Projections of Soil Climate during the 21st Century over the United States High Plains Region with a Focus on Nebraska

Soil moisture and temperature parameters, as well as so called hydric and thermic soil regimes, are inherently more stable and quantifiable than their atmospheric counterparts and are essential in determining the environmental conditions of any region. In order to investigate the impacts of climate change in the selected regions, a model called SoilClim was utilized. SoilClim is based on an enhanced daily water balance model that incorporates interactions between the soil and atmosphere through a dynamic module of vegetation cover. The present contribution will summarize the most recent experiments that were carried out in the United States (U.S.) High Plains region, and in Nebraska in particular, focusing on the impact of expected climate change. The issues that will be discussed include: 1) an assessment of the expected change of key soil climate parameters (e.g. overall soil water balance, soil temperature at 50 cm, soil water content or frequency of dry days) during the 21st century; 2) a comparison of the present soil hydric and thermic regimes with those expected under the climate change and the possible consequences (e.g. shifts of pedalfer and pedocal boundary); and 3) a comparison of SoilClim outputs based on a set of downscaled global circulation models (based on the 4th Assessment Report) under various emission scenarios (e.g. SRES A2 and B1) and time horizons (2025, 2050 and 2100). The results will be presented for selected sites representing the U.S. High Plains region and for a 5x5 km grid in the case of Nebraska. Results: According to the projections based on the NCAR-PCM global circulation model, a considerable improvement of water availability in the U.S. High Plains is expected, translating into a longer growing season across the Nebraska and most of U.S. High Plains is to be expected. It should be accompanied by only a moderate increase of soil temperature and a shift of soil hydric regimes toward more wet categories. Meanwhile, the HadCM-based projections show a very different pattern indicating significant drying within the region in the west, with the eastern part of U.S. High Plains remaining relatively wet. These results illustrate that identification of feasible adaptation options (especially those requiring structural changes and large investments) over the U.S. High Plains would be met with difficulty due to the overall uncertainty in the magnitude and even the tendency of the changes. The results will also highlight the potential shortcomings of using only one GCM as an adaptation strategy based on one particular scenario, which might prove to be ill advised. Acknowledgement : Projects KONTAKT ME 844 and OC 187 enabled international cooperation between Czech researchers and the National Drought Mitigation Centre (University of Nebraska, Lincoln) and SoilClim validation was also supported by the COST 734 project. The support of the research plan No. MSM6215648905 'Biological and technological aspects of sustainability of controlled ecosystems and their adaptability to climate change'.