Soil Erosion Produced by Fire

Soil Erosion Produced by Fire

Example: Chaparral Biomes

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Cameron Wuethrich

Chaparral

Regions are defined as:

"scrubland plant communities composed of broad-leaved evergreen shrubs, bushes, and small trees usually less than 2.5 metres"

Chaparral regions in the southwest US have displayed extensive increases in post-burn runoff and erosion

• Fires disrupt layers of "non-wettable" soils found in Chaparral, causing them to sink lower into the soil than normal and leaving easily wettable soils on the top
• The wettable soils on top layers are more easily disrupted by precipitation and runoff, hindering vegetation growth and creating a lack of vegetation cover which ultimately leads to extreme debris slides

Soil eventually recovers and grows enough vegetation to create another fire

Fire disrupts soil properties

Possible Fire & Erosion Cycle

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Case Study:

"Effect of prescribed fire on soil properties and soil erosion in a Mediterranean mountain area"

Sources

Fonseca et al., 2017

Precipitation causes erosion of disrupted soil

Eroded soil causes debris slides

and harms landscapes

• Fonseca, F., de Figueiredo, T., Nogueira, C., & Queirós, A. (2017). Effect of prescribed fire on soil properties and soil erosion in a Mediterranean mountain area. Geoderma, 307, 172–180. https://doi.org/10.1016/j.geoderma.2017.06.018
• Goudie, A. (2019). The human impact on the natural environment: Past, present, and future. Wiley-Blackwell.

Prescribed Burns:

Erosion Risk & Reward

• We know that even low severity fires can impact soil health and cause erosion
• However, prescribed burns help prevent the high severity fires that create extreme soil erosion

• This study ultimately found that even their longest timeline of 36 months was not enough for soil to completely recover after a low-severity burn
• Despite this, many soil health factors recovered to pre-fire levels
• These findings mean that prescribed burns may be worthwhile mitigation measures

Background

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Humans, Fire, and Soil

Soil Erosion from fires are a global phenomenon made worse by warming climates and human encroachment into highly vegetated areas

What is Soil Erosion?

• Soil Erosion is commonly defined as the degradation of the upper layer of soil
• Fires commonly increase soil erosion rates as they destroy vegetation and leave the upper layers of soil overexposed, harming the growth of new plants and allowing for greater runoff

Examples of soil erosion caused by fires

Sidenote:

Fire & Soil Quality

• Low severity fires can be beneficial to agriculture as low-temperature burning rapidly releases nutrients from soils
• Ash from fires can also protect against erosion, but not sufficiently in the long term
• Any fire will ultimately contribute to some amount of nutrient loss and soil erosion