Reconstruction of summer temperature variation from maximum density of alpine pine during 1917-2002 for west Sichuan Plateau, China

摘要

Having analyzed the tree ring width and maximum latewood density of Pinus den-sata from west Sichuan,we obtained different climate information from tree-ring width and maximum latewood density chronology. The growth of tree ring width was responded princi-pally to the precipitation in current May,which might be influenced by the activity of southwest monsoon,whereas the maximum latewood density reflected summer temperature (June–September). According to the correlation relationship,a transfer function had been used to reconstruct summer temperature for the study area. The explained variance of re-construction is 51% (F=52.099,p<0.0001). In the reconstruction series: before the 1930s,the climate was relatively cold,and relatively warm from 1930 to 1960,this trend was in accor-dance with the cold-warm period of the last 100 years,west Sichuan. Compared with Chengdu,the warming break point in west Sichuan is 3 years ahead of time,indicating that the Tibetan Plateau was more sensitive to temperature change. There was an evident sum-mer warming signal after 1983. Although the last 100-year running average of summer tem-perature in the 1990s was the maximum,the running average of the early 1990s was below the average line and it was cold summer,but summer drought occurred in the late 1990s.