Hyy yläinen e al. Sp inge Plus (2015) 4:478
DOI 10.1186/s40064-015-1253-7
RESEARCH
Seasonal andin e -annual a ia ion
in he chlo ophyll con en o  h ee co-exis ing
Sphagnum species exceeds he e ec o sola
UV educ ion ina suba c ic pea land
Anna Hyy yläinen1*, Pasi Rau io2, Minna Tu unen3 and Sa u Hu unen1
Abs ac
We measu ed chlo ophyll (chl) concen a ion and chl a/b a io in Sphagnum bal icum, S. jensenii, and S. lindbe gii, sam-
pled a e 7 and 8 yea s o ul a iole -B (UVB) and empe a u e manipula ion in an open ield expe imen in Finnish
Lapland (68°N). We used plas ic il e s wi h di e en ansmi ance o UVB adia ion o manipula e he en i onmen al
condi ions. The plan s we e exposed o (1) a enua ed UVB and inc eased empe a u e, (2) ambien UVB and inc eased
empe a u e and (3) ambien condi ions. Chlo ophyll was ex ac ed om he capi ula o he mosses and he con en
and a/b a io we e measu ed spec opho ome ically. Seasonal a ia ion o chlo ophyll concen a ion in he mosses
was species speci ic. Tempe a u e inc ease o 0.5–1 °C and/o a enua ion o sola UVB adia ion o ca. one i h o he
ambien (on a e age 12 s. 59 uW/cm2) had li le e ec on he chlo ophyll concen a ion o i s seasonal a ia ion. In
he dominan S. lindbe gii, UVB a enua ion unde inc eased empe a u e led o a ansien dec ease in chlo ophyll
concen a ion. Al oge he , species-speci ic pa e ns o seasonal chlo ophyll a ia ion in he s udied Sphagna we e
mo e p onounced han empe a u e and UVB ea men e ec s.
Keywo ds: Sphagnum bal icum, Sphagnum jensenii, Sphagnum lindbe gii, Chlo ophyll, UVB, Pea lands
© 2015 Hyy yläinen e al. This a icle is dis ibu ed unde he e ms o he C ea i e Commons A ibu ion 4.0 In e na ional
License (h p://c ea i ecommons.o g/licenses/by/4.0/), which pe mi s un es ic ed use, dis ibu ion, and ep oduc ion in any
medium, p o ided you gi e app op ia e c edi o he o iginal au ho (s) and he sou ce, p o ide a link o he C ea i e Commons
license, and indica e i changes we e made.
Backg ound
Sphagna a e c ucial in o ming and sus aining pea -
lands—speci ic ecosys ems ha main ain a unique di e -
si y o habi a s and species (Clymo and Haywa d 1982;
Vi 2000; Rydin e al. 2006; Rydin and Jeglum 2006) and
unc ion as a la ge s o e o o ganic ca bon, pa icula ly
in bo eal and suba c ic a eas (Go ham 1991; Limpens
e al. 2008). As a key componen o he ecosys em, hey
a ec many p ocesses wi hin i ; he e o e, he changes
igge ed in Sphagna by a changing en i onmen may be
e lec ed in he en i e ecosys em. This is impo an , as
hey a e also suscep ible o changes in he en i onmen ,
including shi s in UVB and empe a u e egime (e.g.
Do epaal e al. 2003; Hu unen e al. 2005; Wiede mann
e al. 2007; Gignac 2011), p incipally due o hei spe-
ci ic s uc u e (lea es o one cell laye , absence o waxes
o any o he p o ec i e su ace s uc u es). In open pea -
lands, Sphagnum mosses a e no shielded by ee cano-
pies and can be exposed o high le els o UVB i adiance.
Gi en he impo ance o Sphagna o he sus ainabili y o
pea lands, conside ing ecen inc eased sola UVB i a-
diance (Wea he head e al. 2005) and ele a ed empe a-
u es a high la i udes (Jylhä e al. 2004; McBean 2005),
i is essen ial ha we unde s and how bo h hese ac o s
a ec pea mosses.
