【作者】 党海山；

【导师】 张全发；

【作者基本信息】 中国科学院研究生院（武汉植物园） ， 植物学， 2007， 博士

【摘要】 20世纪全球变暖已是一个不争的事实，全球平均气温在20世纪里大约上升了0.6℃。全球尺度气候的变暖必然会对区域气候产生深刻的影响，根据秦巴地区过去50年来的气象观测数据显示，秦巴地区的气候在过去半个世纪里已经发生了明显的变化。秦巴地区过去半个世纪气候的变化可能已对这一地区的亚高山冷杉林产生了一定程度的影响，而且秦巴山地的亚高山冷杉林可能也已对该区域气候的变化做出了一定程度的响应。因此，本文采用树木年轮学技术，并结合植物群落学的方法分别从种群、群落和景观三个尺度水平上分析秦巴山地亚高山冷杉林对区域气候的响应，得出的主要结论：1)在秦岭地区，年轮指数与气候因子的相关分析表明，巴山冷杉的径向生长在不同海拔和不同坡向受到不同气候因子的影响。在秦岭南、北坡巴山冷杉分布的中海拔(巴山冷杉典型分布区)和低海拔(巴山冷杉林下限)地段，其生长主要受春夏季温度的影响，与降雨的关系不显著；在高海拔(巴山冷杉林上限)地段，巴山冷杉的生长主要受夏季降雨的影响，温度的限制作用不显著；但在秦岭北坡，巴山冷杉当年的生长不受上年气候条件的影响，而在秦岭南坡，其当年的生长则受到上年气候条件的显著影响。2)在神农架地区，年轮指数与气候因子的相关分析表明，不同海拔巴山冷杉的径向长受到不同气候因子的影响。在神农架南坡和北坡，降雨对巴山冷杉生长的限制作用随海拔的升高而减弱，而温度对巴山冷杉生长的影响则随海拔的升高而增强；在中海拔(巴山冷杉典型分布区)和低海拔(巴山冷杉林下限)地段，巴山冷杉的生长受温度和降雨因素的共同影响，而在高海拔(巴山冷杉林上限)地段，巴山冷杉的生长主要受温度的影响；在神农架南、北坡，巴山冷杉当年的生长都受到上一年气候条件的显著影响，而且都与当年春夏季温度和夏季降雨具有显著的相关性。3)在秦岭和神农架的南坡与北坡的亚高山冷杉林中，巴山冷杉种群的分布格局在巴山冷杉林的下限和中间海拔的典型分布区都呈随机分布；而在巴山冷杉林的上限，则呈聚集分布的特点。根据“聚集有利于个体生存”的观点，巴山冷杉沿海拔梯度的这种分布格局也是巴山冷杉对区域气候变化的一种响应方式。4)在秦岭和神农架的南坡与北坡，随着海拔的升高巴山冷杉种群中幼龄级和中龄级的个体数量增多，而大龄级和老龄级的个体数量减少；而且，在巴山冷杉林的下限和中间海拔的典型分布区，巴山冷杉种群表现出一定的衰退趋势，而在巴山冷杉林的上限，巴山冷杉种群的年龄结构表现为正常生长的稳定型特点。5)在秦岭和神农架的南坡与北坡，高海拔地带巴山冷杉林群落发展的起始时间要晚于低海拔地带巴山冷杉林群落发展的起始时间，而且，高海拔地带的巴山冷杉林群落在20世纪的70年代以前有大量的巴山冷杉个体产生，而低海拔地带巴山冷杉林群落在20世纪则没有巴山冷杉个体的形成，说明20世纪气候的变暖导致了高海拔地带亚高山林线处的群落中巴山冷杉个体数量的增加。6)在秦岭与神农架的南坡和北坡，巴山冷杉的年龄表现出随海拔的升高而逐渐减小的趋势，并且在高海拔地段(巴山冷杉林上限)巴山冷杉的年龄显著的小于低海拔地段(巴山冷杉林下限)巴山冷杉的年龄，说明了过去一个世纪气候的变暖导致了巴山冷杉分布范围向高海拔发生了一定程度的迁移。但群落中的共优种桦树的年龄分布在海拔梯度上没有显著的差异，说明区域气候的变化未使桦树的分布范围表现出沿海拔梯度的迁移趋势。更多还原

