Northern Prairie Wetlands Research Articles

Prerequisites for Understanding Climate-Change Impacts on Northern Prairie Wetlands

The Prairie Pothole Region (PPR) contains ecosystems that are typified by an extensive matrix of grasslands and depressional wetlands, which provide numerous ecosystem services. Over the past 150 years the PPR has experienced numerous landscape modifications resulting in agricultural conversion of 75–99 % of native prairie uplands and drainage of 50–90 % of wetlands. There is concern over how and where conservation dollars should be spent within the PPR to protect and restore wetland basins to support waterbird populations that will be robust to a changing climate. However, while hydrological impacts of landscape modifications appear substantial, they are still poorly understood. Previous modeling efforts addressing impacts of climate change on PPR wetlands have yet to fully incorporate interacting or potentially overshadowing impacts of landscape modification. We outlined several information needs for building more informative models to predict climate change effects on PPR wetlands. We reviewed how landscape modification influences wetland hydrology and present a conceptual model to describe how modified wetlands might respond to climate variability. We note that current climate projections do not incorporate cyclical variability in climate between wet and dry periods even though such dynamics have shaped the hydrology and ecology of PPR wetlands. We conclude that there are at least three prerequisite steps to making meaningful predictions about effects of climate change on PPR wetlands. Those evident to us are: 1) an understanding of how physical and watershed characteristics of wetland basins of similar hydroperiods vary across temperature and moisture gradients; 2) a mechanistic understanding of how wetlands respond to climate across a gradient of anthropogenic modifications; and 3) improved climate projections for the PPR that can meaningfully represent potential changes in climate variability including intensity and duration of wet and dry periods. Once these issues are addressed, we contend that modeling efforts will better inform and quantify ecosystem services provided by wetlands to meet needs of waterbird conservation and broader societal interests such as flood control and water quality.

Is consolidation drainage an indirect mechanism for increased abundance of cattail in northern prairie wetlands?

In the Prairie Pothole Region of North America, disturbances to wetlands that disrupt water-level fluctuations in response to wet–dry climatic conditions have the potential to alter natural vegetative communities in favor of species that proliferate in stable environments, such as cattail (Typha spp.). We evaluated the effect of water-level dynamics during a recent fluctuation in wet–dry conditions on cattail coverage within semipermanently and permanently ponded wetlands situated in watersheds with different land use and amounts of wetland drainage. We found that ponded water depth increase was significantly greater in wetlands where water levels were not near the spill point of the topographic basin, where banks were steeper, and in larger wetlands where past dry conditions had less influence on change in pond area. Proportion of the wetland covered by cattail was negatively correlated with increased water depth, bank slope and pond area. Our observations provide evidence that cattail coverage in prairie wetlands is regulated by water-level fluctuations and that land use surrounding the wetland might have an indirect effect on cattail coverage by altering water-level response to wet–dry climate conditions. For example, drainage of smaller wetlands into larger wetlands that are characterized by more permanent hydroperiods, leads to stabilized water levels near their spill point and is therefore a potential mechanism for increased cattail abundance in the northern prairie region.

Relationship between the natural abundance of soil nitrogen isotopes and condition in North Dakota wetlands

A statewide condition assessment of North Dakota wetlands in the summer of 2011 was conducted as part of the U.S. Environmental Protection Agency's National Wetland Condition Assessment (NWCA). Two other wetland condition assessments, the Index of Plant Community Integrity (IPCI) and North Dakota Rapid Assessment Method (NDRAM), were also completed at each wetland. Previous studies have identified how the distinct signatures of stable isotopes can be used to determine different land uses, anthropogenic impacts, nutrient cycling, and biological processes. To evaluate if these relationships existed in northern prairie wetlands, the data collected from the wetland assessments were compared with the natural abundance of soil nitrogen (δ15N) isotopes. Wetland soil δ15N was significantly higher (isotopically heavier) in wetlands surrounded by cropland compared to those surrounded by idle or grazed/hayed grasslands, possibly reflecting anthropogenic impacts and multiple nitrogen sources. Soil δ15N was significantly correlated with floristic quality, IPCI scores, NDRAM scores, and average buffer width, indicating that soil δ15N values may be representative of wetland condition. Soil δ15N exhibited significant differences among wetland types, although limited sample sizes of certain wetland types may have affected this result. Additional studies on the natural abundance of wetland soil isotopes need to be performed in northern prairie wetlands. This study is the first step in exploring the potential applications of wetland soil nitrogen isotopes regarding wetland assessment and surrounding land use and provides important insight for future studies.

