| We select the core of the Dajiuhu basin (DJH) in the western Hubei Province deeped from144cm to450cm, and gain the pollen records aged40000～10000cal.a BP. By comparison with the Gantang peat section (SYZ) in the northern Fujian Province and the Dahu (DH) located in Nanling Mountain in China, We rebuilt the ancient vegetation evolution from40000cal.a B.P to10000cal.a BP in the subtropical mountains of the southern China. The vegetation factors sensitive to climate change includs Abies, Fugas and Alnus. We focus on analysising the ecological habit of the sensitive vegetation to estimate the ancient climate from the middle end of the last glacial period to early Holocene in the subtropical mountains of the southern China.Abies is a constructive species in dark coniferous forest, and Fagus becomes dominant species in the broad leaved forest in the DJH. Fagus and Alnus are constructive arbor in the SYZ. The main species of deciduous broad-leaved forest in the DH is Alnus. According to modern regional distribution of these vegetation types, Abies indicates a relatively cold and wet environment, generally distributed in the high altitude regions in the low and intermediate latitudes and the low altitude regions in the high latitudes. Fagus is adapted to a relatively cool and wet environment, mostly distributed in the shadow of mountainous. Alnus grows mostly in the cool and wet environment such as valleys, mountainous stream, riparian-wetland and so on. We speculate that the climate was cold and wet in MIS2in the subtropical mountains of the southern China, while the climate was slightly warm and wet in the early MIS1and MIS3. The climate evolution model is different from the northern Loess and Tibet plateau.Our records from south of Qinling mountains, Nanling mountains and Wuyi mountains find that the climate was cold and wet in MIS2in the subtropical mountains of the southern China, while the climate was slightly warm and wet in the early MIS1and MIS3. This is intergrated under various factors.(1)Due to the mountains, it develops orographic rain. And effective evaporation is weak at high altitudes. So it is wetter in the Mountains than the plains, western and northern. At the same time it is coldest in MIS2during the last glacial period. Due to the weaker evaporation than that in the early MIS1and MIS3, the environment is wetter. (2)Plains of the middle and lower reaches of the Yangtze river face the China east sea, whose temperature gradient makes moist mass easily to enter the southern inland. Because of Warm and cold air mass meeting and forming frontal rain in the Last Glacial Period, it is likely to bring abundant rainfall.(3)The sea level in LGM is lower. Thus Summer Pacific high center moved toward south. The position of water vapor from ocean landing is farther to south. It likely brings rich rainfallto the southland that develops clod and wet climate, where the precipitation of the north and west is less reason for the farther to the vapour source that forms cold and dry climate.(4)The study said that ocean temperature was firstly warmed during the period of transition to interglacial stage which leaded the climate change in land by3000-4000a. The continent still kept low temperature in the late of MIS2, where the adjacentocean had entered into the last deglaciation. So a lot of water vapor derived from the adjacentocean was transported to the land, where cold high pressure in the north and west regions was in power what resulted in Warm-wet air delaying over the south. Under the affection of mountainous landform, it brought a large number of precipitation to the southern regions,where the northern and western regions was dry lack of water vapor. |
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