Abstract:

The tree-ring width of Chinese fir (Cunninghamia lanceolata) trees in Jinggangshan National Nature Reserve was measured using the dendrochronology method, and then a standardized chronology was established. The radial growth response to climatic factors was further analyzed using wavelet analysis, multivariate regression, and binary wavelet coherence analysis methods. Our findings could provide valuable theoretical insights into the management of Chinese fir in the nature reserves. The results revealed that from 1960 to 2020, the annual average temperature and annual precipitation in the Jinggangshan National Nature Reserve showed an increasing trend. However, the change trend of mean annual relative humidity was not significant. From 1961 to 2022, the standard chronology of Chinese fir was suitable for dendroclimatology analysis, but the interannual variation of radial growth is not pronounced. There were three dominant periodicities: 60y, 37y, and 20y. The radial growth of Chinese fir was primarily influenced by the maximum temperature in the previous July, the average relative air humidity in October , and the precipitation in January. The analysis with crossed wavelet transform showed that the radial growth of Chinese fir exhibited a lag of 6−9 months on a 2−3y time scale, relative to maximum temperature in the previous July. There was a significant positive correlation between covariance periods and average relative air humidity in October and precipitation in January. The radial growth showed a two-period covariance with maximum temperature in the previous July. The first cycle, scaled to 6−7y, showed a lag of 9−10.5 months in relation to the temperature. The second cycle, scaled to 2−3y, displayed a lag of 6−9 months. There was a significant positive correlation between the average relative air humidity in October and the radial growth in the current year. January precipitation in the current year exhibited a lag of 3−6 months on a scale of 1−2y. In a summary, the radial growth of Chinese fir in Jinggangshan National Nature Reserve is primarily influenced by precipitation, temperature, and average relative air humidity, which are the key climatic factors. 

Key words: Chinese fir, Radial growth, Climate change, Crossed wavelet transform, Wavelet coherence analysis