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.     

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.     

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.     

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.     

Hydrologic and biogeochemical controls on trace element export from northern Wisconsin wetlands

Wetlands play an important role in determining the water quality of streams and are generally considered to act as a sink for many reactive species. However, retention of chemical constituents varies seasonally and is affected by hydrologic and biogeochemical processes including water source, mineral weathering, DOC and SPM cycling, redox status, precipitation/dissolution/adsorption, and seasonal events. Relatively little is known about the influence of these factors on trace element cycling in wetland-influenced streams. To explore the role of wetlands with respect to the retention/release of trace elements to streams, we examined temporal and spatial patterns of concentrations of a large suite of trace elements (via ICP-MS) and geochemical drivers in five streams and wetland rivulets draining natural wetlands in a northern Wisconsin watershed as well as in their groundwater sources (terrestrial recharge, lake recharge, and older lake recharge). We performed principal components analyses of the concentrations of elements and their geochemical drivers in both the streams and rivulets to assist in the identification of factors regulating trace element concentrations. Variation in trace and major element concentrations among the streams was strongly related to the proportion of terrestrial recharge contributing to the stream. A dominant influence of water source on rivulet chemistry was supported by association of groundwater-sourced elements (Ba, Ca, Cs, Mg, Na, Si, Sr) with the primary statistical factor. DOC appeared in the first principal component factor for the streams and in the second factor for the rivulets. Strong correlations of Al, Cd, Ce, Cu, La, Pb, Ti, and Zn with DOC supported the important influence of DOC on trace metal cycling. A number of elements in the rivulets (Al, La, Pb, Ti) and streams (Al, Ce, Cr, Cu, La, Pb, Ti, Zn) had a significant particulate cycle. Redox cycling and precipitation/dissolution reactions involving Fe and Mn likely impacted Cu and Mo as evidenced by the low levels in the rivulets. Variance in Fe, Mn and the metal oxy-anions was associated with factors related to redox cycling and adsorption reactions in the wetland sediments. In streams, DOC and metals with a high affinity for DOC were associated with a factor which also included negative loadings for groundwater-sourced elements, reflecting the importance of seasonal hydrologic events which flush DOC and metals from wetland sediments and dilute groundwater sourced metals. Redox processes were of secondary importance in the streams but of primary significance in the rivulets, documenting the importance of anoxic conditions in wetland sediments on groundwater en route to the stream.     

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.     

Utilizing a historical database to refine ground cover vegetation as indicators of wetland hydrology

Indicator species provide an easy and quick method of evaluating ecosystems. The species comprising the most useful indicators of wetlands should be distributed across a range of water depths and inundation durations, while each species is representative of a specific condition. Hydrophytic vegetation is commonly used to determine the existence and type of wetland; however, such indicator systems often depend on assigning species qualitatively to discrete categories based on assumptions about their distribution along a gradient of conditions. The current study proposes a wetland indicator system based on the quantitative responses of individual vegetation species to a gradient of water depths and periods of inundation. A long-term database was utilized to determine species responses to hydrological alterations in a series of wetlands. The hydrophytic plant species investigated (n = 29) displayed relatively narrow ranges of mean hydrologic values and were distributed linearly along multiple hydrologic gradients (hydroperiod, average water depth, and maximum water depth) ranging from Amphicarpum muhlenbergianum which was observed at the shallowest water depths and shortest hydroperiod to Pontederia cordata and Ludwigia repens which were characteristic of wetlands with the deepest water and longest hydroperiod. The species distribution and means along the hydrologic gradients tested indicates they are prime candidates for inclusion in a quantitative or continuum indicator system. The historical database utilized for this study provided valuable information for numerous species common to the Tampa Bay region for which little or no ecological information was previously available. The methodology utilized in this paper provides a cost and time effective method for obtaining the vast amounts of information required to refine plant indicator systems using a large number of species.     

