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Soil Water RepellencyWhat happens when water does no infiltrate in soils?
Antonio JordánMED_Soil Research Group, University of Seville
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Correlation between soil properties and hydrological response in El Algibe range, SW Spain
Zavala and Jordán (2008)
Tp Tr Pr Runoff rate Runoff coef. Infiltration rate SSIR Tr-TpLitter -0.48 - - - - - - -Plant cover -0.48 -0.45 -0.47 - - - - -Soil depth 0.56 0.35 0.36 - - - - -Organic C -0.44 - - - - - - -Coarse elements -0.54 -0.38 -0.39 - - - - -Sand - 0.73 0.74 -0.77 -0.77 0.77 0.78 0.84Clay - - - 0.40 0.40 -0.40 -0.43 -0.54Bulk density 0.50 0.68 0.68 -0.63 -0.63 0.63 0.67 0.54
Correlation between soil properties and hydrological response in El Algibe range, SW Spain
Zavala and Jordán (2008)
Tp Tr Pr Runoff rate Runoff coef. Infiltration rate SSIR Tr-TpLitter -0.48 - - - - - - -Plant cover -0.48 -0.45 -0.47 - - - - -Soil depth 0.56 0.35 0.36 - - - - -Organic C -0.44 - - - - - - -Coarse elements -0.54 -0.38 -0.39 - - - - -Sand - 0.73 0.74 -0.77 -0.77 0.77 0.78 0.84Clay - - - 0.40 0.40 -0.40 -0.43 -0.54Bulk density 0.50 0.68 0.68 -0.63 -0.63 0.63 0.67 0.54
WDPT -0.43 -0.79 -0.78 0.70 0.70 -0.70 -0.73 -0.73
Wettable soil: infiltration rate
decreases during wetting due to
the saturation of the upper layer
Water-repellent soil
Infiltration
rate
Time
INCREASING INTEREST: FIRST STEPSAuthor/s ReviewMolliard, M. 1910. De l’action du Marasmius oreades Fr. sur la vegetation. Bulletin of the Society of Botany t.57
s.4, t.1 (1): 62-69. Bayliss, J.S. 1911. Observations on Marasmius oreades and Clitocybe gigantea as parasitic fungi causing fairy
rings. Journal of Economic Biology 6:111-132.Shantz, H.L., Piemeisel, R.L.
1917. Fungus fairy rings in eastern Colorado and their effect on vegetation. Journal of Agricultural Research 11:191-245
Jamison, V.C. 1943. The slow reversible drying of sandy surface soils beneath citrus trees in central Florida. Soil Science Society of America Journal 7:36-41.
Jamison, V.C. 1946. Resistance to wetting in the surface of sandy soils under citrus trees in Central Florida and its effect upon penetration and the efficiency of irrigation. Soil Science Society of America Proceedings 11:103-109.
Jamison, V.C. 1946. The penetration of irrigation and rain water into sandy soils of central Florida. Soil ScienceSociety of America Journal 10:25-29.
Wander, I.W. 1949. An interpretation of the cause of resistance to wetting in Florida soils. Science-New Series 110. Pp: 299-300.
Van’t Woudt, B.D., 1959. Particle coatings affecting the wettability of soils. Journal of Geophysical Research 64:263-267.Adam, N.K. 1963. Principles of water-repellency. In: Moillet, J.L. (ed.). Water Proofing and Water-Repellency.
Elsevier. London.Bond, R.D., Harris, J.R. 1964. The influence of the microflora on physical properties of soils. I. Effects associated with
filamentous algae and fungi. Australian Journal of Soil Research, 2:111-122.DeBano, L.F., 1966. Formation of non-wettable soils involves heat transfer mechanism. Research Notes PSW-132.
Pacific Southwest Station.Adams, S., Strain, B.R., Adams, M.S.
1969. Water-repellent soils and annual plant cover in a desert scrub community of southeastern California. Symposium on Water-repellent Soils, Proceedings. University of California. Riverside, CA. Pp: 289-295.
INCREASING INTEREST: REVIEWS
Author/s ReviewMüller, K., Deurer, M. 2011. Review of the remediation strategies for soil water repellency.
