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Impac o he mal shock on o es
soils a ec ed by i es o di e en
se e i y and ecu ence
Impac o de choques é micos sob e suelos o es ales a ec ados po incendios de di e en e
se e idad y ecu encia
Impac o de a amen os é micos en solos lo es ais a e ados po incêndios de di e en e
se e idade e eco ência
Lombao A.@, 11
[email p o ec ed]
Ba ei o A.1
Cancelo-González J.2
Ma ín A.1
Díaz-Ra iña M.1
@ Co esponding Au ho
1 Depa amen o
de Bioquímica del
Suelo, Ins i u o de
In es igaciones
Ag obiológicas de
Galicia (IIAG-CSIC).
P.O.Box 122. A da.Vigo
s/n. 15780 San iago de
Compos ela (A Co uña),
Spain.
2 Depa amen o de
Eda oloxía e Química
Ag ícola, Facul ad de
Fa macia, Uni e sidade
de San iago de
Compos ela. Campus
Vida. 15782 San iago de
Compos ela (A Co uña),
Spain.
ABSTRACT
The mal ea men s in he labo a o y we e conduc ed using unbu ned and bu ned samples o wo
soils a ec ed by low- o high se e i y i es in o de o s udy hei impac on o es s ecosys ems wi h
di e en i e egimes (se e i y, ecu ence). Soils samples we e hea ed in a u nace o 15 minu es a 50 ºC,
75 ºC, 100 ºC, 125 ºC, 150 ºC, 175 ºC, 200 ºC and 300 ºC o simula e di e en i e in ensi ies; he
p ocess was epea ed a e a 1 mon h incuba ion o he bu ned, ewe ed samples in o de o simula e
i e ecu ence. The soil empe a u e was measu ed wi h he mocouples a he su ace and 1 cm dep h.
The maximum empe a u e eached (Tmax) and he amoun o hea supplied o he samples (deg ee-hou ,
DH) we e calcula ed om he empe a u e- ime cu es. A o al o 128 empe a u e- ime cu es (4
soil ield samples x 8 hea ing empe a u es x 2 dep hs x 2 successi e hea ea men s) we e analyzed
and he es ima ion o se e al soil physical and chemical p ope ies (colo , mois u e con en , pH, o al
C, o al N, soluble C) was ca ied ou in he di e en soil ea men s. High-se e i y bu ning p o oked
signi ican changes on hese physical and chemical p ope ies, whe eas sligh modi ica ions o e en
no changes we e due o low-se e i y bu ning o soil hea ing unde labo a o y condi ions. The he mal
p ope ies exhibi ed a highe sensi i i y o he de ec ion o he i e egime impac han he physical
and chemical p ope ies. The esul s showed ha he empe a u e- ime cu es and de i ed pa ame e s
(slope, Tmax, DH) can be success ully used o quan i y he impac o he mal shocks a low and high
empe a u es and o e alua e he e ec o i e/hea ing ecu ence on o es s ecosys ems.
RESUMEN
Se ealiza on, en condiciones de labo a o io, di e sos a amien os é micos con mues as no quemadas y quemadas
de dos suelos a ec ados po incendios de al a y baja se e idad con el in de de e mina su impac o sob e ecosis emas
o es ales con di e en e égimen del uego (se e idad y ecu encia). Las mues as se quema on en una mu la du an e
15 minu os a 50 ºC, 75 ºC, 100 ºC, 125 ºC, 150 ºC, 175 ºC, 200 ºC y 300 ºC pa a simula di e en es in ensidades
del uego; as un mes de incubación de las mues as quemadas ehumec adas, se p ocedió a una segunda quema
pa a simula la ecu encia del uego. Se midió la empe a u a del suelo con e mopa es en la supe icie y a 1 cm
de p o undidad y, a pa i de las cu as de empe a u a- iempo, se calcula on la empe a u a máxima alcanzada
(Tmax) y la can idad de calo suminis ada a la mues a (g ados-ho a, GH). Se analiza on un o al de 128 cu as
de empe a u a- iempo (4 mues as de suelo x 8 empe a u as de calen amien o x 2 p o undidades x 2 a amien os
é micos consecu i os) y se ealizó la ca ac e ización ísica y química (colo , humedad, pH, C o al, N o al, C
soluble en agua) de las mues as de suelo some idas a los di e en es a amien os é micos. Las p opiedades ísicas y
químicas expe imen a on cambios signi ica i os como consecuencia del incendio de al a in ensidad y no se de ec a on
a iaciones as el impac o del incendio de baja se e idad y del quemado del suelo en condiciones de labo a o io.
