Biogeosciences, 12, 281–297, 2015
www.biogeosciences.ne /12/281/2015/
doi:10.5194/bg-12-281-2015
© Au ho (s) 2015. CC A ibu ion 3.0 License.
CH4and N2O dynamics in he bo eal o es –mi e eco one
B. ˇ
Tupek1, K. Minkkinen1, J. Pumpanen1, T. Vesala2, and E. Nikinmaa1
1Depa men o Fo es Sciences, P.O. Box 27, 00014 Uni e si y o Helsinki, Finland
2Depa men o Physics, P.O. Box 48, 00014 Uni e si y o Helsinki, Finland
Co espondence o: B. ˇ
Tupek ([email p o ec ed])
Recei ed: 28 Ap il 2014 – Published in Biogeosciences Discuss.: 4 June 2014
Re ised: 13 No embe 2014 – Accep ed: 3 Decembe 2014 – Published: 16 Janua y 2015
Abs ac . In spi e o ad ances in g eenhouse gas esea ch,
he spa io empo al CH4and N2O dynamics o bo eal land-
scapes emain challenging, e.g., we need cla i ica ion o
whe he o es –mi e ansi ions a e occasional ho spo s o
landscape CH4and N2O emissions du ing excep ionally high
and low g ound wa e le el e en s.
In ou s udy, we es ed he di e ences and d i e s o CH4
and N2O dynamics o o es /mi e ypes in ield condi ions
along he soil mois u e g adien o he o es –mi e eco one.
Soils changed om Podzols o His osols and g ound wa e
ose downslope om a dep h o 10m in upland si es o 0.1m
in mi es. Yea ly me eo ological condi ions changed om be-
ing excep ionally we o ypical and excep ionally d y o
he local clima e. The median luxes measu ed wi h a s a ic
chambe echnique a ied om −51 o 586µgm−2h−1 o
CH4and om 0 o 6µgm−2h−1 o N2O be ween o es and
mi e ypes h oughou he en i e we –d y pe iod.
In spi e o he highly dynamic soil wa e luc ua ions in
ca bon ich soils in o es –mi e ansi ions, he e we e no
la ge peak emissions in CH4and N2O luxes and he lux
a es changed minimally be ween yea s. Me hane up ake was
signi ican ly lowe in poo ly d ained ansi ions han in he
well-d ained uplands. Wa e -sa u a ed mi es showed la ge
CH4emissions, which we e educed en i ely du ing he ex-
cep ional summe d ough pe iod. Nea -ze o N2O luxes did
no di e signi ican ly be ween he o es and mi e ypes
p obably due o hei low ni i ica ion po en ial. When up-
scaling bo eal landscapes, p is ine o es –mi e ansi ions
should be ega ded as CH4sinks and mino N2O sou ces in-
s ead o CH4and N2O emission ho spo s.
1 In oduc ion
Soil e ili y, soil wa e con en , and soil ca bon s o age
o bo eal o es s a ies be ween well-d ained mine al soils
mainly ound in uplands and poo ly d ained o ganic soils
mainly ound in pea lands (Seibe e al., 2007; Weisham-
pel e al., 2009). The CH4and N2O luxes om mine al
and o ganic soils a e impac ed by a ying soil mois u e con-
di ions (Solondz e al., 2008; Pihla ie e al., 2004). Typi-
cal mine al soil o es s a e small sinks o CH4and small
sou ces o sinks o N2O (Moosa i and C ill, 1997; Pihla ie
e al., 2007). Spa sely o es ed pea lands a e ypically la ge
o small sou ces o CH4and small sou ces o sinks o N2O
(Ma ikainen e al., 1995; Nykänen e al., 1995; D’Angelo
and Reddy, 1998). Field CH4and N2O s udies o na u al bo-
eal o es –mi e eco ones a e a e (e.g., Ullah e al., 2009;
Ullah and Moo e, 2011) in compa ison o hose o ypical
o es s o mi es. Howe e , he a ea o o es –mi e ansi ions
is ela i ely la ge, e.g., in Finland, o es ed mi es wi h an o -
ganic ho izon <30cm co e 1.5 million hec a e o app ox-
ima ely 7% o he o al o es a ea (Finnish s a is ical yea -
book o o es y, 2013), and a he p esen ime i is no clea
whe he he e es ial–aqua ic in e aces, such as he o es –
mi e ansi ion, ep esen s a biogeochemical ho spo o CH4
and N2O emissions (McClain e al., 2003).
The lagg ansi ional zone in he o es –mi e eco one e-
cei es nu ien s om he adjacen mine al soil uno , and is
hus mo e mine o ophic, biologically di e se, and p oduc-
i e han open mi es o bogs (Howie and Mee eld, 2011).
Fu he mo e, eco ones be ween o es s and mi es a e ecolog-
ical swi ches (Agnew e al., 1993), whe e he ege a ion o
o es s and mi es coincide and soils equen ly unde go luc-
ua ions in wa e le el posi ion and chemis y (Ha sho n e
al., 2003; Howie and Mee eld, 2011), and whe e he CH4
Published by Cope nicus Publica ions on behal o he Eu opean Geosciences Union.
282 B. ˇ
Tupek e al.: CH4and N2O dynamics in he bo eal o es –mi e eco one
and N2O dynamics o o es –mi e ansi ions may be ex-
pec ed o di e gene ally and on a yea - o-yea basis om
hose o ypical o es s and mi es.
