Study on the Impact of Vegetation on Landslides under Heavy Rainfall Conditions: A Case Study of Chinese Fir Forests in Sisui Town

Landslides are common geological disasters in southern mountainous regions, and vegetation has a dual effect on slope stability: root systems can reinforce soil and enhance shear strength; however, canopy interception of rainfall increases soil moisture content, potentially reducing shear strength. This study investigates the mechanisms by which vegetation influences landslide risk under heavy rainfall conditions, taking the landslide event in Sisui Town, Pingyuan County, Guangdong Province on June 16, 2024, as an example. By comprehensively analyzing the spatial distribution of landslide sites, vegetation types, soil characteristics, and rainfall data, we focus on the impact of Chinese fir (Cunninghamia lanceolata) plantations on landslide occurrence. Results indicate that despite high vegetation coverage, landslides frequently occur in areas densely populated with Chinese fir forests. Chinese fir is a shallow-rooted species lacking a prominent taproot, with roots mainly distributed in the surface soil layer, providing limited reinforcement to deeper soil. Under heavy rainfall, the canopy of Chinese fir intercepts large amounts of precipitation, increasing soil saturation. The shallow root system cannot offer sufficient anchoring force, leading to trees sliding along with root-soil complexes during landslides. The study reveals the significant influence of vegetation types and root characteristics on landslide occurrence, highlighting that large-scale monoculture plantations in landslide-prone areas may reduce ecosystem stability and increase landslide risk. The findings provide scientific evidence for landslide risk assessment and mitigation in Sisui Town and similar regions, offering important theoretical and practical implications for optimizing mountainous land-use planning, improving vegetation configuration, and enhancing landslide early warning capabilities.