Las p opiedades é micas mos a on una mayo sensibilidad que las p opiedades ísicas y químicas pa a de ec a
el impac o del égimen del uego. Los esul ados ob enidos demos a on que las cu as de empe a u a- iempo y
AUTHORS
Recei ed: 12.06.2015 Re ised: 22.06.2015 Accep ed: 23.06.2015
DOI: 10.3232/SJSS.2015.V5.N2.06
SJSS. SPANISH JOURNAL OF SOIL SCIENCE YEAR 2015 VOLUME 5 ISSUE 2
166
KEY WORDS
Low- and -high-
se e i y bu ning,
he mal shock,
empe a u e- ime
cu es, Tmax and
deg ees-hou ,
soil physical and
chemical p ope ies
PALABRAS
CLAVE
Quemado de baja
y al a se e idad,
a amien o é mico,
cu as empe a u a-
iempo, Tmax
y g ados ho a,
p opiedades ísicas y
químicas del suelo
PALAVRAS-
CHAVE
Queima de baixa
e al a in ensidade,
a amen o
é mico, cu as de
empe a u a- empo,
Tmax e g aus ho a,
p op iedades ísicas
e químicas do solo
los pa áme os de i ados (pendien e, Tmax, GH) pueden usa se sa is ac o iamen e pa a cuan i ica el impac o del
a amien o é mico a bajas y al as empe a u as y pa a e alua el e ec o de la ecu encia del uego/calen amien o
en los ecosis emas o es ales.
RESUMO
Realiza am-se ensaios de labo a ó io com di e en es a amen os é micos em amos as queimadas e não queimadas
de dois solos a e ados po incêndios de al a e baixa se e idade, pa a de e mina o seu impac o em ecossi emas lo es ais
sob di e en e egime de ogo (se e idade e eco ência). As amos as queima am-se na mu la du an e 15 minu os a
50 ºC, 75 ºC, 100 ºC, 125 ºC, 150 ºC, 175 ºC, 200 ºC e 300 ºC com o objec i o de simula di e en es in ensidades
de queima; após de um mês de incubação das amos as queimadas e umedecidas, oi ei a uma segunda queima pa a
simula a eco ência do ogo. A empe a u a do solo oi medida com e mopa es na camada supe io e a 1 cm de
p o undidade. A pa i das cu as de empe a u a- empo, oi calculada a empe a u a máxima alcançada (Tmax)
e a quan idade de calo o necida (g aus-ho a, DH). Analisa am-se um o al de 128 cu as de empe a u a- empo
(4 amos as de solo x 8 empe a u as de aquecimen o x 2 p o undidades x 2 a amen os é micos subsecu i os) e
ca ac e iza am-se as p op iedades ísicas e químicas (colo , umidade, pH, C o al, N o al, C solú el em agua) das
amos as de solo subme idas aos di e en es a amen os é micos. As p op iedades ísicas e químicas ap esen a am
al e ações signi ica i as com espei o à queima de al a in ensidade e não o am de ec adas a iações após o impac o
da queima de baixa se e idade e ambém não no que diz espei o ao aquecimen o do solo em condições de labo a ó io.
As p op iedades é micas mos a am uma maio sensibilidade que as p op iedades ísicas e químicas pa a a
de eccão do impac o do egime do ogo. Os esul ados ob idos mos am que as cu as de empe a u a- empo e os
pa âme os de i ados (penden e, Tmax, DH) podem se u ilizados sa is a o iamen e pa a a quan i ição do impac o
do a amen o é mico a baixas e al as empe a u as, e pa a a alia o e ei o da eco ência do ogo/aquecimen o nos
ecossis emas lo es ais.
1. In oduc ion
Fo es wild i es mainly con ibu e o he des uc ion o Medi e anean and A lan ic
ecosys ems and hese e en s a e p edic ed o inc ease, aided by a gene al wa ming and
d ying end, bu d i en p ima ily by socioeconomic changes, including u al depopula ion,
land abandonmen and a o es a ion wi h lammable species (Shakesby 2011). Wild i es,
as well as p esc ibed i es, p oduce impo an e ec s on soil, whose physical, chemical
and biological p ope ies a e mo e o less a ec ed depending on he ype o p ope y, i e
in ensi y o soil hea ing and pos - i e clima ic condi ions (Ce ini 2005). In gene al, soil
s uc u e is des oyed, and pH and a ailable nu ien s inc ease, while mic obial communi ies
(densi y, biomass and ac i i y) and o ganic C and N dec ease; he emaining C and N o ms
becoming mo e ecalci an o mic obial a ack (Nea y e al. 1999; Ca ballas e al. 2009;
Almend os and González-Vila 2012); in addi ion, colo soil a ia ions can also be de ec ed
a e high se e i y bu n (Ke e ings and Bingham 2000; Cancelo-González e al. 2014).
