Abstract
Data from United States General Land Office Surveys are commonly used to create vegetation models for the American Pioneer period. These models are then used as baselines for understanding past biotic change. It should be realized that many of these surveys were made near the end of a climatic episode (the Neo-Boreal or "Little Ice Age") when world temperatures were much lower than at the present time. These baselines therefore do not represent vegetational responses to a climatic regime like that of the present, and the vegetation models must be interpreted accordingly.