Use of single versus multiple biotic communities as indicators of biological integrity in northern prairie wetlands

As much as 70% of prairie wetlands in Canada have been lost. Although further degradation of natural wetlands is considered to be somewhat offset by wetland construction and restoration, Canada lacks bioassessment tools that can track ecosystem health in prairie wetlands. Indices of biological integrity (IBIs) use one or more biotic communities to compare the biological condition of a particular site to conditions found in least-impacted reference sites. Using the IBI approach, we evaluated the potential of 5 biotic communities to assess wetland health in northern prairie wetlands in Canada. Vegetation in the wet meadow, emergent and open-water zones as well as wetland-dependent songbirds and waterbirds were sampled at 81 semi-permanent/permanent natural and compensation wetlands spanning an environmental stress gradient. Metrics with strong linear relationships to the stress gradient (R2>0.2) were combined into an IBI for each biotic community and were subsequently validated at a suite of test sites. After validation, the entire data set was combined and each IBI was evaluated based on its linear relationship to environmental stress. Wet meadow zone vegetation was a strong indicator of environmental stress (R2=0.68, p<0.001), as was the wetland-dependent songbird community (R2=0.59, p<0.001). The emergent zone vegetation community was a relatively weak and inconsistent indicator of environmental stress, while the open-water zone vegetation and waterbird communities were poor indicators. To evaluate whether monitoring more than one biotic community provided additional information about a site's biological and environmental condition, we produced a two-taxon IBI that combined wet meadow zone vegetation and wetland-dependent songbird metrics. The two-taxon IBI had a marginally stronger linear relationship to the stress gradient (R2=0.72, p<0.001) than any single biotic community alone, although we argue that this added information would not warrant the extra cost, effort, and logistical barriers of sampling both plants and birds. The wet meadow zone vegetation and wetland-dependent songbird IBIs were strong surrogates of one another (R2=0.57), suggesting that wet meadow zone vegetation can be used to predict the health of wetland-dependent songbirds, and visa versa. Our results suggest that habitat for healthy wet meadow zone vegetation and wetland-dependent songbird communities is being degraded as compensation sites are replacing their natural analogs.

Winter snowfall determines the occupancy of northern prairie wetlands by tadpoles of the Wood Frog (Lithobates sylvaticus)

In the northern plains of North America, the wetland breeding habitat of amphibians and their populations could be reduced by a change in climate that included decreased precipitation. To test this hypothesis, relative abundance of late-stage tadpoles of the Wood Frog ( Lithobates sylvaticus (LeConte, 1825)) was monitored from 1997 to 2010 during a wet–dry–wet cycle in 29 wetlands distributed throughout central Saskatchewan, Canada. The wetlands were dry for up to 7 consecutive years, and for a mean of 3.8 consecutive years. Consequently, tadpole occupancy of the wetlands was reduced to less than 40% for 5 consecutive years and none of the wetlands had tadpoles during the severe drought of 2001 and 2002. However, the drought had no observable long-term effect on either tadpole occupancy of wetlands or tadpole abundance. In 2007, 93% of the wetlands supported tadpoles, and in 2008 the highest mean relative abundance of tadpoles was recorded. Tadpole occupancy of wetlands was related to winter and spring precipitation (R2 = 0.84) with 67% of long-term variation in occupancy related to snowfall from November to February and 17% related to rainfall from March to June. Less than 45 mm of winter precipitation for 6 consecutive years would probably cause regional extinction of populations of the Wood Frog.

