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Scientists have been seeking to quantify the dynamics of plant growth since the early twentieth century by measuring and simulating transpiration and precipitation. In this study the Soil Ecohydrology Model (SEM) was used to simulate soil moisture and forecast plant growth using a yield index at three sagebrush steppe sites, representing a range of vegetation and climate conditions. SEM is a capacitance parameter model that uses a water budget equation to simulate changes in soil moisture and a modification of the de Wit equation to forecast yield. Model simulated soil moisture data were evaluated using long term measured soil moisture data. Yield estimates were forecast using the yield index from SEM and NRCS ecological site descriptions. Results showed no significant difference between measured and simulated total soil water (TSW) values at the three sites. Correlation between measured and simulated TSW datasets was strong at all sites. Study results justify the extension of model outputs to the yield index, which reflected increases and decreases in within year precipitation well. This talk will present the results of the study and outline potential implications for rangeland management.