Changes in soil p ope ies associa ed wi h i e and soil hea ing in he i s cm o he op
laye can be ex eme depending on i e empe a u e and du a ion. The impac o p esc ibed
i es is ela i ely small compa ed o he subs an ial modi ica ions o wild i es; he hea
ans e o soil may explain he obse ed di e ences. Soil esponse can ange om posi i e
ansi o y sligh changes in low in ensi y p esc ibed i es (nu ien s a ailabili y inc ease)
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[ IMPACT OF THERMAL SHOCK ON FOREST SOILS AFFECTED BY FIRES OF DIFFERENT SEVERITY AND RECURRENCE ]
(Ba ei o e al. 2010; Ben o-Gonçal ez e al.
2012; Fon ú bel e al. 2012; Gómez-Rey e al.
2013) o nega i e long las ing, e en i e e sible,
soil quali y modi ica ions (physical, chemical
and biological deg ada ion), in medium- o high
in ensi y wild i es a ec ing sh ublands o o es
ecosys ems (Nea y e al. 1999; Ce ini 2005;
Díaz-Ra iña e al. 2012; Lombao e al. 2014).
Thus, he in ensi y and du a ion o bu ning
de e mine he combus ion o uels and he inpu
o hea o he soils and consequen ly he soil
eco e y a e i e. Al hough i e e ec s depend
on many ac o s such as soil cha ac e is ics,
soil-wa e condi ions, ege a ion ype, e c., he
changes caused in he soil quali y a e di ec ly
ela ed o i e in ensi y and i e esidence ime,
as well as ac o s de e mining he ansmission
o hea h ough he soil (mois u e, ex u e,
o ganic ma e con en , e c.) (Ma ín e al. 2009,
2012; Keeley 2009; Vega e al. 2013a, 2013b).
Su p isingly howe e , despi e i s in e es , he i e
se e i y is no conside ed in mos in es iga ions
conce ning bu ned o es soils.
In o de o p ope ly e alua e he damage caused
by i es on o es ecosys ems, he maximum
empe a u e eached and he ime ha he
hea ing emains should be measu ed, he la e
being conside ed he mos damaging ac o o
i e se e i y o soil (Nea y e al. 1999; Keeley
2009). Unde ield condi ions du ing he wild i e
e en s he empe a u es canno be eco ded,
and i is e y di icul o con ol i e in ensi y and
i e esidence ime in p esc ibed i es due o
i egula uel dis ibu ion and clima ic condi ions.
In con as , soil hea ing unde labo a o y
condi ions allows us o e alua e he he mal
se e i y by eco ding he maximum empe a u e
eached in he soil and he esidence ime o his
hea ing. Applying a ep esen a i e empe a u e
g adien ( empe a u e and du a ion) du ing
he soil hea ing, empe a u e- ime cu es
(hea ing-cu es), which can be de e mined
expe imen ally o p edic ed heo e ically, enable
he e ec o hea and hea du a ion on soil o be
de e mined (Molina and Llina es 2001; Mendes-
Lopes e al. 2003; Cancelo-González e al.
2012; Thomaz and Fachin 2014). In p inciple,
he measu emen o deg ee hou s, gi ing
in o ma ion on he amoun o deg ee o hea
p o ided o soil, can be also used o de e mine
he combined in luence o a gi en empe a u e
h eshold and he du a ion o empe a u e abo e
his h eshold (Busse e al. 2005). Howe e ,
s udies using his me hodology o e alua e he
e ec o he he mal shock a e limi ed o he
soil exchange complex using undis u bed soil
samples hea ed a 200 ºC and 400 ºC du ing a
long- ime pe iod (Cancelo-González e al. 2012,
2015). The e o e, esul s o hese labo a o y
expe imen s canno be ex apola ed o ield
condi ions whe e bo h soil hea ing empe a u e
and exposu e ime a e lowe .
Galicia and he No h o Po ugal a e he a eas
o Eu ope mos a ec ed by o es wild i es,
and wo ldwide hey a e amongs he a eas
wi h he g ea es numbe o i es pe hec a e
and inhabi an . In he las 42 yea s 250,000
o es i es we e egis e ed in Galicia, which
p oduced 1,711,000 ha o bu n su ace om
which 700,000 ha we e wooded su ace
(Ca ballas 2014), causing huge economic and
ecological damages ha p obably will be wo se
in he o eseeing scena io o clima e change.