Sola UV adia ion is an impo an en i onmen al ac-
o , egula ing g ow h, biochemis y and some s uc u al
ea u es in b yophy es (Geh ke 1998; Rozema e al. 2005;
Caldwell e al. 2007). UV e ec s on mosses a e species-
speci ic, possibly e lec ing di e ences in desicca ion ol-
e ance (Csin alan e al. 2001). Sphagnum mosses g owing
unde nea -ambien condi ions seem o be able o hold
mo e wa e as hey a e sho e and s ou e , and ha e
Open Access
*Co espondence: anna.koi uleh [email protected]
1 Depa men o Biology, Uni e si y o Oulu, P.O. Box 3000, 90014 Oulu,
Finland
Full lis o au ho in o ma ion is a ailable a he end o he a icle
Page 2 o 11
Hyy yläinen e al. Sp inge Plus (2015) 4:478
la ge capi ula, han hose g owing unde a enua ed
UVB (Robson e al. 2003, 2004). Changes in he in ensi y
o di e en wa eleng hs o sola i adiance a ec shape
and size o chlo oplas s (Glime 2007), as well as pigmen
concen a ion in b yophy es (Niemi e al. 2002a, b).
E en a small enhancemen (by less han 1°C) o sum-
me empe a u es may ha e a signi ican e ec on g ow h
and co e densi y o pea mosses (Do epaal e al. 2003).
These esponses a e species-speci ic, and seem o co e-
la e wi h he equi emen s o a pa icula species o en i-
onmen al condi ions (Gunna sson e al. 2004; B eeuwe
e al. 2008; Ha aguchi and Yamada 2011). Di e ences in
esponses o inc eased empe a u es may, in he long un,
lead o changes in species composi ion in a gi en ecosys-
em. Whe e inc eased empe a u es do no di ec ly a ec
pea mosses, hey may s ill ha e an impac on ascula
plan s (Wel zin e al. 2000). As a consequence, species
ange and a io may change, and ha may be haza dous
o he ecosys em.
The pho osyn he ic pigmen s in Sphagna a e chlo o-
phyll a and b, and ca o enoids. The abso p ion spec a
o he wo chlo ophylls (chls) di e sligh ly (Po a e al.
1989), and plan s use hese di e ences o adap o a y-
ing ligh condi ions. In mosses, he o al chl con en and
a/b a io changes depending on ac o s such as ligh
a ailabili y, plan i ali y, g ow h phase, and a ious en i-
onmen al s esses (Bax e e al. 1992; Ma ínez-Abaiga
e al. 1994; Ge dol 1996; Ma ínez-Abaiga and Núñiez-
Oli e a 1998; Bonne e al. 2010). A de ici o ligh o en
p omo es chl b p oduc ion, educing he chl a/b a io.
To al chl con en is gene ally highe in species ha g ow
in shady habi a s, and lowe in hose commonly ound in
open sunny si es (Ma in and Chu chill 1982; Ma ínez-
Abaiga and Núñiez-Oli e a 1998). Du ing he g owing
season, he chl con en no mally inc eases wi h dec eas-
ing ligh in ensi y. Seasonal pigmen a ia ion is mo e
p onounced in species g owing in a ying ligh condi-
ions, han hose g owing in pe manen ly shady o sunny
habi a s (Ke shaw and Webbe 1986; Ma ínez-Abaiga
and Núñiez-Oli e a 1998). In Sphagna, chl con en is
species-speci ic (Geh ke 1998; Niemi e al. 2002a, b) and
i depends on he ecological equi emen s o he species
(Ye emo e al. 2000; Naumo and Kosykh 2011). Nigh
chilling may cause apid deg ada ion o chls in some
Sphagna (Ge dol e al. 1994).
In Sphagnum mosses, a posi i e co ela ion be ween
chl concen a ion and ne pho osyn hesis has been
eco ded (Gabe ščik and Ma inčič 1987). Thus, en i on-
men al ac o s a ec ing he chl con en in pea mosses
may also a ec he a e o pho osyn hesis. B yophy es
om open sunny habi a s a e no mally adap ed o pho-
osyn hesise unde in ensi e sunligh , some eaching
Pmax a ~1000µmolm−2 s−1 and dissipa ing ex ensi e
ene gy by non-pho ochemical quenching, NPQ (P oc-
o 2000). Howe e , hose species in open en i onmen s
o en expe ience wa e de ici . On he o he hand, b yo-
phy es om shady o es si es a e adap ed o li e unde
as li le as~100–300µmolm−2 s−1 bu mo e a ely ha e
o sus ain d ough . In his sense, Sphagna species ypi-
cal o lawns and ca pe s o open bogs ha e a e y spe-
ci ic posi ion, as hey g ow unde in ensi e ligh usually
ye wi h no wa e de ici . Howe e , Sphagnum species
o open pea lands a e epo ed o ha e lowe pho osyn-
he ic capaci y and maximum quan um yield han hose
ha g ow in he shade (Hájek e al. 2009).
Syne ge ic e ec s o sola UV wi h o he co- a ying
en i onmen al ac o s in b yophy es may be mo e p o-
nounced (Sonesson e al. 2002; Rinnan e al. 2013) o
e en opposi e (Bjö n e al. 1999) o hose o UV alone.
