Fire Effects on Soils and Water

Question 1

3 factors of fire effects on soil

Answer 1

1. Direct heating of soil from fire (radiative heat)
2. Removal/consumption of vegetation, litter, and duff
3. Development of hydrophobic soils

Question 2

Direct heating depends on:

Answer 2

• amount released during burning (higher intensity = more heating)
• duration heat system stays in one place (residence time); slow-moving/smoldering = more heating
• moisture content of soil (wetter soil = more heating)

Question 3

Fire impact on soil chemistry

Answer 3

Higher intensity = increased damage to soil microbes

Question 4

Legacy carbon

Answer 4

Fires are releasing legacy carbon into atmosphere from soil carbon sink
- higher fire frequency = more legacy carbon released
- fires have predominantly negative effect on soil carbon and nitrogen pools (more significant in high-severity fires, i.e. wildfire vs. prescribed/slash & burn)
- micronutrients increase, release of nutrients (potassium and calcium in needleleaf forests)

Question 5

Change in soil color

Answer 5

More color change = higher severity fire

Question 6

Rainsplash erosion

Answer 6

High-severity fires remove forest canopy and litter layer (expose mineral soil to rainfall)
- decreased interception, infiltration, and transpiration
- increased overland flow
- denser vegetation lowers risk of rainsplash erosion

Question 7

Hydrophobocity

Answer 7

Water-repellent layer of soil that prevents infiltration, derived from plant material burned during fire

Question 8

Effects on water

Answer 8

• increased water temp (direct heating, reduced shading as vegetation cover decreases)
• decreased water quality (erosion sediment enters streams, concentration of nutrients)