Adaptation of farming practices could buffer effects of climate change on Northern Prairie wetlands

Wetlands of the Prairie Pothole Region of North America are vulnerable to climate change. Adaptation of farming practices to mitigate adverse impacts of climate change on wetland water levels is a potential watershed management option. We chose a modeling approach (WETSIM 3.2) to examine the effects of changes in climate and watershed cover on the water levels of a semi-permanent wetland in eastern South Dakota. Land-use practices simulated were unmanaged grassland, grassland managed with moderately heavy grazing, and cultivated crops. Climate scenarios were developed by adjusting the historical climate in combinations of 2°C and 4°C air temperature and ±10% precipitation. For these climate change scenarios, simulations of land use that produced water levels equal to or greater than unmanaged grassland under historical climate were judged to have mitigative potential against a drier climate. Water levels in wetlands surrounded by managed grasslands were significantly greater than those surrounded by unmanaged grassland. Management reduced both the proportion of years the wetland went dry and the frequency of dry periods, producing the most dynamic vegetation cycle for this modeled wetland. Both cultivated crops and managed grassland achieved water levels that were equal or greater than unmanaged grassland under historical climate for the 2°C rise in air temperature, and the 2°C rise plus 10% increase in precipitation scenarios. Managed grassland also produced water levels that were equal or greater than unmanaged grassland under historical climate for the 4°C rise plus 10% increase in precipitation scenario. Although these modeling results stand as hypotheses, they indicate that amelioration potential exists for a change in climate up to an increase of 2°C or 4°C with a concomitant 10% increase in precipitation. Few empirical data exist to verify the results of such land-use simulations; however, adaptation of farming practices is one possible mitigation avenue available for prairie wetlands.

Spatial structure of a diving duck (Aythya, Oxyura) guild: how does habitat structure and competition influence diving duck habitat use within northern prairie wetlands?

What circumstances allow the coexistence of similar species is a common but complex question in community ecology. It is often assumed that sympatric species within the same guild must employ some mechanism of niche diversification to coexist. Diving duck (Anatidae: Aythya Boie, 1822 and Oxyura Bonaparte, 1828) competition is poorly understood and current evidence of coexistence mechanisms is contradictory. In the spring and summer of 2001 and 2002, we tested whether diving ducks foraging within prairie potholes segregate by depth to avoid competition. We sought to explain any segregation by sampling sediment particle size, compactness, and organic content; submergent vegetation; and benthic invertebrate densities in the foraging locations of each species. Our study was conducted at the wetland scale in southwestern Manitoba, Canada. We found that Redheads ( Aythya americana (Eyton, 1838)), Ruddy Ducks ( Oxyura jamaicensis (J.F. Gmelin, 1789)), Canvasbacks ( Aythya valisineria (Wilson, 1814)), and Ring-necked Ducks ( Aythya collaris (Donovan, 1809)) foraged most often at shallow depths (50–100 cm), while Lesser Scaups ( Aythya affinis (Eyton, 1838)) foraged at shallow to intermediate depths (50–150 cm). Thus, most divers did not segregate by depth. These results conflict with an earlier study that reported diving ducks segregated by depth to avoid competition. Diving ducks likely forage where prey abundance is greatest relative to the cost of diving to obtain that prey.

Relationship between hydrological characteristics and dissolved organic carbon concentration and mass in northern prairie wetlands using a conservative tracer approach

The semiarid prairie pothole region of the North American Great Plains is characterized by millions of small, shallow, closed basin wetlands. These wetlands are hydrologically dynamic, often losing considerable water volume and depth seasonally in response to high evaporative stress and/or infiltration rates. However, the consequences of such water loss on wetland water chemistry parameters, in particular dissolved organic carbon (DOC), remain relatively unstudied. Seasonal changes in DOC concentrations in 12 freshwater and saline wetlands at the St. Denis National Wildlife Refuge near Saskatoon, Saskatchewan, Canada, were examined over an 8‐year period (1993–2000). Specific conductivity in the study ponds ranged from 312 μS cm−1 to 33,493 μS cm−1 (seasonal means). DOC concentrations in all study ponds were high (&gt;10 mg L−1) and increased across a gradient of increasing salinity (mean DOC values from fresh water to saline ranged from 19.7 mg L−1 to 102.7 mg L−1). In the majority of ponds, DOC concentrations increased seasonally from spring through fall. On average this increase was 21 mg L−1, with fall values averaging 60% greater than spring. The greatest DOC increases were observed in saline ponds which lost most of their water by evaporation. Although DOC in these ponds was highly correlated with the conservative tracer, chloride, the slopes of these regression lines were always less than 1 as were the DOC:chloride ratios, indicating nonconservative DOC behavior. Additionally, chloride concentrations increased much faster seasonally than did DOC. Taken together, these data indicated that although DOC was not behaving conservatively, at least some of the observed DOC increases could be explained by simple evapoconcentration. These data also suggested that saline ponds appeared to experience net seasonal removal of DOC. Possible removal mechanisms for DOC include infiltration to the pond margin, bacterial utilization, and photolysis. Freshwater ponds, which lost most of their water by infiltration to the pond margin, on the other hand, displayed less seasonal variation in DOC concentrations. In these ponds, the relationship between DOC and chloride ion was not as strong as in the saline ponds; the slope of this relationship was always &gt;1, as were DOC:chloride ratios. These data indicated that although DOC was being lost to the pond margin as water infiltrated, freshwater ponds accumulated DOC seasonally. Decomposition and excretion of DOC by macrophytes, as well as by pelagic and attached phytoplankton, are the likely within pond sources of DOC here. The rapid response of these small, shallow aquatic systems to water loss make them ideal microcosms in which to study effects of climate on DOC concentrations and other water chemistry parameters.

