摘要
华北地区的云杉属和冷杉属在早上新世就有大量的发展。榆社盆地在４．４ＭａＢＰ．时，云杉属在孢粉植物群中的含量达５０％一７０％，与云杉属同时发现的还有一些喜暖植物。根据化石和孢粉学证据、沉积条件、古地形及欧洲的旁证材料推测，上新世云杉属和冷杉属的生态习性与现代生活在寒冷地带的云杉、冷杉不同，它们是一些可以生长在相对暖湿气候条件下的种类。上新世以森林为主的植被在２．３ＭａＢ．Ｐ．时转变为疏林草原，亚热带植物基本迁离榆社盆地。云杉属和冷杉属不仅在孢粉植物群中大量减少，在木本植物中也降为次要组分。古植物的演化和迁移历史反映了冰期气候和东亚季风气候发展的历程。
Modern spruce (Picea) and fir (Abier), as cold-enduring trees, only grow on a few high mountains in North China. They have commonly been used as glacial indicators in interpreting Quaternary climatic history. The earliest expansion of Picea and. Abies in the late Cenozoic sequences was considered as the begining of Quaternary. However, more and more palynological evidence and macro fossil analyses show that Picea and Abier were widely spread in North China during Pliocene. In some eastern areas of the Great Plain of North China, Picea and Abier constitute 20% of. the pollen assemblage. In Yushe basin, Shanxi, Picea became an important component from 4.4 MaB. P. to 2.3MaB. P. and reaches 40%-70% in several pollen zones. Abier developed in this area from 4.1MaB. P. Macro fossils of Picea have also been found in the early Pliocene sediments of the same basin. After 2.3 MaB. P., Picea and Ables decreased and forest prevailing vegetation was replaced by steppe and sparse woods vegetation.Subtropical plants such as Carya, Liquidambar, Podocarpus, Magnolia, Hamamelis,Cycas, Ginkgo, Anacardiaceae, Rutaeeae and Hicriopteris also occur in the Pliocene pollen flora, indicating a warm and humid climate. Picea grew near the ancient lake,as indicated by its high proportion in the pollen assemblage, its fossil remains buried in lacustrine sediments, and the presence of many pollen aggregates of Picea. This suggests that Picea and Ables grew alongside the subtropical plants in the Yushe basin. These Picea and Abler must have different ecological demands compared to the modern species, as they grew under relative warm and humid climatic conditions.Most of the ancient species are extinct nowadays. However, some modern species of Abier have recently been found to grow alongside subtropical plants in at least five areas in subtropical zone of China. They may be the relics of Pliocene species.In Europe, Picea and Abier have also been found together with thermophylousplants in the Pliocene flora. For instance, in the palaeoflora of Willershausen, northern Germany, some fossil species of Picea and Abier have been found together with thermophylous plants such as Carya, Pterocarya, Liquidambar,Hymenocardia,Banisteriaecarpum and so on. These macro fossils obviously derived from surrounding plants. This gives direct evidence for the habitat of Pliocene Picea and Abies. Similar situations have been found in Brunssum, the Netherlands and the Mediterranean areas of France.The modern climate of the North China is of the East Asia monsoon climate. It is characterized by a long-lasting dry season especially in a cold and dry winter which is not favourable for the thermophylous plants, nor for Picea and Abler. The vegetation history in the Yushe basin shows that the monsoon climate was much strengthened after 2.3MaB. P. in this region. The subtropical plants migrated out of the Yushe basin after 2.3 MaB. P. At same time Picea and Abier also decreased.During the Quaternary Picea and Abler moved to high mountains or Northeast China where the climate is humid, and they developed to the modern species, the majority of which is distantly seperated from subtropical plants.The following conclusions can be made from this study:(1) Picea and Abies developed in North China from early Pliocene (4.4MaB. P.).The Pliocene Picea and Abies have different ecological demants from most of modern spedes. They grew under relative warm and humid climatic conditions. The migration history of Picea and Abier cannot be simplified as southwards expansion or downwards movement from high mountains during the glaciation. In the early Quaternary they ingrated towards Northeast etna or to high mountains'(2) The earliest expansion of Picea should not be used to define the Pliocene-boundary. A substantial vegetation change took place around 2.3 MaB. P.when the subtropical plants migrated out and the steppe prevailing vegetation replaced forest prevailing one. This lends support to the time scale which places the Pliocene Pleistocene boundary at about 2.4MaB. P.(3) The development of m
出处
《第四纪研究》
CAS
CSCD
1996年第4期319-328,共10页
Quaternary Sciences
关键词
上新世
云彬属
冷杉属
华北地区
气候指标
Pliocene, Picea, habitat, glaciation, East Asian monsoon climate