The CH4up ake o o es soils is a esul o CH4oxi-
dizing ae obic me hano ophs sensi i e o wa e sa u a ion,
soil po osi y, mois u e, empe a u e, pH, and ammonium
(Moosa i and C ill, 1997; Saa i e al., 2004; Jaa inen e al.,
2004). Unsa u a ed upland o es soils oxidize CH4a highe
a es han mo e wa e -sa u a ed, acidic, and ammonium ich
o es ed pea soils (Saa i e al., 2004). In con as o he CH4
sinks o upland o es soils, and d ained pea lands, na u al
mi es emi CH4 o he a mosphe e (Bubie e al., 1995; Nykä-
nen e al., 1998; Ke unen e al., 1999). CH4p oduc ion in
pea soil is a esul o me hanogenic and me hano ophic ac-
i e bac e ia, whose ac i i y depends on anoxic and oxic con-
di ions below and abo e he wa e le el, empe a u e, and
a ailabili y o ca bon subs a e (Ke unen e al., 1999). In-
c easing soil we ness inc eases anoxic condi ions necessa y
o inc eased me hanogenesis (Juo onen e al., 2005), and as
a esul CH4emissions inc ease (Saa nio e al., 1997; Oja-
nen e al., 2010; Y jälä e al., 2011). Me hane p oduc ion po-
en ial in pea soils gene ally inc eases posi i ely wi h pH
(Juo onen e al., 2005; Ye e al., 2012), whe eas CH4oxida-
ion o o es ed pea lands has a na ow pH op imum a ound
5.5 (Saa i e al., 2004). Inc eased pH le els, e.g., h ough he
in low o less acidic mine al soil wa e , ypically con aining
g ea e calcium and bica bona e concen a ions han pea wa-
e (Howie and Mee eld, 2011), could inc ease CH4emis-
sions om ansi ions.
N2O emissions in well-d ained bo eal o es soils a e con-
olled by soil mois u e, pH, a ailable ni a e, ammonium,
oxygen, and ca bon concen a ions (Regina e al., 1996; Ul-
lah e al., 2008). N2O p oduc ion is limi ed by he amoun
o ni ogen and is subjec o deni i ica ion and ni i ica ion
p ocesses (Ambus e al., 2006). In well-d ained soils NO3
limi a ion, anoxic mic osi es, and la ge soil po osi y may
also p omo e N2O consump ion (F asie e al., 2010). N2O
consump ion o soils co ela es wi h dehyd ogenase ac i i y,
which is a ec ed by oxida ion- educ ion s a us and possi-
bly con olled by soil mois u e (Wloda czyk e al., 2005).
The N2O consump ion by soils is a ibu ed o espi a o y e-
duc ion (Con ad, 1996) caused by deni i ie s and ni i ie s
(Rosenk anz e al., 2006). N2O emissions inc ease du ing
d ie pe iods h ough inc eased ammoni ica ion and ni i ica-
ion (Regina e al., 1996; Nykänen e al., 1995; Von A nold
e al., 2005). In wa e -sa u a ed mine o ophic pea lands ni-
i ica ion supplies ni a e (W age e al., 2001) o deni i i-
ca ion, which is he main bu small N2O sou ce (W ay e al.,
2007; F asie e al., 2010). In nu ien ich mi es, N2O emis-
sions inc ease du ing d ie pe iods h ough inc eased am-
moni ica ion and ni i ica ion (Regina e al., 1996; Nykänen
e al., 1995; Von A nold e al., 2005). Ni i ica ion and he
supply o ni a e o deni i ica ion inc eases wi h highe pH
(Regina e al., 1996). Howe e , i ni a e is a ailable, low pH
inc eases N2O emissions (Weslien e al., 2009). The e o e, i
ni a e we e p esen du ing wa e le el d awdown, he o es –
mi e ansi ions could become sou ces o N2O.
Ou aims we e (1) o es whe he o es loo CH4and
N2O luxes o he o es –mi e ansi ion di e om he yp-
ical upland o es s and lowland mi es o na u al bo eal land-
scapes and (2) how me eo ologically di e en yea s, i.e.,
excep ionally we (2004), ypical (2005), and excep ionally
d y (2006), a ec he luxes.
We add essed he ques ion o whe he inc easing we -
nessin o es –mi e ansi ions p omo esCH4p oduc ion, and
whe he d y condi ions educe CH4p oduc ion and inc ease
N2O emissions. We hypo hesized ha o es /mi e ypes ex-
hibi dis inc le els o CH4and N2O luxes due o he chang-
ing soil s uc u e om Podzols o His osols and due o in-
c easing soil wa e con en om xe ic o sa u a ed. We ex-
pec ed ha he occasionally sa u a ed o gano-mine al soils o
o es –mi e ansi ions a e a iable sou ces o CH4and N2O
luxes. In o de oe alua e he unde lying ac o s behind CH4
and N2O o es loo luxes, we measu ed he luxes and en-
i onmen al a iables, such as soil empe a u e, soil mois-
u e, wa e able dep h, and soil wa e pH, in nine si es along
he o es –mi e eco one du ing excep ionally di e en me e-
o ological condi ions. In o de o de ec s a is ically signi i-
can di e ences be ween CH4and N2O luxes o nine si es
we used wo-way analysis o a iance, and o be e unde -
s anding o lux esponses o en i onmen al ac o s we used
linea and nonlinea eg ession models, and esidual sensi i -
i y analysis.
2 Ma e ial and me hods
2.1 S udy si e cha ac e is ics
The Va iha ju–Lakkasuo eco one o nine o es and mi e
s udy si es o ms a g adien in ege a ion communi ies, soil
mois u e and nu ien condi ions in cen al Finland (61◦470,
24◦190) (ˇ
Tupek e al., 2008). Fo es /mi e ypes we e classi-
ied using he Finnish classi ica ion sys ems (Cajande , 1949;
Laine e al., 2004) based on soil e ili y e lec ed by he com-
posi ion and abundance o o es loo ege a ion, and by he
si e loca ion on he slope. The eco one s udy si es a e si ua ed
along a 450m ansec on a hillslope wi h a ela i e elie o
15m and a 3.3% slope acing NE (Fig. 1a). The e ili y o
he o es /mi e si es inc ease om he poo ly e ile si es a
he xe ic and sa u a ed edges o he eco one owa ds he mos
e ile Oxalis-My illus ype o es (OMT) in he middle o
he hillslope (Fig. 1b).
