Stand Age Class to Size Class Crosswalk by Forest Type Group in Minnesota, USA

Abstract

Many forestry models require the input of stand size class information, a variable with multiple definitions across forest inventories. This work describes a crosswalk between stand age class and stand size class for several forest type groups in Minnesota to facilitate consistency and availability of the latter information. Refinements to the crosswalk include ratio adjustments that redistribute the number of plots (or hectares) from one estimated size class to another, based on known crosswalk error rates. The results showed that 61.9% of all plots were correctly classified, and 95.5% were within one size class. Correct classifications for individual forest type/size class combinations ranged from 16.7–79.2%. Applying the crosswalk to a validation dataset produced percent errors from −46.4% to 49.4%, but with the ratio adjustment, errors dropped to −20.1% to 14.4%. These results suggest that the crosswalk and ratio adjustments provide a coarse, yet reasonable, substitute to using more complex stand size classification methodologies, particularly when forecasting future stand conditions.