Arctic tundra ecosystems are home to cold-adapted plants and include a complex mix of wetter and drier areas as well as histories of fire disturbance. We tested a computer model that includes arctic tundra plant features and soil properties at multiple tundra field sites. We compared simulations that used site-specific data about plant communities and other landscape properties with simulations that only included more general descriptions of landscapes such as would be used in simulations of much larger areas. Comparing simulations to measurements, we found that incorporating more local information about plants and soils made the simulations more accurate.