contrasted response of ash to wetting: The effects of ash type, thickness and rainfall events

After a wildfire the soil is covered by ash. Ash properties depend on vegetation type, amount of fuel and fire intensity. The ash layer controls the post-fire soil hydrologic response, but little is known about the effect of ash thickness and ash type on infiltration, which is relevant for post-fire...

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Bibliographic Details
Published in:Geoderma 2013-11, Vol.209, p.143-152
Main Authors: Leon, Javier, Bodi, Merche B, Cerda, Artemi, Badia, David
Format: Article
Language:English
Subjects:
Ashes
correlation
Covering
ecosystems
equations
fire intensity
Fraxinus americana
Fraxinus nigra
Freshwater
fuels
Hydrology
Infiltration
infiltration rate
Mathematical analysis
rain
Rainfall
rainfall simulation
Runoff
soil
Soil (material)
temporal variation
vegetation types
wildfires
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Summary:After a wildfire the soil is covered by ash. Ash properties depend on vegetation type, amount of fuel and fire intensity. The ash layer controls the post-fire soil hydrologic response, but little is known about the effect of ash thickness and ash type on infiltration, which is relevant for post-fire runoff and soil losses and for ecosystems rehabilitation and restoration. This paper analyses the role of i) ash type (black or white), ii) thickness (5, 15 and 30mm-thick) and iii) temporal variation (0, 15 and 40days) under three simulated rain events (55mm for 1h) on soil surface hydrology. The rainfall was simulated on 0.25m² plots, and time to ponding, runoff and runoff discharge were measured. The infiltration rates, the initial infiltration rate (f₀), the steady-state infiltration rate (fc), and the infiltration decay factor (k), were calculated and the Horton infiltration equation applied. The results show that soils covered with white ash doubled the runoff rates of soils covered with black ash. In general, runoff decreases as the ash thickness increases and the runoff decreases with the number of rainfall events after the fire in plots covered with white ash. Ponding time and k are positively correlated by the ash thickness and f₀ and fc are correlated by the rainfall events (in three runs). Ash type and ash depth are key factors on the soil hydrology after a wildfire.
ISSN:0016-7061
1872-6259
DOI:10.1016/j.geoderma.2013.06.018