A decade of vegetation development on two revegetated milled peatlands with different trophic status

Abstract

Milled peatlands in the Northern Hemisphere are frequently restored in order to mitigate negative effects of climate change and to benefit biodiversity. The aims of this study are to analyse the development of vegetation on milled peatlands in Estonia after restoration using the moss layer transfer technique (MLTT), relate the plant functional type cover with peat chemical factors, and study correlations between bryophyte and vascular plant cover on sites with different vegetation composition. Nutrient-poor (NP) Viru and nutrient-rich (NR) Ohtu milled peatlands in Northern Estonia were restored via MLTT between 2006 and 2008. Plant species cover was determined annually or biannually from 2009 to 2018, on permanent plots established during the restoration of both sites. Plant functional type cover was assessed in relation to peat chemical properties and time since restoration. The nutrient status of the restoration site plays a major role in vegetation succession, even if similar restoration methods have been applied. Vascular plant cover, especially evergreen shrubs, increased with time since restoration, while bryophyte (mainly Sphagnum) cover increased at the NP site and decreased at the NR site. At the NR site bryophyte cover decreased with increasing vascular plant cover, while the opposite pattern was observed at the NP site.

Full text

Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
1
A decade of vegetation development on two revegetated
milled peatlands with different trophic status
Anna-Helena Purre1, Laimdota Truus2, Mati Ilomets2
1 School of Natural Sciences and Health, Tallinn University, Tallinn, Estonia
2 Institute of Ecology, Tallinn University, Tallinn, Estonia
_______________________________________________________________________________________
SUMMARY
Milled peatlands in the Northern Hemisphere are frequently restored in order to mitigate negative effects of
climate change and to benefit biodiversity. The aims of this study are to analyse the development of vegetation
on milled peatlands in Estonia after restoration using the moss layer transfer technique (MLTT), relate the
plant functional type cover with peat chemical factors, and study correlations between bryophyte and vascular
plant cover on sites with different vegetation composition. Nutrient-poor (NP) Viru and nutrient-rich (NR)
Ohtu milled peatlands in Northern Estonia were restored via MLTT between 2006 and 2008. Plant species
cover was determined annually or biannually from 2009 to 2018, on permanent plots established during the
restoration of both sites. Plant functional type cover was assessed in relation to peat chemical properties and
time since restoration. The nutrient status of the restoration site plays a major role in vegetation succession,
even if similar restoration methods have been applied. Vascular plant cover, especially evergreen shrubs,
increased with time since restoration, while bryophyte (mainly Sphagnum) cover increased at the NP site and
decreased at the NR site. At the NR site bryophyte cover decreased with increasing vascular plant cover, while
the opposite pattern was observed at the NP site.
KEY WORDS: moss-layer-transfer technique, peat nutrient content, peatland restoration, plant functional
types, Sphagnum spp.
_______________________________________________________________________________________
INTRODUCTION
Peat milling is ongoing across vast areas of the
Northern Hemisphere and has a detrimental effect on
peatland ecosystems. Estimated losses due to peat
extraction range from about 0.1 % (Clarke & Rieley
2019) up to 10 % of the global mire area (Joosten &
Clarke 2002). About 6 % of the peatland area in
Estonia has been (directly or indirectly) affected by
peat mining (Ilomets 2017), leaving mainly bare peat
areas which are emitting large quantities of CO2 to the
atmosphere. Karofeld et al. (2016) emphasise the
need to prioritise the peatland restoration in Baltic
countries in comparison with other reclamation
options (e.g. afforestation, berry plantation, biomass
production). This reclamation option mitigates the
climate impact of milled peatlands. Abandoned
milled peatlands may remain largely unvegetated for
long periods if not restored. Although vegetation
development after restoration activities can be rapid
(Tuittila et al. 2000, Poulin et al. 2013), species
composition may remain dissimilar to pristine bogs
even decades following restoration (Pouliot et al.
2012). The indicator of successful peatland
restoration activities is considered to be the recovery
of Sphagnum or true moss dominated vegetation in
nutrient-poor and nutrient-rich sites respectively
(Rochefort 2000). Plant functional types (PFTs) are
used for classification of plant species according to
their physical, phylogenetic and phenological
characteristics for describing the ecosystem
behaviour. PFTs such as Sphagnum, true mosses, but
also vascular PFTs e.g. shrubs, sedges and forbs differ
in their stoichiometry (Wang & Moore 2014) and also
carbon exchange (Ward et al. 2009, Kuiper et al.
2014, Purre et al. 2019). In primary mire succession,
plant species richness and functional diversity
generally increase with time during the fen–bog
transition in northern peatlands (Laine et al. 2018).
Active restoration of milled peatlands supports the re-
establishment of peatland-specific plant species,
while unrestored sites are dominated by ruderal
species (Poulin et al. 2013).
During natural succession of bare peat surfaces,
the abundance of pioneer plant species increases and
then decreases rapidly. Plants which are abundant
after the pioneer species have large interannual
fluctuations, while abundant plant species during the
later stages of succession increase their cover steadily
(Feldmeyer-Christe et al. 2011). There are two main