Th oughou he las ew decades, his a ea
has been a ec ed by a change in i e egime
- empo al and spa ial- esul ing in a d ama ic
annual inc ease in he su ace bu ned by
wild i es due o human ac ions, changes in land
use, policies and clima ic i e isk. Soil s udies in
his empe a e humid zone ha e been ocused
on he e ec s o a single i e, dealing mainly wi h
he sho - o medium e m-impac o p esc ibed
i es o wild i es o di e en in ensi ies on soil
quali y (physical, chemical, biochemical and
mic obiological p ope ies); he na u al eco e y
o a wide ange o bu ned o es ecosys ems
unde di e en pos - i e clima ic condi ions
(Ca ballas e al. 2009; Ma ín e al. 2012;
Lombao e al. 2014); and, o a lesse ex en , on
he e icacy and e ec s o he implemen a ion
o pos - i e s abiliza ion and ehabili a ion
ea men s o minimize wild i e isk and o
mi iga e pos - i e soil e osion (Díaz-Ra iña e al.
2010a, 2012; Fon ú bel e al. 2012; Vega e al.
2013b; Ba ei o e al. 2014; Lombao e al. 2015).
Howe e , he e olu ion o bu ned soils wi h ime
and he cumula i e e ec s o successi e i es
on soil p ope ies ha e no been s udied. We
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168
hypo hesized ha p e ious exposi ion o high
empe a u es du ing wild i es, p esc ibed i es o
soil hea ing a labo a o y condi ions can al e he
soil quali y and hence he esis ance o u he
i e e en s. The aim o he p esen wo k is o
s udy he in luence o he mal ea men s unde
con olled condi ions on soil he mal, physical
and chemical p ope ies o o es soils wi h
di e en i e egimen (se e i y, ecu ence). The
opic is o g ea in e es in his empe a e humid
zone (Galicia, NW Ibe ian Peninsula) whe e he
mos dense and high uel load o es s ha e been
a ec ed by i es and cu en i e occu ence isk
is high.
2. Ma e ials and Me hods
2.1. Soil sampling and expe imen al design
Two Galician (NW Spain) soils o e acid ocks,
which a e ep esen a i e o he main sh ubland
ecosys ems a ec ed by i es in his empe a e
humid egion, we e selec ed o s udy. One soil,
which was a ec ed by a wild i e in Sep embe
2010 (1,700 ha o su ace a ec ed), was an
En isol de eloped o e me amo phic ocks
(phylli es) loca ed in Laza (Ou ense, L soil). The
dominan ege a ion was
E ica
spp.,
Vaccinium
my illus, P e ospa um iden a um, Cis us
spp.
wi h e o es ed
Pinus syl es is
(mean heigh o
1-1.60 m). The p e alence o black and whi e
ashes and he o al consump ion o he g ound
plan communi ies ( ege a ion and li e laye s)
sugges ed ha i e se e i y has been mode a e o
high in he s udy a ea (Díaz-Ra iña e al. 2012).
The o he soil, a ec ed by an expe imen al i e,
was a Humic Cambisol de eloped o e g ani e
loca ed in A Es ada (Pon e ed a, E soil) and
had ege a ion domina ed by go se:
Ulex
eu opaeus L.
and some
P e idium aquilinum
(L.)
Kuhn., Ulex gallii Planch., Daboecia can ab ica
(Huds.)
K. Koch
and
Pseudoa enha e um
longi olium Rouy.
The sh ub was cu six mon hs
be o e he bu ning and laid o e he soil o
acili a e i s consump ion and a o hea ans e
o soil. The a e o i e sp ead was slow (0.30-
0.33 m/min) and he soil empe a u e eached,
moni o ed wi h ch omel alumel he mocouples,
was mode a e a he mine al soil su ace (mean
153 ºC, ange 48-420 ºC) and low a 2 cm soil
dep h (mean 34 ºC, ange 22-43 ºC) (Fon ú bel
e al. 2012). A o al o 50 soil subsamples, o
abou 100 g each, we e collec ed immedia ely
a e he i e om he op laye (0-2 cm dep h)
o he A ho izon o he bu ned soil and mixed o
ob ain a ep esen a i e composi e soil sample.
Unbu ned samples om each zone loca ed nex
o he bu ned samples bu no a ec ed by he
i e we e also collec ed a he same dep h. The
soil was sie ed (< 2 mm), homogenized and
s o ed a 4 ºC un il he soil hea ing expe imen .