Agriculture, Ecosystems and Environment, 144 (1), pp. 208-221. Blanco-Canqui, H. 2011. Does no-till farming induce water repellency to soils? Soil Use and
Management, 27 (1), pp. 2-9. Rillig, M.C. 2005. A connection between fungal hydrophobins and soil water
repellency? Pedobiologia, 49 (5), pp. 395-399. Dekker, L.W., Oostindie, K., Ritsema, C.J.
2005. Exponential increase of publications related to soil water repellencY.Australian Journal of Soil Research, 43 (3), pp. 403-441.
DeBano, L.F. 2000. Water repellency in soils: A historical overview. Journal of Hydrology, 231-232, pp. 4-32.
Doerr, S.H., Shakesby, R.A., Walsh, R.P.D.
2000. Soil water repellency: Its causes, characteristics and hydro-geomorphological significance. Earth Science Reviews, 51 (1-4), pp. 33-65.
Terry, J.P. 1992. The effects of water repellency in soils on erosion processes.Swansea Geographer, 29, pp. 89-97.
INCREASING INTEREST: PUBLICATIONS
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Articles Other documents
Ritsema and Dekker (Eds.), Special issue, Journal of Hydrology 231-232 (2000)
Review by Doerr, Shakesby and Walsh, Earth-ScienceReviews 51 (2000)
Jordán, Zavala, Mataix-Solera and Doerr (Eds.), Special issue, Catena 108 (2013)
WHAT IS SOIL WATER REPELLENCY?
Water-repellent sand Wettable sand
Water-repellent soils do not wet readily when in contact with water.
Thus, a water-repellent soil layer may offer strong resistance to theinfiltration of water accumulated on the soil surface or in the upperwettable soil layer during periods of time that may range from a fewseconds to hours, days or weeks
CONSEQUENCES OF SOIL WATER REPELLENCY
Geomor-phology
Plantnutrition
Hydrology
• Decreased infiltration rate
• Enhanced surface flow
• Preferential flow paths
• Increased erosion risk
• Leaching of nutrients
• Competition strategies
Other conse-quences
• Increased aggregate stability
• Increased carbon sequestration
= 0
< 0
Most liquids have a surface tension between 20 and 40 10-3 N m-1 at 20 oC.
But the surface tension of water is exceptionally high: 72.75 10-3 N m-1.
What is soil water repellency?
Mineral particle
Water molecules adhere to most natural surfaces, because these surfaces are positive or negativevely charged and attract the opposite poles of water molecules.
Most of mineral sufaces are wettable…
WHAT IS SOIL WATER REPELLENCY?
Amphiphilic molecules havehydrophilic and hydrophobic ends. A ped covered by an
organic matter layer
… but organic may not
Hydrophilic end Hydrophobic end
Amphiphilic molecule
The surface of aggregates is
hydrophobic due tothe orientation of
the organic moleculecover
Organic moleculesflip due to the
interaction withwater
The surface becomeshydrophilic and
water can spread over it
Modified from Doerr, Shakesby and Walsh (2000)
ORIGIN OF HYDROPHOBIC SUBSTANCES
García-Moreno (2014)
Deciduous trees
Evergreen trees
Organic substances
transformed and/or
concentrated by fire
Organic compounds
released during decomposition
Exudates of roots
Resins and waxes from plant leaves
Substances released by fungi and bacteria
WHERE HAS SOIL WATER REPELLENCY BEEN OBSERVED?
A few decades ago, inhibition of water infiltration was considered exceptional by most soil scientists.
But currently, SWR has been observed in different soils under different climates and vegetation types worldwide.
ONLY IN GOLF
COURSES?
Despicable me 2 minions by Design Bolt
CLIMATE: MOISTURE AND TEMPERATURE
Modified from Dekker et al. (2000)
Volumetric water content
Soil depth
Wettable
Water-repellent
We know that soil moisturecontent is highly relatedwith SWR
CLIMATE: MOISTURE AND TEMPERATURE
González-Peñaloza, Zavala, Jordán, Bellinfante, Bárcenas-Moreno, Mataix-Solera, Granged, Granja-Martins and Neto-Paixão (2013)
OVEN-DRYING DAYS (120 oC)
WDPT (s)
CLIMATE: MOISTURE AND TEMPERATURE
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Intensity of soil water repellency (EPT class)
Pines
Winter Summer
Zavala, González and Jordán (2009)
CLIMATE: MOISTURE AND TEMPERATURE
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Intensity of soil water repellency (EPT class)
Cork oaks
Winter Summer
Zavala, González and Jordán (2009)
CLIMATE: MOISTURE AND TEMPERATURE
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Intensity of soil water repellency (EPT class)
Eucalypts
Winter Summer
Zavala, González and Jordán (2009)
Atmosphere
Smoke:
• Water and other gases
• Solid particles
85-90% of thermal energy is
lost upwards with smoke
10-15% of thermal
energy is transmitted
following a hot-to-cold
gradient in depth
Soil
Volatile organic
substances
condense coating
the surface of
“cold” soil
particles
WHAT HAPPENS DURING BURNING?
