摘要:
文章通过对青藏高原北纬25°～45°,东经75°～106°范围内海拔1000～5700m的地区所采集的598个表土样品的孢粉分析,研究了现代表土中冷杉和云杉花粉的分布与植被、气候和海拔之间的关系。表土样品中冷杉和云杉花粉高含量范围对应着青藏高原南部和东部山地暗针叶林分布区,花粉等值线图较准确地反映了冷杉和云杉的丰富程度及其与植被、环境的关系;冷杉和云杉花粉百分含量随海拔和气候梯度变化表现出单峰分布模式,冷杉和云杉花粉百分含量大于20%的最适宜海拔高度是2500～4000m,最高含量中心限制在海拔3200m左右、年均温2～3℃范围内;较高的花粉百分含量带出现在年均温0～8℃、年均降水量400～850mm的区域。结果显示了青藏高原现代冷杉和云杉花粉的空间分布与植被、气候、海拔的空间变化之间很好的相关性,为利用花粉资料进行青藏高原地区的古气候重建提供了有益的资料
Abstract:
We examine the relationship between modern Abies and Picea pollen, vegetation, elevation and climate in the highest region of the world, the Qinghai Xizang Plateau, using isopoll maps and scatter diagrams. The modern pollen database used in our study is composed of 598 modern pollen sites, which cover latitudes 25°～45° N, and longitudes 75°～106°E at a large altitudinal range from 1 000m to 5 700m above sea level. These samples were collected from many vegetation types, i.e ., forest, shrubland, steppe, desert steppe, subalpine meadow, subalpine steppe, alpine meadow, alpine steppe, alpine desert steppe and alpine desert. Spatial pattern of modern Abies and Picea pollen indicates that their high percentages are near their source areas in the Qinghai Xizang Plateau, where dark conifer forest is the main vegetation type. This shows that the distribution of Abies and Picea can reflect geographical distribution of modern dark conifer forest. The isopoll maps accurately reflect Abies and Picea abundance and their environmental limits, although their pollen can be found occasionally beyond these limits. Both of Abies and Picea pollen percentages show a unimodal pattern along the elevation and climatic gradients, and their optima occur at elevation between 2 500m and 4 000m above sea level, with 0～8℃ as mean annual temperature, and 450～850mm as mean annual precipitation. Our study shows a strong correlation between the spatial distribution of Abies and Picea abundance and the spatial variations in vegetation, climate, and elevation in Qinghai Xizang Plateau, which provides useful information on paleoenvironmental reconstruction using pollen data.$$$$
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