Plot design effects on phenotypic variability and dynamics of field competition between Six Pinus sylvestris L. varieties

Abstract

Competition effects between six varieties of Scots pine in a field trial were studied from age 5 to 15. The spacing was 1.5 ∗1.5 m. Different plot sizes were compared with respect to varietal means, coefficient of variation, and “degree of genetic determination”;, as a substitute for heritability, Differences between plot types were explained well by the hypothesis of a characteristic balance between above‐ and belowground competitive bias, changing over time. ANOVA of data from contrast plots, consisting of pairwise varietal mixtures, allowed estimation of direct varietal, and associate varietal effects. The associate effect was suggested as a measure of the belowground share of competition‐induced variance. Height growth was less sensitive to competition, especially aboveground, than were diameter and volume growth. A competition adjustment method, based on height differences, was applied. The feasibility of this method was related to plot design and competition dynamics.