Chronology Of Tree - Ring Width Of Pinus Massoniana And Its Response To Climatic Factors

Mount Qinling-Huaihe River is an important climatic and geographical boundary in China. Tongbai Mountain and Jigong Mountain both are the border areas between warm temperate region and northern subtropical region in eastern China, and are located in the transition zone of moist zones and humid zones. At the same time, they are the northern boundary of Pinus massioniana distribution. It is one of the most sensitive regions of climate change in china. It is generally considered that tree-ring width’s response to warm and humid climate is not sensitive. So there are limited and conflicting views in research of study area. We explores the sensitivity of the climate response of tree ring width and explore the specific climatic factors which limit the expanding northward, in order to provide guidance for forest tending work of Pinus massioniana.Tree-ring stable carbon isotope is more suitable than ring width for study in warm and humid climate area.The life of Pinus massioniana is not long, so the sequence length of tree width is short, but because the latitude distribution span of Pinus massioniana is large, it is suitable for study differences of stable isotope responce to climate sensitivity in different locations of same species.This paper provides chronological framework for tree-ring stable isotope study in this area.Totally,72cores of22trees were obtained in Tongbai Mountain and66cores of23trees were obtained using increment borers in Jigong Mountain. After laboratory pre-treatment, cross dating is performed by drawing a skeleton plot and the quality is controlled by running COFECHA program. After that, three kinds of chronologies (the standardized tree-ring chronologies (STD),the residual chronologies (RES) and autoregressive standardization chronologies(ARS)) were established by ARSTAN program. By using the method of correlation analysis, we study the response relationship of chronology and meteorological factors such as the monthly mean temperature, monthly precipitation, monthly relative humidity, PDSI index. Select the typical meteorological factors to reconstruct past climate and analysis chronology cycle. The main conclusions are as follows:(1) The tree-ring width chronologies include rich climate information, and it is suitable for provide chronological framework for tree-ring stable isotope study in this area. The analysis of statistical characteristics of chronology and common interval analysis shows that, the average sensitivity of sample (M.S.), the signal to noise ratio (SNR), the expressed population signal (EPS) and the first principal component (PCi) is high.These indicate that core samples are sensitive to the change of environment in study area.(2) In prophase and metaphase of growing season (May and June), low humidity caused by high temperature limit the radial growth of core samples, and it is the main limiting factor of expanding northward. Chronology is negatively related to monthly mean temperature (p<0.05) in prophase and metaphase of growing season (May, June); it is also negatively related to monthly maximum temperature (p<0.05) in growing season (April, May, June, July and August), and is positive related to the monthly average relative humidity (p<0.05) in Prophase and Metaphase of growing season (May, June and August). No significant correlation exists between chronology in Tongbai Mountain and average monthly precipitation; but chronology of Jigong Mountain shows extremely significant positive correlation (p<0.01)with March precipitation. In addition, the chronology of Tongbai mountain shows significant positive correlation with majority of monthly sunshine hours, especially in September; and shows significant positive correlation with growing season PDSI index, especially in July.(3) By using the regression analysis method, we establish a regression equation between STD of Tongbai Mountain and average maximum temperature from May to August and rebuild the historic changes of study area from1915to2011. Reconstruction results show that since1915, there are two obvious rapid warming periods (1950-1963and1995-2002) and an obvious cooling time (1967to1973). It is obvious shown in the reconstruction sequence with2.67-2.78a and4a cycle, which indicates that monthly maximum temperature respond to large-scale global climate change.