VEGETATION,CLIMATE AND FIRE IN THE WEST LAKE BASIN OF DALI,YUNNAN,CHINA SINCE THE INDUSTRIAL REVOLUTION
The pollen/macroscopic charcoal(＞100 μm)analyses of 51 samples obtained at intervals of 0.5～1.0 cm from a 46-cm core(26° 00′54″ N,100° 01′54″ E)taken from West Lake in Dali(26°00′17″～26°01′26″N,100°01′48″～100°03′27″E),Yunnan,were conducted to reconstruct the historical records of vegetation,climate and fires since the Industrial Revolution(1878～2013 A.D.)in the catchment of West Lake in Dali,and the driving factors of fire occurrence were discussed.The age-depth model for this core was established using 21°Pb-137Cs dating and model dating method.A total of 27150 pollen grains of woody,herbaceous and aquatic plants,ferns and algae spores were identified from 51 samples,belonging to 95 families and genus(types).7760 macroscopic charcoals were identified.Our results reveal six stages of vegetation,climate change and the fires since the Industrial Revolution in the West Lake basin:(1)1878～1897 A.D.saw vegetation dominated by grasslands consisting of Poaceae,the occurrence of Pinus yunnanensis forests and evergreen broadleaved forests from low to high elevation,cool and wet climatic conditions,and frequent fires.(2)1897～1932 A.D.witnessed the shrink of forests dominated by Pinus yunnanensis and Alnus nepalenisis,cold and wet climatic conditions,and low risk of fires.(3)1932～1948 A.D.saw a drop of lake water level,the movement of pine forests and evergreen broadleaved forests from high to low elevations,cold and dry climatic conditions,and high frequent fires.(4)1948～1958 A.D.witnessed the rise of lake water level and thus the expansion of wetlands,the shrink of broadleaf forests,warm and wet climatic conditions,the highest frequency of fires,and intensified human activities intensified.(5)1958～1995 A.D.saw the expansions of Pinus yunnanensis and Alnus nepalenisis forests,continued shrink of broadleaved forests,warm and wet climatic conditions,and low frequent fires.(6)1995～2013 A.D.witnessed further expansions of Pinus yunnanensis and Alnus nepalenisis forests,a drop of lake water level,warm and dry climatic conditions,and low frequent fires.The fires of the West Lake basin in Dali were largely controlled by natural factors before the 1950s,and the amount of combustible material was a key factor controlling the frequency of fire.After the 1950s,human activities became the main controlling factor,and human destruction of vegetation and human activities as ignition sources were the main causes of triggering fires.
West Lake in Dalipollencharcoalvegetationclimatefires
万方数据
维普
