陕西红碱淖近百年来的孢粉记录及环境变化

通过孢粉分析,对陕西红碱淖地区近百年来的环境演化进行了探讨,对比钻孔岩性特征、历史记载和器测资料,验证了孢粉记录在短尺度的高分辨率环境变化研究中的有效性.研究表明,1927年以前,红碱淖地区气候非常干旱,不具备成湖条件,植被类型为典型荒漠;1927-1938年,干旱程度有所缓和,湖盆洼地开始积水成湖,植被类型为小灌木荒漠草原植被;1938-1960年,气候相对好转,环境开始变湿,红碱淖在此相对较好的气候条件下,积蓄了一定的水量,形成比第二阶段更深些的湖泊,植被类型为灌丛草原;1960年前后环境有较大的变化,孢粉图谱很好地反映了1960年前后人类活动与降水增加叠加后对环境及湖泊的影响.在1960-2000年期间,气候比前几阶段有明显改善,环境湿润,湖泊面积在1960年前后迅速扩大后维持较高湖面.植被为典型草原植被;近几年来,湖区环境又开始相对转干,植被发育为以藜科为主的草原植被.

Sporopollen Record and Environmental Evolution Since ~100 years in Lake Hongjiannao, Shaanxi Province

Environment evolution is revealed since about 100 years in Lake Hongjiannao, Shaanxi Province according to sporopollen analysis, after comparing with lithological character, historical records and instrumental data. The results show that before 1927 the regional climate was very dry in Lake Hongjiannao with typical hungriness vegetation, and the lake did not come into being. Between 1927 and 1938, the dryness degree of climate gradually eased up, lake basin depression began to collect water and lake formed. The vegetation type turned to be hungriness and brushwood-shrubbery vegetation between 1938 and 1960 as the regional climate relatively got better and local environment began to become wet. Under the relative better climate condition Lake Hongjiannao received more amount of water and became a deeper lake than 1927 - 1938; the vegetation type was grassland and brushwood-shrub vegetation. Around 1960 the local environment had the greatest change, as indicated by sporopollen diagram, which showed the superimposed influence of the human activities and precipitation increase in the region. Between 1960 and 2000, climate evidently improved than that of former several stages. The continuous wet environment led to the steady high-stage lake level after short -time widening in about 1960; the corresponding vegetation was typical, with more flourish grassland and brushwood-brush. In recent years, the lake area began to turn relative dry again. The vegetation type was meadow and grassland vegetation dominated by Chenopodiaceae.