目前一些较高精度的孢粉定量气候重建手段往往难以直接运用到较古老的新近纪甚至早一中第四纪地层的孢粉分析中。近十多年来,共存因子法在新近纪古气候研究中广泛应用,但该方法用于孢粉数据的定量气候转换时仍存在较大误差。本文详细论述了共存因子法的基本原理,并介绍了另一种定量古气候重建方法——孢粉气候区间法。该方法考虑到孢粉含量的意义,具有较高的气候重建精度和捕捉较小幅度气候变化信息的潜力。为比较共存因子法和气候区间法在孢粉一气候定量恢复研究中的精确度,本文同时用两种方法对琼州海峡Cz—XXZT-06钻孔6个不同深度的样品分别进行年均温定量重建,结果显示气候区间法优于共存因子法。然而,上述两种方法都依赖于现代植物类群或孢粉种类与气候的关系。区域植物分布调查数据和现代孢粉谱的数量及样点覆盖范围最终决定上述两种方法气候重建精度。
Based on the assumption of the nearest living relatives (NLRs), the co-existence approach (CA) has been widely used for quantitative pollen-climate reconstruction for the Neogene. Here we discuss CA in detail and present another more vigorous pollen-based quantitative method,the climate amplitude method(CAM). Both CA and CAM are based on the same assumption and depend on datasets of modern plant/pollen distributions and their relationships with climate. CA simply overlaps climate intervals of species to obtain their common range as the description of past climate conditions. The so-obtained "co-existent climate range" is often too large to indicate past climate changes when the method applied to pollen spectra due to the fact that pollen identification can hardly be possible to species level. Taking pollen percentages into consideration, CAM is regarded more powerful for capturing detailed or rapid climate changes. To test the accuracy of the two methods,both CA and CAM were applied to 6 Late Neogene samples from different depths of the core CZ-XXZT-06, which locates in the Qiongzhou Strait (20. 17606°N, 109. 84732°E) and dates back to 3.00 -7.14 Ma B. P., to quantitatively reconstruct mean annual temperature. Results show that CAM performs better than CA.