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
2
successional pathways (towards fen or raised bog
vegetation), which depend on the properties of the
residual peat layer (Triisberg et al. 2014, Renou-
Wilson et al. 2019). Sphagnum and ombrotrophic
sedges prevail in nutrient-poor (NP) areas while
minerotrophic sedges and true mosses are more
dominant at more nutrient-rich (NR) milled peatlands
(Gagnon et al. 2018, Kozlov et al. 2018, Zając et al.
2018, Renou-Wilson et al. 2019). Vegetation
development in NP peatlands is slower than in NR
peatlands (Kozlov et al. 2018). Additional insight is
needed as to how similar restoration activities applied
to different milled peatlands with varying trophic
status affect revegetation dynamics and therefore
restoration success.
Site specific conditions such as type, thickness of
the residual peat layer, and nutrient availability
influence the restoration outcome. After restoration,
the first species to arrive are those that are distributed
by wind or through active restoration, while plant
species that are resilient to harsh conditions (water
table fluctuations, frost heave and so on) increase
their cover more steadily (Triisberg-Uljas et al.
2018). Application of the moss layer transfer
technique (MLTT) (Rochefort et al. 2003) has been
considered likely to be beneficial according to a
synthesis by Taylor et al. (2019). But it depends on
site specific and management factors and can result in
vegetation dominated by Sphagnum and other
peatland species, but also bare peat or Polytrichum
strictum (González et al. 2013, González & Rochefort
2014), which could evolve in the direction of
Sphagnum domination with time (González &
Rochefort 2014).
Knowledge about the long-term development of
peatland vegetation after the restoration of milled
peatlands with MLTT remains limited in Europe
relative to North America. In Europe, MLTT has
mainly been applied on Sphagnum farming sites
(Beyer & Höper 2015, Gaudig et al. 2017, Krebs et
al. 2017), where environmental conditions are kept
favourable for Sphagnum growth and active
management measures are applied throughout the
studies. Such high-level management activities are
not cost-effective to apply on large-scale peatland
restoration sites, where active management is not
carried out after initial restoration practice, and this
distinguishes restoration sites from the Sphagnum
farming sites. In Europe, restoration works are mainly
done using rewetting and without spreading of
bryophyte fragments and mulching (Tuittila et al.
1999, Tuittila et al. 2000, Wilson et al. 2007, Soini et
al. 2010, Beyer & Höper 2015, Wilson et al. 2016),
which does not support the recolonisation of typical
hummock Sphagnum (Smolders et al. 2003, González
et al. 2014a). Only a few studies conducted in milled
peatlands in Europe analyse different aspects of
restoration success on sites, where MLTT or other
ways of Sphagnum reintroduction have been applied
for experimental or restoration purposes (Smolders et
al. 2003, Tuittila et al. 2004, Karofeld et al. 2015,
Järveoja et al. 2016, Purre & Ilomets 2018, Purre et
al. 2019, Karofeld et al. 2020, Purre et al. 2020).
Previously we have demonstrated that two milled
peatland sites restored using MLTT but having
different peat chemistry vary by their bryophyte
biomass production and we related production of
different bryophyte groups to variations in
differences in peat chemical factors (Purre & Ilomets
2018) and the effect of different treatments of MLTT
to restoration outcome based on plant biomass (Purre
et al. 2020). The current paper provides insight to the
development of vegetation cover, including
bryophyte and vascular PFTs and their temporal
variations after the restoration activities in these two
sites in relation with peat chemical factors. The aims
of the study are to (1) relate the plant functional type
cover with peat chemical factors, (2) analyse the
development of vegetation composition for over a
decade on milled peatlands restored using MLTT at
two sites, and (3) study relationships between
bryophyte and vascular plant cover on sites with
different vegetation composition.
METHODS
Study sites
The Ohtu (59° 17' 18" N, 24° 23' 11" E) and Viru
(59° 28' 29" N, 25° 39' 28" E) sites, henceforth NR
and NP respectively, are experimental restoration
sites on milled peatlands in Northern Estonia. At NR
(nutrient-rich), milling continued until Sphagnum
- Carex peat was reached; whereas at NP (nutrient-
poor), some less-decomposed Sphagnum peat was left
in the residual peat layer. NR is bordered by drained
peatland forest dominated by Pinus sylvestris on one
side and by active milled peatland on the other sides.
NP is located in the middle of rewetted milled
peatland (rewetted in 2011–2013) bordered with
P. sylvestris dominated forests and adjoins an old peat
transportation road flanked by Betula pendula.
All sparse vegetation that was present before
restoration was removed with the upper 10 cm layer
of mineralised peat from both sites. Restoration by
MLTT (Rochefort et al. 2003) was carried out in 2006
in NR and 2008 in NP, correspondingly two and 23
years after peat extraction. Plant material for
spreading on both sites was collected from raised
bogs in a natural state. Dactylis glomerata hay was

