五台山高山带植被对气候变化的响应

根据五台山高山带草本群落特征种的生长、分布和高山林线树种的年轮分析,揭示了近20年来气候变暖对高山植被的影响。高山草甸和林线过渡带的某些植物种向上爬升的趋势与同期区域气温升高密切相关。草本群落及其特征种沿垂直梯度的爬升与五台山高山带近年来的增温趋势相符合,进一步说明了高山带植被对气候变暖的响应较为敏感,可作为气候变化的指示体。树木年轮宽度序列分析和响应函数表明夏季降水对五台山的高山带木本植物生长有较大影响。由于夏季温度较高,冻土融化,提高了降水的利用效率,促进了树木生长。根据树轮宽度指数与7月份降水量的相关关系,重建了20世纪五台山地区7月份的降水量,基本反映了其间降水量变化的规律。结果表明:五台山20世纪20年代、30年代中期至40年代是相对比较干旱的时期,30年代初期和50年代是相对湿润期,近年来,降水量有下降趋势。

IMPACTS OF CLIMATE CHANGE ON ALPINE VEGETATION ON WUTAI MOUNTAINS

Characteristics of alpine environment on Wutai Mountains, together with the vegetation background, such as the flora and elements, the classification and ordination of plant communities in alpine regions are studied in this paper. It is clear that cold and humid climate, arctic and alpine flora elements and related distributions, and particular distribution of soil organic material are symbols of alpine environment. According to the growth dynamics of endemic plants, change of their distributions on alpine regions and the tree ring width index analysis, it is known that the climate on alpine regions has been changed distinctly. Besides, certain plant community and species, such as Kobresia pygmaea community, species of Kobresia pygmaea and Trollius chinensis, tend to climb up to the summit of the mountains. The analysis of plant communities shows that the climb of grass communities attributes to the rising temperature in recent years. In particular, the alpine timberline trees (Larix principis-ruppriechtii) in alpine regions of Wutai Mountains are moving to higher places very rapidly in recent years. The move of plant communities and certain endemic plants in alpine regions is consistent with the rising yearly average temperature of the region, which can help explain that alpine vegetation responds sensitively to climate warming. And thus, the alpine vegetation can be regarded as the indicator of climate change. Through tree-ring analysis and the construction of response function, it can be considered that the summer precipitation correlates very well with the tree growth on alpine regions, which can be explained that the summer temperature near alpine timberline stimulates trees to make the best of the summer precipitation, and affects the plants growth. Based on the correlation of summer precipitation and tree-ring width index, the summer precipitation in the first half of 20 th century is reconstructed. It shows that the 1920s, the end of 1930s to 1940s, were several arid periods in the 20 th century, however, the early 1930s and the 1950s were relatively humid periods. According to observatory results, the summer precipitation of recent years tends to decrease slowly.