Dominan ege a ion composi ion changes wi h inc eas-
ing soil mois u e down he slope. Xe ic Sco s pine o es
(CT – Calluna ype) on he summi o glacial sandy es-
ke gi es way o subxe ic Sco s pine No way sp uce o -
es (VT – Vaccinium i is-idaea ype) on he shoulde , and
mesic and he b ich No way sp uce domina ed ypes on
he back slope and oo slope (MT – Vaccinium my illus
Biogeosciences, 12, 281–297, 2015 www.biogeosciences.ne /12/281/2015/
B. ˇ
Tupek e al.: CH4and N2O dynamics in he bo eal o es –mi e eco one 283
Table 1. Si e soil wa e solu ion pH and soil p ope ies.
CT VT MT OMT OMT+KgK KR VSR1 VSR2
mean SE mean SE mean SE mean SE mean SE mean SE mean SE mean SE mean SE
pH 10cm 5.57 0.36 5.14 0.42 5.24 0.08 4.68 0.39 4.58 0.30 4.46 0.14 4.37 0.22 5.06 0.39 4.80 0.44
pH 30cm 6.20 0.06 6.18 0.02 5.91 0.13 5.30 0.11 5.53 0.04 4.91 0.10 4.55 0.08 5.32 0.15 4.79 0.19
Bulk densi y 0–10cm 0.37 0.09 0.28 0.04 0.48 0.03 0.27 0.09 0.31 0.13 0.33 0.05 0.24 0.02 0.40 0.12 0.40 0.12
Bulk densi y 10–30cm 0.92 0.07 0.31 0.12 0.85 0.03 0.90 0.07 0.90 0.07
To C (%) 0–10cm 43.17 24.22 49.63 47.09 45.36 48.68 50.30 45.76 48.20
To C (%) 10–30cm 21.76 53.31 48.33 47.70 49.97
To N (%) 0–10cm 1.02 0.61 1.18 1.59 2.19 1.47 1.12 1.29 0.96
To N (%) 10–30cm 0.96 1.95 1.45 1.87 1.81
C/N 0–10cm 42.32 39.70 42.06 29.62 20.71 33.12 44.91 35.47 50.21
C/N 10–30cm 22.67 27.34 33.33 25.51 27.61
Figu e 1. (a) Ai bo ne in a ed pho og aph shows a 450m long
bo eal o es –mi e eco one loca ed on he NE slope o he glacial
Va iha ju–Lakkasuo eske in Finland (61◦470, 24◦190). (b) The ish-
eye pho og aphs show ee s ands o xe ic (1), subxe ic (2), mesic
(3), he b ich (4), paludi ied (5–7), and sa u a ed (8–9) o es /mi e
ypes. (c) Pho og aphs show g ound ege a ion and (d) soil p o iles
o nine o es /mi e ypes. Upland o es s: 1 CT – Calluna, 2 VT
–Vaccinium i is-idaea, 3 MT – Vaccinium my illus, 4 OMT –
Oxalis-My illus; o es –mi e ansi ion ypes: 5 OMT+–Oxalis-
My illus paludi ied, 6 KgK – My illus sp uce o es paludi ied, 7
KR – sp uce pine swamp; spa sely o es ed we mi e ypes: 8 VSR1
and 9 VSR2 – all sedge pine en.
ype, OMT – Oxalis-My illus ype). The oe slope con-
ains o es –mi e ansi ions o paludi ied mixed sp uce–
pine–bi ch o es s (OMT+–Oxalis-My illus paludi ied,
KgK – My illus sp uce o es paludi ied). The e is a pe -
manen ly we mixed sp uce–pine–bi ch swamp (KR – sp uce
pine swamp) a he mi e edge o he o es –mi e ansi ions.
On he le el o he hillslope he e a e bi ch–pine en mi es
wi h open ee canopies (VSR1 and VSR2 – all sedge pine
en) (Fig. 1b). The o es loo ege a ion is composed o si e-
speci ic mosses and ascula plan s (Fig. 1c).
Soils a e o med by well-d ained Haplic Podzols on he
hillslope, in e media ely d ained His ic and Gleyic-His ic
Podzols in he o es –mi e ansi ions on he oe o he slope,
and pe manen ly we Hemic His osols downslope (Fig. 1d).
We measu ed pH du ing summe campaign 2005 om soil
wa e da a collec ed on all si es by suc ion cup lysime e s.
Th ee lysime e s we e ins alled in 10cm and one in 30cm
dep h below he soil su ace in each si e. De ailed desc ip-
ion o he lysime e s and sampling p ocedu e can be ound
in S a (1985). The pH was measu ed on he day o wa e
sampling in he labo a o y by pH me e equipped wi h a glass
elec ode. The mean acidi y le el o he si es o o es –mi e
eco one was g adually inc easing om pH 5.6 in uplands
(CT) o 4.4 in ansi ions (KR), whe eas mi es we e less acid
han ansi ions wi h pH 5.1 and 4.8 (VSR1 and VSR2, e-
spec i ely) (Table 1). Collec ed soil wa e om 30cm dep h
showed gene ally highe pH han soil wa e pH a 10cm
dep h. Th ee soil co es o each plo we e aken in July 2006
om he op soil (0–10cm) in upland o es s and om he
wo p o ile dep hs (0–10, 10–30cm) in o es –mi e ansi-
ions and in pea lands. The olume o samples was measu ed
be o e he o en d ying a 70◦C o de e mine he bulk den-
si y. The bulk densi y o he uppe o ganic laye anged om
0.24gcm−3(KR) o 0.48gcm−3(MT) and was app oxi-
ma ely hal o he bulk densi y o he o ganic laye om 10
o 30cm dep h (mean o ansi ions and mi es 0.77gcm−3)
(Table 1). The C/N a io was de e mined once o each plo
om he soil o ganic ma e analyzed by d y combus ion wi h
Leco CNS-1000 (Leco Co p., USA). The C/N a io was
wide in he 0–10cm p o ile (mean 37) han in he 10–30cm
p o ile (mean 27). The highes N con en as well as he low-
es C/N a io along he eco one was ound in o es –mi e
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284 B. ˇ
Tupek e al.: CH4and N2O dynamics in he bo eal o es –mi e eco one
ansi ions OMT+and KgK (Table 1). A mo e de ailed o -
es /mi e ype cha ac e iza ion is gi en by ˇ
Tupek e al. (2008).
