土壤侵蚀与第四纪生态环境演变

RELATION OF SOIL EROSION PROCESS TO THE ECOLOGICAL ENVIRONMENT CHANGES IN THE QUATERNARY

本文以考察研究土壤侵蚀区域规律和黄土-古土壤剖面特征为基础,分析讨论了土壤侵蚀与第四纪生态环境的关系。文中对自然侵蚀相对强烈期的判断,沉积-成壤反映的地质事件突变性和渐变性问题,自然侵蚀的时、空分异及其在现代侵蚀过程中的地位和作用均提出了与某些报道不同的见解和新的认识。

It is reported that the soil erosion on the Loess Plateau originated from geological periodunder the case of natural vegetation before mankind society;therefore,the primary factors effect-ing soil erosion might have been tectonic movement and climate;comparatively serious soil ero-sion occurred in the soil-forming period;in the modern soil erosion processes natural ero(?)ion isdominating over the erosion by human's activities.In this paper based on the field survey,physical,chemical and mineral analysis,as well asmicromorphological investigation of the loess-paleosols series on the Loess Plateau,our under-standing seems different from the mentioned above.The soil erosion is the effecting result of multiple factors in macrocycle of atmosphere,lithosphere and biosphere.During the geological period when the human's activities had notinterposed with macrocycle,natural erosion occurred under the natural worsening of vegeta-tions corresponding to the climate changes.Paleosols such as Heiloutu or Cinnamon soil de-veloped under grassland or grass-forest land with fine vegetative cover.The period of soil-forming could not be that of comparatively serious soil erosion.The loess-paleosols series revealed the geological events of sudden change characterizedby alternation of cold-warm,humid-arid and soil-forming and deposition.Nevertheless,thegradual or transitive changes between two sudden changes are often neglected.The duration ofsoil-forming to deposition corresponds to the conditions of modern ecological environment ofthe arid and semi-arid regions.On the basis of natural erosion the irrational reclaiming by human's activities results inthe sharp worsening of natural vegetation and greatly accelerates the soil erosion.The rateof accelarated soil erosion is tens-times to hundreds-times greater than that of natural erosion.It is suggested that to recover or reset vegetation with improving economic benefits andecological environment simultaneously should be the fundamental measures to control soilerosion and to reduce the sediments into the Yellow River.