Unde labo a o y condi ions, he unbu ned and
bu ned samples o bo h soils we e subjec ed
o wo successi e he mal shocks by applying
a ep esen a i e empe a u e g adien
( empe a u e and du a ion) o he soil hea ing
p ocess in o de o simula e ield condi ions, wi h
an in e al o one mon h incuba ion be ween
he wo hea ea men s. The empe a u e- ime
cu es we e analyzed and he amoun o hea
supplied o he soils was calcula ed o each
he mal shock (a o al o 128 empe a u e-
cu es = 4 soil ield samples x 8 empe a u es
x 2 dep hs x 2 successi e hea ea men s). In
addi ion, measu emen s o di e en physical and
chemical soil p ope ies (colo , mois u e con en ,
pH, o al C, o al N, soluble C) we e ca ied ou
in he di e en soil ea men s. A scheme o he
expe imen design is shown in Figu e 1.
[ LOMBAO A., BARREIRO A., CANCELO-GONZÁLEZ J., MARTÍN A. & DÍAZ-RAVIÑA M. ]
SJSS. SPANISH JOURNAL OF SOIL SCIENCE YEAR 2015 VOLUME 5 ISSUE 2
169
2.2. Soil hea ing and incuba ion
The unbu ned and bu ned soil samples (4
samples) om bo h soils we e subjec ed o
8 di e en hea ing ea men s o simula e
di e en i e in ensi ies (50 ºC, 75 ºC, 100 ºC,
125 ºC, 150 ºC, 175 ºC, 200 ºC, 300 ºC) using
a mu le u nace. The lowe empe a u e o his
in e al has been chosen o ensu e ha he
e ec s o low in ensi y i es we e included in
he expe imen ; and he ambien empe a u e
(20 ºC) was also used as e e ence unhea ed
con ol. Soil subsamples con aining abou 200 g
o esh soil we e dis ibu ed in a laye o 2 cm
and placed in a me allic ay. A e eaching
he selec ed hea ing empe a u e in he mu le
u nace, he soil subsamples we e placed in
he o en and we e emo ed a e being kep
a he speci ic empe a u e o 15 minu es (1H,
i s hea ing ea men ). The eal empe a u e
eached by he soil was measu ed each minu e
wi h he mocouples in he sample a 1 cm dep h
and a he su ace. Each hea ed soil subsample
(a o al o 36 = 4 soils x 8 ea men s) was di ided
in o wo pa s; one pa was s o ed and used
o analysis, and he o he pa was ewe ed
wi h dis illed wa e o achie e 75-80% o ield
capaci y, e-inocula ed wi h o iginal esh soil a
1% and incuba ed in plas ic po s a labo a o y
condi ions (da k, 21 ºC) o 1 mon h (1Hi,
incuba ion ollowing 1H). A e soil incuba ion,
he samples we e di ided again in o wo pa s
and one o hem was subjec ed o he same
hea ing p ocess o simula e i e ecu ence
(2H, second hea ing ea men ; 2Hi, incuba ion
ollowing 2H ea men ), hus ob aining a o al o
144 di e en samples (4 soil ield ea men s x
9 hea ing empe a u es x 2 hea ing cycles x 2
incuba ions).
2.3. Tempe a u e- ime cu es and calcula ion o
deg ees-hou
The da a ob ained each minu e om he
he mocouples placed a di e en dep hs we e
used o build he empe a u e- ime cu es. The
exponen ial equa ion y= aebx was used o model
he empe a u e- ime cu es, whe e “a” is he
ascending slope and “b” is he empe a u e peak
eached by he soil, wo pa ame e s used o
de ine he cu e and o analyze he suscep ibili y
o he soil o hea ing. The da a i ing was ca ied
ou wi h O igin P o 8 so wa e. The empe a u e
da a eco ded du ing he soil hea ing we e used
o calcula e he deg ee hou s (DH) ha a ec
each sample as an es ima ion o he amoun o
hea supplied o he samples o he i e se e i y
Figu e 1. Scheme o he expe imen al design o he hea ing ea men . LU, Unbu ned L soil; LB, Bu ned L soil; EU, Unbu ned E
soil; EB, Bu ned E soil.
[ IMPACT OF THERMAL SHOCK ON FOREST SOILS AFFECTED BY FIRES OF DIFFERENT SEVERITY AND RECURRENCE ]
SJSS. SPANISH JOURNAL OF SOIL SCIENCE YEAR 2015 VOLUME 5 ISSUE 2
170
wi h he ollowing equa ion modi ied by Cancelo-
González e al. (2012), DH= Σ (Tx-Ti)/60, whe e
Tx is he empe a u e in ºC measu ed e e y
minu e and Ti is he ini ial empe a u e o he
sample ( oom empe a u e).
