A dendroclimatological approach is very useful in the study of global climatic changes because it provides precise dating, high continuity, high resolution and easily obtained duplicates. Only a few dendroclimatological works have been conducted in tropical and subtropical zones because of the relatively small effect of seasonality there. Tree ring width from the upper tree-line is sensitive to variations in temperature during the early stage of the growing season.Under the recent background of climate warming, tree ring width responded to temperature changes consistently allowing it to provide a historic proxy of past temperature change in this area. A standardized 119-year tree-ring chronology was established based on samples collected. Statistical analysis of the chronology shows a mean first order autocorrelation of 0.53, mean sensitivity of 0.25, and signal-to-noise ratio of 22.60. The results indicate tree-ring chronology records information related to environmental changes and tree-ring chronology can be used for dendroclimatological studies. To explore the climatic significance of tree ring width of Pinus massoniana in this study of dendroclimate, correlation analyses were conducted between the chronology and four climate variables recorded at the Gan County meteorological station from 1951 to 2008: monthly mean maximum temperature, monthly mean temperature, monthly mean minimum temperature and monthly precipitation. This study aims to reveal the changes in some of climatic factors over the past 119 years in the Gan County, Jiangxi Province, China by using the measurement and dating of tree-ring widths from large diameter trees of P. massoniana in the area, as well as to analyze the response of growth of P. massoniana to climate change and the correlation between its radial growth and the variability of some climatic factors in the area. The research procedures follow: 1) core samples were extracted from 47 standing trees selected for experimental sampling from the upper elevations of the site (360m), 2) according to the normal process of tree-ring analysis, tree-ring widths were measured with a LINTAB instrument, 3) measures of cross-dating for sample trees were taken using the COFECHA Program, and 4) correlations between ring width, temperature and precipitation were measured with ARSTAN software. The reconstructed function was T_i = 4.11I _i +7.51 (R² = 0.567, R_adj² = 0.543, < 0.01). Because the instrumental dataset was large and an independent test was applied for the transfer function, all the test parameters indicated the function was stable and reliable.
Results indicated a temperature increase during the growing season enhances P. massoniana growth. Prolongation of the growing season and rising temperatures during the growing season can also accelerate the growth of P. massoniana. The correlation coefficient between the temperature series reconstructed by the regression and the observational data is as high as 0.75; there was strong correlation between the radial growth of P. massoniana and the average monthly temperature in February and March from 1890 to 2008 having a significant impact on plant physiology. The average temperature sequence of February and March was reconstructed. Three cold periods (1892-1906, 1918-1922, 1944-1957) and three warm periods (1909-1917, 1959-1968, 1998-2008) occurred. Our tree-ring width chronology data were strongly correlated to results from previous studies. The results not only further supplement the study of tree-ring width chronologies, but also provide baseline data for the study of dendroclimatological reconstruction in warm and humid areas in subtropical China.