摘要
本文应用青海湖QH85-14C孔取得的具有^(14)C测年数据所支持的原始孢粉资料,进行数值分析(有序聚类、主成份分析、滑动平均和回归分析)。从而对青海湖区11000年以来的植被和气候变化进一步讨论。
The Qinghai Lake is the largest inland saline lake in China. It stretches from 36°32' to 37°5' N and from 99°36' to 100°47' E, with a total area of 4635 square kilometres and an average water depth of about 19.15m. Topography varies from planal to (altitude of 3200m a.s.1) to high plateau and mountains (altitude of over 4000m). In Qinghai Lake region, annual mean precipitation is about 377-399mm, but because annual mean evaporation is 3.8 times of it, climate of Qinghai Lake region is semi-arid. Monthly mean temperature is 12.4°C in July, and the lowest is-12.7°C in January, so climate of Qinghai Lake region is cold. In accord with cold and semi-drought climate, vegetation zone of Qingdao Lake region shows high cold shrub, steppe and meadow, mainly composed of Gramineae, Compositae, Cyperaceae, Chenopodiaceae, and Zygophyllaceae etc. Gymnosperm is very poorly preserved, e.g. Ephedra and Sabina. Fern is also scanty. Only Pteridium aqulinum subalpine needle leaved forest, consisting of Picea, Finus and Betula, is distributed in the Qilian and Datun Mts, in temperate forest-steppe region of Huangshui, and also in valley of Huanghe River (the Yellow River) at an altitude of 2500-3l00m a.s.l. Served as the limit boundary of East Asia monsoon, climatic and vegetational changes are very sensitive in Qinghai Lake. Studies on the natural conditions and changes of the lake level are of great scientific and practical significance. This paper is based on a numerical analysis, including order cluster analysis, principal component analysis, moving average processing and regression equat-ion to discuss palynological datum of QH85-14C in the Qinghai Lake. Some conclutions are stated in the paper.
1. On the basis of the order cluster analysis, it is reasonable that pollen zone Ⅲ mentioned in the previous paper could be divided into two subzones (C1 and C2). And every pollen zone has its owns special characters of time sucoession of 14C dates and vegetation development stages.
2. On the numerical analysis, climatic changes in Qinghai Lake region since 11,000 years B. P. may be divided into three big stages, namely, Anath-ermal (11,000-8,000 or 7500 yr. B. P.), Hypsithermal (8,000 or 7,500-3,500 yr. B. P.)and Katethermal (since 3,500 yr. B. P.)
3. It is emphasized that vegetation and natural environment changed a lot in Qinghai Lake region during the 8,000 or 7,500-3,500 years B. P., when the vegetation was dominated by subalpine conifer forest in temperate zone consisting of Picea, Pinus and Betula; some broadleaf deciduous trees such as Ulmus, Quercus and a few ferns were also growing in Qinghai Lake region-According to distribution of forest vegetation in Hengduan Mountain and Qinghai Province in relation to hydro-thermal conditions (Li Wenhua et al, 1981-Zhou Xingmin et al. 1987), we preliminarily think out that the maximum te' taperature in July was about 2°C higher than present and, therefore, the min imum month was 8-11°C higher than today.
The annual mean precipitation was 500mm or more. The increase of precipitation and decrease of evaporation, rise of the lake level and discovery of fossil wood, show that in the Hypsithermal interval, mixed needleaf everygr-een and broadleaf deciduous forests were widely distributed in Qinghai Lake region, climate was warmer and wetter than present time and annual precipitation was about 100mm more than today. So, numerical analysis of palynolo' gical datum is of great significance in geography, botany and anthropology
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
1990年第3期79-90,共12页
Marine Geology & Quaternary Geology
基金
国家自然科学基金资助项目
关键词
全新世
孢粉
数值分析
古气候
Qinghai Lake Holocene Pollen analysis Numerical analysis Paleoclimate Paleoenvironment
