## 3 Results and Discussion
### Influence of Environmental Factors on Subsurface Erosion  
Songnen Plain, a basin-like concave plain, provides a site for the formation of the mud forest landforms. Since the terrain is slightly concave, groundwater and precipitation tend to accumulate there. This, to some extent, aggravates the occurrence of subsurface erosion. During the Neoid period, gullies formed along the cutting of the earth's crust provided the possibility of erosion and subsurface erosion. Moreover, the uplift caused the inclined rise to the northwest, accompanied by new fault activities, which led to the asymmetry of landform between the east and west sides of the Dabusu Lake (Figure 11). Therefore, erosion and subsurface erosion on the east bank are more intense. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline
**SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **FeO** & **CaO** & **MgO** & **K\({}_{2}\)O** & **Na\({}_{2}\)O** & **TiO\({}_{2}\)** & **P\({}_{2}\)O\({}_{5}\)** & **MnO** & **LOI** \\ \hline
77.38 & 9.76 & 1.26 & 0.54 & 4.29 & 1.16 & 2.96 & 2.24 & 0.58 & 0.07 & 0.07 & 4.74 \\ \hline \end{tabular}
\end{table} 
Table 6: Chemical composition of loess-like soil (major element, in wt.%). Figure 10: Relationships between clay dispersibility (susceptibility to colloidal dispersion) and salt composition (expressed through the PS, TDS and SAR parameters defined in Table 7). The asymmetry of the lake banks is not only the reason why the mud forest landscape began to occur, but also an important geological factor in the subsurface erosion that the mud forest is still experiencing. Due to the control and influence of neotectonic movement, the uplift of Xuezijing was active. In the late Pleistocene (about ten thousand years ago), there was a local uplift in Xuezijing, and the front edge of the second terrace formed a steep ridge more than 20 m high. The leading edge of the terrace floor was raised, showing an abnormal phenomenon that the front edge of the terrace slopes towards the back edge. The height difference between front edge and back edge was nearly 1 m. The terrace floor shows a north-south extension, with high in the middle, low on both sides. As the climate was dry and the ground rose again, the lake level dropped. Long-term, intense erosion and subsurface erosion occurred in lakeshore gullies. [PERSON] and [PERSON] [47] took sporopolen samples from the late Pleistocene lacustrine deposits and analyzed them. The results showed that the main sporopolen of woody plants were pinaceae and betulaceae, and the main sporopolen of herbaceous plants were artemisinin and chemopodiaceae, ephedra and other drought-tolerant plant sporopolen also could be seen. This indicated that the Late Pleistocene climate was a dry and cold climate. This climate period corresponds to the Dali ice age in China. Fossils of fauna that lived in cold climates, such as mammoths and woolly rhinoceros, have been found, confirming a dry and cold climate. In this dry and cold environment, the lake water evaporates and condenses, increasing the salinity of the lake. The lake water with high salt content is deposited in direct contact with the sediments. This exacerbates the dissolution of soluble salts in loess-like soil. Thus, it is more prone to occur subsurface erosion. Affected by the temperate monsoon climate, the study area is hot and rainy in summer and cold and dry in winter. Southwest winds prevail in the study area, with strong spring winds. The average annual wind speed is 4.1 m/s and the average annual maximum wind speed is 28.2 m/s [59]. Large amounts of clay and salt are blown toward the lakeshore. During the summer, some of the material is carried back into the lake by the wind. This ongoing wind cycle has a profound impact on molding the shape and physical structure of the lake basin. At present, the mud forest geological and geomorphic landscape is exposed to the wind, so the cutting and shaping of the lake basin and mud forest by wind force factors cannot be ignored.