Structure of mixed Picea abies (L) Karst, and Betula pendula Roth and Betula pubescens Ehrh. stands in South and middle Sweden

Abstract

Observed diameter distributions of forest stands are adapted to the Johnson S _b probability function. The stands investigated are untreated mixed stands of Norway spruce (Picea abies (L.) Karst.) and birch (Betula pendula Roth and Betula pubescens Ehrh.) aged between 20 and 32 years. The adaptation of the Johnson S_b probability function is made both on mixed spruce and birch, and on each species separately. Altogether 156 observations were tested with observed distributions against calculated distributions in the Kolmo‐gorov‐Smirnov test. The fractiles are predicted with multiple regression and two multivari‐ate techniques, simultaneous‐equation models (multivariate regression) and partial least squares with latent variables. The independent variables are characteristics of site and stand. Both multivariate methods predict diameter distribution well when tested.

Key words:

• diameter distribution
• Johnson S_b distribution
• multivariate parameter prediction
• simultaneous‐equation model
• partial least square with latent variables
• Kolmogorov‐Smirnov test
• mixed stands
• Betula pendula Roth
• Betula pubescens Ehrh.
• Picea abies (L.) Karst