孢粉记录的重庆岩溶槽谷区700年来植被演替与喀斯特石漠化

A 700—year record of vegetation and rocky desertification evolution based on palynological data of the karst valley area,Chongqing City,China

在精确AMS^(14)C测年的基础上,对采自重庆中梁山岩溶洼地的剖面样品进行了孢粉分析,并结合详细的历史文献资料,获取了该地区近700年以来的植被变迁与石漠化演化记录。结果显示:(1)1274—1553 cal a AD研究区周围主要分布以松属、柏科/杉科占优势的亚热带常绿针叶林,伴人植物花粉少量出现,人类活动相对较弱。(2)1553—1780 cal a AD,针叶树松属、柏科/杉科花粉含量下降,伴人植物花粉增多,指示研究区人类活动开始加强。(3)1780—1840 cal a AD,松属花粉含量急剧下降,灌木和伴人植物花粉急剧增加,指示该地区人类活动加剧,石漠化现象出现。(4)1840—2000 cal a AD,玉米花粉含量大幅度增加,表明人类活动更加强烈,石漠化现象进一步加剧。近700年来不断增加的人类活动是重庆地区植被退化、石漠化现象严重的重要因素。该研究结果对重庆岩溶地区的全面治理,恢复和重建自然生态环境具有重要的指示意义。

Karst rocky desertification is the most seriously ecological and geological problem in southwestern China,which severely restricts the economic and social development of karst areas.As one of the main parts of rocky desertification research,the evolution process of rocky desertification not only reflects the changes of regionally ecological environment,but also affects the social and economic development of the region.The research on reconstruction of paleoenvironment in Chongqing is mainly focused on the change of climate itself,rarely involving the change of regionally ecological environment.The research on the evolutionary pattern of ecological environment in the past 1000 years has rarely been reported.As one of the most direct and reliable indicators of paleoenvironment and paleovegetation,spores and pollen play an irreplaceable role in correctly understanding and recovering the past climate and environmental changes.The depressions in karst areas are ideal places for studying regionally environmental changes.The sediment records provide abundant information including vegetation succession,climate change,human activities,and environmental changes.Therefore,in this study,we chose the karst depression area of Zhongliang Mountain as our study area and documented its vegetation changes and rocky desertification evolution during the past 700 years in terms of spores and pollen analysis,AMS^(14)C dating,and detailed historical literature.The results showed that the subtropical evergreen coniferous forests were dominated by Pinus,Cupressaceae/Taxodiaceae with a small amount of pollen of anthropogenic plants during the 1274—1553 cal a AD,which reflected relatively weak human activities.Conversely,during the 1553—1780 cal a AD,Pinus,Cupressaceae/Taxodiaceae overall declined while the pollen of anthropogenic plants increased,indicating that the human activities had begun to strengthen.During the 1780—1840 cal a AD,the pollen content of Pinus decreased sharply,while the pollen content of shrubs as well as anthropogenic plants increased sharply,which was consistent with the intensification of human activities and the occurrence of rocky desertification.During the 1840—2000 cal a AD,the significant increase of Zea mays pollen content indicated that human activities and rocky desertification were further intensified.The increasing human activity in the past 700 years was an important factor in vegetation degradation and serious rocky desertification in Chongqing.The results of this study are significant to improve the comprehensive management,restoration and reconstruction of the naturally ecological environment in Chongqing karst area.