Decision-making criteria to shape mulching techniques for fire-prone landscapes

Summary

Context: Wildfires have severe impacts on landscapes’ hydrological and sediment processes. They are linked to events such as flash floods and droughts, and high erosion rates which lead to loss of soil organic matter and detachment of seeds and seedlings. Mulching is an effective measure implemented directly after a fire to reduce soil erosion and increase soil water retention. However, its implementation has proved a challenge, mainly due to factors such as cost and public acceptance. Objectives: This research aims to optimize the application of post-fire mulching by using decision-making criteria to select “how” and “where” the technique should be used. The specific objectives were to: (i) investigate the decision-making criteria on “how” to apply mulch by interviewing experts; (ii) define the cost-effectiveness relations of erosion modelling scenarios. Methods: The Monchique 2003 wildfire in Southern Portugal was used as a case study Experts’ interviews and literature review were used to construct prioritization scenarios. Post-fire soil erosion was then modelled with the Revised Universal Soil Loss Equation (RUSLE) model and the Sediment Connectivity Index for the three resulting scenarios (the “Soil” scenario, considering the net potential erosion; the “Water” scenario, focusing on th1e protection of water bodies from sedimentation; and the “Road” scenario, focusing on road protection); and at two erosion thresholds (1 and 10 Mg ha⁻¹ year⁻¹). Results: The interviews and the literature review highlighted the importance of socio-economic parameters when it comes to mulch application. Moreover, models showed that small interventions, aimed at areas nearby water bodies and road networks can be more cost-effective than large interventions. Conclusions: Models helped to create a hierarchy of scenarios, enabling land managers to assess decision making tools at the landscape level, linking their priorities with practical issues of emergency stabilization practices.