Response of tree-ring images in different bands to climatic factors.

To deeply explore the climate signals contained in tree rings, we extracted red, green, and blue light intensities from the tree rings of Abies fargesii in the Jinhouling (altitude: 2564 m) and Taiziya (altitude: 2494 m) areas of Shennongjia, using the CooRecorder software. With an age-dependent spline, we fitted the growth trends, established chronologies, and analyzed the correlation between tree ring chronology and climate factors from 1953 to 2020. The results showed that the red, green, and blue light intensities of earlywood of trees from Jinhouling showed a significant positive correlation with mean maximum temperature, mean temperature, and mean minimum temperature in June. In Taiziya, the red, green, and blue intensities of earlywood was significantly positively correlated with the mean maximum temperature in June and significantly negatively correlated with March precipitation. In Jinhouling, latewood red, green, and blue light intensities showed significant positive correlation with mean maximum temperature of June, July and August, as well as with mean temperature and mean minimum temperature in July and August, and significant negative correlations with July precipitation. In Taiziya, latewood red, green and blue light intensities were significantly positively correlated with mean maximum temperature, mean temperature, and mean minimum temperature in August and negatively correlated with August precipitation. The responses of the red, green, and blue bands of tree rings to climate factors often showed a regular trend of variation with wavelength changes, but the trends varied across different bands.