油松年轮记录的河北围场公元1884年以来5～6月平均温度

相关函数分析表明，河北围场的油松年轮宽度指数与 5～6月平均温度显著相关，在此基础上，设计转换方程，重建了该地区1884年至2002年当年5月至6月的平均温度，重建序列的方差解释量达到43.7%(调整自由度后为41.3%)。重建温度序列表明，温度低于多年(1884～2002年)平均温度的时段主要有 1897～1901年、1913～1923年、1949～1978年和 1992～1995年； 高于多年平均温度的时段主要有 1884～1896年、1902～1912年、1924～1942年和 1979～1992年。重建的温度序列具有较大的区域代表性，它与陕西南五台 5～7月温度显著相关，年际尺度上相关系数为r＝0.18(N＝119，p<0.05)，它也与由历史文献记录划分的大同北京二地旱涝指数及亚洲太平洋年代际涛动指数(PDO)均显著相关，表明重建序列在一定程度上反映了大范围的气候变化状况。

TREE RING BASED RECONSTRUCTION OF THE MAY～JUNE MEAN TEMPERATURE SINCE A.D.1884 IN WEICHANG,HEBEI PROVINCE,CHINA

An environmentally sensitive zone with an annual precipitation of 200～400mm，stretches from Northeast to South West China. This is a transitional zone between the semi­arid and the arid condition as well as between the monsoon and the non­monsoon climate. The zone has a diversified variety of climatic and physiographic conditions，and is extremely sensitive and vulnerable to environmental changes. Previously，many high­resolution studies focusing on climate change in the environmentally sensitive zone of North China has been carried out by using tree rings. However，Most of these studies were focused on the reconstruction of precipitation，the reconstruction of temperature reconstruction were poorly reported. In order to obtain a more in­depth understanding of the processes and mechanisms of contemporary climate changes，further studies must be carried out. A group of Chinese pine(Pinus tabulaeformis Carr.)samples were collected in 2004 from Weichang(42.06°N,118.07°E，elevation 1256m)，which is located in a transitional area between Mongolian Plateau and North China Plain and has a temperate semi­arid climate linked to continental monsoon. The ecosystem and environment of this region are extremely vulnerable and sensitive to disturbance. Its precipitation is characterized by marked spatial inhomogeneity and interannual variability，although its annual mean precipitation is around 460mm.
In the laboratory，tree­ring samples were surfaced，cross dated and measured by the standard dendrochronological procedures. The quality control of cross dating was carried out using COFECHA procedure. The individual ring­width measurement series were detrended and standardized to ring­width indices using ARSTAN program. Correlation analyses between the Weichang(WC)STD chronology and the climatic data set of Weichang meteorological station suggest that the WC STD chronology is significantly negatively correlated with the temperatures of current March，May，June and July，with the 95% confidence level. The negative response of ring­width to summer temperature during the growing season demonstrates that high temperature may indirectly limit tree growth by enhancing transpiration. A relatively high correlation between the WC STD chronology and the combination of temperature was given to the mean temperature of May to June(T56)(r＝0.62，N＝51，p<0.0001)by applying multiple regression. A much higher correlation would be obtained(r＝0.66，N＝50，p＜0.0001)，if the data of 1954 was removed. So in this paper，tree­ring width data of Weichang were used to reconstruct the mean May～June temperature of A．D.1884～2002.
Several cold and warm intervals can be observed in the reconstructed temperature series: the time intervals below average temperature(mean of 1884～2002)include 1897～1901,1913～1923,1949～1978 and 1992～1995; the time intervals above average temperature cover 1884～1896,1902～1912,1924～1942 and 1979～1992.The comparison between the reconstructed temperature series and the mean temperature of May to July in the NWT region show that their two curves smoothed by 11­year moving average are changing synchronously，which suggested a probable comparability of temperature in a large­scale spatial frame. On the other hand，a significant correlation was also found between the reconstructed temperature series and the historical document derived dryness/wetness index(average of Datong and Beijing)especially after A．D.1900.The analyses suggest that the warm/cool in the study area might be linked with dry/wet in a larger spatial context. Besides，a synchronous variation trend was also found between the reconstructed temperature series in this study and the reconstructed Asian­Pacific Decadal Oscillation Index(PDO). The similarity in the two time series suggests a decadal­scale relationship between the climatic changes of North China and the PDO，to which the ring width in Weichang showed a response.