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
3
used for mulching in NR and straw was used in NP.
The area of each experimental site is about 0.05 ha.
The uppermost peat layer at the NR site has higher
ash and moisture content and pH, but also higher
nutrient (N, P, K, PO4-P) contents than at the NP
experimental site, which has led to higher Sphagnum
biomass on that site, while forest mosses dominate in
NR (Purre & Ilomets 2018). The range of water table
depth fluctuations is mainly 20–30 cm at NR and 20–
40 cm at NP.
Plant cover determination
Square (25 × 25 cm) permanent plots were
established at each site during restoration (75 plots at
Ohtu (NR) in 2006; 60 plots at Viru (NP) in 2008) and
marked with white plastic pipes. Some plots were left
out of analysis during subsequent years due to loss of
permanent plot markers as a result of human
vandalism or animal activities.
Cover (%) of plant species, lichen, bare peat,
mulch and litter was determined visually from
permanent plots for six years at NR and seven years
at NP (Table 1). Rochefort et al. (2013) support the
use of permanent plots to determine cover changes of
key plants on restored peatlands as it is reliable and
cost-efficient.
Substrate sampling and analysis
Peat samples (30 samples from either site) were
collected from both sites in autumn 2015. The
topmost (0–5 cm) peat samples were collected using
a polyvinyl chloride (PVC) cylinder with a diameter
of 5 cm. During sampling, peat pH was measured in
every sampling point with a “Knick Portamess”
(Knick, Germany) pH-meter. The moisture content
(%) at 60 °C was determined in the laboratory by
drying about 65 g of wet peat sample (exact weight of
each sample was recorded) in an oven at 60 °C for 48
hours. The ash content of the dried peat was then
determined through combustion of the samples on
550 °C for 6 h (Chambers et al. 2011).
The Ca content (%) was measured in the
Laboratory of Chemical Analysis in Tallinn
Technological University using atomic absorption
spectrophotometry using “SpectrAA 220F” (Varian,
USA) spectrophotometer. N (%), P (%), K (%), and
P-PO4 contents (mg kg-1) of peat were determined in
the Laboratory of Plant Biochemistry at the Estonian
University of Life Sciences. The Kjeldahl method
(Parkinson & Allen 1975) was used to determine N
and P content, PO4-P content was measured by
ammonium lactate solubility and K content of the
peat was analysed using the ammonium lactate
extraction method. Chemical analyses are described
in more detail in Purre & Ilomets (2018).
Table 1. Plant cover estimation dates and number of
permanent plots at the study sites. n.d. indicates years
when plant cover photographs were not captured.
Nutrient-rich site
Nutrient-poor site
Year
Date
No. plots
Date
No. plots
2009
29 Oct
59
19 Nov
73
2010
n.d.
n.d.
2011
02 Nov
57
21 Sep
40
2012
n.d.
11 Oct
40
2013
24 Aug
54
14 Aug
39
2014
09 Sep
54
n.d.
2015
24 Sep
54
12 Oct
39
2016
n.d.
n.d.
2017
n.d.
19 Sep
39
2018
20 Jun
51
07 Jun
39
Data analysis
The data were analysed using IBM SPSS Statistics
ver. 23 software. All results were considered
statistically significant when p < 0.05. All results in
the text are presented as mean ± SE. Shapiro-Wilk
tests revealed deviations from the normal distribution
of variables; therefore, nonparametric methods were
used for data analysis. For the analysis of variance we
used the Kruskal-Wallis test, and for the pair-wise
comparison of variables the Mann-Whitney U test.
This was used to test the differences in vegetation
variables between the sites. Spearman correlation
coefficient was used to relate vegetation and substrate
cover to years since restoration, and bryophyte cover
to vascular plant abundance. Fisher r – z
transformation (Fisher 1928) was used to analyse the
similarity of correlation between two sites.
PC-ORD 7.0 software was used for redundancy
analysis (RDA) on vegetation data for the year 2018,
detrended correspondence analysis (DCA) and
Mantel randomisation test. Explanatory variables
with r lower than 0.20 were excluded. RDA was used
to relate peat chemical properties to plant functional
type (PFT) cover. Plant taxa was also divided to
oligotrophic peatland species, minerotrophic peatland
species, generalist species and mineral soil species
according to Kask (1982) for vascular plants and
Kannukene & Kask (1982) for bryophytes. Division
of plant taxa by PFTs and by peatland specific,
mineral soil and generalist plant taxa is shown in
Table 2. Variation partitioning using multiple RDAs
was done based on Borcard et al. (1992). DCA was