FIRE-INDUCED SOIL WATER REPELLENCY
Litter
Ash layer
Water-repellent layer
Wettable layer
Water-repellent
soil
Lowseverity
High severity
Very highseverity
Very high severity
Lowseverity
Wettable soil
High severity
Picture: Artemi Cerdà
Upper soil layer with ash and charred litter
Water-repellent soil layer
Water drops
EFFECT OF BURNING TEMPERATURE ON SWR
(*) Temperature treatments during different time intervals
Temperature (*) Process Reference
100 – 150 oC No changes Zavala et al. (2010)
<175 oC No changes Doerr et al. (2000)
175 – 200 oC Induction of SWR Doerr et al. (2000)
200 oC Induction of SWR DeBano and Krammes (1966)
200 – 300 oC Induction of SWR DeBano et al. (1979); Robichaud and Hungerford (2000)García-Corona et al., (2004)Mataix-Solera and Guerrero (2007)
250 – 300 oC Attenuation of SWR Zavala et al. (2010)
270 – 400 oC Destruction of SWR Robichaud and Hungerford (200)Zavala et al. (2010)
400 – 450 oC Destruction of SWR Zavala et al. (2010)
480 – 540 oC Destruction of SWR DeBano and Krammes (1966)
600 oC Extreme SWR DeBano and Krammes (1966)
800 oC Attenuation of SWR DeBano and Krammes (1966)
900 oC Destruction of SWR DeBano and Krammes (1966)
EFFECT OF BURNING TEMPERATURE ON SWR
The effects of burning on SWR can be highly variable, as fires caninduce orenhance it after moderately severe burning andreduce pre-existing hydrophobicity after highly
severe burning.
The intensity of fire-induced SWR depends mostly on the amount and type of burnt organic matter, temperatures reached and duration of heating and the amount of oxygen available during burning.
EFFECT OF BURNING TEMPERATURE ON SWR
Zavala, Granged, Jordán and Bárcenas-Moreno (2010)
Soil samples of eucalypt forests from Spain, Mexico and Australia heated at different temperatures during 40 minutes
100-150 oC 250-300 oC 400-450 oC
Temperature (oC)
Depth (mm)
Water content 5-10%
Water content 20-25%
EFFECT OF BURNING TEMPERATURE ON SWR
Zavala, Granged, Jordán and Bárcenas-Moreno (2010)
Soil samples of eucalypt forests from Spain, Mexico and Australia heated at different temperatures during 40 minutes
100-150 oC 250-300 oC 400-450 oC
WDPT (s)
Depth (mm)
Water content 5-10%
Water content 20-25%
EFFECT OF BURNING TEMPERATURE ON SOIL WATER REPELLENCY
Jordán, Zavala, Mataix, Nava and Alanís (2011)
Water repellency in soils from Mexican fir forests after different burning intensity and durations
WDPT classes:
RE-ESTABLISHMENT OF ORIGINAL SOIL WATER REPELLENCY IN THE POSTFIRE: IN MONTHS
Zavala, Jordán, Gil, Bellinfane and Pain (2009)
RE-ESTABLISHMENT OF ORIGINAL SOIL WATER REPELLENCY IN THE POSTFIRE: IN YEARS
Granged, Zavala, Jordán and Bárcenas-Moreno (2011)
Soil WR may be re-stablished after burning, althoughorganic matter content stayed below initial value.
HOW MUCH ORGANIC MATTER IS IMPORTANT
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PT
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Erica arborea
Zavala and Jordán (2009)
Positive correlationsScholl (1975)Singer and Ugolini (1976)Rodríguez-Alleres et al. (2007)Zavala and Jordán (2009)
SURE?
