白洋淀地区全新世以来植被演替和气候变化初探

 根据对白洋淀白4号孔的孢粉分析、放射性碳年代测定和野外考察研究表明，白洋淀形成于中全新世。晚全新世以来，随着气候的变凉变干，古白洋淀开始收缩和解体，但在人类活动的利用改造下，使逐渐解体的白洋淀得以保留下来。依据气候地层学的观点，并结合放射性碳年代测定，白洋淀地区的全新世地层可以划分为四期：即古全新世(距今11000—9000年)，气候温和湿润；早全新世(距今9000—7500年)，气候偏凉偏干；中全新世(距今7500—3000年)，气候温暖湿润；晚全新世(距今3000年至今)，气候温凉偏干。

PRELIMINARY DISCUSSION OF VEGETATION SUCCESSION AND CLIMATE CHANGE SINCE THE HOLOCENE IN THE BAIYANGDIAN LAKE DISTRICT

Baiyangdian is a large lake in the North China Plain. Pollen analysis of Bai No.4 Drill and field investigation revealed that Baiyangdian Lake was formed during the Middle Holocene and began to shrink and fall into pieces with the cooling and drying process of the climate since the Late Holocene, but it was reserved and developed by human activities.There are five pollen zones in the profile of the Bai No.4 Drill core. On this basis the Holocene strata of the Baiyangdian Lake district can be divided into four stages by means of 14C dating. Stage 1. Old Holocene (ll000—9000a.BP.), The vegetation was needleleaved and deciduous broad-leaved mixed woodland dominated by Pinus and steppes. The climate was temperate and subhumid. Stage 2. Early Holocene (9000—7500 a. BP.),Pinus woodland and steppes with a semi-cold and semi-arid climate. Stage 3. Middle Holocene (7500—3000 a. BP. ), Pinus-Quercus-Betula woodland to swamp. There were allot of Ceratopteris in the swamp at that time. So we think that the temperature was 2–4℃ higher and the precipitation 200 mm more than that at present. Stage 4. Late Holocene (3000 a. BP. to present), Pinus with deciduous broad-leaved woodland scattered among herbs to artificial lake. The climate was cool and semi-arid. The development of Baiyangdian Lake has been dominated by both natural climate change and human activities.