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
4
used to find the main gradients in plant species data,
as we used data from all of the study years in the
analysis and added time since restoration as a
supplementary variable. Shannon diversity index
based on PFTs abundance was calculated according
to Shannon (1948) also in PC-ORD 7.0:
,=∑

=1 [1]
where H’ is Shannon diversity index, and pi is
proportion of PFT i in permanent plot.
Table 2. Average vegetation coverage (%) at the study sites in 2018 between the nutrient-rich and the nutrient-
poor site, and species type according to Kask (1982) and Kannukene & Kask (1982). The statistical
significance of the difference between the sites is shown according to results of Mann-Whitney test. OP
indicates species typical to oligotrophic peatlands; MP indicates species typical to minerotrophic peatlands;
G indicates generalist species; MS indicates species typical to mineral soils; + indicates that species is present
but with very low (< 0.5 %) cover; - indicates that species or plant functional type is absent from the site.
Nutrient-
rich site
Nutrient-
poor site
Statistical
significance
Species
type
Hummock Sphagna (%)
-
17 ± 4
Z = 5.3; p < 0.01
S. fuscum (%)
-
12 ± 3
Z = 5.1; p < 0.01
OP
S. rubellum (%)
-
5 ± 2
Z = 3.8; p < 0.01
OP
Lawn Sphagna (%)
5 ± 2
39 ± 6
Z = 5.0; p < 0.01
S. angustifolium (%)
4 ± 2
28 ± 6
Z = 3.5; p < 0.01
OP
S. magellanicum (%)
1 ± 1
11 ± 4
Z = 4.2; p < 0.01
OP
Sphagnum (%)
5 ± 2
56 ± 6
Z = 7.2; p < 0.01
True moss (%)
15 ± 4
8 ± 2
Z = 0.3; p > 0.05
Polytrichum strictum (%)
+
7 ± 2
Z = 4.8; p < 0.01
OP
Aulacomnium palustre (%)
8 ± 2
+
Z = 3.1; p < 0.01
MP
Pleurozium schreberi (%)
8 ± 2
+
Z = 2.9; p < 0.01
G
Dicranum polysetum (%)
+
1 ± 1
Z = 1.3; p > 0.05
G
Evergreen shrub (%)
76 ± 3
30 ± 4
Z = 6.7; p < 0.01
Vaccinium oxycoccus (%)
8 ± 2
3 ± 1
Z = 2.0; p > 0.05
OP
Calluna vulgaris (%)
68 ± 3
26 ± 4
Z = 6.4; p < 0.01
G
Andromeda polifolia (%)
-
1 ± 0
Z = 3.1; p < 0.01
OP
Empetrum nigrum (%)
+
-
Z = 1.3; p > 0.05
OP
Rhododendron tomentosum (%)
+
1 ± 0
Z = 0.5; p > 0.05
OP
Deciduous shrub (Vaccinium uliginosum) (%)
+
1 ± 0
Z = 0.8; p > 0.05
G
Ombrotrophic forb (Drosera rotundifolia) (%)
-
+
Z = 2.6; p < 0.05
OP
Minerotrophic forb (Epilobium angustifolium) (%)
+
-
Z = 1.8; p > 0.05
MS
Minerotrophic grasses (Phragmites australis) (%)
+
-
Z = 1.8; p > 0.05
G
Ombrotrophic sedge (Eriophorum vaginatum) (%)
12 ± 3
5 ± 1
Z = 1.1; p > 0.05
OP
Minerotrophic sedge (Carex spp.)
+
-
Z = 1.6; p > 0.05
MP
Evergreen tree (Pinus sylvestris)
7 ± 2
2± 1
Z = 2.0; p < 0.05
G
Deciduous tree (%)
5 ± 1
+
Z = 4.3; p < 0.01
Betula pendula (%)
24± 1
+
Z = 4.0; p < 0.01
MS
Salix spp. (%)
+
-
Z = 1.3; p > 0.05
MP
Populus tremula (%)
1 ± 0
-
Z = 1.3; p > 0.05
MP
Lichen (%)
-
4 ± 2
Z = 3.5; p < 0.01
Litter (%)
12 ± 2
9 ± 3
Z = 2.1; p < 0.05
Bare peat (%)
+
32 ± 5
Z = 7.7; p < 0.01

