Procedures to handle inventory cluster plots that straddle two or more conditions

We review the relative merits and field procedures for four basic plot designs to handle forest inventory plots that straddle two or more conditions, given that subplots will not be moved. A cluster design is recommended that combines fixed-area subplots and variable-radius plot (VRP) sampling. Each subplot in a cluster consists of a large fixed-area subplot for estimating area and tallying large trees, a microplot (small fixed-area subplot) for tallying small trees, and a variable-radius plot for tallying intermediate size trees. Subplots are assigned a condition class based on a classification algorithm. For subplots that straddle conditions, boundaries are mapped for an area estimation, and the condition class of each tree is recorded. For some straddler subplots, there may be insufficient trees for specific conditions to allow unambiguous classification by computer algorithm. We discuss several possible solutions for this problem.