秦岭不同龄组巴山冷杉径向生长对气候因子的响应差异

秦岭地区树轮气候学研究已经引起众多学者的重视，但年龄因素对调节树木径向生长-气候响应关系的研究尚未在当地得到广泛关注。运用树轮气候学方法，建立秦岭牛背梁国家级自然保护区低、中、高3个龄组巴山冷杉(Abies fargesii)的树轮宽度差值年表，探究不同龄组巴山冷杉径向生长与覆盖研究区的0.5°×0.5°分辨率格点气候要素之间的响应关系，以期解译年龄差异对巴山冷杉树木径向生长-气候响应特征的潜在影响。结果表明：不同龄组巴山冷杉差值年表统计特征值存在明显差异，平均敏感度和样本总体代表性随年龄增大而递减，但标准差、样本间平均相关系数和第一特征根变异解释量均以中龄组最低，信噪比却以中龄组最高；春季(3—5月)降水的增加以及秋季(9—11月)气温的升高对低龄组巴山冷杉径向生长的促进作用最强，对中龄组树木生长的促进作用明显减弱，而对高龄组树木生长几乎没有影响；气温对巴山冷杉径向生长的促进作用随树龄增高而增强，差值年表与当年2月、8月、上年5月平均温、平均最高温的相关系数均呈现随龄级增大而逐渐递增的趋势。年龄因素对牛背梁国家级自然保护区巴山冷杉径向生长-气候响应关系存在明确影响，随着年龄的增加，巴...

Age-dependent response of Abies fargesii tree radial growth to climatic factors in the Qinling Mountains

Dendroclimatic research in Qinling mountainous area has attracted extensive attention from numerous scholars, nevertheless the effect of tree age factor on regulating the response relationship between tree radial growth and climate has not gained enough local attention. In this study, the dendroclimatological method was applied to establish the low, middle and advanced age groups of tree-ring width residual chronologies of Abies fargesii from Niubeiliang National Natural Reserve in the Qinling Mountains. We explored the response relationship between radial growth of Abies fargesii from different age groups and climate factors extracted from 0.5°×0.5° resolution gridded data that covered the research region, in order to interpret the potential impact of age differences on the radial growth-climate response characteristics of Abies fargesii. The results unveiled that, there were obvious differences among the statistical characteristic parameters of the Abies fargesii residual chronologies from three different age groups:the mean sensitivity and expressed population signal decreased with the increase of age, but the standard deviation, the mean correlation among all radii and the variants in the first eigen vector were the lowest in the middle age group, while the signal-to-noise ratio was the highest in the middle age group. The increase of mean total precipitation occurred in spring (March to May) and the increase of air temperature in autumn (September to November) had the strongest effect on the radial growth of Abies fargesii in the low-age group, while this promoting effect on the radial growth of middle-aged trees was significantly weakened. However, it had little effect on the radial growth of Abies fargesii in the advanced-age group. The promoting effect of air temperature on the radial growth of Abies fargesii increased with the increase of tree age. The correlation coefficients between the different chronologies and the mean air temperature and the average maximum air temperature in February, August of the current year as well as May of the previous year showed gradual increasing trend with the increase of age class. Age factors had a clear impact on the tree radial growth-climate response relationship of Abies fargesii from Niubeiliang National Natural Reserve. In conclusion, with the increase of age, the restriction effect of precipitation on radial growth of Abies fargesii was weakened while the limitation effect of temperature was enhanced. Hence, the different responses of Abies fargesii to climate should be considered in the dendrochronological studies and the formulation of forest management strategies.