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
5
RESULTS
Vegetation cover and peat chemical factors
By the end of the study period in 2018, the two sites
differed significantly by their vascular plant and
bryophyte cover, but the sites differed also
significantly by their peat chemistry (Tables 2 and 3).
Sum of vascular plant species coverage was
significantly higher in NR (102 ± 3 %; NP 37 ± 4 %;
Z = 8.0; p < 0.01), whereas bryophyte cover was
higher in NP (NR 20 ± 4 %; NP 64 ± 4 %; Z = 5.6;
p < 0.01). Sphagnum was widespread in NP but made
up only about one third of bryophyte cover in NR.
The cover of litter was higher at NR, while cover of
lichens and bare peat was higher at the NP site.
RDA analysis including peat chemical
characteristics and site explained about 38 % of
variation in PFT compositions during the last
measurement year while about 62 % of variance was
undetermined. The first axis of RDA correlated
strongest with Ca, N and pH while the second axis
correlated with P-PO4 and K contents (Figure 1).
Cover of different PFTs was mostly explained by
differences in peat N content and pH, but also peat
Ca, P, P-PO4 and moisture contents. Peat K and ash
contents, and especially peat decomposition levels
had weakest effect on vegetation development
(Table A1 in the Appendix). According to RDA,
higher cover of vascular plant PFTs are related to
higher pH values and nutrient content in the peat,
whereas Sphagnum cover is higher in NP, with lower
peat ash and higher moisture content. According to
randomisation tests of RDA species - environment
correlations and eigenvalues for individual axes were
significant (p < 0.05). Variation partitioning showed
that “site” itself explained about 14 % variation in
PFT matrix, while including only peat chemistry
variables (Ca, N, K, P, ash and moisture contents, and
pH), about 35 % of variation in PFT matrix was
explained. The Mantel test indicates that the
environmental and PFT matrices have positive
relationship (r = 0.26; p < 0.01) in 2015 when both
peat chemistry and plant coverages were analysed.
DCA solution of substrate cover throughout the
study period was significant according to
randomisation test (p < 0.05; Figure 2). First axis in
DCA corresponds to differences in time since
restoration and site nutrient content, while the second
axis can be explained with differences in moisture
conditions indicating wetter conditions in the positive
end of the axis. Similarly, to correlation analysis,
