Spatial Variability in Growth-Climate Relationships of Amur Cork Tree (Phellodendron amurense) and Their Connections With PDO in Northeast China

We used a dendrochronological approach to identify the spatial variability in growth-climate relationships of Amur cork tree (Phellodendron amurense), using a network of 12 sites across its natural range in Northeast China. Results showed that the signal-noise ratio, expressed population signal, and mean interseries correlations of the site chronologies decreased significantly with decreasing latitude. Correlation matrix, cluster, and rotated empirical orthogonal function (EOF) analysis all indicated that the 12 chronologies can be classified into two groups, the southern and northern chronologies. Minimum temperature (T-min) was a major factor limiting Amur cork tree growth at regional scales. Almost all sites had positive correlations with monthly temperature, while correlation coefficients with precipitation were much lower than minimum temperature correlations, and only a few months (January, April, and July) were significant (p<0.05). The positive effects of summer T-min on tree growth were significantly decreased with increasing latitude (except BSL site), while positive effects of summer precipitation increased significantly with latitude and longitude and decreased significantly with altitude. The southern nine site chronologies (EOF-1) were significantly positively correlated with the seasonal or annual Pacific Decadal Oscillation (PDO) index of the previous year and the current spring, while the northern three chronologies (EOF-2) showed different relationships, which is consistent with the spatial relationship between PDO and local temperature. The spatial variability in growth-climate relationships of Amur cork tree can be affected by PDO, which can modulate the spatiotemporal variation of spring onset, autumn termination, and the effective accumulated temperature by affecting local temperature.