologic budget of the wetland was dominated by precipitation and evapotranspiration, although overland flow into the wetland from the subwatershed has increased twenty-fold since 1850. Water level stabilization in the adjacent Yahara River, creek channelization, and groundwater pumping have decreased inputs of groundwater and spring-fed surface water, and increased retention of precipitation. Typha spp. and Phalaris arundinacea L. have increased in the wetland, while Carex spp. have decreased. Phalaris arundinacea was found most often in the driest sites, and the sites with the greatest range of water levels. Typha spp. dominated in several hydrologic settings, indicating that water depth was not the only factor controlling its distribution. The distributions of dominant plant species in the wetland were most closely correlated with site elevation and average water levels, with some weaker correlations with vertical groundwater inflows and specific conductance.     

Vegetation change in created emergent wetlands (1988–1996) in Connecticut (USA)

Changes in hydrology, water quality and vegetation were evaluated in four palustrine emergent wetland pairs, each including created and reference sites. Located along interstate highways, they were initially sampled in 1988 (Confer and Niering, 1992) and again in 1996. Overall, created sites showed significant decreases in open water and water depth between 1989 and 1996 compared to more stable conditions in reference sites. Total nitrogen was generally higher in created sites compared to reference sites, as was specific conductivity, with chloride levels exceeding 800 mg/L, apparently related to road salt. Emergent plant cover increased from 30 to 39% at three created sites, and decreased at a fourth, whereas reference sites remained relatively stable. Wetland species richness also increased from 31 to 39 species at created sites and 35 to 42 species at reference wetlands between the surveys. By 1996 there was an increase in invasive species, particularly Phragmites australis (common reed) and Lythrum salicaria (purple loosestrife). Phragmites increased from <1 to 15% at created sites, while Lythrum increased at one reference site from <1 to 16%. Typha latifolia (common cattail), dominant in the created wetlands in 1988, decreased from 16 to 5% while Typha angustifolia (narrow-leaved cattail) increased from 2 to 10%. At two created sites experiencing increased sedimentation, Phragmites is now dominant or co-dominant with Typha spp., whereas Carex stricta (tussock sedge) and T. latifolia continue to dominate at reference sites. At the one created, permanent flow-through-hydrology wetland, a three-fold decrease in T. latifolia and an eight-fold increase in Phragmites cover have occurred, the latter correlated with sedimentation from road culverts. Increases in alien or invasive species such as Phragmites and Lythrum can serve as indicators of wetland disturbance. Although these created wetlands provide the services of sediment retention, flood storage, and wildlife habitat, a greater range of wetland functions should be possible by constructing two-tiered systems that remove excess sediments and nutrients upstream of the wetland designed to compensate for wetland loss.     

Plants as indicators of wetland water source

At the local scale, plant species distribution is determined primarily by the environmental characteristics of a site. In a wetland, water chemistry and hydroperiod are two of the most important of these environmental characteristics. Both are functions of water source. In central Pennsylvania, groundwater input tends to be continuous, while surface water may be permanent or seasonal. The chemistry of groundwater and surface water differs since groundwater is influenced by the substrate through which it flows. Because of these differences, and because of their effects on plant species distribution, it is possible to use vegetation as an indicator of the dominant water source of a site. Plots within 28 wetlands in central Pennsylvania were sampled, and the plots were classified by water source. The three hydrologic categories were groundwater, seasonal surface water, and permanent surface water. The core of the study was the analysis of half of the plots to identify species that were associated with a particular water source. Several groups of indicator species were identified. Some species, including Nyssa sylvatica, were strongly associated with the presence of groundwater. Others, such as Symplocarpus foetidus, were strongly associated with the presence of seasonal surface water. Several aquatic species were associated with permanent surface water. The remainder of the plots were used to test the predictive ability of the indicator species identified. The vegetation of a wetland plot predicted its hydrologic category with 72% accuracy. The identification of more indicator species could lead to the development of a useful tool for wetland research and management, since monitoring hydrology is often both expensive and time-consuming.     