Vulnerability of Northern Prairie Wetlands to Climate Change

Abstract The prairie pothole region (PPR) lies in the heart of North America and contains millions of glacially formed, depressional wetlands embedded in a landscape matrix of natural grassland and agriculture. These wetlands provide valuable ecosystem services and produce 50% to 80% of the continent's ducks. We explored the broad spatial and temporal patterns across the PPR between climate and wetland water levels and vegetation by applying a wetland simulation model (WETSIM) to 18 stations with 95-year weather records. Simulations suggest that the most productive habitat for breeding waterfowl would shift under a drier climate from the center of the PPR (the Dakotas and southeastern Saskatchewan) to the wetter eastern and northern fringes, areas currently less productive or where most wetlands have been drained. Unless these wetlands are protected and restored, there is little insurance for waterfowl against future climate warming. WETSIM can assist wetland managers in allocating restoration dollars in ...

Avian response to vegetative pattern in playa wetlands during winter

Breeding-bird communities inhabiting northern prairie wetlands have been shown to have higher densities and diversities in wetlands with a well-interspersed 50:50 vegetative cover:water ratio than in those wetlands with a higher or lower proportion of cover. Potential reasons for such a response include increased food or visual isolation and spacing of breeding birds. We manipulated cover:water ratios (75:25, 50:50, 25:75) in Southern Great Plains playas and examined avian response (i.e., species richness, non-waterfowl bird density, and waterfowl density) to these patterns in winter. We found the highest species richness and generally the highest waterfowl densities in the 50:50 cover:water treatment. Because the amount of vegetative food was similar among treatments and waterfowl inhabiting playas during winter are forming pair bonds, it is most likely that the optimal edge and visual isolation provided in the 50:50 cover:water treatment contributed to its high use and richness. Nonwaterfowl bird density was not different among the treatments. Many nonwaterfowl birds using playas in winter, such as McCown's longspur (Calcarius mccownii), occur as nonbreeding feeding flocks, are not forming pair bonds, and likely are not responding to particular cover:water treatments. Playa wetland biologists should create a well-interspersed 50:50 cover:water ratio to optimize waterfowl use and avian species richness.

Seasonal changes in fungal production and biomass on standing dead Scirpus lacustris litter in a northern prairie wetland.

