To obtain fundamental and useful information regarding heartwood color traits in Japanese cedar, the validity of using L* index for expressing heartwood color and genetic and environmental influences on heartwood color were analyzed using 118 clones with 303 individuals aged approximately 30 years. As for three clones with typical reddish and blackish heartwood, relationships between heartwood color and moisture/potassium content, which were pointed out as ones of the causative agents of blackish heartwood, and the color change after approximately 20 years of conservation were investigated.
Based on the continuity, width range, and standard deviation of each index of L*a*b* data, L* was found out to be an appropriate index to express heartwood color in this species. L* values significantly differed between clones. A moderately high repeatability of clones was detected in L* value. Spatial autocorrelation analysis also showed a stronger effect genetically than environmentally. Moisture and potassium contents significantly differed between two groups of reddish and blackish heartwood. Therefore, the absorption and accumulation of water and potassium into trunk may be genetically regulated. As for the L* value of heartwood color after approximately 20 years of conservation, the difference between two groups was still significant, but the lightness in blackish heartwood increased such that the difference was greatly reduced.