Response of wetland plant species to hydrologic conditions

Understanding hydrologic requirements of native and introduced species is critical to sustaining native plant communities in wetlands of disturbed landscapes. We examined plant assemblages, and 31 of the most common species comprising them, from emergent wetlands in an urbanizing area of the Pacific Northwest, USA, in relation to in situ, fine-scale hydrology. Percent cover by plant species was estimated in 2208 1-m² plots across 43 sites, with water depth at time of vegetation sampling measured in 432 plots. Three years of bi-weekly hydrologic data from each of the 43 sites were used to estimate mean surface water level and mean absolute difference (MAD) in surface water level for every plot. Nine assemblages of plant species that co-occur in the field were identified using TWINSPAN. The assemblage richest in native species occurred under intermediate hydrologic conditions and was bracketed by pasture grass dominated assemblages at drier conditions with low water level variability, and Phalaris arundinacea L. assemblages with higher mean water levels and variability. Results suggest minor changes in average water levels (10 cm) or in variability (±2 cm in MAD) could promote a shift from assemblages dominated by natives to those dominated by invasive or alien taxa. Canonical correspondence analysis segregated the species into four groups related to hydrologic gradients. Each species response group was typified by taxa with similar optima for a given environmental variable, with each group related to a characteristic suite of hydrologic conditions. The most common species (P. arundinacea, Juncus effusus L., and Typha latifolia L.), each representing a different response group, exhibited unique responses in occurrence/abundance in relation to water level variability, but were abundant over a wide range of water depth. The realized niches of other species in each response group were more restricted, with peaks in cover confined to narrower ranges of water depth and variability.     

洞庭湖四种优势湿地植物茎、叶通气组织的比较研究

对通气组织的解剖观察有助于了解湿地植物的生长、分布及对不同生境的适应。采用石蜡切片技术,在光学显微镜下对洞庭湖湿地沿水位高程梯度分布的4种优势植物——荻Miscanthus sacchariflorus、水蓼Polygonum hydropiper、红穗苔草Carex argyi、虉草Phalaris arundinacea的茎和叶解剖结构进行了比较研究。结果表明：茎通气组织的形成部位主要在皮层、维管束和髓腔,其中髓腔所占比例最大（〉77%）。茎通气组织大小为：水蓼（57.8%）〉红穗苔草（45.5%）≥虉草（41.7%）≥荻（37.8%）。4种湿地植物的叶均在叶肉组织和（或）维管束内形成通气组织,如荻、虉草的形成部位是维管束,水蓼的是叶肉组织,而红穗苔草在叶肉组织和维管束内均可以形成,但以叶肉组织中为主,占99%。红穗苔草叶通气组织最发达,为33.8%,其它3种植物相对不发达,仅为0.13%～1.68%。除虉草外,其它3种植物通气组织大小与其分布位置具有很好的一致性。可见,湿地植物通气组织与其分布有较好的相关性。     

Effects of nutrient and soil moisture on competition between shape Carex stricta,shape Phalaris arundinacea,and shape Typha latifolia

We investigated the importance of nutrients, soil moisture, arbuscular mycorrhizal fungi (AMF), and interspecific competition levels on the biomass allocation patterns of three wetland perennial plant species, Carex stricta Lam., Phalaris arundinacea L., and Typha latifolia L. A factorial experiment was conducted with high-low nutrient levels, high-low soil moisture levels, and with and without AMF inoculation. Under the experimental conditions, plant inoculation by AMF was too low to create a treatment and the AMF treatment was dropped from the total analysis. P. arundinacea and T. latifolia biomass were 73% and 77% higher, respectively, in the high nutrient treatment compared to the low nutrient treatment. Biomass allocation between shoots and roots remained relatively constant between environmental treatments, although shoot:root ratios of P. arundinacea declined in the low nutrient treatment. For C. stricta, the high nutrient and soil moisture treatments resulted in an increase in biomass of 50% and 15%, respectively. Shoot:root ratios were nearly constant among all environmental conditions. Biomass of T. latifolia and C. stricta was greatly decreased when grown with P. arundinacea. The rapid, initial height growth of P. arundinacea produced a spreading, horizontal canopy that overshadowed the vertical leaves of T. latifolia and C. stricta throughout the study. This pattern was repeated in both high and low nutrient and soil moisture treatments. When grown with P. arundinacea, C. stricta and T. latifolia significantly increased their mean shoot height, regardless of the nutrient or soil moisture level. The results of this experiment suggest that C. stricta and T. latifolia were light limited when growing with P. arundinacea and that canopy architecture is more important for biomass allocation than the other environmental conditions tested. The results also suggest that Phalaris arundinacea is an inherently better competitor (sensu Grime 1979) than C. stricta or T. latifolia.     

