The Response Of Typical Native Tree Species To Climate Change In Yunnan Province

The karst area in southwest China has a fragile ecosystem,which restricts the sustainable development of human activities,economy and so on.Global warming and frequent extreme weather events have had a profound impact on plant growth in karst areas.In this study,the vegetation of Daheishan mountain in Honghe Prefecture,Yunnan province was taken as an example to collect and screen the broad-leaved forest in Daheishan area of Yunnan province by means of field investigation and experimental sampling.Due to the sampling points in steep slope,deciduous tree ring analysis is difficult,finally through the sample actual situation to identify important value calculation,and karst region advantage of Stranvaesia davidiana with the advantage of karst region Lithocarpus hancei in non-karst two typical evergreen broad leaved tree as the research object,explore both under the karst and non karst two features,the similarities and differences in response to the same climate of radial growth of trees,in order to establish the alternative climate data of the region to provide accurate basis.It is of certain reference value to understand the relationship between tree growth and local climatic conditions in the typical karst landform area in Yunnan,so as to provide scientific basis in the karst area for vegetation restoration and protection,and promote the dendrochronology research in the karst area in southwest China.The main indicates of this study are as follows:(1)The standard chronology sequence of Stranvaesia davidiana in karst area and Lithocarpus hancei in non-karst area contains abundant climatic information.By verifying the statistical parameters of the chronology of two native tree species selected in this paper,the quality of the established chronology is higher,and these two native tree species are more sensitive to climate change,which can be used in the study of climatology of tree rings.(2)In karst area,it is a remarkable proactive correlation of Stranvaesia davidiana and the average temperature in November of the same year,with a correlation coefficient of 0.337.There was a significant negative correlation with the precipitation in June and September of last year,and the correlation coefficient was-0.357 and-0.399.There was a significant positive correlation with the extreme high temperature in October of the same year,with a correlation coefficient of 0.317.It was positively correlated with the lowest extreme temperature in August of the same year,with a correlation coefficient of 0.305.According to the climate factors significantly related to wheel width,the interpretation amount of the established ecological model of the response of tree growth to climate factors is 44.5%,and the model simulation results are roughly consistent with the measured values.(3)There was a significant proactive correlation with the monthly average air temperatures of July,January and March of the previous year in the non-karst area,and the correlation coefficients were 0.298,0.45 and 0.437.There was a significant negative correlation with the precipitation in June of the same year,with a correlation coefficient of 0.364.There was a significant positive correlation with the extreme high temperature in November and October of last year,and the correlation coefficient was 0.305 and 0.364.The established model R~2of radial growth-climate factor relationship of Lithocarpus hancei was 52.4%,which further verified the influence of monthly climate factor on radial growth of Stranvaesia davidiana in the current year,and the model could better simulate the radial growth response of Stranvaesia davidiana to climate.(4)The radial growth of the two kinds of trees is different in response to the SPEI drought index at different scales.Stranvaesia davidiana were negatively correlated with the drought from June to March of last year.It was positively correlated with the drought in April-May of that year.On the seasonal scale,it was negatively correlated with drought in spring and winter,and proactive correlation with drought in summer and autumn.Lithocarpus hancei was negatively correlated with the drought from September to May of the previous year and proactive correlation with the drought from April to August of the current year.On the seasonal scale,it is proactive correlation with summer and negatively correlated with spring,autumn and winter.The correlation between the two tree ring widths on the combined effect of temperature and precipitation and humidity is consistent.Whether the tree species in karst areas are more drought resistant than those in non-karst areas remains to be further studied.The correlation of wettability is lower than that of temperature or precipitation in a single month,indicating that the effect of rainfall and temperature alone is more significant than that of hydrothermal synthesis.