New explanations for gully formation on farmlands in China’s Mollisols region: Fissure evidence by spring freeze-thaw actions

Thanks to its higher soil fertility and plains and rolling terrain appropriate for cultivation, the Black Soil region of northeastern China, which represents the Mollisols of Asia among the four Mollisol belts across the globe, has long been a crucial food basket for the country to feed its huge population and safeguard food security (Liu et al. 2012; Tong et al. 2017). However, due to unique soil erosional circumstances and intensive, exploitative farming, agricultural lands in the region have experienced severe soil loss and degradation, leading to eroded topsoil, depleted soil organic matter, and acidification. This poses a threat to conservation of the Mollisols and sustainability of local agricultural production (Kharytonov et al. 2004). As a result, conservation of the Mollisols of the region has been listed among the state’s strategic inventories for current major challenges (China Ministry of Agriculture 2017).

In recent years, a hybrid soil erosion mechanism driven by freeze-thaw, wind, and water erosion processes has been recognized, and these processes must be understood to combat the challenge (Hu et al. 2009; Hu 2012; Hu and Flanagan 2013). Apart from many field erosional processes caused by multiple natural agents of erosion and by improper farming regimes, the phenomenon of widespread gully erosion in Mollisol farmlands has been arousing considerable interest among scientists. According to reports, over 295,000 gullies have developed in the Black Soil region, of which about 80% were found in croplands (Dong et al. 2019). Since the Mollisols region of northeastern …