Soil and Hydrological Drivers of Typha latifolia Encroachment in a Marl Wetland

Aggressive species competition by Typha latifolia in wetland systems on marl-derived soils may threaten the unique vegetation in these areas. We examined historic water and land use, soil chemistry, soil genesis, and topography in a wetland (Harewood Marsh) that is under encroachment by T. latifolia. An earthen road that bisects the wetland and active pastures in and around the wetland were also considered in the study due to their potential influence on wetland hydrology and nutrient inputs. Historic land uses and trends in surface water patterns were determined via aerial photography. In addition local landowners and city officials were contacted for information about historic water use in the area around the marsh. Soils were augered and sampled in seven locations in the wetland, and at each auger site, vegetation was described. Six wells were installed near the earthen road and weekly water depth measurements were taken from January 2002 to January 2003. In February 2002, 10 A-horizon soil samples (per transect) were taken from three 150-m transects that spanned areas with and without T. latifolia. Results indicate that T. latifolia encroachment is facilitated by a rising water table (the result of the termination of a local municipal water supply source) and N and P inputs, most likely from cattle grazing on the wetland. An increase in the numbers of rare plant species associated with marl wetland habitats appears to have also occurred and is believed partly due to current wetter conditions. Our study provides insight into the dynamics of T. latifolia encroachment in a unique marl wetland habitat and demonstrates how local factors controlling nutrient and hydrologic dynamics can have significant effects on changes in plant community composition.     

A test of four plant species to reduce total nitrogen and total phosphorus from soil leachate in subsurface wetland microcosms

Four wetland plant species (Scirpus validus, Carex lacustris, Phalaris arundinacea, and Typha latifolia) were grown in monoculture and as a four-species mixture to compare effectiveness of nutrient removal in controlled 18.93-l outdoor subsurface treatment wetland microcosms. A nutrient treatment that mimicked single-resident domestic effluent consisted of two levels of nitrogen (N) and phosphorus (P) [low (56 mg/l N and 31 mg/l P) and high (112 mg/l N and 62 mg/l P)] of nutrient solution applied three times weekly. The plants were established and maintained for one year before the nutrient treatment and monthly water sampling commenced; water sampling began July 31, 2001 and ended October 23, 2001. We tested four hypotheses: (1) vegetated microcosms are more effective at reducing concentrations of total N and total P from soil leachate than unvegetated, (2) there is a differential species effect on the potential to reduce N and P, (3) plant mixtures are more effective than monocultures at reducing N and P, and (4) the microcosms will be least effective at reducing N and P concentrations in October compared to August. We found support for hypotheses 1, 2, and 4, but our results are inconclusive for the third hypothesis. Total N and total P in the soil leachate were significantly higher from unvegetated microcosms compared to vegetated. S. validus was most effective and P. arundinacea was generally least effective at reducing N and P in monocultures, with treatment capabilities similar to unvegetated microcosms. The four-species mixture was generally highly effective at nutrient removal, however the results were not significantly different from the monocultures. At the end of the growing season (October) treatment efficiency was significantly less than earlier months, especially for the unvegetated treatment.     

