Black soil is the most fertile and suitable soil in the world for farming, a precious and non-renewable natural resource, known as the "giant panda in cultivated land". The northeast black soil area of the mainland is one of the three major black soil areas in the world, and is an important national commodity grain base and green food production base, with an area of 180,000 km2. According to the data released by the National Development and Reform Commission, in recent years, the grain output of the three northeastern provinces has accounted for more than 1/5 of the country, the amount of commodity grain accounts for about 1/4 of the country, and the amount of grain transferred out accounts for about 1/3 of the country. Due to the high organic matter content, loose soil and continuous reclamation of black soil, the erosion of the black soil area is serious (Figure 1). However, the spatial variation of erosion rate and erosion camping force in black soil areas still need to be studied in depth.
Figure 1 Erosion landforms in the black soil area of Northeast China (courtesy of Researcher Xiong Shangfa and Dr. Guo Licheng)
Wang Heng, a master's student of the Key Laboratory of the Cenozoic Institute of Geology and Geophysics, Chinese Academy of Sciences, under the guidance of supervisor Yang Shiling, conducted research in the northeast black soil area (Figure 2), estimated the erosion rate of northeast black soil according to the 137Cs erosion rate model, combined with climatic conditions, discussed the main forces of black soil erosion and proposed corresponding erosion prevention and control measures.
137Cs were mainly released into the atmosphere by the above-ground test explosion of nuclear weapons in 1954–1968, and then quickly adsorbed by aerosols and dust particles, and carried into the surface by precipitation and dust. Once 137Cs enter the soil, they are adsorbed by soil mineral particles and organic matter, and migrate with the movement of soil particles. Accordingly, 137Cs can be used to study soil erosion rates.
Figure 2 Distribution and study sites of typical black soil in northeast China
Based on the black soil erosion rate obtained from 12 study points, combined with the previous data (all obtained by 137Cs erosion rate model), the Kriging interpolation method was applied to obtain the distribution map of black soil erosion rate in Northeast China (Figure 3). The results showed that the erosion rate in the northeast black soil area gradually decreased from the west (>3 mm/year) to the east (0–3 mm/year), with an average erosion rate of 2.22 mm/year. At present, the average thickness of black soil in Northeast China is only 20–30 cm (Fan Haoming et al., 2004). If effective measures are not taken, at an average erosion rate, the black soil will be eroded within ~113 years; its survival time will be shorter (~83 years) due to the more severe erosion in the western part of the northeast black soil area. Therefore, the prevention and control of black soil erosion in northeast China cannot be delayed.
Figure 3 Distribution of erosion rate of black soil in Northeast China. The red dot indicates the study point, and the blue dot indicates the predecessor study point
Analysis of modern surface wind speed and precipitation data (Figure 4a, b) shows that the western surface wind speed in the black soil area is large (>3.2 m/s), the climate is relatively dry (350–500 mm annual precipitation), and the erosion rate is high (> 3mm/year), wind is the main erosion camp force (Figure 4c). The downwind-oriented Ma'aur Lake in Erlong Bay (Figure 2) had an average sedimentation rate of 0.5 mm/year before 1963 and increased to 1.45 mm/year in 1963–2001 (You Haitao et al., 2007). Since there is no surface runoff in Marr Lake, the sediment is mainly from wind and dust material, and the increase in sediment rate indicates that wind erosion has strengthened. In contrast, surface wind speeds in the eastern part of the black earth area are small (
Figure 4 1000 mb average wind speed (a), average annual precipitation (1961-2016) (b), wind erosion (c, from National Geographic of China) and water erosion ditch (d, courtesy of Researcher Xiong Shangfa and Dr. Guo Licheng) in the northeast region(d), researcher Xiong Shangfa and Dr. Guo Licheng). Gray areas indicate black soil; white arrows indicate wind direction; red dots indicate this study point, and blue dots indicate predecessor study points.
In order to achieve the sustainable utilization of black soil resources in Northeast China, it is recommended to take three measures: 1) appropriately reduce the intensity of cultivation in the black soil area; 2) the western part of the black soil area has serious erosion and less precipitation, so it is advisable to return farmland to grassland and increase grassland cover to reduce wind erosion; 3) the eastern area has a large amount of precipitation, and the water and soil can be consolidated through afforestation.
The research results were published in the international academic journals Catena (Wang Heng, Yang Shiling*, Wang Yongda, Gu Zhaoyan, Xiong Shangfa, Huang Xiaofang, Sun Minmin, Zhang Shihao, Guo Licheng, Cui Jingyi, Tang Zihua, Ding Zhongli. Rates and causes of black soil erosion in Northeast China [J]. Catena, 2022, 214: 106250. DOI: 10.1016/j.catena.2022.106250）。
References (swipe up and down to view)
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YOU Haitao, LIU Qiang, LIU Jiaqi, et al. Comparison of striated layer chronology with 137Cs, 210Pb method to study the modern sedimentation rate of Mare Lake in Erlong Bay, Northeast China[J]. Journal of Jilin University: Earth Science Edition, 2007, 37(1): 59–64.
Editor: Chen Feifei
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