广西桂林岩溶区中全新世以来的植被、气候及沉积环境变化

Vegetation, climate and depositional environment changes since the middle Holocene in the karst area of Guilin, Guangxi

在精确AMS^14C年代测定的基础上,对采自广西桂林岩溶区西南村的沉积样品进行了孢子、花粉和淡水藻类分析,获取了该地区中全新世以来的植被、气候和沉积环境变化的记录.结果显示,ca.5390-1990 cal a BP研究区周围分布有亚热带常绿落叶阔叶林和少许针叶林,低山丘陵上生长着以常绿栎为主的常绿落叶阔叶林,较高海拔处分布有少量以松为主的针叶林,气候温暖湿润;ca.1990-380 cal a BP植被演替为亚热带常绿落叶阔叶、针叶混交林,气温较前一阶段有所降低,期间存在冷暖干湿变化.ca.5390-3160,ca.1990-1540和ca.1360-750 cal a BP三个阶段剖面所在位置湿生草本植物莎草科花粉和淡水藻类环纹藻含量同步升高,指示研究区内水域面积扩大;ca.3160-1990 cal a BP发育泥炭;而ca.1540-1360与ca.750-380 cal a BP两个阶段莎草科花粉和环纹藻含量下降,说明水域面积有所缩小.ca.750-380 cal a BP,人类活动不断增强,森林植被和沼泽资源遭受破坏,石漠化日益加剧.

Changes to the vegetation, climate and the depositional environment of the karst area of Guilin, Guangxi were documented from the middle Holocene to the present, using spores, pollen, freshwater algae analysis and AMS^14C dating. The results show that subtropical evergreen broadleaved forest with some coniferous forest, dominated this area ca. 5390-1990 cal a BP, reflecting warm and humid climate conditions. Conversely, ca. 1990-380 cal a BP the vegetation was replaced by subtropical evergreen broadleaved and coniferous mixed forest, indicating that the climate was relatively cold and dry. Three episodes of swamp expansion were recorded during ca. 5390-3160, ca. 1990-1540 and ca. 1360-750 cal a BP, based on the high abundance of Cyperaceae pollen and Concentricystes. A layer of peat developed during ca. 3160-1990 cal a BP. Two episodes, ca. 1540-1360 and ca. 750-380 cal a BP, indicate a contraction of the swamp with a decrease of Cyperaceae pollen and Concentricystes. During ca. 750-380 cal a BP, the increasing level of human activity, especially deforestation, contributedto rock desertification.