祁连山海北高寒湿地气候变化及植被演替分析

分析了近40a海北高寒湿地区域气候变化特征,以及近期湿地退化和植被演替的情况.结果表明:祁连山海北地区自1957年以来年平均气温以0.157℃·10a^-1的倾向率升高,年降水量约以1859mm·10a^-1的倾向率递减,年平均地温比同期气温的增加更为迅速,表现出海北地区气候及土壤性状均向干暖化趋势发展,特别是土壤干暖化程度尤为明显.由于人类活动加剧影响,超载过牧,原生植被遭受破坏,草场退化严重,地表潜在蒸散力加大.深层的多年冻土退化,冻胀草丘坍塌,导致湿地植被发生变化,使沼泽化草甸向典型草甸演替.不同年度调查结果表明,高寒湿地植被在气候干暖化趋势的加剧影响下,植物群落组成发生变异,物种多样性、生态优势度均比湿地原生植被的物种有增多的趋势.原生适应寒冷、潮湿生境的藏嵩草为主的草甸植被类型逐渐退化,有些物种甚至消失,而被那些寒冷湿中生为主的典型草甸类型所替代.组成植物群落的湿中生种类减少,中生种类(如线叶嵩草)大量增加,群落盖度相对降低,群落生产量大幅度下降.

Analysis of Vegetation Succession and Climate Change in Haibei Alpine Marsh in the Qilian Mountains

The regional climate change features of Haibei alpine marsh during the recent 40 years and its possible impacts on marsh degradation and vegetation succession are analyzed. It is found that annual mean air temperature of Tibetan Autonomous Prefecture of Haibei in the Qilian Mountains has increased in the rate of 0.157 ℃·10a^-1, annual precipitation has decreased in the rate of 18.59 mm·10a^-1 since 1957, and the increasing rate of annual mean soil temperature was higher than that of air temperature. A drying and warming trend takes place both in climate and soil in the prefecture, especially in soil. Additionally, intensive human activity and overgrazing bring about some consequences, such as primordial vegetation destruction, grassland degradation and upper transpiration increase. Marsh vegetation change shows marsh meadow transforming into typical meadow, resulting in ancient permafrost degrading and frozen grassy hillock collapsing. Study results indicate that plant community of alpine marsh vegetation is changing under the impact of climate drying and warming. There is an increasing trend of biodiversity and ecological predominance as compared with marsh primordial vegetation. The primordial meadow vegetation dominated by Kobresia tibetica, which is adaptive to shivery and moist environment, is degrading piece by piece and is substituted by some typical meadow, even some species dies away. Species of moist plant decrease and neutral species(Kobresia capillifolia)increase, community coverage reduces relatively and productivity declines largely.