The soil conservation team of the Innovation Team of Soil Health Care of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS), has made a series of progress in addressing issues of soil erosion, gully erosion leading to soil quality decline,and farmland fragmentation in the Mollisol region. The team has clarified the freeze-thaw characteristics of Mollisol profiles, the structure of soil aggregates and pores, and the response mechanisms of farmland destruction to soil erosion. The research findings provide important scientific basis for the prevention and control of erosion degradation and the sustainable utilization of Mollisols. Related research papers, "Initial soil moisture prewinter affects the freeze-thaw profile dynamics of a Mollisol in Northeast China" and "Assessment of soil aggregate pore structure after 8 years of cultivation from the parent material of a Mollisol," have been published in the international journal "CATENA".

The Mollisol region in Northeast China is the most important commodity grain production base in China and has made significant contributions to ensuring national food security. However, Mollisols face problems such as erosion, farmland destruction due to gully erosion, and declining soil fertility. Soil erosion caused by natural forces (wind/water/freeze-thaw erosion) and long-term high-intensity human cultivation disturbance is an important factor in land degradation in this region.

The freeze-thaw characteristics are of great hydrological significance in seasonally frozen agricultural soil and may vary for different initial moisture conditions because of variability in land use, topography, tillage and climate change. However, the initial soil moisture regimes before winter freezing that control the dynamics of profile freeze-thaw cycles remain unclear. This study explored the soil profile freeze-thaw dynamics under different prewinter moisture regimes located in a seasonally frozen Mollisol in China. Our results revealed that the variation in soil water storage occurred after infiltration before winter freezing and lasted throughout the thawing period. Lower prewinter moisture content resulted in more thawed saturated zones in the middle and surface layers of the profile, increased freeze-thaw cycles, and deeper zero-curtains of temperature variation. Our findings suggest that more attention should be given to the top layers and sidewall layers under the lower prewinter soil moisture conditions.

Soil erosion can lead to the exposure of subsoil parent material, and an appropriate soil restoration approach is required to maintain good soil quality. Agricultural recovery strategies (such as land use types, and different amounts of mineral and organic fertilizers inputs) can affect soil quality by manipulating soil structure. However, most of the relevant knowledge comes from studies on mature soils, and there are currently few reports on the influence of agricultural recovery measures on the structure of subsoil parent material. This study, based on a field-based 8-year positional study, found that all the six selected recovery measures improved soil aggregate structure, with the combined application of organic and inorganic amendments showing the most significant effect. However, it is important to note that soil structure restoration is a slow process, and the structure of subsoil parent material after eight years of recovery is still relatively poor compared to mature Mollisol.

Assistant Researcher Wen Yanru from the IARRP and Assistant Researcher Ren Lidong from the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, are the first authors of the research papers, while Prof. Wu Wenbin and Prof. Yao Shuihong are the corresponding authors. The research was supported by the National Key R&D Program Project (2021YFD1500700), the Agricultural Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences (CAASZDRW202202), and the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA28130100).

Original Article Links:

1. Wen, Y., Liu, B., Jiang, H., Li, T. Y., Zhang, B., & Wu, W*. (2024). “Initial soil moisture prewinter affects the freeze–thaw profile dynamics of a Mollisol in Northeast China.” CATENA, 234, 107648.

2. Ren, L., Yao, S.*, Sun, J., Zhou, H. (2024). “Assessment of soil aggregate pore structure after 8 years of cultivation from the parent material of a Mollisol.” CATENA, 235, 107699.