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Title: DOWNSCALING MONTHLY FORECASTS TO SIMULATE IMPACTS OF CLIMATE CHANGE ON SOIL EROSION AND WHEAT PRODUCTION

Author
item Zhang, Xunchang
item Nearing, Mark
item Garbrecht, Jurgen
item Steiner, Jean

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2004
Publication Date: 6/1/2004
Citation: Zhang, X.J., Nearing, M.A., Garbrecht, J.D., Steiner, J.L. 2004. Downscaling monthly forecasts to simulate impacts of climate change on soil erosion and wheat production. Soil Science Society of America Journal. 68:1376-1385.

Interpretive Summary: There is a need to know whether a change in soil conservation practices is warranted under possible climate changes. The objectives of this work were (I) to develop a method that translates monthly climate forecasts to daily weather data for use in erosion assessment and (II) to illustrate the potential impacts of a global climate change scenario during 2056-2085 on soil erosion and winter wheat productivity in central Oklahoma. Changes in monthly precipitation and temperature between 1950-1999 and 2056-2085 for central Oklahoma, projected by a global computer model (HadCM3), were satisfactorily incorporated into daily weather data with the proposed method. The derived daily weather data were then used to run an erosion prediction computer model, called Water Erosion Prediction Project (WEPP). Simulated results showed that an increase in atmospheric CO2 concentration by 50%, increased wheat yield dramatically, and an increase in temperature considerably decreased wheat yield and increased soil loss. With all changes considered, predicted average wheat yield during 2056-2085, compared with the present climate, would decrease by 12%; runoff would increase by less than 7%; and soil loss would increase by less than 8% in the common tillage systems. Overall results indicated that conservation tillage and no-till systems would be effective in controlling soil erosion in the region under climate change. The method developed here can be used by scientists and engineers to assess the impacts of possible climate changes on soil erosion and crop productivity, and the resulting impact information can be further used by conservationists to implement conservation practices that effectively control soil erosion.

Technical Abstract: Climate change can affect agricultural production and soil and water conservation. The objectives of this study were to develop a method for downscaling monthly climate forecasts to daily weather series using a climate generator (CLIGEN), and to simulate the potential impacts of projected mean and variance changes in precipitation and temperature on soil erosion and wheat productivity. Monthly forecasts for the periods of 1950-1999 and 2056-2085 for the Oklahoma region, projected by a general circulation model (HadCM3), were used. Projected mean and variance changes in precipitation and temperatures between the two periods were satisfactorily incorporated into CLIGEN input parameters derived for the El Reno, Oklahoma station. Five climate change scenarios were constructed, and the Water Erosion Prediction Project (WEPP) model was run for each scenario. A projected 50% increase in CO2 resulted in some 26% increase in wheat yield. At the elevated CO2 level, projected decrease in total precipitation decreased surface runoff, soil loss, and wheat yield. However, predicted changes in precipitation variance increased runoff by 15-17%, and increased soil loss by 10 and 19% in conservational and conventional tillage respectively. Predicted increase in mean temperature reduced wheat yield by 31%, and increased soil loss by 40 and 19% in conservational and conventional tillage respectively. With all changes considered, predicted average wheat yield during 2056-2085, compared with the present climate at the present CO2 level, would decrease by 12%; runoff would increase by <7%; and soil loss would increase by <8% in all tillage systems. Overall results indicate that adoption of conservation tillage and no-till systems would be effective in controlling soil erosion under changed climate in the region.