PREDICTING SOIL TEMPERATURES IN A SHORTGRASS STEPPE

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Abstract
This paper reports a simplified soil temperature model, developed to predict hourly and daily maximum and minimum soil temperatures under different amounts of plant cover. As input the model requires daily maximum and minimum air temperature (2 m), plant biomass, initial soil temperature, and the soil thermal diffusivity. The model was developed using hourly soil temperature from four treatments representing different degrees of plant cover during the 1977 growing season at a shortgrass prairie site in northeastern Colorado. Independent data showed that the root-mean-square error for the daily maximum and minimum soil surface temperature was within 3.71 and 1.19°C, respectively, and that daily maximum and minimum root zone soil temperatures (6, 10, 20, and 50 cm deep) had root-mean-square errors less than 2.4°C. Hourly soil temperatures had root-mean-square error terms of 4.42, 3.14, 2.87, and 1.64°C for the soil surface, 4-, 10-, and 20-cm soil depths, respectively. Differences between the predicted and observed soil temperatures generally decrease with depth. The simplified model uses minimum computer time and reduces data input needed to simulate soil temperatures; however, daily maximum and minimum soil temperature data are needed to estimate some of the parameter values. This paper reports a simplified soil temperature model, developed to predict hourly and daily maximum and minimum soil temperatures under different amounts of plant cover. As input the model requires daily maximum and minimum air temperature (2 m), plant biomass, initial soil temperature, and the soil thermal diffusivity. The model was developed using hourly soil temperature from four treatments representing different degrees of plant cover during the 1977 growing season at a shortgrass prairie site in northeastern Colorado. Independent data showed that the root-mean-square error for the daily maximum and minimum soil surface temperature was within 3.71 and 1.19°C, respectively, and that daily maximum and minimum root zone soil temperatures (6, 10, 20, and 50 cm deep) had root-mean-square errors less than 2.4°C. Hourly soil temperatures had root-mean-square error terms of 4.42, 3.14, 2.87, and 1.64°C for the soil surface, 4-, 10-, and 20-cm soil depths, respectively. Differences between the predicted and observed soil temperatures generally decrease with depth. The simplified model uses minimum computer time and reduces data input needed to simulate soil temperatures; however, daily maximum and minimum soil temperature data are needed to estimate some of the parameter values. © Williams & Wilkins 1984. All Rights Reserved.