Contradictory results depending on the type of vegetation or land useJordán et al. (2009)Schnabel et al. (2013)Zavala and Jordán (2009) Zavala et al. (2014)
Negative, low or non significant correlationsDeBano (1981)Jungerius and de Jong (1989)Wallis et al. (1990)Ritsema and Dekker (1994)Scott (2000)
Purple monsters by Jojo Mendoza
HOW MUCH OR HOW PRETTY?
Zavala, González and Jordán (2009)
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Cork oak Eucalypt Pine
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Heath Olive tree
DIFFERENT PLANT RESIDUES INDUCE DIFFERENT SEVERITIES OF SOIL WATER REPELLENCY
Zavala and Jordán (2009)
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Erica australis Erica arborea Quercuscoccifera
Genistatridentata
Rhododendrumponticum
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Wettable Slight water repellency Strong water repellency
Severe water repellency Extreme water repellency
Species Water-repellent samples Reference
Mediterranean heathland 96% (a) Jordán et al. (2010)
Mediterranean heathland 98% (b) Jordán et al. (2010)
Calluna vulgaris 80% Martínez-Zavala & Jordán-López (2009)
Erica arborea 87% Martínez-Zavala & Jordán-López (2009)
Erica australis 87% Martínez-Zavala & Jordán-López (2009)
Erica australis 100% (c), 100% (d) Zavala et al. (2009b)
Eucalyptus globulus 100% (c), 100% (v) Zavala et al. (2009b)
Juniperus oxycedrus 5% Mataix-Solera et al. (2007)
Olea europea 43% (c), 60% (d) Zavala et al. (2009b)
Pinus halepensis 30% Mataix-Solera et al. (2007)
Pinus halepensis 74% Arcenegui et al. (2008)
Pinus pinaster 97% (c), 100% (d) Zavala et al. (2009b)
Quercus coccifera 40% Mataix-Solera et al. (2007)
Quercus coccifera 88% Gimeno-García et al. (2011)
Quercus ilex 95% (e) Cerdà et al. (1998)
Quercus lusitanica 40% Martínez-Zavala & Jordán-López (2009)
Quercus suber 77% (c), 77% (d) Zavala et al. (2009b)
Rhododendron ponticum 73% Martínez-Zavala & Jordán-López (2009)
Rosmarinus officinalis 0% Gimeno-García et al. (2011)
Rosmarinus officinalis 5% Mataix-Solera et al. (2007)
Proportion of water-repellent samples (WDPT > 5 s) under different species from unburned areas reported by different authors in Spain. (a) 0-2 cm depth, field conditions; (b) 0-2 cm depth, laboratory conditions; (c) winter; (d) summer; (e) WDPT > 60 s.
INFLUENCE OF VEGETATION IN UNBURNED SOILS
INFLUENCE OF VEGETATION IN BURNED SOILS
Species Water-repellent samples Reference
Mediterranean heathland 43% (a) Jordán et al. (2010)
Mediterranean heathland 98% (b) Jordán et al. (2010)
Herbaceous vegetation 5% Zavala et al. (2009a)
Pinus halepensis 21% Bodí et al. (2013)
Pinus pinea 100% Zavala et al. (2009a)
Pinus halepensis 33% Arcenegui et al. (2008)
Quercus coccifera 0% Gimeno-García et al. (2011)
Rosmarinus officinalis 100% Gimeno-García et al. (2011)
Shrubland 80% Zavala et al. (2009a)
Proportion of water-repellent samples (WDPT > 5 s) under different species from burned areas reported by different authors in Spain. (a) 0-2 cm depth, field conditions; (b) 0-2 cm depth, laboratory conditions; (c) winter; (d) summer; (e) WDPT > 60 s.
