## 4 Discussion
### The Function of perennial Sweet Peas in Hydrological Regulation  
One study showed that cultivating leguminous plants reduces soil erosion and enhances soil organic matter content [45]. In this study, perennial sweet pea plots exhibited superior physical soil properties compared to bare ground (CK) and naturally vegetated plots. This distinction primarily arises from the influence of soil organic matter content, soil microbial activity, fauna, and vegetation growth on soil physical attributes. This interplay augments soil organic matter content, stimulating microbial activity and expediting organic matter conversion. Stable organic acids produced through microbial decomposition facilitate soil particle binding, promoting aggregate formation and enhancing water stability [46].  
Numerous studies emphasize roots' pivotal role in ameliorating soil structure [47; 48; 49; 50; 51]. Perennial sweet peas' extensive root system enhances soil porosity, reduces bulk density, and improves gas exchange and permeability. Additionally, soil biota significantly influences soil physical properties. Soils cultivated with perennial sweet peas exhibit favorable attributes, particularly increased organic matter content. Soil organisms, particularly earthworms, create larger pores through their activities, further increasing soil porosity and facilitating the necessary soil particle structure. Moreover, fallen leaves and branches non-ish soil organisms and microbes, fostering biological activity that generates pores within the soil. Conversely, the decomposition of these materials produces humus that binds with clay particles, forming minute aggregates that sustain soil porosity and permeability.  
Furthermore, the dense vegetation of perennial sweet peas contributes to rainfall interception, slowing surface runoff and promoting soil water infiltration, thus demonstrating a rainwater conservation effect. Simultaneously, perennial sweet pea cultivation enhances soil porosity, resulting in a well-structured and loose texture. After rainfall, a significant portion of surface runoff transforms into slow-moving soil runoff, percolating through non-capillary pores to lower soil layers due to gravity [52]. Fallen leaves and the formation of minute aggregates increase soil surface roughness, decelerating runoff and enhancing infiltration. Moreover, the well-developed taproot system of perennial sweet peas generates non-capillary pores, further enhancing soil infiltration.  
In conclusion, this study highlights the significant role of perennial sweet peas in soil and water conservation and hydrological regulation. The findings have implications for sustainable land management practices, particularly in regions prone to soil erosion and water scarcity. However, it is important to acknowledge certain limitations of this research. The study primarily focused on a specific geographic area, and the results may not be directly applicable to other regions with differing climatic and soil conditions. Future research could explore the adaptability of perennial sweet peas in various ecological settings and assess their long-term impact on soil and water conservation.