INFLUENCES OF SNOW DISASTERS AND CLIMATE CHANGES ON TREE GROWTH IN CHENZHOU,HUNAN PROVINCE
Global climate change has led to an increased frequency of extreme climate/weather events,which have had significant impacts on both natural ecosystems and the human environment.In January and February of 2008 A.D.,Southern China experienced a widespread extreme snowstorm,resulting in substantial losses to the national economy and human lives.To evaluate the impacts of this snow disaster event and climate change on tree growth,we collected 100 tree-ring cores from Pinus massoniana Lamb.in Yizhang County,Hunan Province(25° 28′N,112°58′E;550～730 m a.s.l).P.massoniana thrives in open standing conditions and is the dominant tree species in the study area.After cross-dating,we established a standardized tree-ring width(STD)chronology using 69 cores from 40 trees spanning a period of 176 years(1846～2021 A.D.),of which 166 years are credible.Surprisingly,there was a marked decrease in the tree-ring width in 2008 A.D.,reaching its lowest record(0.192)within the STD chronology.More specifically,in 2008 A.D.,97％of the cores exhibited a decrease in tree-ring width,and 48％reached historical low.Pearson correlation analysis revealed that the STD chronology exhibited a significant negative correlation with mean minimum temperature from June to October of the current year(r=-0.636,p＜0.01),as well as a significant positive correlation with mean relative humidity from February to December of the previous year(r=0.619,p＜0.01).However,it did not show any significant correlation with precipitation.It manifested that the tree-ring width encompassed integrated hydrothermal signals primarily influenced by temperature but also constrained by drought stress during summer and autumn seasons.Meanwhile,the 31-year moving correlation analysis revealed temporal instability in the relationship between the tree-ring STD chronology and climatic factors,which significantly intensified after the snow disaster in 2008 A.D.To validate the impact of snow disaster on tree growth,snow disaster events in the study area during the historical period were identified from historical documentation(1865 A.D.,1930 A.D.,1955 A.D.,1964 A.D.,1969 A.D.,1976 A.D.,1984 A.D.,1993 A.D.,1996 A.D.,and 2000 A.D.).Results of the Superposed Epoch Analysis(SEA)indicated that tree-ring width slightly decreased only in the year of the snow disaster in the historical period.However,the snow disaster in 2008 A.D.resulted in a significant decrease in tree-ring width in both that year and the following five years,indicating that the snow disaster in 2008 A.D.was the most severe in the past 166 years.Further analysis demonstrated that the East Asian Summer Monsoon(EASM)and the related large-scale circulations such as El Nino-Southern Oscillation(ENSO),Pacific Decadal Oscillation(PDO),and Western Pacific Subtropical High(WPSH),have influenced the climatic conditions of the study area over the past 166 years,thereby affecting tree growth.
tree-ring widthclimatic responsesnow disasterSuperposed Epoch AnalysisEast Asian summer monsoon
NETL
NSTL
万方数据
