Cultivated land is one of the key factors ensuring national food security. Black soils (Mollisols) in Northeast China produce one fourth grain and one third commodity grain across the country, and have played a vital role in ensuring national food security.

However, Mollisols in Northeast China have been converted into agricultural use only since the 19th century, but they have been severely degraded by widely distributed gullies. More than 300,000 gullies that are over 100 meters long have developed in the black soil region of Northeast China, which caused land degradation, thin plough layers and reduced soil fertility and threatens the sustainable use of black soils.

Research on the development history, long-term rates and influence factors of gully erosion is of great scientific significance for understanding black soil erosion and its degradation mechanisms, and it is also important for food security and sustainable development of black soil resources.

Studies have shown that the formation and development of gully erosion are closely related to changes in land use. However, the gully erosion history, rates and causes in this region remained unclear.

The Innovation Team of Smart Agriculture and the Innovation Team of Arable Land Quality Monitoring and Soil Care of the Institute of Agricultural Resources and Regional Planning (IARRP), CAAS chose an area with landforms and land-use history typical of the central Mollisol region of Northeast China to estimate the initiation years and rates of gully erosion from 1968 to 2018 by using high resolution aerial and satellite imaging.

Gully volumes were measured using photos taken from an unmanned aerial vehicle. The deposits of a large gully system were dated by Caesium-137 (¹³⁷Cs) and local farmers were interviewed to verify the results. 

The results showed that gully incision started in the 1950s and 1960s, when the original grassland and forest were completely converted into arable land. From 1968 to 2018, the gully density increased from 1.2 to 2.3 km km^-2 and had become larger and more complex.

Over the past 50 years, the gully heads retreated at speeds from 1.5 to 2.5 m yr^-1, and the soil loss from gully erosion ranged from 25.7 to 44.7 Mg yr^-1 ha^-1. 

In addition to the black soil development and utilization, this study also explored the main factors that affect the development of gully erosion from the aspects of soil freezing and thawing, soil parent material and bedrock, agricultural machinery tillage, and water and soil conservation measures.

The study demonstrates the severity of degradation and the accelerated gully erosion in the black soil region of Northeast China. The results provide key scientific support for in-depth understanding of the development mechanism of gully erosion, the prevention and control of cultivated land erosion in the black soil region, and the implementation of national black soil protection and utilization strategies.

Thirteen soil profiles at the outlet of typical gullies in the black soil land (a), sampling of gully systems (b) and schematic diagram of the black soil layer profile (c)

The research results were published in Land Degradation & Development (impact factor: 4.997) titled A case study on history and rates of gully erosion in Northeast China. Wen Yanru, postdoctoral fellow from the Innovation Team of Smart Agriculture of IARRP is the first author, and Zhang Bin, research fellow from the Innovation Team of Arable Land Quality Monitoring and Soil Care of IARRP, is the corresponding author. This research was funded by the National Key Research and Development Program of China (2017YFC0504202).

Wen Yanru, Till Kasielke, Li Hao, Harald Zepp and Zhang Bin. A case study on history and rates of gully erosion in Northeast China. Land Degradation & Development. 2021.

https://doi.org/10.1002/ldr.4031.