湖南道吾山树轮记录的1815～2013年6～9月平均温度及其与PDO和ENSO的联系

TREE-RING WIDTH BASED JUNE-SEPTEMBER TEMPERATURE RECONSTRUCTION AND ITS TELECONNECTION WITH PDO AND ENSO IN MOUNT DAOWU, HUNAN PROVINCE

树木年轮作为高分辨率气候记录代用指标,在历史时期气候变化研究中发挥着重要的作用.我国东南地区树木年轮气候重建还比较少,制约了对该地区历史气候变化的认识.本文运用树木年轮学标准方法,在湖南省道吾山建立了一条自1808年以来的马尾松树轮宽度年表,根据子样本信号强度大于0.85的标准,年表的可靠时段为1815～2013年.将年表与马坡岭和长沙气象站月平均温度、月最高温度、月最低温度和月降水量进行相关分析,发现6～9月平均温度是研究区马尾松生长的主要限制因子.据此重建了该地区过去199年的6～9月平均温度.重建序列显示,高温时段有1849～ 1889年、1924～ 1940年、1954～ 1972年和1999～ 2013年;低温时段有1815～1834年、1890～1923年、1941～1953年和1973～1998年.重建温度序列的高、低温时段与湖北麻城地区树轮重建温度序列基本一致,表明该重建序列在年代际尺度上具有较大的空间代表性.功率谱分析表明,重建序列具有与太平洋年代际振荡（PDO）相似的37～43年的年代际周期,还具有与厄尔尼诺-南方涛动（ENSO）有关的2～3年的年际周期,而且它们在共同时段对应较好,表明PDO和ENSO对研究区6～9月温度有较大影响.

Tree rings have been widely used in palaeoclimate studies as a high-resolution physical proxy around the world. However, there were few tree-ring based climate reconstructions due to the complex relationships between tree growth and climate in southeastern China that had prevented understanding the historical climate variability there. Therefore, more tree-ring based palaeoclimate studies are needed. In this paper, a 206-year well-replicated robust tree-ring width chronology was developed using 60 tree-ring cores of Masson pine （Pinus massoniana Lamb.） with an average length of 178 years at a low elevation site （200- 350m above sea level, 28° 11 ′N, 113°35′E） in Mount Daowu, Hunan Province. The cores were firstly crossdated and the ring width then measured to 0.001mm precision using the LINTAB 5 measurement system. All the measurement series were detrended by fitting a cubic smoothing spline with a 50% frequency response cutoff equal to 67% of the series length. The ratios between original ring widths and the fitted curves were calculated as the detrended series. The crossdated and detrended series were then merged into a chronology using the biweight robust mean method. Based on the criteria that the subsample signal strength （SSS） was larger than 0.85, the reliable period of the chronology was from 1815 to 2013. The correlation analyses were conducted between the chronology and monthly mean, maximum, minimum temperatures and monthly total precipitation at adjacent Mapoling and Changsha meteorological stations. The results showed that tree growth was mainly limited by June-September temperatures with a correlation coefficient of -0.517 over their common period 1958-2013. Two possible mechanisms might be involved in producing this relationship. One is that water stress may play a role, and the other is that high June-September temperature may inhibit tree growth in the study region. Based on this significant relationship, the past 199-year June-September temperature was reconstructed with an explained variance of 26.7% during 1958 - 2013. According to reconstructed temperature series, high-temperature periods were 1849 - 1889, 1924 - 1940, 1954 - 1972 and 1999 - 2013, and low-temperature periods were 1815 - 1834, 1890 - 1923, 1941 - 1953 and 1973 - 1998. The high-and low-temperature periods of this reconstruction matched a tree-ring based June-September temperature of Macheng of Hubei province quite well, showing the large scale representative of our reconstructed temperature at decadal timescales. Power spectrum analyses showed that the reconstructed temperature series had 37- 43-year inter-deeadal cycles similar to Pacific Deeadal Oscillation （PDO） periodicities and 2-3-year cycles related to E1 Nifio-Southern Oscillation （ENSO） over their common period 1900-2013. Both the actual and the reconstructed June-September temperature series significantly correlated with the PDO and ENSO indices over their corresponding maximum common periods at the 0.05 level. Therefore, both the periodic analyses and the correlation analyses showed that PDO and ENSO may influence June-September temperature through their teleeonnection in Mount Daowu, Hunan province. More similar warm-season temperature reconstructions should be done to give a clearer picture of historical warm-season temperature in Southeastern China in the future. This study indicated a great potential for such kind of studies.