Radial Growth Responses Of Picea Wilsonii To Climatic Variables In Mt.Guandi,China

Ecosystems are affected by global climate change,forest ecology is a part of the ecosystem and its relationship with climate is close and complex.The change of climate affects the physiological and ecological processes of trees directly.Guan Di Mountain is located in the middle of Lv Liang Mountains,which is in the semi-humid area of warm temperate zone in the middle of the north,with complete vegetation vertical band spectrum,good vegetation protection,and less artificial interference during tree growth.Moreover,there are mixed forests in this area with Picea wilsonii and Larix principis-rupprechtii as dominant species in a certain altitude range.Study the relationship between tree radial growth and climate factors in this region not only creates great significance for forest management and protection in this region,but also provides more theoretical support for the study of response between tree and climate factor under regional climate characteristics.Using tree ring width as a tool and Picea wilsonii as a research tree species,three sampling points were set up along the elevation gradient of Pangquangou in Guandi Mountain.A total of 158 tree cores were collected and three Picea wilsonii wheel width chronologies were established.The correlation analysis and response surface analysis were used to determine the relationship between the greenwood tree chronology and climate indexes,and the main climate factors affecting the radial growth of greenwood trees were identified.The stability between climate warming and the main climate factors was further discussed by sliding analysis,and the interannual dynamic response mechanism of climate change to the radial growth of trees was revealed.The main conclusions of the study are as follows:(1)Radial growth characteristics of Picea wilsonii.Four primarily important indicators,the mean sensitivity(MS),sample population representativeness(EPS),first eigenvector percentage(VFP)and signal-to-noise ratio(SNR),which used to characterize tree chronology quality show that the difference chronology(RES)contains more climate information than the standard chronology(STD)and is more constrained by environmental factors.Based on this characteristic,the study also uses the RES chronology as subsequent analytical chronology.A significant correlation was found among the annual GKL values of three elevation gradients,indicating that the interannual growth dynamics of the Picea wilsonii were consistent.(2)The radial growth of Picea wilsonii in the study area is mainly affected by the interaction of water and heat,especially the influence of drought restriction on the radial growth of green skewer is obvious.Mean temperature in June,mean temperature in June,high temperature in the hottest month were negatively correlated with tree width of Picea wilsonii(P<0.05).The water deficit caused by the medium and long term hydrothermal accumulation in the growing season further limits the radial growth of the Picea wilsonii.There was a significant positive correlation precipitation in hot season(P<0.05)?The main performance is the summer temperature of the growing season and the influence of the standardized precipitation evapotranspiration index(SPEI)and the standardized precipitation index(SPI)on the growth of trees in the medium and long term.The values in August,September and October were positively correlated with tree width(P<0.05),and the correlation was mainly concentrated in the later part of the growing season.(3)The influence of seasonal climatic factors on the radial growth of Picea wilsoniiin Guandi Mountain is delayed.The radial growth of Picea wilsonii is negatively correlated with the mean temperature in spring and summer of the previous year(P<0.05).(4)The response of climate factors with the radial growth of Picea wilsonii is different in varying elevation.The change of elevation gradient leads to the change of hydrothermal conditions.Due to the influence of temperature decreasing rate,the temperature decreases and the precipitation increases with the increasing altitude.The conclusion of relevant correlation analysis shows that the continuous hydrothermal conditions in the growing season have significant effect on the growth of tree of Picea wilsonii,but this relationship weakens with the varied elevation gradient.The response of the high altitude to the high temperature and precipitation in the growing season weakens due to the increasing precipitation and decreasing temperature in the high altitude,resulting to improving response of low temperature in later of growing season.At high altitude,the width of tree wheel was negatively correlated with low temperature in November and GDD_0-5(P<0.05).In addition,low altitude is affected by high temperature and water deficiency,and its response to temperature and water in growing season is more intense.The change of altitude also moderates the lag effect of Picea wilsonii caused by hydrothermal factor in the last perennial season.The high temperature in summer of the last year has obvious limitation on the growth of Picea wilsonii at middle and low altitude,whereas this lag effect is not distinct at high altitude.The effect of hydrothermal synergy on the growth of Picea wilsonii at low altitude is more significant as the climate warms.