SWR (unburned soils)
Pines, eucalypts, holmoaks, heaths
Olives, cork oaks, Galloaks, Kermes oaks
Cedars, rosemary, grasslands
SWR (burned soils)
Pinus pinea, rosemary, heaths
Shrubland, Pinushalepensis
Kermes oaks, grasslands
INFLUENCE OF VEGETATION IN SOIL WATER REPELLENCY
Vegetation type pH Organic
carbon
(%)
Sand
(%)
Persistence of WR
(LogWDPT)
Intensity of WR
(contact angle, o)
Shrubland 4.9 ± 0.5 a 1.3 ± 0.3 b 88.1 ± 4.5 c 1.3 ± 0.5 b 102.5 ± 22.8 b
Sparse herbs 4.9 ± 0.5 a 0.3 ± 0.1 a 81.9 ± 5.0 b 0.4 ± 0.3 a 68.7 ± 17.7 a
Pine forest 6.1 ± 0.5 b 3.9 ± 0.6 c 61.4 ± 6.9 a 2.2 ± 0.6 c 131.4 ± 32.9 c
0-3 cm depth samples from burned soils under different vegetation types.Within a column values followed by the same letter do not present significant differences (p<0.05).
Zavala, González and Jordán (2009)
INFLUENCE OF VEGETATION IN SOIL WATER REPELLENCY
Jordán, Álvarez-Romero, González-Pérez, Zavala, González-Vila. Coppola (2012)
Different species caused different WR severitiesin the first centimetres of soil
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Ischia (Castanea, Acacia) Cervinara-1 (Castanea)
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Lago Laceno-2 (Pinus) Roccamonfina (Pinus)
Roccamonfina (Castanea)
INFLUENCE OF VEGETATION IN POST-FIRE SWR
WDPT Etanol (%)WDPT afterextraction
of lipids
Ethanol (%) 0.685p > 0.05
p > 0.05
pH -0.593 p > 0.05 p > 0.05
EC p > 0.05 p > 0.05 0.987
Extractable organic C 0.361 0.514 p > 0.05
Humic acids p > 0.05 0.500 0.811
Fulvic acids p > 0.05 0.515 p > 0.05
Lipids p > 0.05 0.425
N-Kjeldahl p > 0.05 0.414 p > 0.05
Jordán, Álvarez-Romero, González-Pérez, Zavala, González-Vila. Coppola (2012)
Positive correlation betweenWDPT and organic C%, but
not organic matterconstituents
Positive correlationbetween intensity of WR
and organic C, lipids, humicand fulvic acids
Good correlation only afterextraction of lipids: lipidsare more important than
humic acids
INFLUENCE OF VEGETATION IN SOIL WATER REPELLENCY
Quercus suber Pteridium aquilinum Pinus pineaSieve fraction (mm) 1-2 0.25-1 0.05-0.25 <0.05 1-2 0.05-0.25 <0.05 1-2 0.05-0.25 <0.05
WR Severe Severe Severe Severe Strong Strong Severe Strong Slight StrongOrganic matter (%) 35.0 26.8 37.2 46.9 6.2 17.0 27.4 2.9 7.3 21.0
C11 XC12 (lauric acid) X X X
C13 X XC14 (myristic acid) X X X
C15 X XC16 (palmitic acid) X X X X X X X X X X
C17C18 (stearic acid) X
WR linked to C2n long-chained lipids.Hydrophobic organic substances may be inherited soil material.
Jiménez-Morillo, González-Pérez, Jordán, Zavala, de la Rosa, Jiménez-González and González-Vila (2014)
Water-repellent dry soil
Ponded waterHydrostatic pressure breaks SWR
Lateral / hortonian flow
Wet soil
DEVELOPMENT OF UNEVEN WETTING FRONTS IN WATER-REPELLENT SOILS
Thin surface wettable layer
Deep wettable layer
Hydrophobic layer
Banksia attenuata
Banksia woodlands on sand dunes
WHY DO PLANTS INDUCE SOIL WATER REPELLLENCY? AN HYPOTHESIS
WHY DO PLANTS INDUCE SOIL WATER REPELLLENCY? AN HYPOTHESIS
Rainfall
Water infiltrates through macropores (dead root channels,
cracks, …)
INFLUENCE OF SOIL MINERALOGY ON SOIL WATER REPELLENCY
Soil type Lithology Reference
Acid soils Schists, slates Granged et al. (2011a)
Acid sandstone Granged et al. (2011b)
Jordán et al. (2008)
Zavala et al. (2009b)
Zavala et al. (2009c)
Sand dunes Zavala et al. (2009a)
Calcareous soils Limestone Arcenegui et al. (2007)
Arcenegui et al. (2008)
Bodí et al. (2013)
Cerdà and Doerr (2007)
Mataix-Solera and Doerr (2004)
Mataix-Solera et al. (2007)
Calcareous sandstone Arcenegui et al. (2008)
Marly limestone and marls Arcenegui et al. (2008)
Bodí et al. (2013)
Badía et al. (2013)
Gordillo-Rivero et al. (2013)
Calcareous clay Jordán et al. (2008)
Calcareous colluvium Badía et al. (2013)
INFLUENCE OF SOIL MINERALOGY ON SOIL WATER REPELLENCY
Dlapa et al. (2004)
Montmorillonite has limited effects or increases soil WR
Kaolinite reduces soil WR
STRUCTURE AND TEXTURE
Fine texture
Medium texture
Coarsetexture
Leonard F. DeBano (US Forest Service): “Coarsely-textured soils are more prone to develop soil water repellency”
STRUCTURE AND TEXTURE
Fine texture
Medium texture
Coarsetexture
?Is this true or the first studies
were biased?
