Study On The Lag Responses Of Dahurian Larch Radial Growth To Climate Change

Dahurian Larch is the main species tree in Greater Khingan Range, its growth changes are related to the development of the forest ecosystem and the stability of the ecological environment in Greater Khingan Range forest region. Using dendrochronology theory and method research the radial growth lag response rules to climate change contribute to a more accurate prediction of forest development trend and observation of forest ecological environment dynamic change. The main results are as follows:1.Through tree-ring sampling, sample processing, cross-dating, data standardisation and detrending, established 21 "signal-free" tree-ring width chronologies in Greater Khingan Range (main sites are Inner Mongolia). The autocorrelation analyzed for 21 chronologies respectively, and results show the first-order-autocorrelation is higher(0.422-0.892,p<0.01)to all chronologies, and the order is higher(3-15) by 0.01 significance of autocorrelation. It shows that the trees significant affected by more previous climate factors in the study area. Besides, the correlation coefficient is higher between all chronologies, It means trees growth is more consistent with climate in this area.2.The correlation analyzed between single chronology with temperature and precipitation from previous January to current September, the results show some difference of the chronologies response to temperature and precipitation. Spring and growing season are the main period to influence tree growth by temperature, previous spring and growing season temperature also influence trees is greater. The precipitation during growing season is less impact to trees growth, while the autumn and winter (10-2 month) precipitation impact is more. Thus, in the seasonal scale, temperature and precipitation both have a "lag effect" to the radial growth of Dahurian Larch.3.The correlation analyzed between regional chronology with moving averaged previous 5 years,10 years and 15 years for climate factors, the results show that the correlation coefficient obvious increased with the increasing of the length moving years, and the effect season are also clear. The main influence period is from March to September of temperature, precipitation in late growing season is not conducive to the growth of trees, while the winter and spring precipitation were positively correlated with chronology. Comparative analysis by extreme climate and regional chronology, the extreme temperature have a 2-8-years lag period to influence trees growth, and trees are more sensitive to extreme low temperature. The extreme precipitation have a 2-8 years lag period to influence trees growth, and the extreme wet is a greater influence.4.By the Granger Causal Relation Test show:The January and February temperature have a 2-years lag period to influence Dahurian Larch, March temperature have a 1-3-years lag period, June temperature have a 2-3-years lag period, July temperature lagged 3-years, 5-years and 7-13-years respectively is the Granger Cause to Dahurian Larch radial growth, September temperature lagged 3-5-years and 11-13-years. April precipitation have a 2-3-years and 6-9-years lag period, May precipitation lagged 10-15-years is the Granger Cause to Dahurian Larch radial growth. This shows that the lag effect period of temperature to study area trees is still concentrated in the spring and the growing season, while the lag period of precipitation to trees is mainly in the early stage of growing season, and the lag time of temperature and precipitation are very long.