Assessing large-scale surveyor variability in the historic forest data of the original US Public Land Survey

The U.S. General Land Office Public Land Survey (PLS) records are a valuabl e resource for studying pre-European settlement vegetation. However, these data were taken for legal, not ecological, purposes. In turn, the instructi ons the surveyors followed affected the data collected. For this reason, it has been suggested that the PLS data may not truly represent the surveyed landscapes. This study examined the PLS data of northern Wisconsin, U.S.A., to determine the extent of variability among surveyors. We statistically t ested for differences among surveyors in recorded tree species, size, locat ion, and distance from the survey point. While we cannot rule out effects f rom other influences (e.g., environmental factors), we found evidence sugge sting some level of surveyor bias for four of five variables, including tre e species and size. The PLS data remain one of the best records of pre-Euro pean settlement vegetation available. However, based on our findings, we re commend that projects using PLS records examine these data carefully. This assessment should include not only the choice of variables to be studied bu t also the spatial extent at which the data will be examined.