天山不同海拔雪岭云杉径向生长对气候变化的响应

为研究不同海拔雪岭云杉(Picea schrenkiana)径向生长对气候要素的响应关系,分别在新疆伊犁尼勒克喀什河流域森林低、中、高海拔采集雪岭云杉树芯样本,建立不同海拔雪岭云杉树轮宽度年表。树轮年表与气象资料相关分析结果显示:影响3个采样点树木径向生长的气候因子主要是平均气温和相对湿度,对降水响应微弱。高、低海拔树轮径向生长对气温和相对湿度的响应相同,均对气温正响应,与相对湿度负响应,中海拔则与高低海拔相反。自1991年研究区气候突变后,雪岭云杉径向生长发生“生长分异”,高、低海拔树轮宽度指数呈显著下降,而中海拔呈显著上升。气候突变点前后,树木径向生长主要对气温和相对湿度响应关系不稳定,中海拔对5—9月的气温的正相关和对相对湿度的负相关显著增强,而低、高海拔主要与7—8月的气温转为显著负相关,与1—2月、7—8月相对湿度的正相关显著加强。根据雪岭云杉对气候要素的响应模式,气温的快速升温会加快水分蒸发,相对湿度随之下降,从而引起的干旱加剧对低、高海拔林区雪岭云杉生长产生负面影响,而适宜的增温可能对森林中部雪岭云杉生长具有促进作用。

Picea schrenkiana response to climate change at different altitudes in Tianshan Mountains

In order to study the difference in the response of radial growth of Picea schrenkiana to climate factors at different altitudes,the core samples of schrenk spruce were collected from the low,middle and high altitudes forest areas in the Nilka Kashi river basin of the Western Tianshan Mountains,the tree ring-width standard dendrochronology at different altitude was established.The result of correlation analysis between tree ring chronology and meteorological data showed that,The chronology of the three sampling points mainly responded to temperature and relative humidity,but responded weakly to precipitation.The radial growth of tree ring at high and low altitudes had the same response to temperature and relative humidity,both of which have positive response to temperature,and negative response to relative humidity,while the radial growth at middle altitude was opposite to high and low altitudes.Since the study area occured abrupt climate change in 1991,the width of schrenk spruce appeared the“growth differentiation”,the tree-ring width index of low-high altitudes showed a downward trend,while the middle altitude showed an upward trend.Before and after the abrupt transition point,the radial growth of trees had an unstable response to temperature and relative humidity.The positive correlation of the mid-altitude chronology to the temperature from May to September and the negative correlation to the relative humidity were significantly enhanced,The low and high altitude chronology had a significant negative correlation with the temperature from July to August,and a significant positive correlation with the relative humidity from June to August.According to the response model of schrenk spruce to climate factors,the rapid warming will lead to intensified evaporation,and the relative humidity decrease,which may cause negative effects on the growth of schrenk spruce in the low and high altitude forest,and the appropriate temperature increase may promote the growth of schrenk spruce in the middle forest.