2.4. Soil analysis
The physical and chemical cha ac e iza ion o he
soil samples (mois u e con en , pH in wa e and
KCl, o al C con en , soluble C) was pe o med
ollowing he p ocedu es desc ibed in a p e ious
a icle (Lombao e al. 2015). The wa e soluble
C (WSC) was de e mined a e ex ac ion wi h
dis illed wa e (1:5 w/ ) a 20 ºC o 2 h; and he
ho wa e ex ac able C (HWC) a e ex ac ion
wi h dis illed wa e (1:5 w/ ) a 80 ºC o 24 h. The
o al soluble C in he ex ac s was measu ed by
oxida ion wi h dich oma e in an acidic medium.
The colo measu emen s we e pe o med in
quin uplica e wi h a po able spec opho ome e
(Konica Minol a CM-700d) equipped wi h CM-
S100w (Spec aMagicTM NX) so wa e as
p e iously desc ibed by Cancelo-González e
al. (2014) conside ing he CIELAB colo sys em.
Then he mean alues o he Ca esian (L*a*b*)
and cylind ical (L* C*ab hab) coo dina es we e
calcula ed. F om hem, only L* and hab showed
signi ican changes ollowing high empe a u e
s ess ( ield condi ions, labo a o y condi ions)
and we e he e o e conside ed in he p esen
s udy.
3. Resul s and Discussion
3.1. Physical and chemical p ope ies
The wo selec ed soils we e acid (pH in wa e
a ound 4) wi h a high o ganic ma e con en
(L soil, 35% mois u e le el, 23.4 g o al C kg-1,
1.1 g N kg-1, 700 mg soluble C kg-1; E soil, 40%
mois u e le el, 17.4 g o al C kg-1, 1.1 g o al
N kg-1, 589 mg soluble C kg-1) (Figu e 2). The
i e unde ield condi ions modi ied he soil
p ope ies; howe e , in line wi h p e ious s udies
pe o med in he same egion (Fe nández e al.
1997; P ie o-Fe nández e al. 1998; Ca ballas e
al. 2009; Ma ín e al. 2012), a di e en e ec
was obse ed depending on i e se e i y. The
passage o a high se e i y wild i e caused a
dec ease in he soil o ganic ma e con en and
he ela ed mois u e con en ( educ ions o 17%
in mois u e le el, 37% in o al C con en and
50% in soluble C) and an inc ease o soil pH (0.5
uni s); in con as , he p esc ibed i e p oduced
only signi ican changes in he labile ac ion o
he o ganic ma e (50% educ ion in soluble
C). Changes in colo pa ame e s we e also
obse ed as consequence o he i e (Figu e 3).
In he L soil samples he wild i e led o a signi ican
dec ease in ligh ness (L*) o 2.4-2.8 CIELAB uni s;
u he mo e, he di e ences in he L* pa ame e
be ween he bu ned and he unbu ned samples
in he a ea a ec ed by he wild i e we e no ably
highe han hose obse ed be ween he
unbu ned and he bu ned samples in he a ea
a ec ed by he p esc ibed i e, which could be
due o he i e se e i y. Likewise, a signi ican
di e ence (highe han 3 CIELAB uni s) appea s
be ween he L soil bu ned and unbu ned
samples in he colo one (hab, om 60.7 o 64.6)
whe eas only sligh di e ences we e obse ed
in he E soil. Di e ences in bu ning empe a u e
and du a ion can explain he esul s ob ained in
bo h expe imen al a eas. In he E soil, he low
soil empe a u es (a ound 153 ºC and 34 ºC
in he su ace and a 2 cm dep h, espec i ely)
measu ed unde ield condi ions did no p o oke
changes in mos soil p ope ies analyzed, while
in he L soil, d as ic changes in pH, o ganic
ma e pool and soil colo clea ly indica ed ha
he bu ning empe a u es had exceeded 400 ºC
(Fe nández e al. 1997; Ce ini 2005; Ma cos e
al. 2007).
[ LOMBAO A., BARREIRO A., CANCELO-GONZÁLEZ J., MARTÍN A. & DÍAZ-RAVIÑA M. ]
SJSS. SPANISH JOURNAL OF SOIL SCIENCE YEAR 2015 VOLUME 5 ISSUE 2
171
Figu e 2. Soil physical and chemical p ope ies (mean alue o he 8 di e en hea ing ea men s applied o each soil ± SE) in he
unbu ned (U) and bu ned (B) samples o wo s udied soils (L, soil a ec ed by a wild i e; E, soil a ec ed by a p esc ibed i e). C,
unhea ed con ol soil; 1H, i s hea ing; 1Hi, incuba ion ollowing 1H; 2H, second hea ing; 2Hi, incuba ion ollowing 2H.