Howe e , s udies o such combined e ec s a e sca ce.
Li le is known abou esponses o di e en Sphagnum
species o simul aneous changes in sola UV and em-
pe a u e egime o e a p olonged pe iod o ime (Son-
esson e al. 2002; Aphalo 2003). UVB a enua ion may
ha e simila e ec s on pea mosses as inc eased summe
empe a u es, ha include e.g. inc easing leng h inc e-
men and simul aneously dec easing he bulk densi y o
moss co e (Do epaal e al. 2003; Robson e al. 2003,
2004). To s udy he impac o UVB and empe a u e on
pea mosses, we conduc ed an open ield expe imen on
a la k en in no he n Finland. We aimed o s udy how
changes in bo h UVB and empe a u e egime a ec con-
cen a ions o chl a and b, and hei a io in h ee Sphag-
num species: S. bal icum, S. jensenii and S. lindbe gii.
Al hough a ying in co e age, hese we e he mos com-
mon pea moss species on he expe imen al si e.
We hypo hesized ha unde a enua ed sola UVB and
sligh ly ele a ed empe a u e chlo ophyll p oduc ion in
Sphagnum mosses would inc ease. We sugges ed ha
UVB-a enua ion plo s migh p o ide he mos a ou -
able condi ions o plan g ow h, because o he elease
o appa en nega i e UVB e ec s and a pa allel inc ease
in empe a u e. Addi ionally, he polyes e il e s used o
c ea ing −UVB condi ions pa ly ansmi UVA, which
may ha e posi i e e ec on plan s (Niemi e al. 2002b).
Hence, we expec ed a highe chlo ophyll concen a ion
in he mosses g owing in he UVB-a enua ion plo s.
Me hods
The UVB a enua ion expe imen ook place in no h-
e n Finland on a emo e oligo ophic all-sedge Sphag-
num la k en, in Kal io uoma, Vuo so, abou 200 km
om Pola Ci cle [263 m a.s.l., 68˚10′N, 26˚42′E
(75649:34878)] (Soppela e  al. 2006). This open ield
expe imen was a pa o he ECOREIN p ojec (The eco-
logical and socioeconomical esponses o global change
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Hyy yläinen e al. Sp inge Plus (2015) 4:478
on eindee pas u es). The e o e, he expe imen al si e
ep esen ed a ypical eindee summe pas u e, whe e
pea mosses domina ed in he g ound laye , mos abun-
dan being S. lindbe gii, S. jensenii, S. angus i olium,
and S. bal icum. The ield laye was cha ac e ized by
sedges (E iopho um usseolum, E. angus i olium, Ca ex
o unda a, C. os a a, C. limosa, C. magellanica subsp.
i igua, Scheuchze ia palus is), he bs (Menyan hes i-
olia a, Rubus chamaemo us) and sh ubs (And omeda
poli olia, Be ula nana, Vaccinium oxycoccus, V. mic o-
ca pum). Chemical analysis o he uppe subs a e laye
(0–30 cm) ga e he ollowing esul s: pH 4.2, ca bon
( o al o ganic ca bon) 41.5%, ni ogen 0.64%, ca bon/
ni ogen a io 65, ammonium (NH4) 82.9mgkg−1, ni a e
(NO3) <0.2 mg kg−1 and ammonium-lac a e ex ac ed
(i.e., plan -a ailable) nu ien s: phospho ous 45mgkg−1,
calcium 1.680 mg kg−1, magnesium 568 mg kg−1 and
po assium 133mgkg−1 (Soppela e al. 2006; Ma z e al.
2009).
Expe imen al design
In 2001, a si e o abou one hec a e was enced o on he
a ea, o p o ec i om eindee . In 2002, 30 andomly
a anged plo s we e es ablished on he si e (Fig.1). Each
plo was su ounded by a wooden ame (100×100cm).
Th ee ea men s we e used in he expe imen : (1) a en-
ua ed UVB (−UVB) plo s, wi h ames co e ed by a clea
polyes e ilm, 0.125mm hick (Poli oil, KTA L d., Hel-
sinki, Finland), (2) con ol plo s, co e ed wi h a clea
sol en cas ace a e ilm (Cla i oil, De by, UK), and (3)
ambien plo s whe e ames we e no co e ed. Each ea -
men was eplica ed en imes. The polyes e ansmi -
ed less han 1% o UV adia ion below 315nm, 30% a
320nm and abou 70% abo e 330nm, while he cellulose
ace a e il e ansmi ed i adiance abo e 290nm e i-
cien ly bu less han 1% o UV adia ion below 290nm
(Soppela e al. 2006). Howe e , due o di use adia ion,
ac ual UVB alues eaching he mosses unde he il e s
we e highe . Unde he polyes e il e s he adia ion was
on a e age 20% and unde cellulose ace a e il e s abou
72% o ha in ambien plo s (12.1± 0.3 uW/cm2 in
–UVB, 42.1±1.1 uW/cm2 in con ol, and 58.6±3.1 uW/
cm2 in ambien plo s, mean±SE).
