Abstract:

The characteristics of azimuth distribution of in Cryptomeria fortunei tree rings in Tianmu Mountain regions was studied by means of statistic methods including variance analysis，composition analysis and empirical orthogonal function (EOF) analysis. The effects of environmental factors on the interannual alternation of azimuth distribution patterns were also investigated by correlation analysis. The results showed that in Cryptomeria tree rings aried along with both azimuth and time significantly. The variation along with azimuth can be represented by four basic azimuth distribution types (denoted by Types 1,2,3 and 4). Type 1 : the anomalies in all azimuths are positive, and they are >0.5 in north (N), west (W), southwest (SW) and south (S) and between 0.2-0.4 in the other four directions. Type 2 : also with positive anomalies in all azimuths as in Type 1, but the anomalies are in the interval 0.2-0.4 in most directions except for N (<0.2). Type 3 : the anomalies are about -0.4 in the NW and NE, and in the range of -0.3 to -0.2 in all other directions. Type 4 : the anomalies in NE, E and SE directions are near 0.0 while at 0.1, in the NW, -0.2 in N, and -0.3 in the other 3 directions. The variation with time can be presented by either the alternation of the four basic types or by the first two principle components (PC1 and PC2) of the eight-azimuth time-series. Furthermore, the PC1 significantly positively correlated with the total precipitation for the period from January to March and negatively correlated with the total rainfall for the period from August to December of the last year. There was a positive correlation between average temperature for the period from August to January along the PC2 axis. The azimuth distribution type varies under different climatic conditions. The favorable environmental factors for types 1 and 2 include: 1) shortage of precipitation from August to December of the preceding year; 2) richness of rainfall from January to March, and 3) lower temperature from March to July and higher (lower) temperature from last August to present January. The opposite climatic conditions were favorable to types 4 and 3. This phenomenon suggests that the azimuth distribution types may contain environmental information, which could be used to established more detailed historical climate data by both averaged in whole tree ring and its azimuth distribution type time series. 