DCA shows, that with time since restoration,
substrate cover of permanent plots succeeds from
mulch and bare peat, to bryophytes, and then to
vascular plants (mainly tree and shrub species) at NR
site and peatland plant communities at NP site.
Table 3. Average species group coverage (%) at the study sites in 2018, and peat chemical properties according
to Purre & Ilomets (2018) between the nutrient-rich and the nutrient-poor site. The statistical significance of
the difference between the sites is shown according to results of Mann-Whitney test. * indicates data from
Purre & Ilomets (2018); species were grouped according to Kask (1982) and Kannukene & Kask (1982), see
Table 2.
Nutrient-
rich site
Nutrient-
poor site
Statistical
significance
Oligotrophic peatland species (%)
26 ± 3
72 ± 6
Z = 5.3; p < 0.01
Minerotrophic peatland species (%)
8 ± 2
0 ± 0
Z = 4.0; p < 0.01
Generalist species (%)
83 ± 4
29 ± 4
Z = 6.9; p < 0.01
Mineral soil species (%)
5 ± 1
0 ± 0
Z = 4.3; p < 0.01
Peat moisture content (%)*
80.2 ± 0.6
84.4 ± 0.6
Z = 4.5; p < 0.01
Peat ash content (%)*
4.9 ± 0.4
1.4 ± 0.1
Z = 7.5; p < 0.01
Peat decomposition level (von Post)*
H2 – H8
H3 – H6
Z = 0.6; p > 0.05
pH*
4.1 ±0.1
3.1 ± 0.0
Z = 6.4; p < 0.01
N (%)*
1.40 ± 0.05
0.90 ± 0.02
Z = 5.1; p < 0.01
P (%)*
0.06 ± 0.00
0.05 ±0.00
Z = 4.1; p < 0.01
K (%)*
0.04 ± 0.00
0.03 ± 0.00
Z = 3.3; p < 0.01
Ca (g kg-1)*
303 ± 20.9
92.3 ± 6.2
Z = 6.6; p < 0.01
P-PO4 (mg kg-1)*
60.9 ± 3.4
45.7 ± 3.0
Z = 3.0; p < 0.01

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
6
Figure 1. Redundancy analysis of substrate properties and PFT cover. Eigenvalues for the first and second
axis are 4.4 and 1.9 respectively. Decid_tree = deciduous trees; Everg_tree = evergreen trees; Deci_Shrub
= deciduous shrubs; Ever_shrub = evergreen shrubs; Miner_grasse = minerotrophic grasses; Miner_forb =
minerotrophic forbs; Ombro_sedge = ombrotrophic sedges; Lawn_Sph = lawn Sphagnum; Hum_Sph =
hummock Sphagnum. Minerotrophic sedges and ombrotrophic forbs were left out from the analysis due to
their very low occurrence at the study sites. Peat decomposition and K content were left out during forward
selection of variables for RDA.
Figure 2. Detrended correspondence analysis (DCA) of plant species at the study sites during the study
period. Eigenvalues for the first and second axes are 0.636 and 0.413, respectively. Gradient lengths for
the first and the second axes are 4.469 and 3.092, respectively.

