Adjusting forest density estimates for surveyor bias in historical tree surveys
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The American Midland Naturalist. 167: 285-306.
The U.S. General Land Office surveys, conducted between the late 1700s to early 1900s, provide records of trees prior to widespread European and American colonial settlement. However, potential and documented surveyor bias raises questions about the reliability of historical tree density estimates and other metrics based on density estimated from these records. In this study, we present two complementary approaches to adjust density estimates for possible surveyor bias. We addressed the problem of surveyor bias of density estimates by simulating the effects of (1) rank of selected trees (compared to assuming the nearest trees were selected) and (2) specific surveyor bias in selection of (a) quadrant location, (b) quadrant configuration, (c) azimuth, and (d) combined species and diameter. We then developed regression equations to calculate adjustment quotients for these biases, making the adjustment quotients transferable to any similar datasets.
Hanberry, Brice B.; Yang, Jian; Kabrick, John M.; He, Hong S. 2012. Adjusting forest density estimates for surveyor bias in historical tree surveys. The American Midland Naturalist. 167: 285-306.