天山雪岭云杉径向生长响应气候变化的海拔分异OA北大核心CSTPCD

[Objective]To study the trend of radial growth change,response to climatic factors and ecological resilience to drought stress of Picea schrenkiana at different altitudes in the central Tianshan Mountains,and to provide theoretical references for predicting the community development trend of P.schrenkiana forests along the altitudinal gradient in the Tianshan Mountains under climate change.[Method]The core samples of P.schrenkiana were collected at the lower,middle and upper forest line of P.schrenkiana forest in the middle section of the northern slope of Tianshan Mountains.Three tree-ring standard chronologies were established,and the basal area increment was calculated.The relationship between the radial growth of P.schrenkiana and climatic factors was analyzed.The resistance,recovery and resilience were used to analyze the response of P.schrenkiana to drought.[Result]In the past 61 years,the radial growth of P.schrenkiana at all altitudes in the study area was significantly inhibited.The degree of inhibition was the highest at the lower forest line,followed by the middle forest belt,and the upper forest line was lighter.There are differences in the main climatic factors affecting the radial growth of P.schrenkiana at different altitudes.The radial growth of P.schrenkiana at the lower forest line is mainly negatively correlated with the temperature from April to July of the current year,and is significantly positively correlated with the precipitation in June of the previous year(P<0.05),April and June of the current year,and the self-calibrated Palmer drought index(scPDSI)from August to September of the current year(P<0.05).The radial growth of P.schrenkiana at the middle forest belt is mainly negatively correlated with the temperature from June to August of the previous year,from March to April and June to July of the current year(P<0.05).The radial growth of P.schrenkiana at the upper forest line is mainly positively correlated with the temperature from February to July of the current year,and is significantly positively correlated with August of the previous year(P<0.05).There was a significant positive correlation between the precipitation in April and scPDSI from June of last year to May of this year(P<0.05).The response of radial growth of P.schrenkiana to climatic factors was different in altitudinal gradient and temporal gradient.The negative correlation with air temperature decreased successively and the positive correlation with precipitation and scPDSI decreased successively from underline to overline.The correlation with air temperature decreased gradually and the positive correlation with precipitation and scPDSI increased gradually in temporal gradient.The ecological resilience of P.schrenkiana to drought at different altitudes is different.The resistance and resilience are shown as upper forest line>middle forest belt>lower forest line,and the recovery is shown as lower forest line>middle forest belt>upper forest line.P.schrenkiana is more sensitive to drought,and its growth decreases significantly under drought stress.When the reverse balance between resistance and resilience is not broken,P.schrenkiana is not affected by the residual effect of drought.[Conclusion]Due to the rapid increase of temperature and slow increase of precipitation in the study area,P.schrenkiana at different altitudes is more and more seriously affected by drought stress.Among them,the radial growth of P.schrenkiana in the lower forest line decreased the most,the resistance was the smallest,and the risk of growth decline was the highest.