Vegetation along hydrologic, edaphic, and geochemical gradients in a high-elevation poor fen in Canaan Valley, West Virginia

Wetland plant community composition and pattern are regulated by a host of abiotic/environmental gradients and biotic factors. We used multivariate analyses to classify wetland plant communities and determine the relation of hydrologic, edaphic, and geochemical gradients on community composition and spatial distribution among 18 vegetation, hydrology, and soil sampling points in Abe Run, a botanically unique poor fen in northeastern West Virginia. We also examined the interactions of disturbance with the physical environment and species composition. A total of 179 vascular plant species were identified from sample plots. Vegetative composition and structure, dominant soil texture, and hydrology lacked the distinct concentric zonation of northern peatlands; instead, all were patchy and varied considerably over short distances. Graminoid-forb meadows with primarily silt-loam mineral horizons, greater depth to groundwater, and fewer days of inundation characterized the lower reaches of the wetland. These plots were more acidic, with absent or shallow O horizons, and lower concentrations of soil base cations (Ca, Mg, K). In the upper reaches of the wetland, mixed herb-shrub-tree dominated communities were structurally and compositionally more complex; here, organic horizons were much more prominent, peat depth ranged from 80 to 100 cm, and the average depth to water table was 10 cm less than for wells in the lower reaches of the wetland. Plots from upper transects (3–6) tended to have more shrub and tree cover, and higher concentrations of soil base cations. Much of the variability among plots in the upper and lower reaches of the wetland are consistent with beaver inundation of a large portion of the wetland during the 1980s. Multiple-response permutation procedures verified the difference (P < 0.0001) between vegetation of plots in the lower and upper reaches of the watershed. Because fens are connected to groundwater, these habitats are particularly vulnerable to disturbances, particularly those that alter existing land use and land cover. Minimization of disturbances in the surrounding watershed, controls on an excessive deer population, removal of exotic, non-native species, and control on foot traffic are all integral to maintaining the integrity of this high-value wetland.     

Hydrologic similarity to reference wetlands does not lead to similar plant communities in restored wetlands

Few wetland restoration projects include long‐term hydrologic and floristic data collection, limiting our understanding of community assembly over restored hydrologic gradients. Although reference sites are commonly used to evaluate outcomes, it remains unclear whether restoring similar water levels to reference sites also leads to similar plant communities. We evaluated long‐term datasets from reference and restored wetlands 15 years after restoration to test whether similar water levels in reference and restored sites led to vegetation similarity. We compared the hydrologic regimes for three different wetland types, tested whether restored wetland water levels were different from reference water levels, and whether hydrologic similarity between reference and restored wetlands led to similarity in plant species composition. We found restored wetlands had similar water levels to references 15 years after restoration, and that species richness was higher in reference than restored wetlands. Vegetation composition was similar across all wetland types and was weakly correlated to wetland water levels overall. Contrary to our hypothesis, water table depth similarity between restored and reference wetlands did not lead to similar plant species composition. Our results highlight the importance of the initial planting following restoration and the importance of hydrologic monitoring. When the restoration goal is to create a specific wetland type, plant community composition may not be a suitable indicator of restoration progress in all wetland types.     

Negative per capita effects of two invasive plants, Lythrum salicaria and Phalaris arundinacea, on the moth diversity of wetland communities

Invasive plants have been shown to negatively affect the diversity of plant communities. However, little is known about the effect of invasive plants on the diversity at other trophic levels. In this study, we examine the per capita effects of two invasive plants, purple loosestrife (Lythrum salicaria) and reed canary grass (Phalaris arundinacea), on moth diversity in wetland communities at 20 sites in the Pacific Northwest, USA. Prior studies document that increasing abundance of these two plant species decreases the diversity of plant communities. We predicted that this reduction in plant diversity would result in reduced herbivore diversity. Four measurements were used to quantify diversity: species richness (S), community evenness (J), Brillouin's index (H) and Simpson's index (D). We identified 162 plant species and 156 moth species across the 20 wetland sites. The number of moth species was positively correlated with the number of plant species. In addition, invasive plant abundance was negatively correlated with species richness of the moth community (linear relationship), and the effect was similar for both invasive plant species. However, no relationship was found between invasive plant abundance and the three other measures of moth diversity (J, H, D) which included moth abundance in their calculation. We conclude that species richness within, and among, trophic levels is adversely affected by these two invasive wetland plant species.     

