An analysis of agreement between volunteer- And researcher-collected urban tree inventory data

In partial fulfillment of a grant to assess the potential impact of emerald ash borer on Minnesota, U.S., community forests, six communities were selected in 2009, and eight communities were selected in 2011, to complete tree surveys or inventories. Trained volunteers in each community were used to identify, measure, and assess their community trees. Training methods, technical assistance, and measurement tools utilized were updated between 2009 and 2011 based on input from community volunteers and university training staff, allowing for a post hoc study of volunteer efficacy to be conducted. To assess volunteer efficacy and the effect of updated training protocols on data quality, comparisons between volunteer-collected data and university-collected data were analyzed for agreement in genus and species identification, tree measurements, and condition rating for a subsample of trees in each community. Agreement was the greatest for tree identification at the genus level (>90%) and the lowest overall for condition rating (<70%) for all communities. Statistically differences between the 2009 and 2011 communities were detected with 2011 communities having higher levels of agreement on average. The increased probability of agreement with university researchers is likely attributable to increased focus on field-instruction, technical assistance, and more sophisticated tools used by the 2011 communities. However, detailed volunteer demographic data for each community was not available for analysis and could provide further insight into differences detected. Decisions to use volunteer collected data should incorporate appropriate levels of training and tool sophistication for the level of specificity required for a project.