Methodological aspects to generate density management diagrams based on the diagrams based on Reineke´s index

Abstract

Density represents the degree of crowding of trees in a stand; their changes affect both the timber yield from a site and the sizes of the individual trees on it. Reineke´s model and its stand density index (SDI) are used in the construction of density management diagrams (DMDs). The SDI defines the upper limit for self-thinning and the minimum point of total site occupancy. Despite the importance of DMDs, in their construction there is often ignorance or lack of clarity about relevant methodological aspects. The objective of this paper is to present basic theoretical elements that those responsible for forest management should take into account to generate a DMD. Under the classical approach to modeling Reineke’s function, concepts about density, the type and characteristics of the source of dasometric information to be used, this research addresses the selection of high-density sites, the statistical adjustment of the function, the methodological criteria to move and delimit the line of self-thinning, and the bases for determining the growth areas of Langsaeter. It emphasizes that the self-thinning line can be delimited by using sampling sites for timber inventory and that high-density sites are selected using the maximum SDI approach (SDI_max). The linear ordinary least squares method for adjusting Reineke's function is robust and corrects heteroscedasticity. For maximum volume growth, stands should be maintained between 35 and 65 % with respect to the SDI_max. Optimal density levels should be determined by species.