It appears that two main factors hinder the effective incorporation of ecological information derived from computer modeling in resource management at large spatial scales: (1) some models are not ecologically sound and (2) most models based on ecological principles are often too sophisticated or detailed, having complex structures and requiring a large range of input data. This paper employs a generic model based on well-established ecological principles, but with appropriate detail, to better serve decision-making in sustainable resource management. The model was used to simulate aboveground net primary productivity (ANPP), foliage projective cover (FPC), and the evaporation coefficient (k) for large arid areas in northwest China, where there has been serious desertification recently. Observation data of ANPP and FPC in the study area were used to validate the model, and the model results were in good agreement with observation data and other published data. The model was then used to simulate the evaporation coefficient, FPC, and ANPP for the study area. The simulation results indicated that except for several sites, the k parameter was lower than 0.35 x 10 and implied a typical arid climate in the study area. Estimated FPC of the plant community was lower than 50% at most sites, and the annual ANPP was very low-less than 1 tons * ha * yr at 93.8% of sites. These simulation results could serve as references for vegetation restoration and livestock husbandry management in arid areas of China.