Seed dispersal, germination and seedling growth of six helophyte species in relation to water-level zonation

1. Seed dispersal, germination, and seedling growth characteristics of six helophyte species. Iris pseudacorus, Phalaris arundinacea, Phragmites australis, Typha angustifolia, T. latifolia and Scirpus lacustris, were investigated in relation to their water-level zonation. 2. The experiments demonstrated a large variation in these characteristics between the species. 3. Propagule floating capacities range from < 1 h (S. lacustris) to > 1000 h (I. pseudacorus). 4. Seed germination in a water-level gradient revealed two groups with respect to germination percentage - exposed soil species (I. pseudacorus, Phalaris arundinacea, Phragmites australis) and submerged soil species (T. angustifolia, T. latifolia). 5. There were two contrasting types of seedling growth response to submergence and exposure: one group of species formed longest leaves under exposed conditions (Phalaris arundinacea, Phragmites australis, I. pseudacorus), and the other under submerged conditions (S. lacustris, T. latifolia, T. angustifolia). 6. The results suggest that early life-history characteristics of the species relate to their locations in the riparian zonation: Phalaris arundinacea and Iris pseudacorus at the higher end, Phragmites australis intermediate, and Typha spp. and Scirpus lacustris at the lower end. Species occurring at lower locations show adaptations to (periodical) flooding of the soil (submersed germination and growth), while those from higher locations require prolonged exposed soil conditions to germinate and to survive the establishment stage.     

Early development of plant community in a created mitigation wetland as affected by introduced hydrologic design elements

The goal of this study was to investigate early plant community development in two sites (i.e., higher and lower elevation sites—LC1 and LC2, respectively) of the Loudoun County (LC) mitigation wetland created in the Virginia Piedmont. The effects of hydrologic design elements incorporated during the construction (i.e., disking-induced microtopography—MT and site level elevation difference) on vegetative and hydrologic attributes (e.g., species richness, biodiversity, plant cover, floristic quality assessment index, wetland indicator status, soil moisture content, and water table depths) were investigated. The study was conducted at the end of two growing seasons in 2008 and 2009 (i.e., second and third growing seasons). Drought conditions that persisted into the second growing season resulted in the abundance of a seeded cover grass, Lolium multiflorum (Italian ryegrass), intentionally planted during initial seeding for erosion control. L. multiflorum was subsequently phased out and replaced by facultative wet and obligate wetland species by the third growing season when above-average precipitation occurred, leading to a decrease in total percent cover. Prevalence index changed in both LC1 and LC2, dropping from overall facultative status in 2008 to obligate status in 2009 when obligate species such as Bidens cernua, Carex frankii, and Juncus effusus thrived and expanded with the change of hydrologic regime in 2009. Microtopographic treatment (i.e., disked or undisked) positively influenced vegetation development for LC1 site in 2008, but the positive influence was not consistent for LC2, which experienced an additional month of standing water conditions in the same year, nor for either site in 2009 when above-average precipitation occurred. The site differences in elevation, and thus hydrologic regime, seemed to overwhelm the effects on vegetation of disking-induced microtopography in each site when precipitation was at or above average range. Although shown on short spatial and temporal scales in this study, incorporation of micro- and macrotopographic design elements in creating a mitigation wetland can be beneficial to the early development of diverse vegetation communities wetland under varying climate conditions.     

Spatial patterns and determinants of wetland vegetation distribution in the Kumasi Metropolis,Ghana

The contribution of wetlands to livelihood in the forms of resources of direct consumptive uses, fishing and agriculture are of great importance to riparian communities in sub-Saharan Africa. It is unfortunate to note that these same areas are being degraded and converted to informal settlements through uncontrolled urbanisation. To improve urban environments and meet the various development targets, efforts are being made to rid sub-Saharan African cities of these informal wetland associated slums. The difficulty, however, lies in delineating wetland boundaries. This research is therefore aimed at determining the vegetation diversity of wetlands in Kumasi, Ghana and to identify and characterise the typical urban wetland and factors that influence the small scale heterogeneity in distribution of the wetland vegetation. Ten relatively large wetland sites associated with streams within the Kumasi Metropolis were selected for this study. Sampling in each site was done using 1 m² quadrats laid at 10 m intervals from the water channel. All plant species in each quadrat were identified. The soil and hydrologic conditions of each site were studied. A total of 112 species were identified in the 10 study sites. The study sites were found to be significantly different from each other in environmental conditions and species distribution. Species in these study sites could, however, be grouped into clusters according to the presence or absence of surface water. A wetland in Kumasi was found to be typified by high percentage organic carbon with Thelypteris palustris as the dominant species.     

