黄土高原历史时期植被变化

研究黄土高原历史时期植被变化是认识其环境演变的基础。文章在文献研究的基础上分析了黄土高原历史时期的植被变化。得出:西周以前及西周战国时期黄土高原植被保持着天然状态;秦汉时期天然植被仍占较大比重,人类活动尚没有改变黄土高原的植被面貌;唐宋时期河谷、平原地区已无天然森林,丘陵、山地植被也遭到破坏,北部沙漠开始扩张,自然环境处在恶化之中;明清时期植被遭到毁灭性破坏。造成黄土高原历史时期植被变化的根本原因是人为开垦土地,采伐森林和过度放牧。据推算春秋战国时期黄河中游森林覆盖率为53%;秦汉时期下降为42%;唐宋时期下降至32%;明清时期下降至4%。黄土高原濯濯童山主要是近600多年来人类活动对植被破坏的结果。

Vegetation Variation of Loess Plateau During Human History

It is the basis to understand the environment changes by researching the variation of vegetation of Loess Plateau. Based on the historical documents and related research achievements, this research studies the vegetation variation during human history on Loess Plateau and some results have been achieved. Firstly, before Bronze Age and Bronze Age-Zhanguo period, the vegetation kept natural condition. Secondly, Qing-han period, in large-scale, Loess Plateau was covered by forest and forest steppe. In that time, human activity had not changed natural vegetation of Loess Plateau. Thirdly, Tang-Song period, in river valley and plain there was no natural vegetation, in the same time vegetation in hilly and mountains region had been damaged. Desert had expanded in the northern Loess Plateau, the environment had begun to worsen. Fourthly, it was the time that the natural vegetation was been destroyed in Ming-Qing period. How about those above mentioned results, cultivation, deforestation, excessive using pasture are the essential reasons. From calculation, the vegetation cover rate of Loess Plateau during human historyis 53% in Chunqiu-Zhanguo period, descended to 42% in Qing-han period, descended to 32% in Tang-Song period, finally descended to 4%in Ming-Qing period.So now baring mountains on Loess Plateau, are produced by human being through destroying the natural vegetationmainly since about 600 years.