Ambien UV i adiance was measu ed wi h a spec o-
pho ome e B ewe MKII (SCI-TEC, Canada), ins alled
on he oo o a building a he A c ic Resea ch Cen e
o he Finnish Me eo ological Ins i u e (FMI-ARC) in
Täh elä, Sodankylä (67˚22′N, 26˚38′E), as desc ibed in
Ma z e  al. (2007). The ambien biologically e ec i e
UVB (UV-BBE) i adiance was calcula ed acco ding o
Caldwell e al. (1980), and e e s o UV-BBE calcula ed
wi h he gene alized plan ac ion spec um (Caldwell
1971) (Fig.2a). We also pe o med UVB measu emen s
in he ield in 2008, while sampling, using a po able
me e AIRAM UVM-8 (Ka a Tekniikka Oy, Helsinki),
equipped wi h a UVM-8B senso (wa eleng h a ea: 270–
370nm, max sensi i i y 310nm) (Fig.2b). Addi ionally,
Fig. 1 View o some o he plo s and he walkway in he UVB a enu-
a ion expe imen in Vuo so, no he n Finland
b
a
Fig. 2 a Sola UV-BBE daily maxima in 2007–2008 (FMI, Sodankylä).
b Sola UVB i adiance measu ed in Vuo so expe imen al si e in 2008.
The labels p esen mean da a ±1 SD
Page 4 o 11
Hyy yläinen e al. Sp inge Plus (2015) 4:478
we measu ed he pH o he subs a e wa e wi h a po -
able pH me e (Tes o 206, Lenzki ch, Ge many) (Fig.3).
Each plo was equipped wi h a po able empe a u e
da alogge (Tiny Talk II, −40 o 75°C; OTLM So wa e,
O ion Componen s, L d., Chiches e , UK), a ached o
he cen al pole abou 15cm below he il e and 15cm
abo e he su ace o he Sphagnum laye a he begin-
ning o each g owing season. Tempe a u e was eco ded
e e y 1.5h. Due o he ilm co e , he empe a u e in
−UVB and con ol plo s inc eased up o 1°C, compa ed
o he ambien plo s. The a e age empe a u e o he
pe iod o eco d in 2008 (14 h June–27 h Augus ) was
13.8±0.09°C in ambien , 14.8±0.09°C in con ol, and
14.5±0.09°C in –UVB plo s (mean±SE). Di e ences
in empe a u e among he h ee ea men s we e s a is i-
cally signi ican (F2,26=30.5, p<0.001).
E e y yea we e-ins alled he ames a he si e, adjus -
ing new plas ic il e s in May–June, as soon as wea he
condi ions allowed access o he expe imen al si e, bu
be o e he plan s s a ed o g ow. Du ing he g owing
season, he ames we e g adually aised, o allow he all-
es sedges o g ow eely unde he ilms. The il e s we e
also sligh ly ele a ed in he cen e by a e ical pole so
ha he ainwa e d ained o he sides, keeping he il e
d y. No addi ional wa e was gi en o he plo s, because
e en in a e y d y summe he wa e able in he en
emains s able (Fig.4). The expe imen al pe iods we e as
ollows: 6 June–5 Sep embe 2002 (91days), 19 May–3
Sep embe 2003 (107days), 17 June–6 Sep embe 2004
(81days), 29 June–9 Sep embe 2005 (72days), 31 May–
18 Sep embe 2006 (110days), 16 June–20 Sep embe
2007 (96days), 14 June–28 Augus 2008 (74days).