Leonard F. DeBano (US Forest Service): “Coarsely-textured soils are more prone to develop soil water repellency”
Mataix-Solera, Arcenegui, Zavala, Pérez-Bejarano, Jordán, Morugán-Coronado, Bárcenas-Moreno, Jiménez-Pinilla, Lozano, Granged and Gil (2014)
SIZE MATTERS
Soil WR of sand sieve fractions during a 10-days period of air-drying for different proportions of hydrophobic organic matter (stearic acid)
González-Peñaloza, Zavala, Jordán, Bellinfante, Bárcenas-Moreno, Mataix-Solera, Granged, Granja-Martins, Neto-Paixão (2013)
BUT IN SOILS WITH SIMILAR TEXTURE, PARTICLE SIZE IS NOT THE ONLY IMPORTANT THING
Zavala, González-Peñaloza and Jordán (2009a)
BUT IN SOILS WITH SIMILAR TEXTURE, PARTICLE SIZE IS NOT THE ONLY IMPORTANT THING
Persistence of WR(WDPT test)
Intensity of WR(ethanol test)
Species Winter Summer Winter Summer
Pine ** *** ** ***
Cork oak * * * *
Eucalyptus *** *** ** ***
Heath * * * *
Olive tree * ** * **
All species ** *** ** ***
Mann-Whitney U test p-values (F/C): * (p>0.001), **(p≤0.001), ***(p≤0.0001).
Zavala, González-Peñaloza and Jordán (2009b)
There are other important factors like climate or vegetation type
THE RELATION BETWEEN TEXTURE AND WATER REPELLENCY MAY VARY WITH SCALE OF WORK
Zone B SD p-value R2
All zones (4) Interception -0.343 1.150 NS 0.254
Clay (%) 0.805 0.233 *
Soils below fir forest in the Tancitaro Volcano Interception -80.970 14.524 ** 0.793
Sand (%) 1.277 0.218 **
p-values: * (p≤0.01), ** (p≤0.001).
Jordán, Zavala, Nava and Alanís (2009)
WATER REPELLENCY MAY VARY BETWEEN AGGREGATES
Low severily burned Mexican volcanic soils
Jordán, Zavala, Mataix, Nava and Alanís (2011)
WATER REPELLENCY MAY VARY BETWEEN AGGREGATES
Low severily burned Mexican volcanic soils
Jordán, Zavala, Mataix, Nava and Alanís (2011)
WATER REPELLENCY MAY VARY BETWEEN AGGREGATES
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LB-B
2006
2007
2008
2009
2010
2011
LB-U
2006
2007
2008
2009
2010
2011
T1-B2006
2007
2008
2009
2010
2011
T1-U
2006
2007
2008
2009
2010
2011
T2-B
2006
2007
2008
2009
2010
2011
T2-U
2006
2007
2008
2009
2010
2011
Fire-induced SWR in sieve fractions. Codes: CF (Cortes de la Frontera), JF (Jimena de la Frontera), LB (Los Barrios), T1 (Tarifa), T2 (Tarifa); U (burnt), B (unburnt).
Jordán, Gordillo-Rivero, García-Moreno, Zavala, Granged, Gil, Neto-Paixão (2014)
Very thin dark ash layer after a wildfire in a pine woodland, Huelva, Spain (2004). Photo: Lorena M. Zavala
Depending on fireseverity, vegetationtype and density orsoil litter, different
types and amounts of ash may be produced.
