天山北坡东部叉子圆柏(Sabina vulgaris)树轮宽度气候重建潜力评估

Dendrochronological Potential Evaluation of Tree-ring Width of Sabina vulgaris at the Northern Slope of Eastern Tianshan Mountains

叉子圆柏(Sabina vulgaris)年轮边界清晰,广泛分布于天山北坡海拔1 200~3 100m范围,比雪岭云杉的海拔分布范围更广。该树种最大树龄在200a以上,目前还未见利用这一树种开展树轮年代学研究的报道。建立了天山北坡东部木垒山区叉子圆柏的树轮宽度年表,分析其年表特征及其与木垒气象站降水量、降水日数、气温、蒸发量和标准化降水蒸发指数(SPEI)的相关关系,评估叉子圆柏的气候信息含量及其用于气候重建的潜力。结果表明:叉子圆柏树轮宽度具有较高的敏感度和序列间的一致性,树木径向生长受到当年生长季(3—8月)及其前期降水和蒸发的综合影响,宽度年表与当年的降水量和降水日数显著正相关,与气温和蒸发量显著负相关,与当年4—7月SPEI的正相关最为显著(n=55,r=0.650,P<0.0001)。基于一元线性方程(Y=2.783 X-2.975,R^2=42.2%,R_(adj)~2=41.1%),利用叉子圆柏树轮宽度重建了东天山北坡木垒4—7月SPEI变化。与基于雪岭云杉树轮宽度重建的东天山降水记录的比较表明:1860—2013年间二者相关系数为0.381,低频变化都记录了1910—1940年的持续干旱期。SPEI序列中的部分极端干旱年与降水记录并不一致,SPEI记录的20世纪90年代以来的持续偏干趋势在树轮降水记录中并不明显,可能是由于两个重建的要素和时段不一致,SPEI指数考虑了增温引起的蒸发作用加剧的影响。叉子圆柏主要分布在阳坡(雪岭云杉一般生长在阴坡),特别是可以在天山北坡雪岭云杉下树线以下的区域生长,叉子圆柏树轮宽度反映的气象要素和时段与雪岭云杉存在差异,因此在天山山区树轮年代学研究中能作为雪岭云杉的有益补充。

A juniper shrub species,Sabina vulgaris,is widely spread at Tianshan Mountains at the elevation of 1 200-3 100 m.The elevation range of its distribution is more extensive than Schrenk spruce.Its maximum age reaches above 200-years with distinct annual ring boundary.To our knowledge,the species of Sabina vulgaris has not been used for dendrochronological research.In this study,tree-ring width chronology of Sabina vulgaris is developed at the northern slopes of eastern Tianshan Mountains.The characteristic of tree-ring width chronology and its response to precipitation,number of precipitaiton days,temperature,evaporation and standard precipitation evaporation index（SPEI）were analyzed,and the dendroclimtological potential was evaluated.Correlation analysis revealed that tree-ring width index is significantly positive correlated with the precipitation from March to June and the number of precipitation days from March to July,and significantly negative correlated with the maximum,mean and minimum temperature from April to July and evaporation from March to June.SPEI from April to July,as a comprehensive index of precipitation and evaporation,is significantly positive correlated with tree-ring width index（n=55,r=0.650,P〈0.0001）.A linear tranfer function between tree-ring width index and SPEI was established to reconstruct the SPEI of Mulei.the correlation coefficient between reconstructed SPEI and precipitation record in Mulei is 0.381 during 1860-2013.They both recoreded the lasting drought period during 1910-1940,however the drought trend since 1990 s in the SPEI series is not obvious in the precipitation record.Three of the five extreme drought years in the SPEI series are consistent with thoes in the precipitation series.Sabina vulgaris grows at the sunny slopes,and it also can grows at the area lower than the lower limit of Schrenk spruce.At the same time,the climate factor and period which tree ring width of Sabina vulgaris contain are also different as Schrenk spruce.It could be regarded as the the useful supplement for Schrenk spruce in dendrochronological research at the northern slopes of Tianshan Mountains.