基于树木年轮的贺兰山东麓河流径流量的重建

Annual Runoff in the Eastern Slope of Helan Mountains Reconstructed from Tree-ring Width for the Past 259 Years

以采自贺兰山的5个采样点的树轮宽度资料为基础,建立区域标准化年表和差值年表,发现区域差值年表中包含的年径流总量信息多于标准化年表,并最终用区域差值年表序列重建了贺兰山东麓过去259 a的年径流量。相关分析发现降水和温度变化对于树木年轮生长及贺兰山东麓河流年径流总量的形成均有重要影响,是本文从树木年轮重建年径流量的气候水文学基础。校准方程的相关系数为0.638,可解释校准期内年径流总量变化总方差的40.8%,交叉检验的误差缩减值达0.328。分析259 a重建年径流量的变化特征发现:(1)重建流量经历了12个枯水期(1751—1759年,1765—1771年,1788—1802年,1809—1820年,1835—1840年,1847—1855年,1860—1866年,1877—1884年,1899—1908年,1924—1932年,1962—1967年,1980—1994年)和位于其间及1995—2004年的14个丰水期,以平水年份出现最多,但259 a来年径流量的变化较为剧烈。(2)年径流总量出现了持续≥10 a的4次持续枯水期和4次持续丰水期;持续枯水期中以1788—1802年的枯水期强度最大(平均距平百分率-14.9%),而强度第二的持续枯水期(平均距平百分率-10.4%),持续时间也长达15 a(1980—1994年);持续丰水期中以1867—1876年的丰水期强度最大(平均距平百分率+17.9%)。

We present tree-ring-based annual total runoff reconstruction （CE 1750-2008）for theeastern slope of Helan Mountains,China. Spruce and pine forests grow on the hillsides near valleys.All increment cores were collected from living trees at 5 sites of the Helan Mountains in 2008. Afternaturally drying,mounting and sanding in the laboratory,annual ring widths were measured atresolution 0.001 mm by a Velmex measuring system. The quality of the measurement and cross-dating of ring -widths was checked by the COFECHA program. The tree -ring width chronologieswere developed by the ARSTAN program. We used the stepwise regression reconstruction method toreveal the potential of reconstructing runoff from the tree -ring width chronologies. The resultsindicated that the explained variance of the residual chronology to annual total runoff is 40.8%.Finally,based on three residual chronologies,a model was used to estimate the annual total runoff.The model accounted for 40.8% of the instrumental data variance and allowed us to reconstructrunoff for the period 1750 -2008. Cross-validation tests were employed to evaluate the statisticalfidelity of our reconstruction model. The reduction of error is positive,which indicates significantfidelity of our reconstruction model. The reduction of error is positive which indicates significantskill in the tree-ring estimates. Low runoff periods occurred during 1751-1759, 1765-1771, 1788-1802, 1809-1820, 1835-1840, 1847-1855, 1860-1866, 1877-1884, 1899-1908, 1924-1932, 1962-1967, 1980 -1994,whereas high runoff periods were also identified. In according to our runoffreconstruction,the longest low and high runoff periods lasted about 15 years （from 1788 to 1802）and 19 years（from 1933 to 1951）,respectively.