2.2 Mic ome eo ological condi ions
The mic ome eo ological measu emen s along he Va iha ju–
Lakkasuo o es –mi e eco one we e aken weekly du ing he
summe s o 2004 (July–No embe ), 2005 (May–No embe ),
2006 (May–Sep embe ), and mon hly du ing he win e s
(Decembe –Ap il). The o es loo soil empe a u es (◦C) a
dep hs o 5, 15, and 30cm (T5,T15, and T30) we e measu ed
using a po able he mome e connec ed o he mocouples
ins alled pe manen ly in he soil. The olume ic soil mois-
u e (%) a dep hs o 5, 10, and 30cm (soil wa e con en
– SWC5, SWC10, and SWC30) was measu ed by a po able
The aP obe (Del a-T De ices L d.) in diagonally ins alled
pe o a ed PVC ubes, o ensu e he same compac ness o he
soil.The dep ho wa e ablewasmeasu ed insidePVC ubes
(∅30mm) ins alled a each si e. P ecipi a ion was measu ed
by an au oma ed bucke sys em a a s a ion o moni o ing
o es – a mosphe e ela ions, SMEARII (Ha i and Kulmala,
2005), loca ed 6km no h – wes om he o es –mi e eco-
one. Missing soil empe a u e and mois u e da a o eco one
we e gap illed by linea eg ession be ween con inuous mea-
su emen s o soil empe a u e and mois u e a SMEARII.
2.3 CH4and N2O luxes
The ield gas sampling was conduc ed weekly in he 2004
and 2005 seasons, bi-weekly du ing he 2006 season, and
mon hly du ing he win e s. The gas sampling was done
wi hin 3-days in e al o he mic ome eo ological measu e-
men s. I he e was packed snow on he g ound, he gas sam-
ples would be aken om he op and bo om laye s; and he
CH4(µgm−2h−1) and N2O (µgm−2h−1) luxes we e cal-
cula ed by he snowpack di usion me hod using each gas
concen a ion di e ence, snow dep h, po osi y and empe -
a u e, and gas di usion coe icien s as in Somme eld e
al. (1993). O he wise, i he e was no snowpack, he sam-
ples would be aken om h ee opaque, en ed, closed, s a ic
chambe s (∅315mm, h295mm) placed ai igh ly on p e-
ins alled colla s. On each measu ing occasion a sample o
ambien gas and ou 15ml samples om each o he h ee
chambe s we e d awn in sy inges a in e als o 5, 10, 15,
and 20min om chambe closu e, o aling 13 samples o
each si e. Chambe empe a u e was moni o ed du ing he
sampling. A e he sampling e en , he gas samples we e
s o ed in coole s a +4◦C and analyzed wi hin 36h in a lab-
o a o y wi h a gas ch oma og aph. The gas ch oma og aph
(Hewle -Packa d, USA) model numbe HP-5890A was i -
ed wi h a lame ioniza ion de ec o (FID) o CH4and an
elec on cap u e de ec o (ECD) o N2O de ec ion. The gas
ch oma og aph was also equipped wi h a mois u e ap. P io
o analysis o ield samples and a e each se o 13 samples
a e e ence gas sample o known CH4and N2O concen a-
ion was analyzed. The CH4(µgm−2h−1) and N2O (µgm−2
h−1) luxes we e calcula ed om he slope o linea eg es-
sion be ween he se o ou gas concen a ions and sampling
ime, ime elapsed a e he chambe closu e, and by apply-
ing empe a u e co ec ion. Fo he lux calcula ion we used
a MATLAB (The Ma hwo ks Inc.) sc ip de eloped a he
Dep . o Physics, Uni e si y o Helsinki.
The me hod quan i ica ion limi (MQL) o he gas ch o-
ma og aph was based on 100 subsequen ly analyzed sam-
ples o e e ence gas o known CH4and N2O concen a ions
(mean± wo SD: 1.837±0.055 and 0.295±0.023ppm, e-
spec i ely) and e e ence gas samples analyzed be o e he se
o ield samples o each si e. The MQL was a gas-speci ic
s anda d de ia ion o he andom luxes de i ed om 1000
andom se s o ou CH4o N2O concen a ions o e e -
ence gas samples (22µgm−2h−1 o CH4and 18µgm−2h−1
o N2O). In o de o minimize he andom e o ela ed
o gas sampling in he ield, luxes we e e i ied using he
ambien ield ai sample analyzed be o e each sequence o
chambe samples adop ing simila c i e ia as used in Alm e
al. (2007). Due o gas sampling dis u bances in he ield and
poo gas ch oma og aph accu acy 17% o CH4and 49% o
N2O luxes we e disca ded.
