Contributors: Dave Clay, Sharon Clay, Carter Johnson, Dave Meyer, Don Olson, Maribeth Price, Craig Spencer, Larry Stetler, Dan Swets, Kerri Vierling, Kate Webb
The prairie pothole region of the North American continent includes the glaciated regions of North and South Dakota, Minnesota, Montana, and south-central Canada. The agroecosystems of the prairie pothole region are extremely important for their agricultural aspect in world food production and their natural resource aspect in migratory waterfowl production. The prairie pothole region provides habitat and cover for a wide array of both nonmigratory species and migrating birds including ducks and geese. In fact, this region and the wetlands of the Nebraska Sandhills produce up to 90% of the North American continents duck population annually (Batt et al., 1990).
In addition, the wetlands of this region are an important natural ecological resource for the area. These wetlands provide water catchmen areas to reduce flooding of states bordering the Mississippi and Missouri rivers and provide a natural buffer to reduce the impact of natural and manmade contaminants.
A problem in studying agroecosystems containing wetlands is that the boundaries between agricultural areas and wetlands change due to the wetlands dynamic nature during a single season and cyclically over years and decades. The classification scheme of wetlands, permanent, semi-permanent, and temporary, reflects the dynamic nature of thee habitats. A dramatic example of such changes is the history of Lake Albert in Hamlin County, SD. During the dust bowl era, the lakebed was dry and used for cropland. Today, the 100+ acre lake is a productive fishery for walleyes and northern pike and provides habitat for ducks, geese, and other animals. The changes in the prairie pothole landscape are primarily influenced by climate (which is being influenced by human activities) and secondarily by human land use in and around these areas.
Global climate change and its possible effects on natural and agricultural ecosystems are of national concern. Climate change has been documented with four of the warmest years on record occurring in the 1990s and 9 out of the past 11 years being warmer than any previous years on record (Kerr, 1998). Model simulations based on projected increases in greenhouse gases and aerosols indicate that the rate of warming in the next century will be greater than any increases seen during the past 10,000 years (Graham, 1995; Houghton et al., 1996). Winter temperatures in the high northern latitudes are expected to increase along with warmer land than sea temperatures (Houghton et al., 1996). Increased precipitation is expected globally; however, regional forecasts vary with some areas wetter and some drier than their current norm (Cushman and Spring, 1989; Grotch and MacCracken, 1991).
Climate change models on inland prairie wetland ecosystems have not been studied sufficiently to predict the possible changes that may occur in these areas. The northern Great Plains is classified as subhumid or semiarid, and the wetland resources in this area are affected by climate variability. Wetland water levels and vegetation already fluctuate widely in these areas (Borchert, 1950; Kantrud et al., 1989; Larson, 1995). Global climate change is predicted to influence the distribution and functions of wetlands by altering their hydrologi regimes (changing water availability and the depth, duration, frequency, and season of flooding) outside their normal range (Poiani and Johnson, 1993).
Many forces threaten to alter the productivity and biodiversity of the prairie wetland landscapes. Studies of their current dynamics and their interactions with agricultural production while protecting and maintaining the many functions of the wetlands located in the prairie pothole region.
Ecosystem-scale experiments are difficult to conduct in the field. However, historical remote sensed information, modeling, and weather data should allow accurate estimation of how the prairie pothole region has developed and changed in the past. Ground-based sampling, modeling, and current imagery may give an indication of how the region may change in the future. In addition, remote sensing will provide a tool to link scales of spatial information.
The vulnerability of these agroecosystems depends both on the direction and magnitude of the predicted climate change and the agricultural use of upland habitats. For example, model simulations that used slightly increased temperatures and slightly lower rainfall amounts than todays norm indicate that semi-permanent wetlands (areas wet in most years, with balanced emergent cover:water ratio) could shift to completely closed based basins with no open water areas and could dry up by midsummer in most years (Poiani et al., 1996). This would lower waterfowl production and wetland values. Land management exacerbate or ameliorate the impacts of global climate change.
Several specific issues, requiring careful and complete study, need to be addressed when beginning to understand the basic dynamics of the agroecosystems in the prairie pothole region. These issues include: the impact of global climate change on water cycling, C sequestering , and nutrient cycling at the individual pothole scale and regionally; the interaction among water, carbon, plant species, and nutrient on biomass production and biodiversity; and the importance of the potholes in the reducing downstream flooding and chemical contamination to subsurface aquifers. This information is needed to be able to predict and maintain the environmental health of the systems in the region. The following discussion will expand on each of these issues as it relates to the wetland portion of the agroecosystem. The impacts of the agronomic side may be addressed in the paper by Dalsted et al.
Impacts of land disturbance on erosion and water quality via paleolimnological and remote sensing analysis.
Ongoing work including analysis of lake sediment cores from three northwest Montana lakes reveals substantial correlation between mass sedimentation rate (MSR) of fine sediments and past human land disturbance activities. Accelerated logging was followed by increases in MSR of up to fourteen times the pre-European settlement rate (Spencer 1999, Schelske 1994). While natural land disturbance activities, including floods and wildfires, appeared to have some impact on MSR, human activities, lead by logging activity and associated road construction, appeared to be the greatest contributor to increased MSR. We intend to establish relationships between the NASA Ames Research Center and the research being done at Augustana College, specifically utilizing remote sensing to characterize land cover change resulting from timber harvest and other human disturbances on a watershed basis. Most of the timber harvest activity involves large clearcuts that are distinctly visible on Landsat (MSS) images. The NASA Ames Research Center, Earth Science, Ecosystem Science research activities are "directed to advanced understanding of the physical and chemical processes of biogeochemical cycling and ecosystem dynamics of terrestrial and aquatic ecosystems through the utilization of aerospace technology." Linkages that may be established could involve, for example, the use of high resolution sensors on aircraft to enhance the preliminary remote sensing work done with the Advanced Very High Resolution Radiometer (AVHRR) satellite imagery.
Lake sediment cores will be analyzed to document historical changes in sediment accumulation rate, primary productivity, and other limnological parameters. Attempts will be made to correlate changes in these parameters with historical changes in various land disturbance activities, both anthropocentric and natural. Our primary study area will be in NW Montana where timber harvest, fires, and floods represent major land disturbance activities. Preliminary results from core sample analyses in this region have produced promising results (Spencer and Schelske 1998, Schelske et al. 1994).
This project is a multidisciplinary effort involving biogeochemical analysis of sediment cores to document changes in lake conditions linked with time series analysis of remote sensing images to help document land-cover change in the lake basins. Logging in NW Montana has been characterized by large clearcuts (> 1km2), which are visible on Landsat images which date back to the early 1970's. In some cases however, alpine meadows, avalanche chutes, and burns may be confused with clearcuts. We will use time series analyses together with geometric (e.g., Hough Transform [Ballard and Brown 1982]) or feature space transformations (e.g., SHOSLIF [Swets and Weng, 1999]) to help distinguish between these features. Stratigraphic analysis of core samples with include a wide variety of parameters including nutrients, metals, pollen, and charcoal, as well stable isotopes (for estimation of primary productivity).
This work will involve scientists in the Biology, Computer Science, and Chemistry Departments at Augustana College. We are open to collaborative work with other SD EPSCoR labs for some of the analytical work. Remote sensing work will likely involve collaboration with the EROS Data Center and NASA Ames.
Preliminary List of Techniques:
Preliminary List of Techniques:
Simulation modeling using climatic data from today and predicted.
Determine energy flux into and out of agroecosystems in the Prairie Pothole region.
Lake core sampling to map history of land use, sedimentation rates, infiltration rates, contaminant degradation rates
Mapping and transect studies to determine baseline biodiversity and changes
Natural abundance isotope work to determine C sequestering, N cycling
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