The Influence of Slow-Moving Landslides on Soil Carbon Recovery: Decoupling Soil Organic Carbon and CO₂ Fluxes

Soils store a considerable amount of global carbon. Landslides, meanwhile, impair the soil’s ability to store carbon by disturbing vegetation and removing organic soil layers. In this context, it is becoming increasingly important to account for post-failure soil carbon recovery, and more specifically, for both structural and functional components of soil carbon recovery. We hypothesise that soil CO₂ efflux follows soil organic carbon content during post-event recovery. However, field evidence is still scarce, particularly regarding soil carbon recovery mechanisms and CO₂ efflux dynamics in slow-moving post‑landslide systems in temperate grasslands. This study compares soil organic carbon and CO₂ effluxes in post-failure and non-failure slow-moving landslides and suggests potential sources of carbon inputs in landslide-susceptible pre-Alpine managed grasslands.

 

To achieve this, we conducted two years of observations in control areas and slow-moving landslide areas that experienced a large landslide event in 2013 and have since exhibited slow creep with varying dynamics. Monthly monitoring includes land displacement velocities derived from manual and automatic inclinometer measurements, UAV surveys, greenhouse gas sampling, vegetation parameters, and land-use activity. Additionally, we collected a number of physico-chemical soil characteristics such as soil texture and structure, soil nitrogen and carbon properties, soil pH and electrical conductivity. All of this enabled us to analyse the recovery of CO₂ fluxes and soil organic carbon under different landslide conditions.

 

We found that CO₂ fluxes in the post-failure area recovered to 39% over a decade, which is slower than in lower-latitude regions. However, soil organic carbon recovered even more slowly, reaching only 17% relative to other slow-moving landslide areas and 25% relative to the control site. This divergence between CO₂ effluxes and soil organic carbon recovery dynamics is consistent with current literature. Our observations reveal a clear decoupling between CO₂ fluxes and SOC, suggesting that functional recovery may precede structural carbon recovery; we assume that CO₂ effluxes are influenced mostly by inputs of dissolved and labile organic carbon via surface and groundwater runoff. These findings may have implications at the global scale, given the thousands of landslides occurring worldwide each year and their potential influence on the global carbon cycle. Moreover, highlighting the distinct roles of structural and functional components of soil carbon recovery could support the development of more robust approaches to assess the soil carbon recovery trajectories and management strategies for post-event landslide areas.