Prairie Wetlands and Climate Change - Droughts and Ducks on the Prairies

The Prairie Pothole Region (PPR) contains 5-8 million small wetlands and is one of the most ecologically valuable freshwater resources of the Nation. These wetlands provide abundant ecosystem services, including groundwater recharge, water for agriculture, water purification, and recreation. The PPR is best known as the “duck factory” of North America. By some estimates, this region produces over 50% of the ducks in North America

Model Estimation of Land-Use Effects on Water Levels of Northern Prairie Wetlands

Wetlands of the Prairie Pothole Region exist in a matrix of grassland dominated by intensive pastoral and cultivation agriculture. Recent conservation management has emphasized the conversion of cultivated farmland and degraded pastures to intact grassland to improve upland nesting habitat. The consequences of changes in land-use cover that alter watershed processes have not been evaluated relative to their effect on the water budgets and vegetation dynamics of associated wetlands. We simulated the effect of upland agricultural practices on the water budget and vegetation of a semipermanent prairie wetland by modifying a previously published mathematical model (WETSIM). Watershed cover/landuse practices were categorized as unmanaged grassland (native grass, smooth brome), managed grassland (moderately heavily grazed, prescribed burned), cultivated crops (row crop, small grain), and alfalfa hayland. Model simulations showed that differing rates of evapotranspiration and runoff associated with different upland plant-cover categories in the surrounding catchment produced differences in wetland water budgets and linked ecological dynamics. Wetland water levels were highest and vegetation the most dynamic under the managed-grassland simulations, while water levels were the lowest and vegetation the least dynamic under the unmanaged-grassland simulations. The modeling results suggest that unmanaged grassland, often planted for waterfowl nesting, may produce the least favorable wetland conditions for birds, especially in drier regions of the Prairie Pothole Region. These results stand as hypotheses that urgently need to be verified with empirical data

Wetland Issues Affecting Waterfowl Conservation in North America

This paper summarises discussions by invited speakers during a special session at the 6th North American Duck Symposium on wetland issues that affect waterfowl, highlighting current ecosystem challenges and opportunities for the conservation of waterfowl in North America. Climate change, invasive species, U.S. agricultural policy (which can encourage wetland drainage and the expansion of row-crop agriculture into grasslands), cost and competition for water rights, and wetland management for non-waterfowl species were all considered to pose significant threats to waterfowl populations in the near future. Waterfowl populations were found to be faced with significant threats in several regions, including: the Central Valley of California, the Playa Lakes Region of the south-central U.S., the Prairie Pothole Region of the northern U.S. and western and central Canada, the boreal forest of northern Canada, the Great Lakes region and Latin America. Apart from direct and indirect threats to habitat, presenters identified that accurate and current data on the location, distribution and diversity of wetlands are needed by waterfowl managers, environmental planners and regulatory agencies to ensure focused, targeted and cost-effective wetland conservation. Although populations of many waterfowl species are currently at or above long-term average numbers, these populations are thought to be at risk of decline in the near future because of ongoing and predicted nesting habitat loss and wetland destruction in many areas of North America

Riparian Vegetation Diversity Along Regulated Rivers: Contribution of Novel and Relict Habitats

1. The creation and maintenance of spatial and temporal heterogeneity by rivers flowing through floodplain landscapes has been disrupted worldwide by dams and water diversions. Large reservoirs (novel ecosystems) now separate and isolate remnant floodplains (relict ecosystems). From above, these appear as a string of beads, with beads of different sizes and string connections of varying lengths. 2. Numerous studies have documented or forecast sharp declines in riparian biodiversity in relict ecosystems downstream from dams. Concurrently, novel ecosystems containing species and communities of the former predam ecosystems have arisen along all regulated rivers. These result from the creation of new environments caused by upper reservoir sedimentation, tributary sedimentation and the formation of reservoir shorelines. 3. The contribution of novel habitats to the overall biodiversity of regulated rivers has been poorly studied. Novel ecosystems may become relatively more important in supporting riverine biodiversity if relict ecosystems are not restored to predam levels. The Missouri River of the north-central U.S.A. is used to illustrate existing conditions on a large, regulated river system with a mixture of relict and novel ecosystems

