Cryptomeria Fortunei Tree-ring Width Index With Responses To Climate Change In The Southwestern Of Sichuan

Under the background of global warming,dendroclimatology,as a new approach for studying climate change,plays a more and more important role in the climate reconstruction research. In recent years,the number of researchers who choose to conduct research in Humid region is growing. Because the research results can better explain the mechanism between the radial growth of trees and climate change,the dendrochronology data gradually turns into an alternative data for the climate research and provides reliable scientific bases for a long period climate reconstruction and prediction in local areas.Cryptomeria fortunei is a common coniferous species in southwest of Sichuan Province.We took samples in the open and then conduct the cross-dating and then the ring series were removed growth trend and normalized,finally,we establish the tree-ring index standalized chronology of Cryptomeria fortunei..Through comparison analysis between tree-ring index series and the trend of climate change in recent decades and correlation analysis between tree ring index and meteorological data so that we can find out the main climatic factors affecting tree radial growth. After this,we draw three-dimensional response surface graphs by building the response model between the radial growth and climatic factors. The research results showed as follows:(1) Different tree-ring chronologies had different sensitivities to climate,the sensitive of radial growth of elderly group to climate factor exceeds young group and the early wood radial growth to climate factor is higher than that of latewood in sensitivity.(2) Over the 50 years,the temperature showed a upward trend and the annual average temperature increased approximately 0.3℃ while the average annual precipitation remained stable.In addition,the trend between the climate change and Cryptomeria fortunei radial growth is not consistent and showed a "separation phenomenon".(3) To be more specific,the correlation of Cryptomeria fortunei and radial growth of "three point temperature" is not consistent,in March,there was a high correlation between the Cryptomeria fortunei radial growth and three point temperature and the correlation coefficient between the radial growth and the mean,the minimum temperature was+0.283、+0.286 respectively,both reached significant level(p<0.05).In June,the radial growth existed extremely significant correlation with the high temperature and the correlation coefficient was-0.398(p<0.01).In terms of the rainfall,the correlation of Cryptomeria fortunei radial growth of each month between the precipitation were all not significant(p>0.05).What is more,Cluster analysis results showed that the precipitation in August and July is good to the Cryptomeria fortunei growth to a certain degree.(4) The climate factors presented different impact on the different ages of Cryptomeria fortunei. And the younger group is mainly affected by the three point temperature and precipitation.The correlation coefficient of the ring series and the "three point temperature" was+0.409、+0.335、+0.335,respectively and showed a significant correlation(p<0.05),and the correlation coefficient of precipitation for February of that year was-0.313(p<0.05).On the other hand,the elder group,it is mainly affected by the average temperature and maximum temperature while the rainfall just presented little effect on it.The correlation coefficients between the ring index and the mean temperature,maximum temperature was+0.291 and +0.295(p<0.05),and the r was-0.283 and-0.299 in Sep(p<0.05).(5) There was a relatively significant diffrence between the growth of early wood,latewood and climate factors.The correlation coefficients between early wood radial growth and the average temperature in April,the maximum temperature of Sep. Oct. last year were+0.352、+0.298、+0.309,existing significant correlations(P<0.05).The r value of the average maximum temperature in April,the mean temperature in July and the minimum temperature in November of last year were-0.297、0.356、-0.293 and all are significant(p<0.05).For the latewood,the r was+0.296(p<0.05) between the radial growth of the latewood and the mean maximum temperature in Oct.But the rainfall did not exist significant correlation with the growth of both earlywood and latewood.(6) The function model between Radial growth of Cryptomeria fortunei and climatic factors (temperature,precipitation) is below: Y=0.947-0.108P+0.125T2+0.141P2.1037*P-0.093P3+0.43 T2*P+P2 (R=0.679,R2=0.460,F=5.241,p<0.01)(7) Overall,the radial growth of Cryptomeria fortunei is significantly affected by the temperature and precipitation.of growing season(4-8 month).This was because the temperature and precipitation had influence on metabolic activity of Cryptomeria fortunei,leading to the change of the radial growth.