Sampling andmeasu emen s
Fo chlo ophyll analysis, we chose S. lindbe gii, S. jensenii,
and S. bal icum, which make up, espec i ely 87, 5 and
3% o he g ound co e in he expe imen al plo s (co e
pe cen ages calcula ed as a mean alue om he 30 sam-
ple plo s). We sampled S. lindbe gii (n=8–10 samples
pe ea men ) in 2007 (12 July, 26 July, 23 Augus , 27
Sep embe ) and 2008 (13 June, 3 July, 24 July, 28 Augus )
o ollow bo h seasonal and yea - o-yea changes in chlo-
ophyll concen a ion. Each sample is a pooled sample o
10 capi ula collec ed om each o he 30 expe imen al
plo s. When analysing yea - o-yea changes in chl con-
cen a ion, di e ences in he sampling da es be ween he
2yea s had o be aken in o accoun . To analyse in e -
species and seasonal a ia ion, we also collec ed S. bal-
icum and S. jensenii (n=5–10 pe ea men , due o
smalle co e age o he species in he plo s) in 2008 (3
July, 24 July, 28 Augus ). The samples we e immedia ely
imme sed in liquid ni ogen and anspo ed o he labo-
a o y o he Na u al Resou ces Ins i u e Finland (Luke)
in Ro aniemi. The ma e ial was kep in a supe eeze
(−80°C) p io o analysis. I was hen lyophilized and
g ound. Exac ly 15mg (DW) o each sample we e scaled,
and used o chlo ophyll ex ac ion wi h pu e me hanol
(1.5ml pe sample) in 24h, a +4°C, in he da k. The
abso bance o he me hanol ex ac was measu ed a
652.0, 665.2 and 750nm wi h a spec opho ome e (Shi-
madzu-1700), and he concen a ion o chlo ophyll a and
b, and o al chlo ophyll (µgml−1) was calcula ed ollow-
ing Po a e al. (1989).
S a is ical analysis
The da a we e analysed by he means o linea mixed
models in which he sampling da e was aken as he
Fig. 3 pH measu emen s in he ield showed ha subs a e acidi y
did no signi ican ly di e in di e en ea men s. Values a e es i-
ma ed ma ginal means ± 90 % con idence in e als
Fig. 4 No addi ional wa e was gi en o he plo s, because e en in
a e y d y summe he wa e able in he en emains s able unde
hese cool and humid condi ions. Ca ex sp., Menyan hes i olia a and
Sphagna seen in he pic u e seem o g ow s aigh on wa e
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Hyy yläinen e al. Sp inge Plus (2015) 4:478
epea ed ac o . In cases whe e he chlo ophyll concen-
a ions o all he h ee species we e compa ed, bo h he
species and he ea men we e ixed ac o s. The species
was no aken as a ac o when analysing chlo ophyll con-
cen a ion in S. lindbe gii alone, and subs a e pH unde
di e en ea men s. Due o he epe i i e sampling om
he same plo s he da a con ained a co ela ion s uc u e.
The co a iance s uc u e o he epea ed ac o was he -
e ogeneous i s -o de au o eg essi e (ARH1), which was
selec ed on he basis o he lowes Akaike’s in o ma ion
c i e ia (AIC) alue. Fo linea mixed models, Es ima ed
Ma ginal Means (EMMEANS) and 90 % con idence
in e als we e compu ed, and a e p esen ed in Figs.3,
5 and 6. Hence, hose means wi h non-o e lapping
con idence in e als a e s a is ically signi ican ly di e en
(a p<0.05; Figs.3, 5, 6). Co ela ions be ween en i on-
men al and chlo ophyll concen a ion da a we e com-
pu ed as Pea son’s co ela ion coe icien s (Addi ional
iles 1, 2). Co ela ions be ween he chlo ophyll con en
and subs a e pH we e compu ed as Spea man’s co ela-
ion coe icien s. S a is ical analyses o he da a we e pe -
o med using IBM SPSS S a is ics 19.0.
Resul s
Seasonal andin e ‑annual a ia ion
P io o sampling, he h ee co-exis ing Sphagnum spe-
cies g ew unde a enua ed UVB and enhanced empe a-
u e condi ions o six g owing seasons (2002–2007). We
a
b
c
Fig. 5 Seasonal a ia ion o o al chlo ophyll con en in a Sphagnum bal icum, b S. jensenii and c S. lindbe gii unde ambien (open ba s), con-
ol (da k g ey ba s) and −UVB ea men (ligh g ey ba s). Fo S. lindbe gii, he da a o 2007–2008 a e shown. Values a e es ima ed ma ginal
means ± 90 % con idence in e als

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Hyy yläinen e al. Sp inge Plus (2015) 4:478
de ec ed signi ican species-speci ic seasonal a ia ion in
chlo ophylls a, b, a+b, and chl a/b in hese species du -
ing he expe imen (2007–2008, Figs.5, 6; Table1). The e
was also signi ican in e -annual a ia ion in Sphagnum
lindbe gii (Tables1, 2; Figs.5c, 6).
