Evaluation of Air Pollution by the Tree Ring Widths

The widths of annual rings of Cryptomeria japonica and Chamaecyparis obtusa were measured and the method finding out anomalies in circumstances was studied. Results obtained are as follows. 1 ) The secondary growth of trees is not influenced by the temperature of the preceding year but it is effected positively by the temperature of that year. 2 ) It is effected positively by the yearly rainfall between June of the preceding year and April of that and negatively by the yearly rainfall between June and September of that year. 3) The widths of annual rings of samples taken from almost every area in the western Japan were decreased remarkably in the period between 1965 and 1975. This decrease is probably caused from air pollution