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Results
In the southern fen, FRP under warming in wet
conditions, W, showed an increasing trend, which was
not significantly different from FRP under ambient
conditions, however. In contrast, W resulted in lowering
FRP trend compared to ambient in the northern fen
(Fig.1)
Neither drying, WTD, nor warming under drier
conditions, WWTD, affected FRP significantly in the
southern fen. However, in the northern fen, both WTD
and WWTD showed an increasing trend in FRP as
compared to ambient. In addition, FRP was significantly
different between W and WWTD in the northern fen (Fig
1).
Your text would go here.
Responses of fine root production to warming under different water-table
level scenarios in sedge fens
Rabbil Bhuiyan1,2 Päivi Mäkiranta2 Petra Straková2 Timo Penttilä2 Kari Minkkinen1 Hannu Fritze2 Eeva-Stiina Tuittila3 Raija Laiho2
1Department of Forest Sciences, University of Helsinki, Finland 2Natural Resources Institute Finland (Luke) 3University of Eastern Finland , Joensuu, Finland
Introduction
In boreal sedge fen peatlands, carbon sequestration is largely
mediated by sedge roots. Most of sedge biomass, in some cases
more than 90%, is allocated belowground to the root systems
(Sjörs 1991, Saarinen 1996). Thus, roots provide a direct input of
organic matter to the peat, and their turnover is a major
component of the C cycle. A small fraction of change in root
production can thus affect the ecosystem C sink. Climate warming
may affect the production patterns both per se and by shifting
peatlands towards drier conditions. In order to predict the scale
and nature of the likely effects of the warming climate, the
responses of root production in sedge fens need to be assessed.
Methods and aims
Here we examine the effect of warming under wet (ambient) and
drier conditions on fine root production (FRP) and its depth
distribution at two sedge fens in Finland: northern (Lompolo-
jänkkä) and southern (Lakkasuo), using ingrowth cores. FRP was
estimated using ingrowth-dividing method (Bhuiyan et al. 2017).
Warming was induced with open-top chambers (OTC) and drying
with shallow ditches. Contributions to FRP by different plant
functional types were estimated utilizing infra-red spectroscopy.
Figure 1. Fine root production for C- control, W- warming, WTD- water-table drawdown, WWTD-
warming + water-table drawdown) in the southern and northern fens. Bars are standard error of
mean. Different superscript letters indicate significant difference (p˂0.05) between the
treatments. Note the difference in y-axis scales between the two fens.
In the southern fen, warming showed greater FRP for
each depth class compared to ambient , the difference
being significant in the 30-40 cm depth class (Fig 2). In
the northern fen, the depth classes below 10 cm
showed several significant differences between
treatments : C vs WWTD in 10-20 cm, 20-30 cm, 30-40
cm and WTD vs WWTD in 40-50 cm depth class. Only
WTD and WWTD showed any FRP at 50-60 cm.
Figure 2. Distribution of FRP by depth classes for each treatment in the southern and northern
fens. Bars are standard error of mean. The superscript letters indicate significant difference
(p˂0.05) between treatments for each depth class.
In both sites, sedge contribution to FRP was more than
70% under wet (ambient water-level) conditions.
However, after drying (WTD) sedge contribution
decreased in the 0-10 cm of the southern fen and in 10-
60 cm layer of the northern fen, while those of shrubs
and forbs increased (Fig 3).
Figure 3. Relative abundance (%) of each plant functional type (PFT): sedges, forbs, shrubs
estimated by infrared spectroscopy using regression models . Wet represents C+W treatments
and Dry represents WTD+WWTD treatments.
Conclusions
Our results show that FRP can vary widely both between and within sites representing the same habitat type. They further
suggest that the responses of FRP to climate change are in general minor. However, there may be changes in depth
distribution and plant group composition that depend on the moisture regime. Such subtle changes in both the depth
profile and decomposability of the organic matter inputs may yet affect the C cycle of sedge fens in the future.
Correspondence email: rabbil.bhuiyan@helsinki.fi
References:
Bhuiyan R, Minkkinen K, Helmisaari H-S, Ojanen P, Penttilä T, Laiho R (2017) Estimating fine-root production by tree species and understorey functional groups in two contrasting peatland forests. Plant and Soil: 412 (1): 299-316
Saarinen T (1996) Biomass and production of two vascular plants in a boreal mesotrophic fen. Canadian Journal of Botany 74: 934-938
Sjörs H (1991) Phytomass and necromass above and below ground in a fen. Holarctic Ecology 14: 208-218
Southern fen
C W WTD WWTD
R
oo
tp
ro
du
ct
io
n,
g
m
-2
y-
1
0
100
200
300
400
500
Northern fen
C W WTD WWTD
R
oo
tp
ro
du
ct
io
n,
g
m
-2
y-
1
0
50
100
150
200
250
 a
 b
ab
ab
a
         a
 a
 a
Southern fen
Root production, g m-2 y-1
0 20 40 60 80 100 120 140 160 180
S
oi
ld
ep
th
,c
m
60 cm
50 cm
40 cm
30 cm
20 cm
10 cm
C
W
WTD
WWTD
    a
Northern fen
Root production, g m-2 y-1
0 20 40 60 80 100 120
C
W
WTD
WWTD
b
a
a b
b
a
b
a
b
Southern fen
Wet (0-10) Dry (0-10) Wet (10-60) Dry (10-60)
R
el
at
iv
e
ab
un
da
nc
e
of
P
FT
,%
0
20
40
60
80
100
Se
dg
es
Fo
rb
s
Sh
ru
bs
Northern fen
Wet (0-10) Dry (0-10) Wet (10-60) Dry (10-60)
R
el
at
iv
e
ab
un
da
nc
e
of
P
FT
,%
0
20
40
60
80
100
Se
dg
es
Fo
rb
s
Sh
ru
bs
Experimental setup with OTCs and shallow ditches in Lompolojänkkä site