In 2008, concen a ion o chlo ophyll in he dominan
S. lindbe gii inc eased sha ply om e y low concen-
a ions in mid-June o be ween wo and six imes ha
amoun by July, hen emained ai ly s able o he es
o he season. In bo h S. jensenii and S. bal icum, chlo-
ophyll concen a ion dec eased signi ican ly owa ds he
end o he summe in all he ea men s (Fig.5). S. bal i-
cum had signi ican ly lowe chlo ophyll alues han he
o he wo species.
In S. lindbe gii, chlo ophyll concen a ion was no ice-
ably lowe in 2007 compa ed o 2008 (Fig.5c). I also
a ied signi ican ly du ing he g owing season o 2007,
being highes in July, dec easing a he end o summe
Fig. 6 In e annual a ia ion o chlo ophyll a/b a io in S. lindbe gii unde ambien (open ba s), con ol (da k g ey ba s) and −UVB ea men (ligh g ey
ba s). Values a e es ima ed ma ginal means ± 90 % con idence in e als
Table 1 E ec o UVB ea men , species, andsampling da e onconcen a ion o chlo ophyll a andb, o al chlo ophyll
(a+b) anda/b a io
Fo each e ec and hei in e ac ions F alues and s a is ical signi icance o mixed linea model analysis a e p esen ed
Sou ce Chl aChl bChl a + bChl a/b
F p alue F p alue F p alue F p alue
T ea men 4.3 0.017 2.8 0.067 3.8 0.025 0.5 0.636
Species 52.1 <0.001 63.8 <0.001 56.4 <0.001 13.4 <0.001
Da e 90.7 <0.001 79.9 0.000 90.8 <0.001 7.3 <0.001
T ea men × species 1.0 0.391 0.7 0.620 0.8 0.500 0.4 0.776
T ea men × da e 3.4 0.003 2.3 0.037 3.2 0.005 1.7 0.124
Species × da e 11.1 <0.001 7.2 <0.001 10.1 <0.001 8.3 <0.001
T ea men × species × da e 2.0 0.050 1.6 0.127 1.8 0.088 4.7 <0.001
Table 2 E ec o UVB ea men andsampling da e onconcen a ion o chlo ophyll a andb, o al chlo ophyll (a+b)
anda/b a io inSphagnum lindbe gii
Fo bo h e ec s and hei in e ac ion F alues and s a is ical signi icance o mixed linea model analysis a e p esen ed
Sou ce Chl a Chl b Chl a+b Chl a/b
F p alue F p alue F p alue F p alue
T ea men 0.69 0.504 0.43 0.65 0.59 0.559 4.97 0.01
Da e 66.7 <0.001 55.4 <0.001 64.5 <0.001 47.4 <0.001
T ea men × da e 2.16 0.03 1.81 0.07 2.13 0.032 1.48 0.158
Page 7 o 11
Hyy yläinen e al. Sp inge Plus (2015) 4:478
and inc easing again in Sep embe . The chl a/b a io in
his species was signi ican ly lowe in 2007 han in 2008
(Fig.6).
T ea men e ec s
Th oughou he expe imen , combined empe a u e and
UVB manipula ion had only mino e ec s on he chosen
Sphagnum species in his habi a , and hese e ec s we e
da e-dependen (Tables 1, 2; ea men e ec includes
bo h UVB and empe a u e manipula ion). A ansien
UV e ec was de ec ed on he 3 d July 2008 in S. lind-
be gii as a highe chl a+b concen a ion in he plan s
unde con ol condi ions, compa ed o hose in he UVB-
a enua ed ea men (Fig.5c).
A signi ican empe a u e e ec was obse ed in S.
lindbe gii in 2008 (Figs.5c, 6). By he end o he g owing
season in 2007 (27 h Sep embe ), plan s unde di e en
ea men s had app oxima ely he same concen a ion
o o al chlo ophyll and chl a/b a io. Howe e , when
he nex season s a ed (13 h June 2008), chlo ophyll
concen a ion and a/b a io inc eased signi ican ly in
only he ambien plo s, while in he plan s unde he il-
e s hese pa ame e s emained a he le el o he p e-
ious yea . By con as , la e in he season o 2008, he
chlo ophyll concen a ion inc eased sha ply ( ou –six
old) in S. lindbe gii unde he il e s, while in ambien
condi ions less so ( wo old). The chl a/b a io in his
species emained s able in ambien condi ions o he
whole g owing season in 2008, while in he plo s wi h
inc eased empe a u e he a io was signi ican ly lowe
a he beginning o he season (Fig.6). Addi ionally, he
empe a u e e ec was obse ed in S. lindbe gii on 23 d
Augus 2007, as a highe chl a/b in ambien compa ed o
con ol plo s.
