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Constructing a mathematic transfer function of pollen and climatic factors is one of the most important approaches in the quantitative reconstruction of paleoclimate elements. In the function building, the key point is the response sensitivity to the climate change for different pollen families and categories. As an example in this paper, the pollen samples from the surface and stratum in Dajiuhu basin, Shennongjia are used to estimate the sensitivity of pollen factor-temperature in the transfer function by the EOF analysis, multiple regression and stepwise regression techniques. Thereafter, the selection methods of pollen factors are discussed and compared with other results from different researchers. The results show that in the pollen samples, the quantity of woody plants is larger than others, but the woody plants have relatively lower sensitivity and slow responses to the climate evolution and abrupt climate change. While the pollens from lower grade plants (herb and fern) have a relatively high sensitivity to the temperature change and fast response to the abrupt climate changes. Therefore, the pollen of herb and fern may significantly record the extreme events in the climate change. Also in different regions, the pollen samples have different sensitivity and optimum combination in the transfer functions. Final conclusion is that the stepwise regression is one of the best methods for transfer function building since it can obtain the maximum multiple correlation coefficients and optimum combination of sensitive pollen factors. [ABSTRACT FROM AUTHOR]

Climate change and hydrologic process response in the Tarim River Basin over the past 50 years are the tocus of more and more researchers' attention. In this paper, both temperature and precipitation time series were found to present a monotonic increasing trend using nonparametric tests. Noticeably, a significant step change in both temperature and precipitation time series occurred in 1986. By contrasting the trends of natural water process in headstream and mainstream, we found that it was anthropogenic activities not climate change that caused the river dried up and vegetation degenerated in the lower reaches of Tarim River. The results of gray correlation analysis show that the runoff of higher latitude distributing river is more closely associated with winter snow stocking, while that of lower latitude is more closely related to summer temperature. Runoff in the headstream is more sensitive to precipitation, while that in the mainstream is more sensitive to evaporation. The strong evaporation caused by increasing temperature weakened runoff to some extent in spite of the fact that precipitation increased over the past 50 years. [ABSTRACT FROM AUTHOR]

The identified results of 121 surface sediment spore-pollen samples in Shennongjia and meteorological data base of 30 years (January, 1971-December, 2000) of 7 meteorological stations around Dajiuhu, Shennongjia are used in this study. Selecting 55 species of common spore-pollen with the method of space fitting and stepwise regression we construct the pollen climate factor transfer function of annual mean temperature: T= 7.649 - 2.33097XAbles-0.10873XBetula-0.17352XCompositae-0.131 76XCruciterae + 0.13356XEuphorbiaceae-0.83069XCampanuiaceae + 1.96494XPyrrosia + 0.38411 XPteris + 2.77741 XSelaginetta + 0.04439XMonoIites. We had reconstructed annual mean temperature series by use of the sporo-pollen samples concentration percentage in peat section with 297 cm thickness in Dajiuhu since 15.753 kaBP. The temperature series reflect well the character of climatic change since the late glacial, which indicates extreme cold climate event of the Oldest Dryas, the Older Dryas, the Younger Dryas and the 8.2 kaBP, the same to the climate fluctuations of Boiling Warm Period and Allerod Warm Period, and the character of temperature change fluctuating frequently at the transition age from the late glacial to the Holocene. The reconstructed temperature also indicate Holocene Optimum, late Holocene warm-dry climate, and the character of climatic change in Dajiuhu in the last 1 ka. The conclusion is that the sporo-pollen samples have important climatic significance to surface sediment and the section of Dajiuhu, Shennongjia and important reference value to studying climatic change during the last glaciation by the temperature transfer function and reconstructed temperature series. [ABSTRACT FROM AUTHOR]