The Study On The Response Of Tree Ring Width Of Pinaceae Tree Species To Climate Factors And Climate Reconstruction In Nanling Region

Since the 20th century, the effect of global climate change on ecological system had been more profound. Mountain forest ecosystem is fragile and very sensitive to climate change. It is very important for us to understand global change, to study the response of mountain forest ecosystem to climate change. Nanling, climate demarcation line between north and south, is the largest mountains in southern China. It is a typical mountain forest ecosystem. The unique landscape and the vast virgin forest supply the advantaged conditions for us to study forestry adapting to climate change. To carry out systematic dendroclimatology study in this area is beneficial for gaining profound knowledge on the influences and consequences of climate change to forest ecosystem. It is also conductive to forecasting the time-space distribution patterns of forest ecosystem in the future.Regarding Pinus massoniana,Pinus Kwangtungesis Chun and Abies beshanzuensis var. ziyuanensis as the research object, After surveyed and sampled within and around the transects, we developed the corresponding chronologies and age structures for tree species. At the same time, we simulated the month climate factors for each sampling site using the software of MTCLIM. And then, through correlation and component analysis, correlation function and response function analysis, and pointer year analysis, we revealed tree radial growth patterns and recruitment dynamics influenced by climate, because of tree species, latitude, elevation and age. Climatic variables were monthly mean, maximum and minimum temperature and monthly total precipitation over the period from previous June through current December. We also try to establish the growth model in nature condition to discuss the effect of climate change on typical tree’s growth. Taking into account the impact of precipitation and temperature on tree-ring at that time, the following year and another year, using the regional tree-ring chronology, more than 100 years mean temperature and precipitation series were well reconstructed. It was verified that the reconstructed precipitation and temperature series were reliable. The main conclusions can be drawn as follows:(1) Different response of differential species to climate factors occurred in the same environmental condition. Radial growth of P. massoniana, P. Kwangtungesis Chun was consistent with the trend rising of temperature. The key was caused by the positive response of temperature and precipitation conditions. On the contrary, radial growth of Abies beshanzuensis var. ziyuanensis was not consistent with the trend rising of temperature. Important factor was the rising temperature lead to water stress.(2) Abies beshanzuensis var. ziyuanensis from the tree line were disaggregated into different age class to discuss the relationships between tree-ring width and climate by using correlation coefficients and response function. The results suggested that the radial growth:of young Abies beshanzuensis var. ziyuanensis were significantly correlated with temperature and precipitation from the current growth period:but the tree-ring widths from the aging trees were more influenced by the climate of the end of previous growth period or by the temperature and precipitation prior to current growth period. Chronologies responded to climate differently if they concluded different age-class tree-ring cores. The wider age class of age-independent tree-ring models one chronology contains the less accurate reconstructions of past climate this chronology could give.(3) Different response of differential altitude gradient to climate factors occurred, In low altitude, radial growth was mainly inhibited by high temperature and precipitation of the growing season, mainly affected by precipitation. Sufficient precipitation was conductive to the growth, and too high temperature was harmful. With the increase of altitude, the limit of the tree growth from the temperature became stronger; on the contrary, the limit from the precipitation became weaker. In the central region, plenty of the precipitation from previous autumn was favorable for the growth, while too high temperature of the growing season was not favorable. In high altitude, radial growth was mainly inhibited by high temperature and precipitation of the growing season, mainly affected by temperature. High temperature of the growing season was favorable for the formation of wide tree-rings, but too much precipitation was easy to form narrow tree-rings.(4) Different response of differential latitude to climate factors occurred. The tree-ring width from the northern region region were mainly influenced by the climate of the temperature of winter and summer. The rising temperatures of winter and summer promoted the radial growth of P. massoniana. Also the central latitude region, the rising temperatures of winter promoted the radial growth, while the rising temperatures of summer, to some extent, inhibited the radial growth. The tree-ring widths from the southern region region were mainly influenced by the climate of summer. The rising temperatures of summer inhibited the radial growth of P. massoniana. The radial growth was significantly associated with precipitation of the southern region. The radial growth of the central latitude region was related with precipitation in previous October, but not significant.(5) The radial growth of P. Massoniana was significantly correlated with the monthly mean temperature from current May to July in the northern region. The monthly mean temperature in May to July was reconstructed by using the regression method, and it could exhibit that four cold periods (1840-1866,1879-1902 1914-1924 and 1932-1940) and three warm periods (1869-1877,1905-1913 and 1925-1930). It increased quickly after 1999.The radial growth of P. Massoniana was strong positively correlated with monthly mean temperature in current February and March in the central region. The average temperature sequence of February and March was reconstructed. Three cold periods (1892-1906,1918-1922 and 1944-1957) and three warm periods (1909-1917, 1959-1968 and 1998-2010) occurred.The radial growth of P. Massoniana was inhibited by the monthly mean precipitation in September and October in the southern region. The average precipitation sequence of September and October was reconstructed. The reconstruction showed that the precipitation in September and October had experienced three dry periods (1913-1921,1941-1968 and 1978-1988) and four wet periods (1897-1912,1922-1940,1969-1977 and 1989-2010).