Superficial and hyporheic oligochaete communities as indicators of pollution and water exchange in the River Moselle, France

Benthic oligochaetes were sampled on three occasions (June, August and October 1992) in the upper (0–10 cm) and hyporheic (35–45 cm depths) sediments at five sites of the River Moselle, from upstream of the town of Epinal to Velle-sur-Moselle. The first site (upstream from Epinal) is considered as unpolluted and the four remaining sites are polluted by industrial effluents. The most polluted stations were generally dominated by the pollution tolerant taxon Limnodrilus. Numbers of individuals of this taxon decreased at the less polluted last site in recovery zone, and were also scarce in the first unpolluted site. It is noteworthy that these tendencies were observed in both superficial and hyporheic substrates and to the greatest degree in hyporheic ones. At the unpolluted site, the hyporheic habitat is dominated by the groundwater species Propappus volki, Pristina spp., Pristinella spp. At the less polluted site (last site), the deep sediments are dominated by groundwater species and the Tubificidae without hair setae decrease from June to October. As a result of water exchange between superficial and subterranean waters, superficial substrates of the first and the last stations tend to be colonised by a high proportion of hyporheic species that suggests that flow is primarily from subterranean to superficial waters. The contrary is the case at other polluted stations which are characterised by the invasion of hyporheic substrates by the pollution tolerant superficial taxa Limnodrilus. This suggests that water flows from the river to the deeper groundwater. These two stations are located near drinking water plants which utilise groundwater, thus increasing the vulnerability of groundwater to surface contaminants.     

Effects of an African grass invasion on vegetation,soil and interstitial water characteristics in a tropical freshwater marsh in La Mancha,Veracruz (Mexico)

Abstract

The transformation of freshwater wetlands to pastures is a common practice in Mexico. This rapid loss of wetlands contrasts with the scarce information that exists about these ecosystems. To identify the environmental factors that control vegetation structure of a freshwater wetland invaded by the African grass Echinochloa pyramidalis, we characterized the vegetation (species composition, cover and aerial biomass), soil (moisture, redox potential, bulk density and topography) and water (water depth level, electric conductivity and pH) in two seasons of the year (dry and rainy). In addition, we analyzed the soil and water of three vegetation areas in the wetland, one dominated by E. pyramidalis, another by Sagittaria lancifolia and a third by Typha domingensis. The parameters associated with the hydrology of the wetland (water level, soil moisture, redox potential and bulk density) explained the plant species distribution. The invasive grass dominated in the relatively drier areas in the wetland while native species such as S. lancifolia, T. domingensis and Pontederia sagitatta dominated wetter sites. Introduction of E. pyramidalis has caused negative changes in the wetland, in particular a decrease of the diversity of plant species. In addition, we believe that the invader grass, as a C4 species, has more efficient use of water than the native plants, as well as a larger biomass, characteristics that can change the hydrological pattern of this wetland.     

Native and invasive plant interactions in wetlands and the minimal role of invasiveness

The effects of invasive plants on plants native to areas that are being invaded can be quite variable, depending on the species of the invasive plant involved as well as the physical characteristics of the location being invaded. My study focuses on the effects of Phragmites australis Linnaeus (common reed) and Lythrum salicaria L. (purple loosestrife) on the same native plant community. Uninvaded plots dominated by native plants Typha angustifolia L. (narrowleaf cattail) and Typha latifolia L. (broadleaf cattail) served as the control. I surveyed percent cover of species during early summer and midsummer for 3 years in six Hudson River freshwater tidal wetlands (sites). Differences in species richness, composition and abundance were small, but significant among invaded and uninvaded plots and among sites. However, these differences remained significant when data for dominant species (invasive and native) were removed. Differences in native plant species abundance were attributed to invasive plant species-specific characteristics and differences in species richness and composition were attributed to physical location (zonation) in these freshwater tidal marshes. “Invasive” status of a dominant plant species was less important in invasive plant–native plant interactions than species-specific characteristics and zonation. Further research into the effects of site and land-use on invasive plant impacts is recommended.     