Moderately thick ash and litter alter after a wildfire in a cork oak forest, Huelva, Spain (2004)Photo: Lorena M. Zavala
Very thick ash layer after a wildfire in a pine forest in Gorga, Alicante, Spain (2011)Photo: Antonio Jordán
Thick layer of white and black ash after a prescribed fire in a shrubland, Almadén de la Plata, Spain (2012)
ASH EFFECTS ARE IMPORTANT IN THE SHORT TERM
Ash may represent a protection for soils versus erosion risk and runoff generation, although ash layers are highly unstable and may be rapidly removed by wind or runoff
ASH WATER REPELLENCY
WDPT Ash and needlecovered ground
Ash cover only(needles removed by hand)
Bare ground(needles removed by hand and ashbrushed away)
Ash Soil Ash Soil Ash Soil
Mean 0.37 4.67 0.41 4.77 0.39 4.53
SD 0.23 1.53 0.26 1.49 0.29 1.34
WDPT (s) values for the top of the ash layer and on the mineral soil surface after removal of ash
Wettability of ash may be very different of soil wettability
modified from Cerdà and Doerr (2006)
ASH REPELLENCY VARIES WITH SPECIES AND BURNING TEMPERATURE
Different degrees of WR may be found after a wildfire
Bodí, Mataix-Solera, Doerr and Cerdà (2011)
ASH REPELLENCY VARIES WITH SPECIES AND BURNING TEMPERATURE
Water repellency (WDPT; s) of ash produced by the combustion of differentplant species after heating at different temperatures.
Bodí, Mataix-Solera, Doerr and Cerdà (2011)
ASH COLOUR IS A GOOD PREDICTOR OF WETTABILITY AT LOCAL SCALE
0
5
10
15
20
25
30
Black ash Dark grey ash Light grey ash White ash
Ash
thic
kne
ss(m
m)
1-day
15 days
Modified from Pereira, Cerdà, Úbeda, Mataix-Solera, Arcenegui and Zavala (2013)
Depending on fire severity, arange of ash colors betweenblack and white can beobserved after a wildfire
THE DARKER ASH, THE MORE HYDROPHOBIC CONDITION
Bodí, Mataix-Solera, Doerr and Cerdà (2011)
Relationship between colour (Munsell value) and water repellency (log WDPT) for different ash samples.
ASH REPELLENCY VARIES WITH ASH COMPOSITION
Relationship between ash water repellency (log WDPT) and the peak area ratio of absorbance bands assigned to aliphatic hydrocarbons (A3000–2800) and to calcite (A875).
Relationship between ash water repellency (log WDPT) and the peak area ratio of absorbance bands assigned to organic matter (carboxylic and aromatic groups, A1800–1200) and to calcite(A875).
Dlapa, Bodí, Mataix-Solera, Cerdà and Doerr (2013)
A WETTABLE ASH LAYER REDUCES THE RUNOFF COEFFICIENT
Zavala, Jordán, Gil, Bellinfante and Pain (2009)
A WETTABLE ASH LAYER REDUCES SOIL LOSS
Zavala, Jordán, Gil, Bellinfante and Pain (2009)
0
100
200
300
400
500
600
700
800
0 20 40 60 80 100
Soil
loss
(g
m-2
)
Runoff rate (%)
LITTER+ASH
ASH
BARE SOIL
ASH WATER REPELLENCY CONDITIONS SPLASH EROSION
WATER-REPELLENT ASH LAYERWETTABLE ASH LAYER
RAINDROP
DETACHED
PARTICLES
RUNOFF
Jordán et al. (Published online)
High intensity burn Low intensity burn
Stones increase the heating of subsurface soil layer
Lengthened residence of temperature peaks is alsoobserved
High degree of SWR
• Rock fragments protectsoil from heating
• Low or unaffected SWR isobserved
Heated soil
Cold soil
High intensity burn
Heating and smoulderingbetween neighbour stones may
occur in areas with high rock fragment cover
Uncontinuous gradient of heating is observed in areas
with low stone cover
FUTURE INSIGHTS
Background data
Implementation in regular soil analyses
Dynamics in the short- and long-term
Impacts at different scales Landscape Soil Intra-aggregate Molecular
Impact on connectivity of water and sediments
Geochemical markers
Ecological implications
Impacts on agricultural soils
Restoration and amelioration