Climate-growth Relationships Of Pinus Sylvestris Var. Mongolica And Their Age Effects In Daxing'an Mountains, China

Daxing'an Mountains is the most northern and largest forest area in China. Under global warming, it is one of regions showing significant warming in the 20th century in China. Dendroclimatology is one of the most important methods for studying global climate change.This study in daxinganling area sampling the seven regions,studying Pinus sylvestris var. mongolica the tree-ring growth characteristic and the response to climate change. Scots pine(Pinus sylvestris var. mongolica) is one of the two major conifer tree species in boreal forests in the northern Daxing'an Mts., China. Firstly, to detect possible influence of climate change on boreal forests in this area, climate-growth relationships of Scots pine were investigated using 7 site tree ring-width chronologies (in total 230 cores) developed from Mohe, Tahe, Mangui, Honghuaerji, Huma and Bizhou in the Daxing'an Mountains. Seven residual chronologies were developed from the cross-dated ring width series using the program ARSTAN. The relationships between climate and tree-ring index were analyzed using bootstrapped response functions analysis of the software DENDROCLIM2002. Response analysis showed that the chronologies of Bizhou, MoheⅠand MoheⅡwere negatively correlated with June temperature of the current year, while the chronologies of Mangui and Mengkeshan were positively correlated with October temperature of the previous year. The above analysis indicated that temperature is the major limiting factor for the growth of Scots pine in the northern Daxing'an Mts. With the synthesis of Pinus sylvestris var. mongolica chronologies and regional climatic analysis, Using the principal component/the second principal components and climate factors to accomplish correlation analysis. The results are basically similar with front climate factor correlative analysis. The analysis shows that the temperature and precipitation are important to the growth, in contrast temperature seems more effective. Secondly, Tree-ring width chronologies from 230 Scots pine cores taken in the Daxing'an Mountains China were used to analyze spatial and age-dependent growth-climate response relationships. The regional representative will have six sites which divided into less than 80 years (A80),81-150 (A100)and 151-200 (A150) than to 201 (A200) 4 year-old level, Correlation analyses between monthly total temperature/precipitation and the four age-class chronologies, do get the correlation round between the four different age class tree-ring growth and climate. The result shows that the 7 sites chronologies with previous October of precipitation or temperature has significant correlation, there are four sites' with the precipitation of previous October has a significant positive correlation. Which indicate the precipitation of previous October has significant influence on tree-ring growth. To Consider the altitude and latitude factors, show that the correlation coefficients between lower elevations of the chronologies and October are more high, but the correlation coefficient of precipitation in high altitude chronologies and October rainfall is negatively related to the general relationship. Thus, in the different sits of Daxing'an Mts, altitude has an influence on climate factor and the tree-ring width. The study tested the fundamental assumption that the climate-growth of Scots pine was age independent after the removal of size trends and disturbance signals. Bootstrapped correlation function analyses suggested that the response of Scots pine radial growth to climate differed between trees <200 years old and >200 years old. Mean sensitivity and standard deviation for trees decreased with age in the≤150 years old tree class; whereas trees>150 years old had no significant relationship with age. These results showed that the assumption of age-independent climate-growth relationship is invalid at these sites. Physiological processes and/or hydraulic constraints dependent on tree age, together with detrending techniques could be the possible causal factors of clear age-dependent responses. These results suggested the importance of incorporating trees of all ages into the chronology to recover a detailed climatic signal in a reconstruction of Pinus sylvestris var. mongolica for this region.