SEASONAL RHYTHMS OF XYLEM GROWTH MEASURED BY THE WOUNDING METHOD AND WITH A BAND-DENDROMETER - AN INSTANCE OF CHAMAECYPARIS-OBTUSA

The pinning method for the measurement of xylem growth was modified fo r easier application. Trunks of Chamaecyparis obtusa were monthly inci sed with a knife instead of a thin needle. Two years later, xylem bloc ks including wounded areas were harvested. For comparison, circumferen tial increases of the same trees were measured with a band-dendrometer . Measurements from the wounding method indicated a tendency for cambi al cell production to accelerate twice a year, around April and August . Circumferential increase measured with the band-dendrometer differed from radial growth measured from wounding. Circumferential increase w as very small around August and continued after the cessation of cell production. The climatic data near the plantation suggested that the c ircumferential size of the trunk probably is affected by the physical shrinkage of trunks because of water shortage during drought season an d trunk swelling following precipitation. Circumferential increments d id not reflect the seasonal rhythms of xylem growth. Therefore, for de tailed information on radial growth within a season, the wounding meth od is recommended.