| Obtaining quantitative estimates of climatic parameters represents a fundamental goal in paleoclimate studies. Investigations of marine sediment, especially after oxygen isotope studies provided quantitative paleoclimate data, have played an important role in the studies of temperature changes of sea surface and bottom water. In contrast, it is much more difficult to reconstruct parameters quantitatively for terrestrial paleoclimate. Since plant is believed to be an important environmental record-keeper, many quantitative methods of reconstructing paleooclimate in terrestrial system have appeared based on plant fossils. Among the approaches is the Coexistence Approach (CoA) by Mosbrugger & Utescher (1997). It follows the ??nearest living relative philosophy?ˉ, with the assumption that the climatic tolerance of a fossil taxon is same/similar to those of its systematically closest living relative. A coexistence interval of all nearest relatives?ˉ climatic tolerance ranges is obtained based on their individual climatic data, and used to estimate the paleoclimate of the region where the fossil flora lived. In this paper, we discussed the method of the Coexistence Approach and the basic theory of tolerance which was rarely mentioned in the paper of Mosbrugger & Utesche (1997). Within the distribution area of each nearest living relative, the chosen of meteorological stations for obtaining the extreme (maximum and minimum) values of climate parameters should according to detail records of specimen collections. And then, using the modern plant specimen records and the metrological records in China, we quantitatively reconstructed the paleoclimate of three localities based on its palynological data. The results are as follows: 1 Quantitative reconstruction of early Holocene climate in Lake Hulun of Inner Mongolia, China The parameter intervals are: MAT: 4.4~10.2℃ ; MWMT: 22.9~24.1 ℃; MCMT: -18~-9.1 ℃; DT: 33.5~40.9 ℃ ; MAP: 354.3~686.7mm; MMaP: 103.8~191.9mm; MMiP: 2.7~7.3mm. According to information provided by pollen, spore and Pediastrum, the vegetation and climate changes during 10.9~10.2ka B.P. was revealed. And the climate was reconstructed quantatitively during 10.4~10.2 ka B.P.. It provided new evidence for general understanding of the climate changes in the Lake Hunlun area and the changes of the summer monsoon in East Asia. 2 Quantitative reconstruction of Late Pliocene climate in the Eryuan of Yunnan, China The parameters intervals are: MAT: 13.3~18.6 ℃ ; MWMT: 24.6~27.5 ℃; MCMT: 1.9~12.1 ℃; DT: 14.2~16.6 ℃; MAP: 619.9~1484.3mm; MMaP: 143.8~245.6mm; MMiP: 12.7~16.4mm. The results was compared with the two recent studies, Yangyi and Longling, both in Pliocene and modern climate. Among the three locations, the MAT changes accorded with the latitude trend, and the MAPs are almost same value in Pliocene. But now, Eryuan and Yangyi have changed very little. The MAT of Longling decrease and the MAP doubled, it may provide new evidence for the uplifting of the Longling area since then. 3 Quantitative reconstructions of Eocene and Miocene climate in Hunchun of Jilin, China The Eocene parameters intervals are: MAT: 14.3~14.9 ℃ ; MWMT: 25~26.3 ℃; MCMT: 1.9~3.7 ℃; DT: 21.7~23 ℃; MAP: 797.5~1344mm; MMaP: 185.3~209.8mm; MMiP: 14.2~16.4mm. The Miocene parameters intervals are: MAT: 14.3~14.9 ℃ ; MWMT: 24.3~25.4 ℃; MCMT: 2.1~3.7 ℃; DT: 21.7~22.7℃; MAP: 658.7~817.7mm; MMaP: 158.9~174.6mm; MMiP: 7.4~7.6mm. The Eocene climate in Hunchun area belonged to the north subtropical climate, the Miocene climate changed to south warm temperate climate which was regarded as north subtropical climate, It showed that the climate change between Eocene and Miocene in NE China had the same trend of Cenozoic global cooling.
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