2.4 S a is ical analysis
Two-way analysis o a iance (ANOVA) was used o es
whe he CH4and N2O luxes o o es /mi e ypes ha e com-
mon means in we , ypical, and d y yea s. Pos hoc Tukey
HSD (hones signi ican di e ence) es s we e used o es
he pai wise di e ences be ween he o es and mi e ypes
and yea s changing om we o d y. Fo CH4 luxes we an
ANOVA es s wice, i s on he whole da a se including nine
o es /mi e ypes and hen on a subse o da a including up-
land o es s and o es –mi e ansi ions, and excluding mi es.
Fo es ing signi ican di e ences be ween he wo g oups
o da a we pe o med Welch’s wo sample es , e.g., be-
ween he N2O luxes om he snow on he g ound season
(Janua y–Ap il in 2006) and he N2O luxes om he snow-
less seasons (May–No embe in 2005 and May–Sep embe
in 2006).
In addi ion o ANOVA, we es ed he dependence be-
ween he measu ed CH4(µgm−2h−1) and he gap illed
hal -hou ly en i onmen al a iables in sepa a e models o :
(a) he upland o es s on mine al soils (CT, VT, MT, OMT),
and (b) o es –mi e ansi ions on o gano-mine al soils and
(OMT+, KgK, and KR) (c) mi es (VSR1, VSR2).
CH4 luxes (µgm−2h−1) o uplands and ansi ions we e
i ed by wo linea mixed-e ec s eg ession models wi h a
andom e ec o o es ypes (Pinhei o e al., 2013). Fo bo h
g oups o o es ypes, we e alua ed he e ec o all ou en i-
onmen al a iables on CH4 oge he and hei combina ions
i e a i ely by selec ing he model combina ion o a iables
ha we e signi ican .
Biogeosciences, 12, 281–297, 2015 www.biogeosciences.ne /12/281/2015/
B. ˇ
Tupek e al.: CH4and N2O dynamics in he bo eal o es –mi e eco one 285
The CH4 luxes o upland o es s and ansi ions included
soil mois u e a 10cm (%) (SWC10) and soil empe a u e a
5cm (◦C) (T5) as p edic o s in sepa a e models (Eqs. 1 and
2):
yuij =βCTSWC10 +βVTSWC10 +βMTSWC10 (1)
+βOMTSWC10 +βCTT5+βVTT5+βMTT5+βOMTT5
+bCT +bVT +bMT +bOMT +εij ,
y ij =βOMT+SWC10 +βKgKSWC10 +βKRSWC10 (2)
+βOMT+T5+βKgKT5+βKRT5+bOMT+
+bKgK +bKR +εij ,
whe e yuij and y ij a e he CH4 lux (µgm−2h−1) o up-
land o es s o ansi ions and o a pa icula i h o es ype
and he j h obse a ion, βCT h ough βKR a e he ixed e -
ec coe icien s o a pa icula i h o es ype (CT, VT, MT,
OMT Eq. 1, o OMT+, KgK, and KR Eq. 2), SWC10, and
T5a e he ixed e ec a iables (p edic o s) o obse a ion
jin o es ype iwhe e each o es ype’s p edic o is as-
sumed o be mul i a ia e no mally dis ibu ed, bCT h ough
bKR a e in e cep s o he andom e ec o a pa icula i h
o es ype, and εij is he e o o case jin o es ype i
whe e each o es ype’s e o is assumed o be mul i a ia e
no mally dis ibu ed (Table 2).
The CH4 luxes (µgm−2h−1) o mi es we e i ed by using
a mul iplica i e nonlinea eg ession model wi h a combined
esponse o wa e able dep h and soil empe a u e a 5cm
Eq. (1):
yij =a0e−0.5WT-WTop
WT ol 2e−0.5T5-Top
T ol 2+εij ,(3)
whe e yij is he CH4 lux (µgm−2h−1) o he i h mi e
(VSR1,VSR2) and o he j h case, WT (cm) is wa e able
dep h, T5 (◦C) is soil empe a u e a 5cm, and a0, WTop ,
WT ol, Top , and T ol a e pa ame e s (Table 3).
The N2O luxes (µgm−2h−1) o all o es /mi e ypes we e
i ed by using one mul iplica i e nonlinea eg ession model
wi h a combined esponse o soil mois u e and soil empe a-
u e a 5cm Eq. (4):
zij =a0SWC5e−0.5T5-Top
T ol 2+εij ,(4)
whe e zij is he N2O lux (µgm−2h−1) o he i h mi e
(VSR1,VSR2) and o he j h case, SWC5(%) is soil mois-
u e a 5cm, and T5 (◦C) is soil empe a u e a 5cm,and a0,
Top , and T ol a e pa ame e s (Table 4).
To illus a e he sensi i i y o CH4and N2O lux esponse
o en i onmen al ac o s we pe o med a esidual analysis by
simula ing a alue o each da a poin wi h only one ac o
allowed o a y and he o he se o i s mean le el. To exam-
ine co ela ions be ween CH4and N2O luxes and pH, and
soil p ope ies we p e o med he Pea son’s co ela ion es s.
The s a is ical analyses we e pe o med in MATLAB R2012a
(The Ma hwo ks Inc.) and in R (R Co e Team 2013) so wa e
en i onmen s.
3 Resul s
3.1 Mic ome eo ological condi ions
The la ges di e ences be ween yea s 2004, 2005, and 2006
we e seen in changing summe p ecipi a ion pa e ns (mea-
su ed nea by he SMEARII s a ion). The a e age June–
Augus mon hly p ecipi a ion was educed om 94 o 44mm
om a we 2004 o a d y 2006, while ambien empe a u e
inc eased om 14 o 17◦C. In he coldes summe (2004)
he a e age p ecipi a ion in June and July was o e 117mm,
and d opped o 47mm in Augus . In he ypically wa m sum-
me o 2005 he mon hly p ecipi a ion g adually inc eased up
o 123mm in Augus , and d opped o 58mm in Sep embe .
