Andic soils and flow-like landslides: Cause-effect evidence from Italy

Flow-like landslides are extremely hazardous phenomena that cause fatalities and damage to natural environments, such as loss of fertile soil cover and vegetation and damage to infrastructure. In the Campania region (southern Italy), previous studies have proved that the most catastrophic flow-like mass movements involve and evolve within a specific soil type: Andosols. Recent findings show that both Andosols and andic soils are widely diffused in the mountain ecosystems of Italy. In this framework, we aim to evaluate whether catastrophic flow-like landslides, historically recorded in Italy, took place where these soils are settled. Soils collected in 12 flow-like landslides that occurred in Italy in the last 70 years were investigated. Chemical, physical and hydrological properties of soil samples collected from the detachment areas under different environmental and geological settings were analysed. Soils showed evidences of the andosolization process that enabled their identification as andic soils. Topsoils were well developed, demonstrating low soil erosion in spite of the high-to-moderate slope steepness and the anthropic stress due to land management. High water-retention capacity, marked chemical and physical fertility, high organic carbon content and prevalent loamy texture are common properties of all the studied soils. Therefore, despite the lithological heterogeneity of the bedrock and other environmental factors, the 12 soils revealed considerably homogeneous properties. Our study suggests a direct relationship between flow-like mass movements and andic soils in the studied environments. These findings shed new light on the pedological similarity of the materials involved in flow-like landslides in Italy.