Fire season along the West Coast of United States has been pretty amazing this year. Firefighters from all over the world have been flown in to assist with major fires from Washington to California. The massive fires take out buildings and infrastructure in addition to thousands of acres of grasses, shrubs, and trees. However, during these catastrophic events these forested ecoystems are often not totally destroyed. Part of this has to do with soil! For the International Year of Soil's September theme, we will explore how "Soils Protect the Natural Environment" in the context of wildfires in forests.
When forest fires occur, the soil temperature will raise a certain amount depending on the fuel present (amount of burning material), initial soil moisture, and the speed of the fire. In a fast moving fire with moist soils, you can have very little heating of soil. With minimal heating, the seedbank (seeds from plants in the area) can survive and regenerate after the fire. The plants help to reestablish the ecosystem and improve damage soil properties. These seeds are protected in the soil often for years until some sort of disturbance takes place!
Soil can also protect existing trees if the base or the roots are covered by it. The tissue that was protected by the soil (organic or mineral) and remained alive can resprout and grow again. In essence, the tree can go on living. This is seen in redwood forests where the parent tree may have been affected by fire (note: redwoods do a pretty darn good job resisting damage from fire due to high tannin and low resin content). The sprouting and growth of new trees from the base or roots of the parent tree creates what is commonly called a "fairy ring".
Soils can be severely affected by fires, but their sacrifice fortunately provides protection for the vegetation and seedbank present. This is one of many ways soils protect the natural environment, but one that is quite relevant given the state of our forests in the west!