Comparison of biomass and nutrient content equations for successive rotations of loblolly pine plantations on an Upper Coastal Plain Site

This study compared first- and second-rotation biomass and nutrient equations between successive loblolly pine plantations on an Upper Coastal Plain Site in Alabama. Nutrient concentration relationships with crown position were explored in order to evaluate their significance for biomass studies determinations. Trees were destructively sampled from across the diameter distribution of the stand for each rotation. Tissues were separated into foliage, branch, stemwood, and stembark and analyzed for nutrient concentration and dry weight. Distance from the top of the tree was recorded for all tissues of the selected second-rotation trees and plotted against nutrient concentrations. Regression equations for individual tree tissue biomass and nutrient content were fit for each rotation and compared. Analyses of nutrient concentration relationships with crown position indicated that mobile nutrient (N, P, K, Mg, S, and Zn) concentrations of stemwood, bark, and branches decreased with distance from the top of the tree and height of the live crown. Foliar nutrient concentrations and non-mobile nutrients (Ca and B) for other tissues showed no patterns with tree height. Stemwood biomass regression equations were equivalent after two rotations. However, biomass and nutrient content regression equations for foliage, branches, and bark differed between rotations. Major differences between rotations were in stemwood N and P, and foliage, branch and bark B concentrations, which suggested reduced availability of these nutrients in the second-rotation stand.