Simulated Effects of Stream Restoration on the Distribution of Wet‐Meadow Vegetation

Meadow restoration efforts typically involve the modification of stream channels to re‐establish hydrologic conditions necessary for the maintenance of native vegetation. To predict change in the distribution of common meadow plant species in response to meadow restoration, a hydrologic model was loosely coupled to a suite of individual plant species distribution models. The approach was tested on a well‐documented meadow/stream restoration project on Bear Creek, a tributary to the Fall River in northeastern California, U.S.A. We developed a surface‐water and groundwater hydrologic model for the meadow. Vegetation presence and absence data from 170 plots were combined with simulated water‐table depth time series to develop habitat‐suitability models for 11 herbaceous plant species. In each model, the habitat suitability is predicted as a function of growing‐season, water‐table depth, and range. The hydrologic model was used to simulate water‐table depth time series for the pre‐ and post‐restoration conditions. These results were used to predict the spatial distribution of habitat suitability for the 11 herbaceous plant species. Model results indicate that restoration changed water levels throughout the study area, extending well beyond the near‐stream region. Model results also indicate an increase in the spatial distribution of suitable habitat for mesic vegetation and a concomitant decrease in the spatial distribution of suitable habitat for xeric vegetation. The methods utilized in this study could be used to improve setting of objective and performance measures in restoration projects in similar environments, in addition to providing a quantitative, science‐based approach to guide riparian restoration and active revegetation efforts.     

Monitoring temporal dynamics of Great Artesian Basin wetland vegetation,Australia, using MODIS NDVI

The Great Artesian Basin springs (Australia) are unique groundwater dependent wetland ecosystems of great significance, but are endangered by anthropogenic water extraction from the underlying aquifers. Relationships have been established between the wetland area associated with individual springs and their discharge, providing a potential means of monitoring groundwater flow using measurements of vegetated wetland area. Previous attempts to use this relationship to monitor GAB springs have used aerial photography or high resolution satellite images and gave sporadic temporal information. These “snapshot” studies need to be placed within a longer and more regular context to better assess changes in response to aquifer draw-downs. In this study we test the potential of 8 years of Moderate Resolution Imaging Spectroradiometer Normalised Difference Vegetation Index data as a long-term tracer of the temporal dynamics of wetland vegetation at the Dalhousie Springs Complex of the Great Artesian Basin. NDVI time series were extracted from MODIS images and phenologies of the main wetland vegetation species defined. Photosynthetic activity within wetlands could be discriminated from surrounding land responses in this medium resolution imagery. The study showed good correlation between wetland vegetated area and groundwater flow over the 2002–2010 period, but also the important influence of natural species phenologies, rainfall, and anthropogenic activity on the observed seasonal and inter-annual vegetation dynamics. Declining trends in the extent (km²) of vegetated wetland areas were observed between 2002 and 2009 followed by a return of wetland vegetation since 2010. This study underlines the need to continue long-term medium resolution satellite studies of the GAB to fully understand variability and trends in the spring-fed wetlands. The MODIS record allows a good understanding of variability within the wetlands, and gives a high temporal-frequency context for less frequent higher spatial resolution studies, therefore providing a strong baseline for assessment of future changes.     

Dynamic hydrochemical and vegetation gradients in fens

The mixing of groundwater, river water and precipitation was studied in a discharge and a recharge fen in the Vechtplassen area, the Netherlands. The aim of the study was to characterize relationships between vegetation in fens, the chemical composition of the fen water, and the hydrologic regimes. We were particularly interested in the influence of polluted water from the river Vecht on vegetation and nutrient dynamics. Analyses were made for Ionic Ratio (IR = 2[Ca]/(2[Ca] + [Cl]), molar concentrations) and Electrical Conductivity (EC), all indices of the relative importance of each of the three main water sources: groundwater, river water and precipitation.During winter, water in the discharge fen was strongly influenced by calcium-rich groundwater (high IR, moderate EC), while the recharge fen was entirely fed by precipitation (low IR and EC). During summer, river water with a moderate IR and high EC infiltrated the fens and caused a dramatic change in the chemical composition of the fen water. In the discharge fen, infiltration occurred predominantly as sheetflow, causing inundation of the entire fen surface. River water infiltration affected the surface peat of this fen more severely than deeper peat layers. Spatial variation in water chemistry along the transect was small, and only one type of plant community was found. In the recharge fen, river water infiltration occurred in subsurface water, and rainwater that had accumulated during the winter persisted in the central parts of the fen. Gradients in fen water chemistry were correlated with the observed distribution of three plant associations. Differences in water chemistry could also be attributed to intra-site variation in the relative importance of the three water sources. In both fens, there was considerable temporal variation in the chemical composition of the fen water, clearly related to dynamics of the hydrologic regime, particularly infiltration of river water. There are indications that characteristic mesotraphent fen plant communities are negatively affected by water from the river Vecht. River water supply should therefore be avoided as much as possible if these fen plant communities are to be maintained.     

