POLLEN/CHARCOAL RECORD OVER THE PAST 13 300YEARS FROM FUXIAN LAKE IN THE YUNNAN-GUIZHOU PLATEAU
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Abstract:
Fuxian Lake is a well-known rift deep-water lake on the Yunnan-Guizhou Plateau. Its sediments contain abundant environmental information in its drainage region during geologic times.Pollen/charcoal analysis on 46 samples from a 900 cm core of this lake provides a history of vegetation,climate,and forest fire in its drainage region during the last 13 300 years.The results of pollen/charcoal analysis and principal component analysis on pollen data show five-stage vegetation succession,climate change,and forest fire:1)13 300-10 400 cal.a BP,the vegetation was dominated by pine forests,accompanied by dark coniferous forests and evergreen broadleaved forests,indicating cold and wet conditions;high frequent forest fires occurred in this stage,and especially more fires appeared as the humidity decreased in its late period.2)10 400-5 700 cal.a BP,the shrinkage in pine forest,expansion in evergreen broadleaved forest,and appearance of deciduous broadleaved forest indicated relatively warm and dry conditions;forest fires occurred frequently like the previous stage as climatic conditions became warm and dry at the early period of this stage until 9 500 cal.a BP,when relative humidity increased and forest fires decreased obviously.3)5 700-1 800 cal.a BP,the pine and evergreen broadleaved forests still dominated,but Liquidambar forests favoring warm and hot climate first appeared,showing warm and wet conditions;the occurrence frequency of forest fire was low.4)1 800-500 cal.a BP,the expansion of pine forest and the shrinkage of deciduous broadleaved forest with an increase of upland herbaceous plants indicated relatively cold and dry conditions;forest fires were more than the preceding stage but less than the first stage.5)500 cal.a BP to the present,the shrinkage of pine forests and a significant increase of upland herbs showed cool and dry conditions,and suggested increasing human activities.