Adjustment of Riparian Vegetation to River Regulation in the Great Plains, USA

The Missouri River and the Platte River provide opposite examples of the way riparian vegetation responds and adjusts to regulation by dams and diversions.Populus-Salix woodland has expanded rapidly into Platte River channels, while it has failed to regenerate in gaps between reservoirs along the upper Missouri River. This divergent response is the result of different geomorphologies and water-use patterns. The Platte River is a braided-type stream with a significant portion of its flow diverted for cropland irrigation. The Missouri is a meandering-type stream with low irrigation usage. I developed a graphical model that characterizes the different ways that riparian vegetation has adjusted to regulation. The model identifies two time periods: pre-regulation and post-regulation adjustment, with the latter divided into phase 1 and phase 2 subperiods. In the pre-regulation period, woodland composition shifts according to weather extremes and climate change. During phase 1, braided rivers adjust by channel-narrowing and expansion of pioneer woodland (Populus-Salix), while meandering rivers cease meandering. During phase 2, after major geomorphic adjustments are complete, both types of rivers, show sharp declines in pioneer woodland Replacement communities in the new equilibrium (post-adjustment period) will be dominated by later successional woodland or grassland species. Geomorphic factors of importance to vegetation establishment adjust relatively quickly (decades), but the subsequent adjustment of vegetation through succession is relatively slow (century or more)

Effects of Weevil Larvae on Acorn Use by Blue Jays

Blue jays (Cyanocitta cristata L.) are important consumers and dispersers of the nuts of oaks and other fagaceous trees in eastern North America. Acorns compose much of the jay diet, especially during the autumn when jays may consume or cache a significant portion of an acorn crop. However, jays do not appear to possess physiological adaptations for countering the protein-binding properties of secondary compounds (tannins) found in acorns. We offered captive blue jays a mixture of infested and uninfested pin oak (Quercus palustris Muenchh.) acorns to see if the birds would selectively consume nuts containing weevil larvae (Coleoptera: Curculionidae) as a protein supplement to a high-tannin, all-acorn diet. Acorns were X-rayed to determine infestation status and then offered to individual jays in an outdoor aviary. Jays handled, opened, and consumed uninfested nuts significantly more often than infested nuts, and use of infested nuts did not increase during continued exposure to a high-tannin diet

Strategic Use of Native Species on Environmental Gradients Increases Diversity and Biomass Relative to Switchgrass Monocultures

Switchgrass (Panicum virgatum) monocultures are a leading feedstock choice for producing cellulosic biofuels. However, in natural stands, switchgrass is only dominant in a narrow ecological niche of the Tallgrass Prairie. This suggests that strategically selected monocultures or binary mixtures of species, adapted to particular ecological niches, might outyield switchgrass monocultures while increasing biodiversity at the field and landscape scales. To test this hypothesis, we planted monocultures of switchgrass and three alternative species at each of three landscape positions (shoulderslope, midslope, and footslope). Alternative species were also mixed with switchgrass such that they composed 33 or 67% of the total number of plants in each plot. Alternative species at each position included a C3 grass, a C4 grass, and a forb. Biomass data were collected in autumn during each of the two consecutive years following the establishment year. (see more in article

The Dammed Missouri: Prospects for Recovering Lewis and Clark\u27s River

The world’s dams and reservoirs are aging. The ecological effects of a half-century or more of flow regulation and sediment alteration are becoming apparent. What remains of the highly dynamic channel and riparian ecosystem of the Missouri River described by Lewis and Clark has become static. Recent long-term studies have determined that some of the impacts on the Missouri River ecosystem turned out as predicted, such as the failure of cottonwood-dominated riparian forests to successfully establish and survive on a broad scale. Other changes were surprises, such as the effect of disease eliminating a formerly dominant tree species and the appearance of mainstem and tributary deltas affecting channel slope, floodplain hydrology, and vegetation. Restoration of the river’s hydrologic and sediment regime has been delayed long enough that the chances of functional ecosystem restoration have been greatly reduced and complicated. Two phases are now needed to attempt to restore the riparian ecosystem: one to repair the effects of post-dam changes (channel incision, bank stabilization) and another to reestablish pre-dam flow and sediment regimes. The prospects for restoration of this valuable ecosystem, rich in history and in goods and services provided to the public, are dim. Time has diminished the chances that restoration or even rehabilitation can be achieved