Discussion
Seasonali y in physiological cha ac e is ics is ypi-
cal o b yophy es, oge he wi h wide a ia ion in ligh
esponses be ween he species (P oc o 2000). Whe e
ligh in ensi y a ies subs an ially du ing he g owing
season ( o example, in a deciduous o es —due o can-
opy closu e), chlo ophyll con en and chl a/b a io in
mosses change no iceably in line wi h ligh a ailabili y. In
open pea lands, by con as , Sphagnum mosses expe i-
ence ela i ely high i adiance, which emains s able o
a p olonged pe iod o ime. This may explain why in S.
lindbe gii, bo h o al chlo ophyll concen a ion and chl
a/b a io we e ai ly s able in July–Augus 2008 (Figs.5c,
6). This is in compliance wi h he esul s ound by Mish-
le and Oli e (1991) in hei s udy o b yophy es in open
sunny habi a s. Highe and mo e s able o al chlo ophyll
concen a ion and highe chl a/b a io in S. lindbe gii in
2008 compa ed o 2007 could ha e been due o highe
(253mm in 2008 s. 220mm in 2007) and mo e e enly
dis ibu ed p ecipi a ion du ing summe ha yea (FMI
2007–2008) (Fig.7a).
An inc ease in o al chl wi h dec easing ligh in ensi y
and day leng h may be expec ed in au umn (Ke shaw and
Webbe 1986; Niemi e al. 2002b), as we eco ded om
he samples o S. lindbe gii in au umn 2007. Howe e , in
S. bal icum and S. jensenii, he o al chl con en ell a he
end o he g owing season, as consis en wi h he indings
o Lappalainen e al. (2008) and Ge dol (1996). These spe-
cies wi h low co e age on he si e ha e mo e speci ic sub-
s a e equi emen s. S. bal icum is usually ound on e y
poo omb o ophic bogs wi h subs a e pH<4.5, while
S. jensenii al hough g owing a wide pH ange (4.1–5.9),
p e e s mo e mine o ophic condi ions o poo and in e -
media e ens (Woj uń e al. 2013). The dominan S. lind-
be gii is compa a i ely lexible, success ully g owing in a
wide a ie y o ophic condi ions, om omb o- o min-
e o ophic si es, wi h pH o he subs a e anging wi hin
ca. 4.0–5.8 (Gunna sson e al. 2004; Laine e al. 2009;
Woj uń e al. 2013). In he la e species, he chlo ophyll
concen a ion did no dec ease a he end o he g owing
season in 2008. The di e ences be ween he species a e
clea ly seen when analysing co ela ion be ween chlo o-
phyll con en and pH o he subs a e wa e . A signi ican
nega i e co ela ion was ound be ween he con en o
chl a and chl b and subs a e pH in bo h S. bal icum and
S. jensenii, whe eas in S. lindbe gii chl con en did no
seem o be co ela ed wi h pH in none o he ea men s
(Table3).
Tempe a u e and ligh in ensi y oge he a ec pho o-
syn he ic a es in mosses (P oc o 2011), and hus may
ha e po en ial o a ec chlo ophyll con en in Sphagna;
empe a u e e ec s on pho osyn he ic pigmen s in pea
mosses depend on ligh in ensi y (Ha aguchi and Yam-
ada 2011). Ce ain Sphagnum species a e adap ed o
ha e high pho osyn he ic a es a high empe a u es and
in ensi e ligh , o a low empe a u es and low ligh le -
els. Low empe a u es a high ligh in ensi y may ha e a
nega i e e ec on hei pho osyn hesis (Ha aguchi and
Yamada 2011) and may ha e been one o he easons o
low chlo ophyll con en obse ed in S. lindbe gii in mid
June 2008. Low chlo ophyll con en a he beginning
o he season migh also be due o ac i e g ow h, when
shoo s a e g owing as , and chlo ophyll biosyn hesis
a es do no ma ch hose o shoo g ow h (Ke shaw and
Webbe 1986). La e in he season, in ensi e ligh com-
bined wi h high ambien empe a u e may explain he
inc ease in o al chlo ophyll in S. lindbe gii (Fig.7).
Du ing his expe imen , he species-speci ic seasonal
changes in chlo ophyll concen a ions obse ed we e
mo e p onounced han he ea men e ec s (Table4).
