Background The definition of main soil types, which was one of the most important reference for the delineation of typical black soil regions of Northeast China, is quite controversial at present, thus it is necessary to conduct in-depth research.

Methods Taking the national digital soil map with the scale 1:1 000 000 drawn by the Nanjing Soil Research Institute, Chinese Academy of Sciences as the base map, the study counts the area and spatial distribution of black soil, chernozem and meadow soil in Northeast China, and points out that.

Results 1) The total area of black soil in Northeast China is 60 434.78 km². Black soil, which has two concentrated distribution regions and located in the eastern-northeastern part of Songnen Plain (51 807.20 km²) and the Sanjiang Plain (7 075.73 km²) accounting for 97.43% of the total area, can be used as one important reference for delineation of typical black soil regions. 2) The area of chernozem in Northeast China is 92 680.32 km². Chernozem, which also has two concentrated distribution regions and located in the western part of Songnen Plain (45 368.20 km²) and the East Four Alliance (46 881.22 km²) cities based on the Hulun Buir League in Inner Mongolia Autonomous Region, accounting for 99.53% of the total area, can be used as another reference for the delineation of typical black soil regions. 3) The area of meadow soil is 225 980.75 km². Meadow soil, which is almost linear shape throughout all the valley lowlands in Northeast China and does not have concentrated distribution characteristics, can't be used the reference for the delineation of typical black soil areas in Northeast China.

Conculsions The typical black soil regions of Northeast China, including four typical black soil regions of Hulun Buir, western Songnen Plain, eastern Songnen Plain and Sanjiang Plain, can only be delineated around black soil and chernozem. The meadow soil, which although accounts for a high proportion in the four typical black soil regions, cannot be used as a reference for demarcation. In order to maintain the consistency of the delineation and definition of the typical black soil area in Northeast China, meadow soil should be excluded the definition of soil types. The research results are conducive to guiding the production practice in typical black soil regions of Northeast China, and have a certain theoretical guidance for the in-depth study of typical black soil regions of Northeast China.