中国的冻土

GELISOLS OF CHINA

中国冻土面积大,分布规律特殊,对于研究世界冻土的形成、分布具有重要意义。中国冻土有高纬度冻土和高海拔冻土两种。高纬度冻土分布于东北地区,北纬53—46°N,面积38.2×10~4km^2,纬度高而海拔较低,这类冻土的一系列特征主要受高纬度的影响;高海拔冻土主要分布于青藏高原和西部高山,面积176×10~4km^2,占北半球高海拔冻土面积的75.7%,居世界首位,大部分分布于北纬35°N以南,最南达27°左右,纬度低而海拔高,其一系列特征主要受海拔高度的影响。两类冻土的土壤类型和性状各具特点,差异很大。高纬度冻土具有湿寒特点,植被为森林,土壤有机质含量高,pH低,不含CaCO_3,盐基不饱和;高海拔冻土具有干寒特点,植被为草原和荒漠,土壤有机质含量很低,PH高,盐基饱和,大多富含石灰,部分含石膏磐层。目前中国及国际上均未将冻土列为独立的土壤分类单元,我们建议在中国土壤中,增设一个冻土土纲,下设正常冻土(高纬度冻土)和高寒冻土(高海拔冻土)两个亚纲。

China has a large area of gelisols distributed with a particular pattern, which is of great importance to the research on formaticn and distribution of gelisols in the world.The gelisols of China have two types: high-latitude and high-altitude gelisols. High-latitude gelisols are distributed in the Northeast region, 53—46°N latitude, with an area of 38.2×10~4 km^2. As their latitude is high but altitude is low, the soils have a series of characteristics influenced by the high latitude. High altitude gelisols mainly occur in the Qinghai-Xizang plateau and western high nountains, with an area of 176×10~4 km^2 which accounts for 75.7% of the total area of high-altitude gelisols in the Northern Hemisphere and ranks the first in the world. Most of them are dispersed in the regions south to 35°N latitude, and some even to 27°N latitude. Their location is high in altitude but low in latitude, and their characteristics are affected by the altitude.The two kinds of gelisols differ greatly in soil types and properties. Highlatitude gelisols, covered by frost, possess humid and cold features, high content of soil organci matter, low soil pH and unsaturated base, but do not contain CaCO_3. High-altitude gelisols, however, have arid and cold chracteristics, low content of soil organic matter, high soil pH and satuated base; most of them are rich in lime; some contain gypsic and gypsipanic horizon; their vegetation is steppe and deserta.At present, the gelisols have not yet been regarded internationally as an independent classification unit. We suggest to add an order of gelisols, which contains two, suborders of Orthic gelisols (High-latitude gelisols)and Altocryic gelisols(Highaltitude gelisols), in Chinese soil classification system.