天山北坡玛纳斯河流域晚冰期以来植被垂直带推移

Shifting of vertical vegetation zones in Manas River drainage on northern slope of Tianshan Mountains since the Late Glacier

建立了反映天山北坡玛纳斯河流域典型花粉类型与气候指标(湿润指数和温暖指数)的统计函数。基于前人研究得出的玛纳斯湖沉积剖面中不同花粉的百分含量复原了晚冰期以来玛纳斯河流域古气候的变化,并基于山地植被—气候—地形关系推断了玛纳斯河流域的植被演变过程。研究结果表明:该区晚冰期以来经历了暖干—冷湿—暖干—偏冷偏湿—暖干—冷湿—暖干的气候变化过程,植被垂直带基带相应为荒漠—荒漠草原(在局部低洼地段发育有草原和低湿地草甸)—极旱荒漠—荒漠化草原—荒漠—荒漠草原(局部发育低湿地草甸和草原)—荒漠的演化过程。当气候由暖干转为冷湿时,玛纳斯河流域所有的植被界限均向下移,此时荒漠化草原面积增大,针叶林的下限可以到达今天的禾草草原,同时森林带的面积有所增加。当气候由冷湿转为暖干时,玛纳斯河流域所有的植被界限均向上移,荒漠的面积大增,禾草草原和森林的面积均有所减小。

The statistical relationships between climate indexes （moisture index and warmth index） and typical pollen taxa were established with linear regression method on the Manas River drainage on the northern slope of the Tianshan Mountains. Climate and vegetation developments in this region were reconstructed based on the different pollen taxa content of a previously published sediment sequence from the Manas Lake, a desiccated end lake of the Manas River, as well as modern climate, vegetation and land- form relationships. Since 13 000 a BP, the palaeoclimate change in this area has experienced several important stages： warm-dry, cold-moist, warm-dry, cold-moist, warm-dry, cold-moist and warm-dry, in correspondance with the climate change, ancient vertical vegetation change around the area has experienced a series of succession processes： desert, desert steppe （to develop lowland meadow and stepped locally）, extreme arid desert, desert steppe, desert, desert steppe, desert. When the climate in the Manas River drainage changed from warm-dry to cold-moist, all vegetation boundaries in the area moved downward,hence the area of desert and forest was enlarged and the lower limit of conifer may get to current steppe. When the palaeoclimate changed from cold-moist to warm-dry, all vegetation boundaries moved upward, the area of desert was enlarged, while the area of steppe and forest was decreased, and the lower limit of conifer may get to current alpine and sub alpine meadow.