Stand density management diagram and its thinning applications in Drimys winteri second-growth forests in southern Chile

Abstract

Stand density management (DMD) diagrams are graphical models of uniform stands at different ages that reflect the relationship among size, density, competition, site occupancy and self thinning. DMDs allow planning of thinnings through the definition of a target stand and the upper and lower limits of site occupancy. In this study we developed a DMD for Drimys winteri second-growth forests in southern Chile by using 300 sampling units with at least 70 % basal area of this species. The resulting DMD allowed the determination of the maximum density line, the volume and height isolines, and the evaluation of its use with information from permanent plots thinned 21 years ago. The results of the functions in the DMD present acceptable predictive power, and illustrate the usefulness and precision of this tool to plan silviculture activities. Results from applying the DMD suggest maintenance of site occupancy levels between the subutilization zone (30 % relative density index (RDI)) and the imminent mortality zone (45 % IDR), executing at least three thinnings to reach a target stand that will produce sawtimber and veneer at an age of at least 80 years for the study site. With this scheme the windfall risk is reduced and therefore so is the potential loss of production.