Howe e , in he wa mes summe (2006) he mon hly p e-
cipi a ion ne e eached mo e han 48mm. In July 2006, wo
ainless weeks induced a d ough . By d ough we mean ha
he soil wa e con en in he uppe soil laye (in mine al soils)
was so low ha mosses wil ed and d ied (all along he eco-
one). The d ough condi ions lessened in mid-Augus and
ended in Sep embe wi h inc easing ains owa ds au umn.
La e au umn was excep ionally wa m and snowless.
Mon hly median soil empe a u es a 5cm (T5) anged
om a ound 5◦C in May, culmina ed o a ound 15–16◦C
in July and Augus , and subsided again o a ound 5◦C in Oc-
obe . The non- ege a i e season T5minimum was close o
0◦C. The wa mes T5was in upland o es CT and he cold-
es was in uppe o es –mi e ansi ion OMT+. Soil empe -
a u e sligh ly inc eased om o es –mi e ansi ions owa ds
mi es. In spi e o he ambien ai empe a u e di e ence
h oughou all he mon hs in he 3 yea s, we de ec ed di -
e ences mainly du ing ea ly and la e season in 2004, 2005,
and 2006 T5(Fig. 2a).
The median wa e able (WT) showed he ob ious ise
om 10m a he summi o he hill, o a ound 1m in he
mid-slope, be ween 0.5 and 0.1m a he oe slope, and close
o 0.01m on he le el (Fig. 2b). The seasonal WT ise in 2005
was obse ed be ween he July and Augus medians. Du ing
he d ough o 2006, he WT alues d opped less han 0.1m
o he uppe mos o es si es, bu d opped hea ily by ∼1m
in he o es –mi e ansi ions, and mo e han 0.5m in he low-
e mos pea land si es.
Volume ic SWC in 10cm dep h anged om a d y alue
o a ound 10% in he mine al soils o a wa e -sa u a ed alue
o a ound 80% in swamp and mi es (Fig. 2c). The la ges
d ough educ ion o SWC was in Augus 2006 on he well-
d ained sandy Podzols a he summi o he hill, and also on
he poo ly d ained His ic Podzols on he oe slope.
3.2 CH4 luxes
The median luxes om he o es loo a ied om −51
o 586µgm−2h−1 o CH4among indi idual si es du ing
he en i e pe iod (Fig. 3a). The small nega i e CH4 luxes
associa ed wi h p e ailing oxida ion we e mos ly obse ed
www.biogeosciences.ne /12/281/2015/ Biogeosciences, 12, 281–297, 2015

286 B. ˇ
Tupek e al.: CH4and N2O dynamics in he bo eal o es –mi e eco one
Table 2. Pa ame e es ima es and hei s anda d e o s o end coe icien s o CH4 luxes (µgm−2h−1) o he upland o es ypes (CT, VT,
MT, and OMT, Eq. 1), and o he o es –mi e ansi ions (OMT+, KgK, and KR, Eq. 2). Bo h equa ions a e unc ions o olume ic soil
mois u e a 10cm (%) and soil empe a u e a a dep h o 5cm (◦C).
Eq. (1) bi G oup bi G oup bi SE βi1βi1 SE βi2βi2 SE NRMSE
CT −39.345 −43.632 9.102 0.762a0.299 −1.249 0.223 137 35.2
VT −26.213 143 25.1
MT −50.984 139 25.2
OMT −57.985 144 32.1
Eq. (2)
OMT+ −49.898 −50.248 7.507 0.638 0.105 −0.109b0.226 139 22.3
KgK −48.216 146 17.9
KR −52.630 149 31.5
Eq. (2) soil empe a u e excluded om i ing
OMT+ −51.799 −52.466 6.341 0.660 0.099 139 22.3
KgK −50.404 146 17.9
KR −55.196 149 31.5
p < 0.001 o all pa ame e s, excep ap=0.011,bp=0.629.βi1– soil mois u e a 10cm,βi2– soil empe a u e a 5cm.
Table 3. Pa ame e es ima es and hei s anda d e o s o end coe icien s o CH4 luxes (µgm−2h−1) o he mi es (VSR1, VSR2, Eq. 3).
Equa ion (3) is a unc ion o wa e able dep h (cm) and soil empe a u e a a dep h o 5cm (◦C).
Eq. (3) a0a0 SE Top Top SE T ol T ol SE WTop WTop SE WT ol WT ol SE NRMSE
mi es 1207.1 126.7 13.9 1.4 6.4 1.3 −18.0 2.2 16.6 2.8 324 656
VSR1 1570.3 155.1 13.0 0.8 5.8 0.8 −18.6 1.6 15.5 1.7 162 424
VSR2 801.3 190.8 16.6a6.8 8.7b4.5 −17.3c5.3 20.7d9.7 162 558
p alues<0.001, excep ap=0.016,bp=0.053,cp=0.002,dp=0.035.
in uplands and in ansi ions, while mi es ypically showed
la ge posi i e CH4 luxes associa ed wi h p e ailing p oduc-
ion. The CH4 lux dynamics changed exponen ially wi h
inc easing le els o he g ound wa e able om small up-
ake o la ge emissions (Figs. 2, 3). The median CH4 luxes
o uplands (CT, VT, MT, OMT), ansi ions (OMT+, KgK,
KR), and mi es (VSR1, VSR2) a ied om −38, −48,
and 392µgm−2h−1, espec i ely (Fig. 3b). Momen a y CH4
luxes o uplands and ansi ions anged om −342 o
143µgm−2h−1, whe eas in mi es he luxes anged om
−12 o 6808µgm−2h−1(Fig. 3b). The median CH4 luxes
o one upland (VT) and all he ansi ions (OMT+, KgK,
KR) we e ound inside he ange o he gas ch oma og aph
de ec ion limi s (MQLCH4=22µgm−2h−1). In o es –mi e
ansi ions he g ound wa e le el in Augus 2005 inc eased
owa ds he su ace and app oached he le els ypically ound
in mi es (Fig. 2b), bu he soil wa e sa u a ion in ansi ions
was no ollowed by CH4emissions such as hose ound in
mi es.
