不同去趋势方法的新疆东天山高低海拔雪岭云杉树轮宽度年表对气候的响应

The response of tree-ring chronologies of Schrenk spruce (Picea schrenkiana Fisch. et Mey.) to climate change at high- and low- elevations of the eastern Tianshan Mountains, Xinjiang, using different detrending methods

利用新疆东天山高低海拔雪岭云杉(Picea schrenkiana Fisch.et Mey.)年轮样本,采用样条函数法、负指数函数法和区域曲线法3种去趋势方法研制树轮宽度标准化年表,通过分析不同去趋势方法的新疆东天山高低海拔云杉树轮宽度标准化年表特征、年表与气候响应的关系和年表间在不同频域互相关,及其与其它资料对比发现:(1)3种去趋势法对东天山年表质量影响较小,低海拔树轮年表含有更多可靠的气候变化信息。(2)高海拔的雪岭云杉树木径向生长与6—9月平均气温均呈显著正相关,其中标准化树轮年表与7月平均气温相关系数达0.553(P<0.01,n=58),夏季温度可能是东天山高海拔雪岭云杉径向生长的主要限制因子;低海拔雪岭云杉树木径向生长与春季降水显著正相关,同时与春季平均气温显著负相关,春季高温和缺水共同作用的春旱可能是影响低海拔雪岭云杉径向生长的主导因子,且负指数函数年表对气候响应更敏感。(3)区域曲线法能够保留树轮标准化年表中更多低频信息,但优势不明显。高低海拔标准化年表在低频域相关系数较大,并和历史干旱事件有很好的对应。在东天山高低海拔雪岭云杉的去趋势方法研究中,负指数函数法比样条函数法和区域曲线法更适合。

Tree-ring samples from Schrenk spruce (Picea schrenkiana Fisch. et Mey.) were collected from high-and low-elevations of the eastern Tianshan Mountains, Xinjiang. Three detrending methods (smoothing spline, negative exponential function, and regional curve) were used to develop tree-ring width chronologies. The characteristics of these chronologies and the relationship between radial growth and climate change at different elevations were compared. The results showed that (1) detrending method had little effect on the reliability of the chronologies, and the chronologies from low elevations contained more reliable climate change information.(2) The radial growth at high elevations positively correlated with the mean temperature from June to September;the correlation coefficient for the standardized tree-ring chronology and temperature in July was 0.553 (P < 0.01, n=58). The temperature in the summer may be the main limiting factor for the radial growth of these trees at high elevation. Meanwhile, the radial growth of trees at low elevation was positively correlated with precipitation in spring, and negatively correlated with mean temperature in the spring. Higher temperatures and lower precipitation in the spring combined to cause a drought in the early growing season. Furthermore, the drought in the spring limited the radial growth of trees.(3) The regional curve method retained more low-frequency information in the tree-ring standardized chronology, but the advantage was not obvious. There were higher correlation coefficients in the low-frequency of the chronologies between high elevation and low elevations. In summary, the negative exponential function method may be more suitable than the smoothing spline and regional curve methods for dendroclimatology studies on the eastern Tianshan Mountains.