[ IMPACT OF THERMAL SHOCK ON FOREST SOILS AFFECTED BY FIRES OF DIFFERENT SEVERITY AND RECURRENCE ]
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Figu e 3. Colo pa ame e s (L, ligh ness; hab, one o colo ; mean alue o he 8 di e en hea ing ea men s applied o each
soil±SE) o he unbu ned (U) and bu ned (B) samples o he wo s udied soils (L, soil a ec ed by a wild i e; E, soil a ec ed by
a p esc ibed i e). C, unhea ed con ol soil; 1H, i s hea ing; 1Hi, incuba ion ollowing i s hea ing; 2H, second hea ing; 2Hi,
incuba ion ollowing second hea ing.
As expec ed, he soil mois u e le el was modi ied
by he soil hea ing unde labo a o y condi ions,
a nega i e and signi ican ela ionship being
obse ed be ween he deg ee-hou alues
and he loss o mois u e con en (R = 0.8795,
p < 0.005, n = 96). In con as , no a ia ions
in he physical and chemical p ope ies (colo
pa ame e s, pH, o al C, o al N, soluble C) we e
de ec ed unde labo a o y condi ions in he
unbu ned and bu ned samples o bo h selec ed
soils as consequence o he he mal shock
in he empe a u es ange o 50-300 ºC (da a
no shown). The e o e, in o de o acili a e he
compa ison o da a, o each soil he mean alue
o he 8 di e en soil hea ing ea men s (± SE)
was calcula ed. The alues clea ly showed no
changes o sligh changes in soil pH and o al
C con en due o he successi e he mal shock
ea men s (C, unhea ed con ol; 1H, i s hea ing
ea men ; 1Hi, incuba ion ollowing 1H; 2H,
second hea ing; 2Hi, incuba ion ollowing 2H).
This beha io can be explained by he ac ha
he combus ion o he o ganic ma e occu ed a
highe empe a u es han hose in ou expe imen
( empe a u e measu ed wi h he mocouples 28-
255 ºC) (Díaz-Ra iña e al. 1992; Fe nández e
al. 1997; Almend os and González-Vila 2012).
Howe e , he soluble C showed a ia ions wi h
peaks a e he he mal shock, he changes
being mo e p onounced in he E soil ollowing
he i s soil hea ing e en (1H); and in he L
soil ollowing he second hea ing e en (2H).
These da a a e consis en wi h he indings o
se e al au ho s showing inc eases in he labile
C a e soil hea ing below 200 ºC (a ibu ed
o nu ien s p oduced by he dea h and lysis
o mic oo ganisms) and a u he dec ease
a e he incuba ion pe iod caused by he use
o his labile pool as sou ce o ene gy du ing
he eco e y o he mic obial popula ion (Díaz-
Ra iña e al. 1992; P okushkin and Toka e a
2007). The esul s seem o sugges ha , despi e
o he low alues o he Tmax eached by he
soil samples, somehow he successi e he mal
shocks can p o oke changes in he quali y o he
o ganic ma e . This suppo s he ac ha labile
ac ions o he soil o ganic ma e (soluble C,
mic obial C, ca bohyd a es) a he han he o al
o ganic ma e con en should be used o de ec
he impac o i e (P ie o-Fe nández a al. 1998;
Villa e al. 2004; Díaz-Ra iña e al. 2010b;
Ma ín e al. 2012; Almend os and González-
Vila 2012). As obse ed o mos physical
and chemical p ope ies, no modi ica ions in
colo pa ame e s (L, ligh ness; hab, one) we e
de ec ed a e consecu i e he mal shocks (H1
and H2) unde labo a o y condi ions.
3.2. Tempe a u e- ime cu es (TTC) and
deg ees-hou
A o al o 128 empe a u e- ime cu es (su ace,
1 cm dep h) we e ob ained o he di e en soil
[ LOMBAO A., BARREIRO A., CANCELO-GONZÁLEZ J., MARTÍN A. & DÍAZ-RAVIÑA M. ]
SJSS. SPANISH JOURNAL OF SOIL SCIENCE YEAR 2015 VOLUME 5 ISSUE 2
173
hea ing ea men s (da a no shown). The esul s
showed ha he soil esponse di e ed no ably
depending on he soil hea ing empe a u e; o
he soil samples hea ed a 50-75 ºC he da a i ed
o he linea model R2 = 0.821-0.984 (p < 0.001)
whe eas o he soil samples hea ed in he ange
o 100-300 ºC he da a i ed o he exponen ial
model R2 = 0.741-0.987 (p < 0.001). An example
o he ime- empe a u e cu es ob ained o
some hea ed samples o he L soil is illus a ed
in Figu e 4. The Tmax alues es ima ed om he
exponen ial me hod (pa ame e “b”) we e almos
iden ical o he maximum empe a u e measu ed
by he he mocouples ( eal empe a u e) ( alues
o 28-255 ºC in su ace; 23-240 ºC a 1 cm
dep h). I should be no iced, howe e , ha
hese alues we e lowe (a ound 20-122 ºC)
han he heo e ical empe a u e applied o soil
(mu le u nace empe a u e 50-300 ºC). The
di e ences be ween he eal ( he mocouples)
and he heo e ical empe a u es a ied
depending on bo h he empe a u es applied
and he soil cha ac e is ics (soil ype, dep h, i e
his o y), highe di e ences being de ec ed in he
su ace a highe empe a u es (mean di e ence
alues o 20 ºC, 40 ºC and 80 ºC o he soil
empe a u e anges o 50-100 ºC, 100-200 ºC
and 200-300 ºC, espec i ely). The da a clea ly
poin ou o he impo ance o he measu emen
o he eal empe a u e in labo a o y hea ing
expe imen s. I should be no iced, howe e ,
ha mos published s udies conce ning he mal
shock impac on soil p ope ies a e ela ed o
he u nace empe a u e (Díaz-Ra iña e al.