ANOVA showed ha o es loo CH4 luxes di e ed sig-
ni ican ly o he nine o es /mi e ypes o he eco one F(8,
1252) =108, p < 0.001 and o he we , ypical, and d y
yea s F(2, 1252)=10, p < 0.001. The e was a signi ican in-
e ac ion be ween CH4 luxes o o es /mi e ypes and we ,
ypical, and d y yea s F(16, 1252)=5, p < 0.001. The pos
hoc Tukey compa ison o he nine o es /mi e ypes indi-
ca ed ha he mi es had signi ican ly highe CH4 luxes han
he o es s. Di e ences in means (M) and 95% con idence
limi s (CI) anged om minimum VSR2–KgK (M=481,
95% CI [352, 610]) o maximum VSR1–OMT (M=793,
95% CI [668, 918]) a p < 0.001. Also he CH4 luxes o
he mi es we e signi ican ly di e en om each o he VSR2–
VSR1 (M= −260, 95% CI [−384, -137]), p < 0.001. Di -
e ences be ween he yea s we e signi ican a p <0.001 o
d y– ypical (M= −96, 95% CI [−149, −43]) when CH4
luxes o mi es we e highly educed. The compa ison o
mean CH4 luxes o ypical–we (M=51, 95% CI [−6,
108]), p=0.089, and d y–we yea s did no show a signi -
ican di e ence (M= −45, 95% CI [−111, 20]), p=0.237.
Di e ences be ween he o es ypes ( ansi ions, up-
lands) we e no signi ican when analyzed oge he wi h he
CH4 luxes o mi es, bu became signi ican ly di e en F(6,
976)=71, p < 0.001, when ANOVA was un wi hou mi es.
Though unlike he nine o es /mi e ype da a se , o he
Biogeosciences, 12, 281–297, 2015 www.biogeosciences.ne /12/281/2015/
B. ˇ
Tupek e al.: CH4and N2O dynamics in he bo eal o es –mi e eco one 287
Figu e 2. The panels (a–c) show he mon hly medians o en i onmen al a iables: (a) soil empe a u e a a dep h o 5cm, (b) g ound wa e
le el, and (c) olume ic soil mois u e a 10cm dep h obse ed along he o es –mi e eco one du ing we (2004), in e media e (2005), and
d y yea s (2006). The op–down a angemen o si es mimics he loca ions on he slope (see Fig. 1). The e o ba s ep esen he 25 h and
75 h pe cen iles.
Table 4. Pa ame e es ima es and hei s anda d e o s o o es loo N2O luxes (µgm−2h−1) o all o es /mi e ypes (CT–VSR2) in one
g oup Eq. (4). Eq. (4) is unc ion o olume ic soil mois u e a 5cm (%) and soil empe a u e a a dep h o 5cm (◦C).
Eq. (4) a0a0 SE Top Top SE T ol T ol SE NRMSE
o es s/mi es 4.034 0.635 11.268 0.183 1.414 0.181 400 36.2
p < 0.001 o all pa ame e s.
g oup o uplands wi h ansi ions he e was no di e ence be-
ween we , ypical, and d y yea s F(2, 976)=1, p=0.292, o
hei in e ac ions F(12, 976)=1, p=0.135. The mean CH4
up ake o he upland o es s (−42.9µgm−2h−1) was o he
whole pe iod signi ican ly la ge han he mean CH4up ake
o he o es –mi e ansi ions (−12.8µgm−2h−1) acco ding
o Welch’s wo sample es (994)=15.56, p < 0.001. The
pos hoc Tukey compa ison o he di e ences in he mean
CH4 luxes o 21 pai s o se en upland and ansi ional o -
es ypes was signi ican o 17 pai s a p < 0.001 and anged
om OMT–VT (M= −35, 95% CI [−45, −25]) o KR–
OMT (M=51, 95% CI [41, 61]). The pos hoc Tukey com-
pa isons showed non-signi ican p alues o 4 o he 21 pai s
o CH4 luxes o ansi ional and upland o es ypes(MT–CT
0.056, OMT+–VT 0.965, OMT–MT 0.431, and KR–KgK
0.999).
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288 B. ˇ
Tupek e al.: CH4and N2O dynamics in he bo eal o es –mi e eco one
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Figu e 3. The box plo s o o es loo CH4 luxes (µgm−2h−1) o each o es /mi e ype (a), and (b) o uplands (CT, VT, MT, OMT),
ansi ions (OMT+, KgK, KR), and mi es (VSR1, VSR2) du ing he whole pe iod. The le – igh a angemen o si es mimics he loca ions
on he slope (see Fig. 1).