The interacting effects of temperature and plant community type on nutrient removal in wetland microcosms

Treatment wetlands can remove nutrients from inflow sources through biogeochemical processes. Plant composition and temperature play important roles in the nutrient removal efficiency of these wetlands, but the interactions between these variables are not well understood. We investigated the seasonal efficiency of wetland macrophytes to reduce soil leachate concentrations of total nitrogen and total phosphorus in experimental microcosms. Each microcosm contained one of six vegetation treatments: unplanted, planted with one of four species (Carex lacustris, Scirpus validus, Phalaris arundinacea and Typha latifolid) in monoculture or planted with an equal abundance of all four species. Microcosms were also subjected to two temperature treatments: insulated microcosms and microcosms exposed to environmental conditions. A constant nutrient solution containing 56 mg/l N and 31 mg/l P was added to all microcosms three times a week. Water samples were analyzed monthly for total dissolved nitrogen and total dissolved phosphorous. Microcosms exhibited a typical pattern of seasonal nutrient removal with higher removal rates in the growing season and lower rates in the winter months. In general, planted microcosms outperformed unplanted microcosms. Among the plant treatments, Carex lacustris was the least efficient. The four remaining plant treatments removed an equivalent amount of nutrients. Insulated microcosms were more efficient in the winter and early spring months. Although a seasonal pattern of nutrient removal was observed, this variation can be minimized through planting and insulation of wetlands.     

Hydrologic processes in a southern Ontario wetland

A 12 month investigation on the hydrology of a southern Ontario wetland was completed. The mass flux of water and concentrations of total phosphates, ortho-phosphates, and chlorides were measured in all components of the hydrologic budget; over 800 grab samples were analyzed.The study showed that both groundwater recharge and discharge could occur within a wetland; data on these opposing flows must be quantified in order to develop effective long-term wetland management strategies and to accurately determine nutrient budgets. The study concluded that theoretical formulae may greatly underestimate summer evapotranspiration rates for hydrophyte dominated marshes. Storm inputs of physio-chemical parameters were found to be very significant, accounting for 32 to 51 percent of the total surface water loadings; failure to measure and/or model these inputs would have greatly distorted the study findings. Finally, since flow rates and concentrations of the chemical parameters were less variable at the wetland outflow, it was concluded that the wetland moderates event response inputs into stable response outputs.Over the study period total phosphate imports were double that of total phosphate exports while the ortho-phosphate discharge from the wetland was 22 percent more than the inputs. This indicates that the wetland is transforming sediment-bound phosphate to plant available ortho-phosphate, thus contributing to downstream eutrophication problems.     

Landscape reclamation at a central Florida phosphate mine

A 13-ha parcel of phosphate-mined land at the Gardinier Mine near Ft. Meade, Florida, USA, was reclaimed to test several design principles, establish planting and seed-dispersal trails, and monitor groundwater and surface water. The site was designed as a complete hydrologic unit with perched, basin, and lake-fringe wetland communities in upland communities. The design and placement of ecological communities resulted from the reclaimed topography and site hydrology. The percent growth for 11 wetland and mesic tree species averaged 127% (weighted average) in 3 years; some species averaged more than 160%. Percent survival ranged from 0% (Cephalanthus occidentalis) to 100% for several mesic forest tree species (Fraxinus pennsylvanica, Liquidambar styraciflua, Magnolia grandiflora). The percent survival of wetland species (weighted average) was 94.6%. An adjacent forested, floodplain wetland was evaluated as a source of windblown and bird-dispersed seeds to the site. Windblown seeds decreased in densities as distance from forest edge increased. Densities were from 125/m² to 380/m² within the forest, 50/m² to 120/m² at the forest edge and decreased exponentially as distance increased. Bird-dispersed seed densities at the base of constructed perches and tree “snags” ranged from 100/m² to more than 300/m². Rainfall and surface-water inflow along the edge of the site were the largest inputs to the reclaimed landscape's hydrologic budget. Groundwater flow and seepage were more important to growth and survival of planted species because of the maintenance of higher soil moisture during periods of drought.