【Abstract】 It is widely accepted that global warming had occurred with an increase ofapproximate 0.6℃in the global mean air temperature by the end of the 20thcentury. In the Qinba Mountains, meteorological station records show that theregional climate has obviously changed with increases in mean airtemperature and precipitation during the past fifty years. Such changes mayhave affected the regional subalpine fir (Abies fargesii) forests and, in turn,these forests have been responsive to the regional climate changes. Thus,chronological techniques, coupled with methodology of plant community, wereemployed to explore the responses of the subslpine fir forests to regionalclimatic changes from multiple-scale level, including population, communityand landscape, in the Qinba Mountains. The main results are as following:Correlation analyses indicate that the radial growth of Abies fargesii variesalong the elevational gradient and in different aspects in response to differentclimate variables in the Qinling Mountains. At the middle elevations (typicaldistribution zones of the fir forests) and lower limits of the subalpine fir forestson both the south and north aspects of the Qinling Mountains, the radial growthof A. fargesii is significantly affected by the spring and summer temperatures ofthe current year, while precipitation has no significant effects on A. fargesiiradial growth. As to the upper limits of the subalpine forests on both the southand north aspects of the Qinling Mountains, precipitation in current summerimposes noticeable effects on its radial growth, but temperature does not havesignificant effects. In addition, climatic variables of the previous year havesignificant effects on A. fargesii radial growth of the current year on the southaspect but not on the north aspect of the Qinling Mountains.Correlation analyses between ring-width index and climate variables alsoindicate that radial growth of A. fargesii in different elevations is influenced bydifferent climate factors in the Shennongjia Mountain. At the middle elevations (typical distribution zones of the fir forests) and lower limits of the subalpine firforests on both the south and north aspects, radial growth of A. fargesii issignificantly limited by a combination of temperature and precipitation; At upperlimits of both the south and north aspects, however, temperature is the mainfactor limiting its radial growth. So, the influence of precipitation on A. fargesiiradial growth decreases with the increase in elevation, while the influence oftemperature increases with the increase in elevation. Additionally, climatevariables of previous year have significant effects on A. fargesii radial growthon both the south and north aspects of the Shennongjia Mountain.Distribution of A. fargesii shows random patterns at lower limits andmiddle elevations, while clumped patterns at upper limits of the subalpine firforests in the Qinba Mountains. According to the viewpoint "clumpeddistribution conduces to individual survival", we believe the characteristics ofdistribution patterns of A. fargesii along elevation gradient to be one mean ofthe fir forests’ responses to the regional climate changes.Age-class distribution along the elevation gradient shows that the numberof fir individuals on small age-class and middle age-class increases with theincrease in elevation, but the number of fir individuals on the large age-classdeclines with the increase in elevation in the Qinba Mountains. In addition, theage structure of fir population exhibits a declined trend in the middle elevationsand lower limits, and a stable trend in the upper limits of the subalpine firforests on both the north and south aspects in the Qinba Mountains.On both the south and north aspects in the Qinba Mountains, the standoriginated later in the higher elevations than that in the lower elevations. At thehigher elevations, especially in the upper limits of the subalpine fir forests inthe Qinba Mountains, a considerably large number of fir trees were recruitedinto the stand before the 1970s in the 20th century, while little recruitment of firtrees occurred in the lower elevations during the 20th century, demonstratingthat climatic warming in the 20th century resulted in recruitment of fir trees aswell as an increase in the amount of fir trees at the higher elevations, especially in the upper limits of the subalpine fir forests in the QinbaMountains.Analysis of the age structure of fir (A. fargesii) population shows that themean age of fir trees declines with the increase in elevation on both the southand north aspects in the Qinba Mountains. The fir tree age in the upper limits issignificantly smaller than that in the lower limits of the subalpine fir forests,suggesting that the distribution range of the subalpine fir forests has shiftedupward during the past century, attributable to the regional climate warming inthe Qinba Mountains. However, as a codominant species in the fir forests,birch age does not exhibit significant difference along altitude gradient,indicating no distinct shift of birch distribution range under the context ofregional climate warming in the Qinba Mountains.更多还原