抄録
We developed a ring-width chronology using living trees of old-growth Sugi (Cryptomeria japonica) in Yanase, Kochi Prefecture, Japan. The studied site is situated in a national forest in the mountainous area of southeastern Shikoku Island, where Sugi-dominant stands mixed with Tsuga and Abies are distributed. A total of 18 cross-cut disks were used to measure ring widths at the precision of 0.01 mm for paired radii of a sample. Tree-mean curves were all successfully crossdated, and the final raw ring-width chronology were generated, covering CE 1768–2004. Crossdating statistics and the visual assessment of the ring-width series showed that the chronology is enough capable of dendrochronological use in future studies. A conventional method to detect pointer years was improved by producing a chronology for the percentage of agreement of increase or decrease of ring widths from those of the previous years. Mean ring-width series of age-aligned tree-mean curves showed the aging trend of the forest dynamics in radial growth, i.e., rapid depression in the very early stage, successive slow recovery, and then gradual, exponential decrease. The result suggested that the variability of the ring-width series are governed not only by the climate but also greatly by the ecological conditions.
