太白山树木年轮宽度资料对过去生态气候要素的重建

采用太白山高山林线附近的太白落叶松树木年轮资料,按照树木年轮学要求和方法进行前期处理、交叉定年,建立树轮宽度指数序列.基于气候要素影响当年和次年树木生长的原理,利用多元回归技术探讨了树轮宽度指数与生态气候要素--温暖指数之间的相关关系,重建了太白山地区近3∞年的温暖指数.结果表明:1745～1765年、1845～1855年、1880～1900年以及1905～1915年为几个较为明显的冷期;1725～1745年、1765～1775年、1800～1810年、1865～1875年和1890～1905年相对而言属暖期.太白山地区气候的冷暖变化有大约30～40年的变化周期.将本项研究结果与国外相关研究对比还说明,太白山地区的气候变化可能具有一定的全球性特征.

RECONSTRUCTION OF PAST ECO-CLIMATE BY TREE-RING WIDTH INDEX OF LARIX CHINENSIS ON MT. TAIBAI

Tree ring increment cores of Larix chinensis were sampled from alpine timberline at an altitude of about 3 400m to 3 500m, on Mt. Taibai, located in Shaanxi Province.The natural conditions there are very harsh with an average annual temperature of -3.2℃ and annual precipitation of 160 mm, which is quite different from places at the foot of the mountain with average annual temperature and annual precipitation of 12.7℃ and 609 mm respectively. Plants at this transitional zone are very sensitive to climate change, and it is very ideal sampling places, and the tree species is also very ideal. According to the discipline of dendrochronology, the relationship between tree ring width index( TRWI , in STD chronology) and climate variables were studied. It was found that warmth index ( WI ) is closely correlated with tree ring width index, not only chronology of the selected year's ( TRWI n), but also the chronology of last year's ( TRWI (n+1) ). As a result, the WI in the last 300 years were reconstructed by the following formula:WI=58.17+0.57TRWI n +0.07TRWI ( n +1)  The results show that climate during periods of 1745～1765, 1845～1855, 1880～1900, and 1905～1915 were cold periods; but that during periods of 1725～1745, 1765～1775, 1800～ 1810, 1865～1875 and 1890～1905 were relatively warmer than normal years. These results are in good agreement with many other studies upon the Little Ice Age climate, and can be of great value to studies on climate change during Little Ice Age in China.Moreover, a 30 to 40 years' cycle was found in temperature changes in the region. Finally, the comparison between this study and Overpeck's results shows that the climate change in the adjacent areas of Mt. Taibai is in phase with the global climatic changes.