The s udied pea mosses, coexis ing in he same habi a ,
Page 8 o 11
Hyy yläinen e al. Sp inge Plus (2015) 4:478
a
b1
b2
c
Fig. 7 En i onmen al da a: a P ecipi a ion in June–Augus 2007–2008 (FMI, Sodankylä). b Tempe a u es, measu ed du ing he g owing season
in he expe imen al si e in Vuo so. Mean, maximum and minimum alues in di e en ea men s a e shown. c Daily sum o ne adia ion, no mal-
ized, kJ/m2 (FMI, Sodankylä). Ve ical lines poin he sampling da es (dashed o 2007, solid o 2008)
Page 9 o 11
Hyy yläinen e al. Sp inge Plus (2015) 4:478
showed qui e uni o m esponse o expe imen ally al e ed
condi ions, bu di e ed in hei esponses o na u al sea-
sonal changes in ligh and empe a u e egime. Tempe a-
u e and UVB manipula ion we applied seemed o play
a lesse ole in plan acclima ion han ecophysiological
cha ac e is ics o a species, he unique combina ion o i s
niche equi emen s. In he gi en condi ions, S. lindbe -
gii seemed o be able o acclima e o a wide spec um o
en i onmen al condi ions, and o wi hs and en i onmen-
al changes be e han he mo e omb o ophic S. bal-
icum o mo e mine o ophic S. jensenii (Gignac 2011).
I is possible ha he abili y o sus ain he le el o chlo-
ophyll du ing he g owing season is one o he ea u es
ha helps S. lindbe gii o keep i s dominan posi ion,
compa ed o he o he wo Sphagna, in he gi en habi a .
Ini ially we hypo hesized ha Sphagnum mosses g ow-
ing in he UVB-a enua ion plo s would ha e highe
chlo ophyll con en as compa ed o he mosses in he
ambien o con ol condi ions. Howe e , measu emen s
e ealed a highe chlo ophyll concen a ion and chl a/b
a io in S. lindbe gii sampled om ambien plo s a he
beginning o he season in 2008. This may be due o
be e o e win e ing abili ies and highe pho osyn he ic
ac i i y in he plan s in ambien condi ions compa ed
o hose g owing unde inc eased empe a u es (Gun-
na sson e al. 2004). Highe o al chlo ophyll con en in
S. lindbe gii in he con ol compa ed o −UVB plo s on
3 d o July 2008 may also be explained by he highe UVA
adia ion doses unde cellulose ace a e il e s.
A he end o he g owing season in 2008, we de ec ed
no s a is ical di e ences be ween he ea men s; ins ead,
he e we e signi ican di e ences among he species in
each ea men . This indica ed ha i was no he changes
in empe a u e and UVB i adiance ha a ec ed he
chlo ophyll seasonali y mos , bu a he species adap -
abili y and hei habi a equi emen s.
Conclusions
A sligh empe a u e inc ease and/o a signi ican a enu-
a ion o sola UVB adia ion ( o less han 1% o he ambi-
en ) had no clea e ec on he chlo ophyll concen a ion
o i s seasonal a ia ion in he Sphagnum species g owing
in an open en. Al oge he , he species s udied seemed o
be adap ed o he changes in he en i onmen hey we e
Table 3 Co ela ion be weenpH o  he subs a e andchlo ophyll con en in he h ee co-exis ing Sphagnum species
inambien andexpe imen ally al e ed empe a u e andUVB condi ions
*Co ela ion is signi ican a he 0.05 le el (2- ailed)
**Co ela ion is signi ican a he 0.01 le el (2- ailed)
pH ina ea men S. bal icum S. jensenii S. lindbe gii
Chl aChl bChl aChl bChl aChl b
Ambien
Spea man’s ho −.506** −.535** −.522** −.494** .150 .055
p alue .008 .005 .004 .007 .446 .781
N26 26 29 29 28 28
Con ol
Spea man’s ho −.464* −.630** −.607** −.566** −.189 −.308
p alue .030 .002 .000 .001 .327 .105
N22 22 29 29 29 29
–UVB
Spea man’s ho −.449* −.594** −.404* −.326 .167 .217
p alue .024 .002 .041 .105 .387 .259
N25 25 26 26 29 29
Table 4 Co ela ions (Pea son co ela ion coe icien s) be ween he o al chlo ophyll concen a ion (Chl) o  he h ee
s udied species and empe a u e andUVB on he h ee di e en da es he UVB was measu ed andsamples collec ed
The empe a u e is he daily mean o he p eceding da e. S a is ically signi ican (p<0.05) co ela ion coe icien s ma ked wi h as e isk
Da e Chl inS. bal icum Chl inS. jensenii Chl inS. lindbe gii
Tempe a u e UVB Tempe a u e UVB Tempe a u e UVB
3.7.2008 .238 −.169 .193 .148 .282 .431*
24.7.2008 .076 −.240 −.349 .351 .220 −.129
28.8.2008 −.214 .352 −.055 .092 .005 −.036