Microrefuges from drying for invertebrates in a seasonal wetland

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塔里木河中下游地区不同地下水位对植被的影响

 根据近几年塔里木河中下游地区的大量监测结果,分析了不同地下水位对植被的影响。结果显示：1)在塔里木河中下游,地下水位与植被盖度和植物种类的回归模型分别可以表示为：Y=159.32e-0.314 8X,R2=0.819 3,　p<0.01;Y=9.113e-0.162 3X,R2=0.606 7, p<0.01。2)地下水位对植被的影响在很大程度上是通过改变土壤含水率来实现的,当地下水位在1～4 m时,其回归模型为：Y=64.898e-0.515X,R2=0.727,p<0.01;当地下水位在4～12 m时,Y=21.147e-0.178X,R2=0.658,p<0.01。当地下水位在3.5～4.0 m时,土壤含水率出现明显变化,因此认为3.5 m是塔里木河中下游地区草本植被生态恢复的最低水位。3)通过胡杨叶脯氨酸(Pro)和脱落酸(ABA)在不同水位条件下的含量变化,可以认为引起胡杨水分胁迫的地下水位出现在5.0 m。其后随着水位的降低,胡杨脱落酸的积累更加明显,地下水位与胡杨叶脱落酸含量可以表示为：Y=0.703 5e0.408X,R2=0.830 4, p<0.01。4)通过塔里木河下游输水后的植被调查,当地下水位出现明显升高后,植被的地表生态响应非常明显,乔灌草植被在水位升高至不同水位后均出现相应的变化,说明以上的分析是符合实际的。     

Plant species diversity and composition of wetlands within an upland forest

Though often overlooked, small wetlands in an upland matrix can support diverse plant communities that increase both local and regional species richness. Here we characterize the full range of wetland vegetation within an upland forest landscape and compare the diversity and composition of different wetland plant communities. In an old-growth forest reserve in southern Quebec, Canada, we sampled wet habitats including lakeshores, permanent and seasonal ponds, swamps, glades, and streamsides. We used clustering, indicator species analysis, and nonmetric multidimensional scaling ordination to identify and compare vegetation types. The wetlands contained 280 species of vascular plants, 45% of the reserve's flora, in only 1.1% of its area. Local diversity averaged 24 ± 0.7 species per 7 m(2), much higher than in the surrounding upland forests. Plant communities sorted into five types, whose strongest indicator species were Osmunda regalis, Glyceria striata, O. cinnamomea, Deparia acrostichoides, and Matteuccia struthiopteris, respectively. Both local species richness and compositional variation among sites differed among the vegetation types. By combining species representative of the region's major wetlands with species from the upland forest matrix, the plant assemblages of these wetlands make disproportionately important contributions to landscape-level diversity.     

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.     

Testing a Passive Revegetation Approach for Restoring Coastal Plain Depression Wetlands

Restoration of coastal plain depressions, a biologically significant and threatened wetland type of the southeastern United States, has received little systematic research. Within the context of an experimental project designed to evaluate several restoration approaches, we tested whether successful revegetation can be achieved by passive methods (recruitment from seed banks or seed dispersal) that allow for wetland "self-design" in response to hydrologic recovery. For 16 forested depressions that historically had been drained and altered, drainage ditches were plugged to reestablish natural ponding regimes, and the successional forest was harvested to open the sites and promote establishment of emergent wetland vegetation. We sampled seed bank and vegetation composition 1 year before restoration and monitored vegetation response for 3 years after. Following forest removal and ditch plugging, the restored wetlands quickly developed a dense cover of herbaceous plant species, of which roughly half were wetland species. Seed banks were a major source of wetland species for early revegetation. However, hydrologic recovery was slowed by a prolonged drought, which allowed nonwetland plant species to establish from seed banks and dispersal or to regrow after site harvest. Some nonwetland species were later suppressed by ponded conditions in the third year, but resprouting woody plants persisted and could alter the future trajectory of revegetation. Some characteristic wetland species were largely absent in the restored sites, indicating that passive methods may not fully replicate the composition of reference systems. Passive revegetation was partially successful, but regional droughts present inherent challenges to restoring depressional wetlands whose hydrologic regimes are strongly controlled by rainfall variability.     

