1. Artemi Cerdà, Soil Erosion and Degradation Research Group. Department of Geography, Valencia University, Blasco Ib, Spain
Soil erosion is one of the key processes to understand the World Land Degradation. Forest fires results in the removal of the vegetation cover and changes in the soil surface cover. The surface wash increase in forest fire affected land. Runoff is generated faster and with higher discharges, and the sediment detachment is more efficient. A key factor of the immediate post-fire effects on soils is the ash layer that can act as mulch.
The research carried out about the changes in soil erosion rates after forest fires shown that there is a sudden increase in soil losses the year after. The concept of Window of Disturbance explains how as a consequence of the forest fires soil erosion process are more active temporally. Although the window of disturbance issue is fully accepted by the scientific community, there are clear evidences that immediately after forest fires soil erosion is controlled by the ash cover that act as a mulch and increase the infiltration rates and reduce the soil losses as avoid the runoff generation.
The research of the last decades highlighted that after forest fires reallocate of the water repellency at 2 cm depth. The water repellency is triggered after the forest fire due to the volatilization and condensation of plant substances at different soil depth, which is highly dependent on the soil properties and fire temperature. There is a debate about if fire reduces or enhances the soil water repellency. This is related to the fire characteristics and type of plants. Some plant species produce substances that are highly repellent, meanwhile others do not; and high temperature volatize those substances. The debate is open, and there is a need of more research about how the water repellency is redistributed during the fire. What is widely accepted is the importance of organic matter on soil water repellency such it was found in the Sierra de Enguera study site in Eastern Spain.
Forest fires were understood as the cause of Desertification and Land Degradation around the world. However, the positive influence of the studies in Ecology soon shown that the forest fires are part of the ecosystems and that fire is part of the nature. The recovery of the vegetation after forest fire is a natural response of the ecosystems. The recovery of the biomass will end in the lowering of the soil erosion rates. The comparison of the fire affected land with other human disturbed land such as agriculture land shows that fire fire affected land does not show the largest erosion rates, meanwhile the citrus and olive plantations, and vineyards show extremely high erosion rates. Then, forest fire is not so bad.
Forest fires are part of the Ecosystems. The increase in the soil erosion rates after the fire are temporally controlled by the ash cover but soon (few weeks or months) the soil yield large quantities of water and sediments. The recovery of the pre-fire conditions for soil erosion rates is found after some years (2-10). We need to research more in the water repellency changes and in the role of plants and ash in the fate of the soil and water yield. Definitively, forest fires are not as bad as we thought.
Acknowledgements
The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 603498 (RECARE project), POSTFIRE Project (CGL2013-47862-C2-1 and 2-R) and POSTFIRE_CARE Project (CGL2016-75178-C2-2-R) sponsored by the Spanish Ministry of Economy and Competitiveness and AEI/FEDER, UE. This paper was written as a result of the collaboration that was initiated due to the COST ActionES1306: Connecting European Connectivity research.
Тематска област:
Екологија шума и очување природних ресурса
Датум:
10.09.2017.
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