黄土高原气候变迁、植被演替与土壤干层的形成

2 .5Ma B.P.以来 ,受地球轨道要素周期性变化和青藏高原阶段性强烈隆升的影响 ,黄土高原地区气候存在着干期与湿润交替出现的现象 ,但总的趋势是向干旱化方向演化。黄土高原第四纪以来草本植物一直较为繁茂 ,木本植物仅在少数几个时期处于优势地位。现代黄土高原人工林草植被普遍存在着土壤干层问题。土壤干层的形成是气候干旱化过程中必然出现的现象 ,它是导致植被演替的直接原因之一。人工植被激发并强化了土壤干层的形成。土壤干层的形成是气候干旱化和人工植被选择不当两个方面综合作用的结果 ,但有望通过有关人工措施使其危害得到缓解

Climatic Change、Vegetation Evolution and Low Moisture Layer of Soil on the Loess Plateau

Since 2.5Mabp, under the influence of periodical change of globe orbit and periodical uplift of the Qinghai-Xizang Plateau, the dry and wet periods of climate on the Loess Plateau have occurred alternately, but the general tend of climatic evolution is to drought. The herbage on the Loess Plateau has been thriving since the Quaternary, but xylophyta flourshed during only few periods. The problem of low moisture layer of soil (LMLS) exists in almost all artificial vegetation conditions on the recent Loess Plateau. The formation of LMLS is a specific phenomenon during the process of climatic drought, and is one of the direct causes of vegetation pattern evolution.Artificial vegetation has aroused and strengthened the formation of LMLS. So the formation of LMLS is the result of the interactions of climatic drought and unsuitable selection of artificial vegetation. Whereas the damage may be mitigated by certain artificial approaches.