Assessment of post-fire erosion mitigation tools: impact on carbon stocks and soil quality

Abstract

During the last decades, wildfires have become a major environmental disturbance in Mediterranean countries. Wildfires are often followed by strong runoff and erosion and may cause a drastic alteration of soil organic matter (SOM) which is the soils¿ most functional fraction and key attribute of soil quality, and also carbon cycling and balance. Post-fire mulching is a very effective measure to mitigate soil erosion and has been found to improve the physical structure of soils. However, mulch materials and application rates may vary greatly, reducing its effectiveness to control soil erosion and organic matter losses. Some mulch materials such as straw, have been widely used, but novel materials such as biochar (pyrolised biomass) has never been tested in burned areas despite their potential to mitigate soil losses and improve soil quality. This study will show the effects of traditional and novel mulching treatments on burned areas of 2018 in southern Spain and Portugal not only in relation to erosion rates but also to soil quality and carbon stabilisation. Preliminary results showed that straw mulch at a rate of 1 Mg ha-1 reduced soil erosion by 71%, while straw+biochar mulch application at a rate of 1+15 Mg ha-1 reduced erosion by 64%, compared with untreated plots. Both Thermogravimetric and Total Organic Carbon analysis revealed that straw+biochar enriched the organic fraction of sediments. Ongoing research is being designed to study the carbon pools of burned and treated soils, as well as to identify the the fate of carbon forms in soils via analytical pyrolysis and nuclear magnetic resonance.