黄土高原侵蚀期研究

黄土高原在沉积的同时也存在着侵蚀 ,主要是流水、重力等因素造成的。这种侵蚀会受到气候、构造运动以及人类活动控制。资料显示 ,黄土高原存在 3种基本的侵蚀期 ,一是气候侵蚀期 ,二是构造侵蚀期 ,三是人为因素侵蚀期。此外还有气候与构造共同作用产生的侵蚀期和构造与人类共同作用产生的侵蚀期。温湿期风尘堆积少 ,降水量增多 ,流水动力增强 ,是黄土高原理论上的侵蚀期。构造抬升引起侵蚀基准面下降 ,进而导致黄土高原加快侵蚀 ,出现构造侵蚀期。人类活动破坏了黄土高原的植被和土层结构 ,导致黄土高原侵蚀加剧 ,从而出现了人类因素引起的现代侵蚀加速期。在黄土发育的冷干期 ,由于植被稀疏 ,侵蚀量大于温湿期 ,但堆积量远大于侵蚀量。要改变现代侵蚀状况 ,就应当加强黄土高原生态环境治理。

Study on Erosion Periods in Loess Plateau

There are three kinds of basic erosion periods in the Loess Plateau. The first is caused by climate, the second by tectonic movement and the third by human activities. During the warm and moist climatic period, there was rich precipitation and the vegetation grown luxuriantly, which held back the activity of sandstorm. So in this period, the accumulation of aeolian dust became slow or came to stop. But because of much precipitation, the acting force of the running water became stronger and the formed loess would be somewhat eroded. This period is the climate-caused erosion period of the Loess Plateau in theory. In fact, the loess became soil easily and the warm and moist climate benefited the vegetation growing, the erosive action was held back. So in this period, the loess erosion was not very strong, which is proved by a lot of red-brown paleosol formed during the warm and moist period. During the cold and dry climatic period, wind-force became strong; it was helpful to the Loess Plateau's development. If no cold and dry climate, there would be no Loess Plateau. Although the erosion was stronger in cold and dry period than in warm and moist period, the eroded volume was less than the accumulated volume. So the cold and dry climatic period isn't absolutely the erosion period of the Loess Plateau. Tectonic uplifting caused the base level of erosion to descend and strengthened water erosion made erosion fast along the edge of the loess tableland. This period was the tectonic erosion period. The observation on the terraces indicates that the Loess Plateau has experienced six tectonic erosion periods in its developing processes. Although the erosion scale in the tectonic erosion period was different, it is the main reason that causes the Loess Plateau to break up and naturally erode. The unreasonable human activities deteriorated the natural vegetation and the structure of the soil, which resulted in the extensive erosion of the Loess Plateau in modern times. Besides, there were erosion periods comprehensively caused by climate and tectonic movement and by tectonic movement and human activities. It is the human activity that speeds up the erosion in present days. It is necessary to take biological and engineering measures to control the soil erosion in the Loess Plateau.