| The current global warming has exceeded 1 ℃ compared with that at the end of the19 th century,and the trend is continuing.In this context,climate changing will continue and profoundly affect the tree growth process in forest ecosystem,such as the forest growth decline and tree death,the tree growth divergence,the tree growth phenology changing etc.Due to its ability to record high-resolution climate change signals,tree-ring data has become one of the important proxies for studying the climate change in the past centennial-millennium scale.In addition to climate factors and tree genetic factors,the site environment(such as elevation and slope)can also result in a complex and diverse tree growth environment by redistributing water and heat conditions,which ultimately affects the tree growth.Therefore,we respectively collected 4 sample sites of Pinus armandii Franch.from the Jijiaojian area and the Baoduzhai area on the western Funiu Mountains,with a total of 86 trees and 172 cores,and finally established the standard tree-ring width chronology(STD).Firstly,this study analyzed the correlation between the STD chronology and the monthly climate data from each meteorological station,so as to analyze the different response between tree growth and climate factors in different area of Funiu Mountain,and explore the main limiting climate factor of tree growth.Then,VS-oscilloscope model was used to simulate the physiological mechanism of the relationship between tree growth and climate factors at different area,and to explore the phenological change in tree growth season and the relationship between phenological change and climate factors.Finally,according to the analysis results,this study reconstructed the climate change in Funiu Mountains and analyzed its driving mechanism.The main results of this study are as follows:(1)The results of the correlation between the standard width chronology of Pinus armandii Franch.and climate factors show that temperature is the main limiting factor of tree growth in this region,but the tree growth is affected by temperature at different times due to the altitude difference.The mean monthly temperature before the growing season mainly limited the tree growth at Jijiaojian area,while the mean monthly temperature in the middle of the growing season mainly limited the tree growth at Baoduzhai area.(2)We simulated the radial growth of Pinus armandii Franch.in Funiu Mountains from 1964 to 2003 through the VS-oscilloscope model,and a high fitting degree was achieved between the simulated sequence and the measured sequence.The results of daily radial tree growth rate simulated by the model show that the growth rate of Pinus armandii Franch.in Funiu Mountains during the growing season is mainly limited by temperature,and the growth rate of Pinus armandii Franch.in Baoduzhai area shows a "bimodal" pattern,and the valley of growth rate appears in the middle growing season,indicating that the temperature in the middle growing season was the main limiting factor of the Baoduzhai area tree growth.(3)During the simulation period,there is no significant change trend in the growing season phenology of Baoduzhai area,but a significant change trend in the growing season phenology of Jijiaojian area(p<0.05).And the specific trend is as follows: from 1964 to 2003,the start growth date(SOS)of JJJ01 and JJJ04 both advanced by 0.36d/y,the end growth date(EOS)is delayed by 0.41d/y and 0.22d/y,and the growth season days(DOS)is increased by0.77d/y and 0.58d/y,respectively.In addition,there are differences in the growing season phenology at different area.Compared with Jijiaojian area,the SOS of Baoduzhai area is earlier,while the EOS is later,and the DOS was longer.(4)The correlation analysis results of STD chronology and the simulated SOS and EOS show that the tree-ring width index of Pinus armandii Franch.in Jijiaojian area is significantly negative correlated with SOS,which indicates that the start growth date will affect the tree-ring width index of Pinus armandii Franch.in Jijiaojian area.However,there are no significant correlation between the SOS and EOS and the tree-ring width index of Pinus armandii Franch.in Baoduzhai area,which indicates that the beginning and ending of tree growth have little limit on the tree growth in this area.(5)The correlation analysis results between the simulated SOS and EOS of 4 sample sites with climate factors during the simulation period show that the start growth date of Pinus armandii Franch.are negatively correlated with temperature in Funiu Mountains,and the end growth date are significantly positively correlated with temperature,which indicates that the influence of temperature on the tree growth season phenology at different area is relatively stable.Meanwhile,the temperature rise in the early growing season will promote the advance of SOS,while the precipitation in the early growing season will not conducive to the advance of SOS,the temperature rise in the late growing season is conducive to the delay of EOS,while the precipitation in the late growing season is conducive to the advance of EOS.(6)In this study,the reconstructed prior December to current March mean temperature series of Funiu Mountains from 1915 to 2003 from experienced 3 warm periods and 2 cold periods,including 9 extremely high temperature years and 6 extremely low temperature years,which is consistent with the correspondence of drought events recorded in historical documents and others reconstructed series.In addition,the reconstructed series can well represent the winter-half year temperature in the central,eastern and northwestern China regions,and there is significant the North Atlantic Oscillation cycle(NAO)around 24.3a in the reconstructed series.Although the results of this study are conducive to understand the impact and evolution of climate change on the forest ecosystem of Pinus armandii Franch.in Funiu Mountain,there are still some deficiencies.In the future,supplementary studies will be made by combining observational data or tree ring width,isotope or density,so as to provide accurate basic data services for forest management and forest tending in this area. |
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