摘要
以中国北方215块表土孢粉样品分析结果中的13种花粉类型与4种气候参数为基础资料建立花粉-气候因子转换函数。同时选取内蒙中部调角海子DJ钻孔岩芯高分辨率孢粉分析结果为材料,定量重建该地区10000～2100 a BP古气候因子数值特征。研究结果表明:内蒙古调角海子地区进入全新世后温湿状况较前全新世有了明显好转,在中全新世形成最为良好的气候要素组合。最高年平均温度比现在高4℃左右,最低年平均温度比现在低2℃左右。7月份和1月份平均温度的分析结果表明,1月份平均温度变化趋势较7月份的更接近年平均温度的变化趋势,说明该地区冬季温度占主导地位。在气候转折时期,气温和降水随时间的变化梯度明显加强,波动幅度为4～5℃。
The 2.4 meter-long core was extracted from the Diaojiao lake (41°18'N, 112°21'E) at the foot of the northern part of Daqingshan Mts. Pollen analysis from collections subsampled in the laboratory at 2 cm intervals, revealed plentiful pollen and spores from over 10 arboreal genera, including Pinus, Betula, Picea, Abies, Carpinus, Quercus, Ulmus and more than 20 non-arboreal genera, mainly of Artemisia, Labiatae, Nitraria, Polygonaceae, Ranunculus, Thalictrum, Umbel-liferae, Caryophyllaeeae and Cyperaceae. Fern spores, aquatic pollen and algae were also observed in some parts of the core. The transfer functions were established by the stepwise regression analysis using the climatic factors and 13 pollen taxa. The different F1 and F2 value were used as the threshold value of F test (i.e. used for selecting and deleting factors) . Each regressed equation was obtained from 70 times of calculations with a step-wise increase of 0.1 for F1 and F2 and those having the smallest regression deviation and the largest multiple correlation coefficient were the final four transfer functions. Substituting the pre-factor obtained from the stratigraphic sampled into the regression equations, the estimates of temperature and precipitation in January and in July, and annual mean temperature values could be calculated. Some climatic stages were inferred from total pollen influx and pollen percentage from the core using a transfer function: humid-cool (from 10 000 to 7 800 a BP), arid-cold (9 200 to 7 900 a BP), arid-warm (7 900 to 7 100 a BP), humid-warm (7 100 to 4 400 a BP), arid-warm (4 400 to 3 000 a BP), arid-cold (3 000 to 2 100 a BP). The highest annual mean temperature during Holocene was ca. 4℃ higher and the lowest was ca. 2℃ lower than the present temperature. Annual precipitation was 250 mm higher and 300 mm lower than the present.
基金
国家自然科学基金(No.49502035
49472133)