Decaying macrophytes are an important source of carbon and nutrients in fungal and bacterial communities of northern prairie wetlands. Dead macrophytes do not collapse into the water column immediately after death, and decomposition by fungi and bacteria begins while the plants are standing. The seasonal variations in fungal biomass and production on Scirpus lacustris stems, both above and below water, were measured to assess which environmental factors were dominant in affecting these variations in a typical prairie wetland. Fungal biomass and production were measured from early May to November, just prior to freeze-up. Fungal decomposition began and was greatest in the spring despite low water temperatures. The fungal production, as measured by the incorporation of [1-(14)C]acetate into ergosterol, ranged from 1.8 to 376 microg of C g of ash-free dry mass (AFDM)(-1) day(-1), and the biomass, as estimated by using ergosterol, ranged from nondetectable to 5.8 mg of C g of AFDM(-1). There was no significant difference in biomass or production between aerial and submerged portions of Scirpus stems. The water temperature was correlated with fungal production (r = 0.7, P < 0.005) for aerial stem pieces but not for submerged pieces. However, in laboratory experiments water temperature had a measurable effect on both biomass and production in submerged stem pieces. Changes in fungal biomass and productivity on freshly cut green Scirpus stems decaying in the water either exposed to natural solar radiation or protected from UV radiation were monitored over the summer. There was no significant difference in either fungal biomass (P = 0.76) or production (P = 0.96) between the two light treatments. The fungal biomass and rates of production were within the lower range of the values reported elsewhere, probably as a result of the colder climate and perhaps the lower lability of Scirpus stems compared to the labilities of the leaves and different macrophytes examined in other studies performed at lower latitudes.

Diffuse geographic distribution of herbicides in northern prairie wetlands

AbstractThe concentrations of herbicides in water from wetlands on landscapes where herbicides are not used should be less than on farms with moderate (conventional farms) and intense (minimum‐till farms) herbicide use. In general, this hypothesis was not supported for wetlands situated in the Boreal Plains Ecozone of central Saskatchewan, Canada. The overall detection frequency of 10 commonly used herbicides was not significantly different among wildlife habitat with no pesticide use (44.4%), farms with no pesticide use (51.6%), conventional farms (54.9%), and minimum‐till farms (56.5%, χ2 = 5.64, p = 0.13). The herbicides (4‐chloro‐2‐methylphenoxy) acetic acid (MCPA), 2,4‐dichlorophenoxyacetic acid (2,4‐D), bromoxynil, dicamba, mecoprop, and diclorprop accounted for 87% of all detections. In general, detection frequencies and concentrations of individual herbicides were similar on all land‐use types. For example, the mean concentration of 2,4‐D in water on the four land types ranged from 0.12 ± 0.104 to 0.26 ± 0.465 μg/L, and MCPA ranged from 0.08 ± 0.078 to 0.19 ± 0.166 μg/L. However, in the year of application, mean concentrations of MCPA and bromoxynil, but not 2,4‐D, were significantly higher by about twofold in wetlands situated in fields where these herbicides were applied compared with all other wetlands. We propose that many agricultural pesticides are rapidly lost to the atmosphere at the time of application by processes such as volatilization from soil and plant evapotranspiration. Then, the herbicides used throughout the region may be directly absorbed to the surface of wetlands from the atmosphere, or they become entrained in local convective clouds, and are redistributed by rainfall in a relatively homogenous mixture over the agricultural landscape. The low levels of individual herbicides we found in most of the wetland waters would not cause chronic effects to aquatic biota.

Diatom communities as ecological indicators of recovery in restored prairie wetlands

Diatoms were employed to assess the recovery of northern prairie wetlands restored after drainage. We predicted that diatom species diversity and equitability are lower in restored wetlands than in reference wetlands and that diatom communities are similar among reference wetlands because communities should be relatively stable over time. Conversely, we predicted that diatom communities in restored and reference wetlands differ because species recovery after restoration may be incomplete or unattainable depending on environmental conditions or dispersal limits. Eight undisturbed, unrestored (reference) wetlands were compared to eight wetlands restored after drainage. Diatom communities on artificial substrates were transplanted from restored to reference wetlands and vice versa to test for environmental control and dispersal limits to community composition. Species richness was similar at restored and reference wetlands. Diversity and equitability at restored and reference sites were similar within a sampling period, but diversity and equitability decreased over the growing season in reference sites. Based on multidimensional scaling analyses, restored and reference sites could not be distinguished by species composition either early or late in the season. Transplanted diatom community assemblages became similar to those in the wetlands to which they were transferred, suggesting a strong environmental control over diatom assemblages. Diatoms, as a whole, responded rapidly to environmental conditions; yet, dispersal still may limit some species’ re-establishment, while resistance to disturbance may produce little response among other diatom species. Diatoms may have limited utility as ecological indicators in prairie wetlands because of the unique interaction between diatom life history and the cyclic hydrology of prairie wetlands and because diatom community structure is highly variable among reference wetlands.