1992; Te e e e al. 2008; Ma cos e al. 2007;
Bá cenas-Mo eno and Båå h 2009); he e o e,
his makes di icul he compa ison be ween
di e en s udies.
Fo bo h L and E soil samples, he pa ame e s
ob ained om he exponen ial model (a,
ascending slope and Tmax, maximum
empe a u e) a ied depending on p e ious
soil i e his o y. The e a e no able di e ences
be ween he unbu ned and bu ned samples
ollowing he p esc ibed i e o he wild i e ( ield
condi ions) and be ween he unhea ed and
hea ed samples ollowing he he mal shocks
( i s and second hea ing unde labo a o y
condi ions, 1H and 2H) (Figu e 4). Fo all soil
hea ing ea men s, he empe a u e eached by
he soil was highe in he su ace han a 1 cm
dep h (e.g. 1H LU300, Tmax 184 ºC and slope
0.204 a he su ace; 1H LU300, Tmax 177 ºC
and slope 0.167 a 1 cm dep h), which can be
a ibu ed o he low he mal conduc i i y o he
soil (Te e e e al. 2008; Badía-Villas e al. 2014).
In mos cases, he Tmax and slope alues (a)
we e also highe in he bu ned samples a e he
wild i e o p esc ibed i e ( ield condi ions) han
in he co esponding unbu ned ones (i.g. LU300,
1H Tmax 184 ºC and slope 0.204; LB300, 1H,
Tmax 199 ºC and slope 0.249) as well as in he
samples subjec ed o he second he mal shock
ea men (labo a o y condi ions, 2H ea men )
compa ed wi h he co esponding i s he mal
shock (1H ea men ) (i.g. LB300, 1H Tmax 199 ºC
and slope 0.249; 2H, Tmax 268 ºC and slope
0.221). The samples p e iously hea ed unde
ield o labo a o y condi ions also showed a
lowe ampli ude in he di e ence o empe a u es
be ween he su ace and 1cm dep h compa ed
wi h he co esponding unbu ned samples,
indica ing ha p e ious hea ing had an e ec on
he e ical hea ansmission. The da a a e in
acco dance wi h a p e ious s udy o Massman
e al. (2008) indica ing di e ences in he su ace
empe a u e ollowing a p esc ibed i e; a a
bu n si e he ampli ude o he daily cycle o soil
hea ing and cooling could be as much as 10 ºC
g ea e wi hin he bu n a ea han a a nea by
no-bu ned a ea, whe eas o he annual cycle,
he ampli ude di e ence was abou 2 ºC g ea e .
The deg ee-hou s (DH) applied o he whole
da a se samples (a o al o 128) a ied om
2.1 o 74.6 DH (da a no showed). The DH
alues o he he mal ea men s we e di e en
depending on he ange o empe a u es
( alues <10 DH o ea men s lowe han
100 ºC; 10-30 DH o ea men s in he ange
o 100-200 ºC; and > 30 DH o soil hea ing a
300 ºC). These alues we e lowe han hose
ob ained in p e ious s udies pe o med wi h
soils o he same a ea (Cancelo-González e
al. 2012, 2014), which can be explained by
di e ences in bo h soil hea ing empe a u e and
exposu e ime (28-255 ºC du ing 15 minu es
in ou expe imen , 200-400 ºC o mo e han
100 minu es in he abo e men ioned s udies).
[ IMPACT OF THERMAL SHOCK ON FOREST SOILS AFFECTED BY FIRES OF DIFFERENT SEVERITY AND RECURRENCE ]