3.3 Fac o s con olling CH4 luxes
The mean le el o CH4 luxes o upland and ansi ional
o es s di e ed (Table 2, pa ame e g oup bi), hough he
sensi i i y esponse o en i onmen al ac o s was simila
(Fig. 4). The la ges pa o he CH4 luxes emained un-
explained wi h ou models, as he p opo ion o explained
a iance was ela i ely low o uplands (10%) and ansi-
ions (15%) and sligh ly highe o mi es (22%). The mod-
eled CH4 lux esponse o he upland and ansi ional o -
es si es o soil mois u e a 10cm was nea ly la , al hough
he soil mois u e pa ame e was signi ican (p=0.011, Ta-
ble 2). In he ansi ional Oxalis-My illus paludi ied o es
ype OMT+, whe e he soil mois u e a 10cm anged om
20% (in he uplands) o o e 70% (in he mi es), he mod-
eled CH4 lux esponse be ween d y and wa e -sa u a ed soil
di e ed by 50µgm−2h−1. A s onge g adien han ha in
he soil mois u e was de ec ed by modeling s onge empe -
a u e esponses o CH4 luxes o he uplands and he nea ly
la esponse o he ansi ions (Fig. 4). The model pa ame e
o soil empe a u e a 5cm in he uplands was highly signi i-
can a p < 0.001, in con as o ansi ions whe e he empe -
a u e pa ame e was insigni ican p=0.629 (Table 2). In he
mi es he obse ed ange o wa e le el du ing we , ypical,
and d y yea s spanned om he su ace o a dep h o 54cm
and showed a sigmoidal esponse wi h lowe CH4 luxes o-
wa ds he ex eme ends. The op imum wa e le el o CH4
emissions was 18cm below he su ace wi h 16.6cm ole -
ance which is de ia ion o wa e le el up o 60% o CH4
lux maximum (Fig. 4; p < 0.001, WTop and WT ol in Ta-
ble 3). Op imum nea -su ace pea empe a u e o he CH4
emissions was ound a 13.9◦C wi h 6.4◦C ole ance (Fig. 4;
p < 0.001, Top and T ol in Table 3).
3.4 N2O luxes
Du ing he ypical and d y yea s he momen a y o es
loo N2O luxes o o es /mi e ypes anged om −107 o
248µgm−2h−1. The median N2O luxes we e simila o
he o es /mi e ypes and anged only om 0 o 6µgm2h−1
(Fig. 5). The median N2O luxes o all o es /mi e ypes we e
ound inside he ange o he me hod quan i ica ion limi s
(MQLN2O=18µgm−2h−1). The N2O luxes o he snow
on he g ound pe iod we e signi ican ly lowe han he N2O
luxes o he snowless pe iod acco ding o Welch’s wo sam-
ple es (297)=5.094, p < 0.001. Fo es loo N2O luxes
did no di e signi ican ly o he nine o es /mi e ypes
o he eco one o he snowless pe iods F(8, 284)=0.708,
p=0.684. Though, he momen a y N2O luxes we e sig-
ni ican ly di e en in ypical and d y snowless seasons F(1,
284)=6.157, p < 0.014. N2O luxes we e lowe du ing d y
snowless seasons and a small inc ease was obse ed only in
one o es –mi e ansi ion (KR – sp uce pine swamp) and in
one mi e (VSR2 – all sedge pine en) (Fig. 6).
In gene al N2O luxes we e low and did no show clea
spa ial di e ences in ela ion o inc easing soil mois u e om
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B. ˇ
Tupek e al.: CH4and N2O dynamics in he bo eal o es –mi e eco one 289
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MT
2 = 8.5 %
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OMT
2 = 9.3 %
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OMT+
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KR
2 = 3.1 %
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10 30 50
0 2000 4000 6000
wa e able dep h (cm)
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VSR1
2 = 9.8 %
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5 15 25 35
wa e able dep h (cm)
adjus ed CH4 (ug m−2 h−1)
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VSR2
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0 5 10 15 20
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CT
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VT
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MT
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OMT+
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KgK
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2 = 12.3 %
soil mois u e a 10 cm (%) wa e able dep h (cm)
soil empe a u e a 5 cm (°C)
adjus ed CH4 (ug m−2 h−1)
Figu e 4. Compa ison o sensi i i y o o es loo CH4 luxes (µgm−2h−1) o en i onmen al ac o s o nine o es /mi e ypes. Modeled
in he uppe panels is CH4 lux esponse o soil mois u e a 10cm (uplands and ansi ions) o o wa e able dep h (cm) (mi es) o uplands
(CT, VT, MT, OMT) Eq. (1), o ansi ions (OMT+, KgK, KR) Eq. (2), and o mi es (VSR1, VSR2) Eq. (3). Wa e able dep h is indica ed
as nega i e when i is abo e he soil su ace. In he lowe panels, CH4 lux esponse (Eqs. 1–3) is modeled o soil empe a u e a 5cm o he
same o es /mi es ypes and du ing he same pe iod as in he uppe panel. The CH4 lux esponse o each indi idual en i onmen al ac o is
illus a ed so ha he simula ed alue o each da a poin was ecalcula ed by allowing only one ac o a a ime o a y while he o he was
se o i s mean le el. To he adjus ed CH4 lux esponses (black poin s) he co esponding esidual o each da a poin was added in o de o
desc ibe he unexplained model a ia ion (g ay poin s). The 2(%) is he p opo ion o explained a iance. The le – igh a angemen o
si es mimics he loca ions on he slope (see Fig. 1).
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−100 −50 0 50 100 150 200 250
o es /mi e ypes
o es loo N2 O (ug m−2 h−1)
Figu e 5. The box plo o o es loo N2O luxes (µgm−2h−1) o each o es /mi e ype (uplands – CT, VT, MT, OMT; ansi ions –
OMT+, KgK, KR; and mi es – VSR1, VSR2) du ing he pe iod including ypical and d y yea s. The le – igh a angemen o si es mimics
he loca ions on he slope (see Fig. 1).
xe ic uplands o wa e -sa u a ed mi es, bu he N2O luxes
we e lowe in he d y han in he ypical yea . The pos hoc
Tukey es s o means and 95% con idence limi s o N2O
luxes o all pai s (excep one) showed insigni ican o -
es /mi e ype pai wise di e ences du ing he whole pe iod
and also du ing he snowless pe iods o we o d y yea s
(Fig. 6). The signi ican N2O lux di e ence o VSR2–OMT
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