Agricultural pesticides threaten the ecological integrity of northern prairie wetlands

The northern Great Plains of North America has millions of small wetlands, and these are often dispersed through cultivated fields. We investigated relationship between pesticide occurrence and precipitation in selected wetlands in a 30.4×10 4 km 2 area of the Great Plains with relatively uniform farming practices and 1 777 600 wetlands (southern Saskatchewan, Canada). By early July after pesticides have been applied to crops, the mean number of pesticides detected in wetlands ranged from 1.8 in regions with little precipitation (<21 mm rain during the previous 15 days) to 3.2 in regions under higher rainfall (>90 mm). The proportion of wetlands in which at least one pesticide exceeded Canadian guidelines for the protection of aquatic life increased from 0% to 60% over this same precipitation range. The maximum number of pesticides detected in a single wetland was six. Concentration of lindane in wetlands increased with increasing precipitation. Using geographic information on rainfall, wetland densities, area seeded to crops, and region specific relationships between pesticides and precipitation, we estimated the number of wetlands in Saskatchewan with elevated levels of pesticides. In early July, during 3 of the 6 years, the number of wetlands subjected to pesticide levels that exceeded guidelines for the protection of aquatic life was significant, ranging from 152 000 to 424 000 wetlands or 9–24%, respectively, of the total. Lindane and triallate exceeded the guidelines most frequently.

Soil indicators of agricultural impacts on northern prairie wetlands: Cottonwood lake research area, north Dakota, USA

Potential damage to wetlands by land-use practices has prompted a need for relatively inexpensive, reliable indicators in monitoring ecological conditions. In this study, soil classification and the following soil tests, sodium bicarbonate-extractable P, nitrate (NO3 −), organic matter (OM), pH, clectrical conductivity (EC), and137Cs distribution, were used to compare four wetlands surrounded by cultivated land or grassland. Cumulic A horizons greater than 60-cm thick were found covering the wet meadow zone of the wetland surrounded by cultivated land. No cumulic A horizons were observed in wet meadow zones adjacent to grassland. Laboratory analyses of surface (0–15 cm) soil showed that the wetland surrounded by cultivated land had P cencentrations 2.5 to 6 times higher in the wet meadow and shallow marsh zones than did the other wetlands. In the wetland surrounded by cultivated land, the dominant soil separate in the wet meadow was silt, while sand was the dominant soil separate in the wet meadow zone in the other three wetlands. Phosphorus, OM, and NO3 − concentrations in wet meadow subsoils (15–60 cm) were higher in the wetland surrounded by cultivated land than in the wetlands surrounded by grasslands. Cesium-137 activities were about 3 to 6 times greater in surface (0–15 cm) soils collected from upland grassy slopes compared to cultivated slopes. Soil morphology,137Cs, P, and OM data indicate higher sedimentation and fertilization rates in wetlands next to cultivated fields.

Avian Habitat Selection and Prairie Wetland Dynamics: A 10-Year Experiment

Northern prairie wetlands play a vital role in the life cycle of a wide array of bird species. Prairie wetlands used by birds span the entire range from shallow ephemeral ponds inundated for short periods each spring to large permanent water bodies that seldom, if ever, go dry. The objective of this study was to determine the response of blackbirds, waterfowl, and American Coots to changes in habitat structure induced by water level fluctuations in prairie wetlands. The study was conducted on a series of experimental marshes within the Delta Marsh in southern Manitoba, Canada. Water levels were adjusted following a predetermined schedule to simulate the wet–dry cycle of prairie marshes. Aerial photographs were taken annually, and habitats were characterized using Geographic Information System (GIS) techniques. Weekly avian censuses were related to habitat features using Principal Components Analysis (PCA) procedures. Yellow-headed Blackbirds selected shallowly flooded habitats with a mixture of open water and emergent vegetation, while Red-winged Blackbirds were found in shallower areas with dense vegetation. Coot habitat was consistent over the seasons. They preferred deep-water habitats with interspersed vegetation. As a group, dabbling ducks were generally found in hemi-marsh conditions (equal amounts of cover and water in an interspersed pattern) throughout much of the year. Some species moved to deeper, more open habitats during the fall season. As a group, diving ducks chose areas with deeper water and less vegetation than dabbling ducks. However, there was considerable variation among diving duck species, with Canvasbacks using hemi-marsh sites in spring, and Ruddy Ducks and Lesser Scaup using the most open sites found on the study areas. The wet–dry cycle characteristic of prairie marshes presents a wide array of habitat conditions for avian species. Although hemi-marsh conditions during the cycle result in maximum use for a large number of species, they do not meet the requirements of all species in all seasons. Conservation programs should include wetland complexes of varying water depth and flooding duration to ensure the widest array of habitat types for avian species.

