Reporters were informed on the 20th by the Institute of Geology and Geophysics of the Chinese Academy of Sciences (CAS) that researchers from the institute have conducted extensive field surveys and sample collections in Northeast China's black soil area, and discovered through the analysis of collected black soil samples that the substance of black soil was initially transported by wind. The relevant research findings were published online in the international academic journal Catena.
Black soil is widely recognized as one of the world's most fertile soils and is hailed as the "giant panda of arable land". Northeast China's black soil area is an important grain production base for China. However, against the backdrop of intensifying human activities, Northeast China's black soil is facing a severe threat of erosion. "Clarifying the genesis and depositional background of Northeast China's black soil will facilitate targeted erosion prevention and control measures for the region's black soil," said Yang Shiling, corresponding author of the paper and a researcher at CAS's Institute of Geology and Geophysics.
Researchers analyzed the grain sizes and optically stimulated luminescence (OSL) ages of collected black soil and underlying sediment samples from Northeast China to investigate the genesis and depositional environment of the black soil. Grain size distribution results show that the black soil in western Northeast China is similar to the sandy loess in the northern Loess Plateau, exhibiting typical characteristics of eolian deposition. In contrast, the black soil in eastern Northeast China is similar to the secondary loess on the alluvial plain, indicating a later stage of hydraulic modification. In addition, the average median grain size and sand content results of the black soil show that the overall grain size of the black soil in Northeast China becomes finer from west to east, and its spatial variation is entirely consistent with the wind direction during the dust storm season in Northeast China.
"We believe that although there is local hydraulic modification in the eastern black soil, it does not change the spatial variation pattern of the grain size on a large scale. The black soil matter was initially transported by wind," said Dr. Zhang Shihao, the first author of the paper.
Chronological studies show that the black soil in Northeast China was mainly formed in the Holocene Epoch, about 10,000 years ago, while its underlying sediments were mainly formed during the last glacial period and have a wide age range (12,000–65,000 years ago). "This result means that during the last glacial period, the geomorphic conditions of the black soil area in Northeast China were unstable and subjected to different degrees of erosion, which may be closely related to the enhanced wind erosion during the glacial period and the water erosion caused by the meltwater of surrounding mountain glaciers. In contrast, the warm and humid climate and vegetation development in the Holocene Epoch allowed dust particles to be preserved and developed into organic-rich black soil," explained Zhang.
Yang Shi嶺 said that this research is of great significance for the conservation of black soil in Northeast China. Considering the importance of vegetation for the accumulation of dust particles and soil development, appropriate vegetation restoration will be conducive to the sustainable development of black soil resources.
