Development and evaluation of a biomass increment-based index for site productivity

Measures of forest productivity generally rely on site index, which can be problematic for multi-cohort and mixed-species stands. Using stand growth and dominant tree height-age (i.e., site tree) measurements from ~10,900 plot locations from Maine, Nova Scotia, New Brunswick, and Prince Edward Island, a forest productivity model for the Acadian Region was developed as a function of climate, lithology, soils, and topographic metrics. Approximately 65% of variation in observed above-ground dry-biomass growth rate (BG) was explained by a Chapman-Richards function of temperature, bedrock, soil root space, slope, and depth to water in combination with stand structure and species predictors. Productivity was then defined in terms of the predicted asymptote of BG, holding structure and species constant, which was termed biomass growth index (BGI); i.e., the site-influenced component of the BG relationship. BGI was mapped on a 20 m grid throughout the region. BGI explained 0-30% of the variability in spruce (Picea sp.) and balsam fir (Abies balsamea) site index, and had similar site index predictive performance (Âą 5%) when compared to existing land productivity classifications in each province. BGI provides a direct relationship between site variables and growth and can help guide forest management decisions and future research.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author