Rebuilding Soil After a Fire

What a tough week it’s been in the North Bay. Following the devastating fires that have swept through large swaths of California, we’re all coming out of initial shock and moving through stages of grief and onto thoughts of rebuilding.

fire-2578857_640As a gardener, in the moments I’m not mourning all the tangible things people have lost, I’m thinking of the forest and soil ecosystems and wondering: what happens next?

I’ve learned that once the fires calm down, the forest service will move into affected areas and begin a process called a BAER or Burned Area Emergency Response. After assessing immediate damage and potential threats to safety and water quality, they will examine other long-term yet less immediately threatening impacts.

Two major consequences of fires in our woods are erosion and destruction of the soil leading to an inability to hold water, or, hydrophobicity. Erosion can start to occur after the forest floor is left bare from fire. Any subsequent rainstorms will leave the forest floor susceptible to cascades of water with no leaf litter or plant roots to slow and absorb the flow. If water is left to run freely and quickly down hills, it won’t have a chance to be absorbed into the soil.

arid-21799_640Problems related to rain runoff are exacerbated by soil that becomes hydrophobic. This happens during extreme fires when plant matter burns off and released gasses that penetrate the soil surface, eventually cooling and coating the soil in a waxy layer that repels water.

There are, however, tried-and-true steps to preventing erosion and promoting soil health that can be taken after destruction from fire. Here are some key steps.

  • Re-Seed grass in affected areas
  • Mulch to create a permeable layer and foster seed germination
  • Cut down dead trees and lay them down to create terraces on steep hillsides
  • Create dams with straw bales in steep areas

grass-2406908_640For additional resources, check out the following publications: