雪岭云杉树轮宽度对气候变化的响应

Tree Ring-width Response of Picea schrenkiana to Climate Change

利用新疆伊犁地区雪岭云杉的6个树轮宽度年表,通过相关分析的方法,分析不同地形条件下雪岭云杉树轮宽度对于气候要素的响应.统计分析表明,雪岭云杉对气候变化比较敏感,在北天山南坡的森林下限,雪岭云杉生长与生长季7～8月降水关系显著;在南天山北坡的森林下限,雪岭云杉生长对生长季前11-次年1月最低温度存在显著正相关.地形对雪岭云杉与气候要素之间的关系影响较大,在南天山北坡,由于森林上下限树木抗寒性的差异,森林下限树木生长对温度的响应强于上限树木;南北坡引起的降水量水平的差异,使得天山不同坡向的树木生长响应不同的气候要素.

The Yili Valley of west Tianshan is located in semi-arid area of Northwest China. Tree ring increment cores were sampled for Picea schrenkiana from the upper and lower treelines of three sites, which present warm-dry, warm-moist and cool-moist climate patterns respectively. Six standardized chronologies were developed using a 60-year spline function, the correlation between tree ring-width and climate was analyzed. Comparison of chronology statistics among chronologies indicated that ring-width at the lower treeline showed stronger high- and low-frequency signals than those at the upper line. Correlation analysis showed that the growth of Picea schrenkiana was significantly sensitive to climate variations. However, there were different relationships between the tree growth and climate at different aspects of slope and altitude of the valley: tree growth at lower treeline on the south-facing slope was positively correlated (p<0.05) with precipitation in July and August during the current growing season, while at the lower line of the north-facing slope, tree growth showed a significant (p<0.05) positive correlation with monthly minimum temperature from November to January prior to the growing season, whereas there was no significant correlation between tree ring-width and climate variations at the upper line of both north- and south-facing slopes. These results suggested that different climate signals revealed in tree-ring width of Picea schrenkiana may be caused by the influence of topography: the variation of precipitation between the upper- and lower-treeline and the difference of temperature between the two aspects of the slope. In conclusion, there is not only precipitation signal but also temperature information in the tree ring-width of Picea schrenkiana. This dendroclimatological potential provides a possibility for past climatic reconstruction of both precipitation and temperature in this area.