Effects of stand structure on growth in selection stands dominated by todo fir (Abies sachalinensis)

Abstract

This paper examines Ehe relationship between growth and stand structure in selection forests dominated by todo fir (Abies sachalinensis (FR. SCHMIDT) MASTERS). Trees were classified into six Classes by their species (conifers or broad-leaved trees) and diameter (small, medium or large trees). A principal component analysis showed that the six class volumes were well summarized by the first two principal components obtained from the class volumes. The first principal component contrasted the volume of small and medium-sized conifers with the volume of large conifers and broad-leaved trees. The second principal component contrasted the volume of medium and large conifers with the volume of large broad-leaved trees. Next, a multiple regression analysis showed that there were correlations of net increment, gross increment and mortality with the principal components ; and the relationships between stand volume growth and six class volumes were shown numerically. The first principal component reflected a constant effect (i. e., independent of time since selection cutting) of stand structure on volume growth and the second principal component reflected the effect depending on selection cutting. In conclusion, selection stands with many medium-sized conifers grew more than stands containing fewer medium-sized conifers or than stands containing more trees assigned to other classes; and large conifers suppressed stand volume growth less if the selection cutting cycle was short.