AVIAN HABITAT SELECTION AND PRAIRIE WETLAND DYNAMICS: A 10-YEAR EXPERIMENT

Northern prairie wetlands play a vital role in the life cycle of a wide array of bird species. Prairie wetlands used by birds span the entire range from shallow ephemeral ponds inundated for short periods each spring to large permanent water bodies that seldom, if ever, go dry. The objective of this study was to determine the response of blackbirds, waterfowl, and American Coots to changes in habitat structure induced by water level fluctuations in prairie wetlands. The study was conducted on a series of experimental marshes within the Delta Marsh in southern Manitoba, Canada. Water levels were adjusted following a predetermined schedule to simulate the wet–dry cycle of prairie marshes. Aerial photographs were taken annually, and habitats were characterized using Geographic Information System (GIS) techniques. Weekly avian censuses were related to habitat features using Principal Components Analysis (PCA) procedures. Yellow-headed Blackbirds selected shallowly flooded habitats with a mixture of open water...

Climate change and northern prairie wetlands: Simulations of long‐term dynamics

A mathematical model (WETSIM 2.0) was used to simulate wetland hydrology and vegetation dynamics over a 32‐yr period (1961–1992) in a North Dakota prairie wetland. A hydrology component of the model calculated changes in water storage based on precipitation, evapotranspiration, snowpack, surface runoff, and subsurface inflow. A spatially explicit vegetation component in the model calculated changes in distribution of vegetative cover and open water, depending on water depth, seasonality, and existing type of vegetation.The model reproduced four known dry periods and one extremely wet period during the three decades. One simulated dry period in the early 1980s did not actually occur. Simulated water levels compared favorably with continuous observed water levels outside the calibration period (1990–1992). Changes in vegetative cover were realistic except for years when simulated water levels were significantly different than actual levels. These generally positive results support the use of the model for exploring the effects of possible climate changes on wetland resources.

Effects of Phorate on Ducklings in Northern Prairie Wetlands

Phorate is a toxic organophosphorus insecticide that has been associated with accidental wildlife poisonings. Because of concern for effects on waterfowl, we studied the effects of phorate on mallard (Anas platyrhynchos) ducklings in littoral mesocosms in South Dakota wetlands. In each of 3 wetlands, we constructed 4 mesocosms. One mesocosm was a control, and to the others we applied phorate at rates of 1.2, 2.4, and 4.8 kg/ha, respectively. Phorate caused mortality to ducklings at all concentrations. Ducklings in control mesocosms (0.0 kg/ha) survived longer (P < 0.05) than those in treated mesocosms. Ten-day-old ducklings were more sensitive (P < 0.05) to phorate than were 21-day-old ducklings. Brain and blood cholinesterase (ChE) activity of treated ducklings was reduced (P < 0.01) compared with that of reference ducklings. Phorate concentrations in prairie wetlands can reduce duckling survival; therefore, alternatives to phorate should be considered.

Environmental Fate of Phorate and Its Metabolites in Northern Prairie Wetlands

ABSTRACT The environmental fate of the organophosphate insecticide phorate and its metabolites, phorate sulfone and phorate sulfoxide was examined in mesocosms placed in South Dakota wetlands. Three treatment concentrations of phorate (1.2, 2.4, and 4.8 kg/ha) were applied to wetland mesocosms. Phorate, phorate sulfone, and phorate sulfoxide were present in water and sediment during the entire study (28 days) in all treatments. Maximum phorate concentrations in water were measured one day after treatment and decreased significantly during a 28-day period. The metabolites of phorate increased significantly in the water during the study. Phorate was present in higher concentrations in sediments than either phorate sulfone or phorate sulfoxide throughout the study.