## 4 Discussion
### Root Strength Affects Root-Soil Strength  
An increase in plant root strength not only enhances the root-soil complex but also improves soil cohesion. According to existing studies [36], plants can release specific substances into the soil, thereby modifying soil stabilization. The experimental findings suggest that in inundated conditions, vegetation can enhance the rate at which soil shear strength and cohesion decrease. Although their influence on the internal friction angle of the soil appears to be minimal, the internal friction angle may be more sensitive to the physical characteristics of the soil. These findings are still very important [37]. The findings of the six-month flooding study revealed that the shear strength of vegetated soils was significantly greater than that of unvegetated soils. Although the reduction in the shear strength of vegetated soils was greater than that of unvegetated soils, it decreased with an increasing duration of flooding. _Carex_ was most effective at three to four months of soil consolidation, while _Cynodon_ maintained a consistent performance throughout the entire period, and _Eleusine_ was more suitable for short-term soil consolidation. Floodplain plants need to be flood-tolerant; however, once the water has receded, the ability of the plants to quickly recover growth indicators directly affects their survival in subsequent floods [38]. Under flood stress, _Carex_ can maintain its leaf growth and ornamental properties in a flooded environment because of its good shade tolerance and strong self-seeding ability [39]. However, the relatively slow growth rate of _Carex_ does not provide significant competitive advantages in the floodplain environment, especially compared with _Cynodon_ and _Eleusine_[40]. Therefore, we consider _Carex_ to be unsuitable for mixed planting with these two species. As a common slope protection plant and a dominant species in flood-plains, most of the leaves of _Cynodon_ rot and fall off during winter floods, affecting the aesthetics of the environment [41]. However, _Cynodon_ is capable of rapid regrowth and can occupy the growing area once the water has receded [42], achieving high cover within a few months. Notably, while _Eleusine_ is not suitable for prolonged flooding, its seeds are better adapted to the soil and germinate earlier than those of _Cynodon_[43, 44]. Research has shown [45] that in mixed growth studies with _Cynodon_, _Eleusine_ was able to enhance soil fixation and growth to a certain extent. Therefore, under short-term flooding conditions, a mixture of the two may further enhance flood tolerance.  
_Carex_ has excellent flood tolerance but a lengthy growth cycle, making it suitable for long-term ecological planning. In contrast, _Cynodon_ possesses stable strength and a shorter growth cycle, making it more appropriate for a variety of protective applications. While _Cynodon_ offers significant advantages in terms of root strength, its drawback is that it becomes unsightly when the water recedes. Conversely, _Eleusine_ has distinct advantages in specific environments because of its remarkable growth rate and early maturity. During the ecological restoration process, appropriate plants can be selected at various elevations on the basis of the characteristics of different species [46]. This approach not only increase the effectiveness of plant restoration, but also improves soil shear strength and enhances the aesthetics of the affected area.