Relationship between black soil development and climate change and geomorphological evolution in Northeast China
东北典型黑土区气候 、 地貌演化与黑土发育关系

Soil on slopes of the gentle hilly black soil region in Northeast China, one of the most important bases of cash rice, degraded seriously after dozens of years of intensive cultivation. The thickness of soil humus layer becomes thinner and less fertile year after year. So it is very essential to deepen the researches of soil restoration and improvement after severe soil erosion. Analysis of main reasons for black soil degradation revealed that the cultivation activities halted the accumulation of organic matter and then baffled the soil development which cannot compensate the decrease of the thickness of soil humus layer caused by soil erosion. Soil developing process and conditions are the most important foundation for soil restoration. So the developing history of black soil and chernozem was reconstructed and the geomorphological and climatic factors, which were the key factors affecting the formation of black soil, were analyzed through studying both the formation time of the underlying strata and the local climate change history since the late Pleistocene. The conclusion is that black soil and chernozem formed in different periods, from early period of late Pleistocene and the beginning of Holocene respectively. The former period was warm and wet, while the latter period was warm and dry. And they formed in different places, the black soil was mainly distributed on the second and the third terraces and the chernozem on the first terrace of the Nenjiang River, which is lower than the distributing places of black soil and can accept more carbonate from the highland to form the characteristic illuvial layer. The processes of the soil formation were very slow, so it is hard to restore. These results provide important basis for forulating policies to improve the quality of soils in the region.