Spatial pattern, patch dynamics and successional change: chironomid assemblages in a Lake Erie coastal wetland

1. Distribution patterns in 1994 and 1995 of chironomid larvae in the sediments of wetlands on Presque Isle, Pennsylvania were used to determine whether relationships exist among species composition and wetland age, position or environmental characteristics. Canonical correspondence analysis was used to relate wetland age, degree of isolation, vegetation abundance and water chemistry to species composition.
2. Of forty-two chironomid taxa collected, Tanytarsus lugens group, Paratanytarsus sp. and Cladotanytarsus mancus group were the most widespread, but Lauterborniella agrayloides , Stictochironomus sp. and Cryptochironomus sp. were locally abundant in several sampling sites.
3. The canonical ordination based on all site characteristics was statistically significant and accounted for 54.9% of the variance in the species data and 69.5% of the variance in the species–environment relationship. The variables that contributed significantly to the ordination model were macrophyte abundance, conductivity and wetland area.
4. Partial canonical ordination based on environmental conditions with wetland age and position effects as covariables showed that environmental conditions explain a significant proportion of the variance in species composition among sites. Neither wetland age nor position variables explain a significant proportion of the variance in species composition.     

Spatial pattern, patch dynamics and successional change: chironomid assemblages in a Lake Erie coastal wetland

1. Distribution patterns in 1994 and 1995 of chironomid larvae in the sediments of wetlands on Presque Isle, Pennsylvania were used to determine whether relationships exist among species composition and wetland age, position or environmental characteristics. Canonical correspondence analysis was used to relate wetland age, degree of isolation, vegetation abundance and water chemistry to species composition.
2. Of forty-two chironomid taxa collected, Tanytarsus lugens group, Paratanytarsus sp. and Cladotanytarsus mancus group were the most widespread, but Lauterborniella agrayloides , Stictochironomus sp. and Cryptochironomus sp. were locally abundant in several sampling sites.
3. The canonical ordination based on all site characteristics was statistically significant and accounted for 54.9% of the variance in the species data and 69.5% of the variance in the species–environment relationship. The variables that contributed significantly to the ordination model were macrophyte abundance, conductivity and wetland area.
4. Partial canonical ordination based on environmental conditions with wetland age and position effects as covariables showed that environmental conditions explain a significant proportion of the variance in species composition among sites. Neither wetland age nor position variables explain a significant proportion of the variance in species composition.     

Long‐term impacts of nitrogen and sulphur deposition on forest floor vegetation in the Northern limestone Alps,Austria

Question: Are there effects of long‐term deposition of airborne nitrogen and sulphur on the forest floor vegetation from permanent plots collected in 1993 compared to 2005. Location: Northern limestone Alps in Austria. Methods: Single species responses were analysed by correlating trends in cover‐abundance values, as derived from marginal models, with Ellenberg indicator values. Changes in the species composition of plots were analysed by correlating changes in mean Ellenberg indicator values with the displacement of plots within a multidimensional scaling ordination. Results: Trends in single species abundance were positively correlated with indicator values of soil pH but were independent of nutrient availability. A general trend towards the homogenisation of vegetation, due to convergent time vectors of the relevés, became obvious. Oligotrophic sites previously situated at the distal ends of ordination axes shifted towards the centre since they were enriched by species preferring mesotrophic conditions. The bulk of plots with intermediate site conditions hardly showed any trends. A concomitant analysis demonstrated that temporal changes in species composition exceed the variation in cover abundance estimates among different field botanists. Conclusions: N deposition can lead to a homogenisation of forest floor vegetation. Larger limestone areas with diverse soil conditions, such as the Northern limestone Alps in Austria, as a whole are thus negatively affected by airborne N deposition. Nevertheless, the vegetation was at least as strongly affected by an increase of basiphilous species as a result of decreasing S deposition.     

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.