第四纪环境演变与中国北方的荒漠化

QUATERNARY ENVIRONMENTAL EVOLUTION AND DESERTIFICATION IN NORTH CHINA

从第四纪环境演变的观点出发 ,研究中国北方荒漠化的正逆演变过程。在末次冰期极盛期(18～ 15kaB .P .) ,气候恶劣、干冷 ,沙漠、黄土面积扩大。全新世 (11kaB .P .)以来气候开始转暖 ,9～5kaB .P .为全新世的高温、高湿期 ,温带森林植被几乎取代了北方地区的干旱荒漠和干旱半干旱草原 ,在沙层和黄土地层中发育了多层古土壤。中全新世 (5～ 2 .5kaB .P .)以来气候向干冷方向转变 ,但仍有古土壤发育 ,自然和人文因素促使荒漠化的正逆演化。晚全新世 (2 .5kaB .P .- )气候向干冷方向转变 ,直到 2 0世纪下半叶全球变暖 ,加速了全球性荒漠化的发展。指出荒漠化问题的复杂性 ,对荒漠化的概念进行了讨论 ,并将我国主要的荒漠化分为 4大类型 ,即风蚀荒漠化、水蚀荒漠化、盐碱荒漠化与石漠化 ,还划分了 10个亚类。

From the viewpoint of Quaternary environmental evolution,the ev ol ution processes of development and retrogression of desertification in North Chi na have been studied. In the hemera of the kataglacial epoch(18～15 kaB.P.) the c limate was inclement, cold and dry, and the area of deserts and loess expanded. Since Holocene (11 kaB.P.) the climate became warm and 9～5 kaB.P. was the most h ot and humid in Holocene. The dry desert plants and semi-arid and arid grassland on north area were replaced by temperate forest and there were many layers of p aleosol in the sandy and loess layers. Since the middle Holocene (5～2.5 kaB.P.) the climate turned to dry-cold but still develop paleosol layers. The natural an d man- made factors cause desertification evolution of development and retrogres sion. In the later Holocene (2.5 kaB.P.～) the climate of dry-cold continued unt i l the climate of warm came in the latter half of 20 th and desertification develop rapidly in the whole world. The complexity of desertification problem ha s been indicated and the concept about the desertification has been discussed in the paper. The desertification has been classed into 4 types and 10 sub-types, they are sandy, aqueo-residual, saline-alkali and rock desertification. The conc lusion and suggestion about desertification study have been put forwarded.