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
7
Development of vegetation cover
Time since restoration correlated significantly with
some PFTs cover (Figure 3, Table A2). Evergreen
shrub cover has increased in both sites with time after
the restoration, while Sphagnum cover increased in
NP while decreased in NR. Mulch cover vanished in
both sites completely during the first few years after
restoration. Lichens were present in low abundance at
NP but were absent from the NR site (Figure 4).
From NR throughout the study period, 29 plant
taxa were found, compared to 17 different taxa at NP
(Table A2). Although averaged during the
experiment, the amount of PFTs (NR 3.4±0.1; NP
2.9±0.1; Z = 5.7; p < 0.01) and Shannon diversity
index calculated based on PFTs cover (NR 0.8±0.0;
NP 0.7±0.0; Z = 3.5; p < 0.01) was significantly
higher at NR. By the end of experiment in 2018 the
amount of PFTs (NR 3.3±0.2; NP 3.6±0.2; Z = 1.0;
p > 0.05) and Shannon diversity index (NR 0.8±0.1;
NP 0.9±0.1; Z = 1.5; p > 0.05) were higher at the NP
site. Shannon diversity index was positively
correlated with time since restoration at NP (r = 0.44;
p < 0.01), while no such correlation was found at NR
(r = –0.05; p > 0.05) (Figure 5).
The NP site was dominated by the oligotrophic
peatland species, while during the end of the
experiment some small increase in generalist plant
species was observed in this site (Figure 6). At the NR
site, abundance of peatland specific species has
declined, and generalist species have increased their
abundances. Over the study period at the NR site also
mineral soil species have increased their abundances
slowly.
Vascular plants and bryophytes
At NR, increasing vascular plant cover throughout the
study period and all plots correlates with decreasing
bryophyte (r = - 0.65; p < 0.01) and Sphagnum
(r = - 0.24; p < 0.01) cover (Figures 3, 4). Conversely
higher vascular plant cover correlates positively with
bryophyte (r = 0.23; p < 0.01) and Sphagnum
(r = 0.19; p < 0.01) cover at NP. Differences in those
correlations were statistically significant (Z < –12.72;
p < 0.01) according to Fisher’s r – z transformation.
Figure 3. Changes in PFT cover at the study sites. Average values are brought with ±95 % confidence
intervals. Deciduous shrubs, minerotrophic grasses, minerotrophic forbs and minerotrophic sedges were
excluded from the figure due to their very low cover on all years and sites.

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
8
Figure 4. Changes in substrate cover at the study sites. Average values are shown with ±95 % confidence
intervals.
Figure 5. Shannon diversity index of PFTs at the study sites. Average values are shown with ±95 %
confidence intervals.

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
9
Figure 6. Changes in cover of minerotrophic and oligotrophic peatland, generalist and mineral soil species
at the study sites throughout the study period. Average values are shown with ±95 % confidence intervals.
DISCUSSION
Vegetation and peat chemistry
The two restored milled peatland sites with different
peat nutrient contents differ by their vegetation
composition - the NR site has higher cover of vascular
plants while the NP site is dominated by Sphagnum.
Cover of different PFTs in the study sites were mainly
explained by peat Ca and N contents and pH.
According to Hájková & Hájek (2004) and Gagnon et
al. (2018), pH creates the main environmental
gradient on peatlands, so creating conditions for the
development of different plant communities - lower
pH leads to vegetation similar to bogs, while higher
pH to dominance of fen vegetation. This pattern was
also observed in the current study, as increased
vascular plant PFTs cover, presence of minerotrophic
peatland and mineral soil species were connected
with higher pH and nutrient contents, while
Sphagnum and oligotrophic peatland species were in
the other end of the gradient. Similar results were
reached by Triisberg et al. (2014), Paal et al. (2016)
and Renou-Wilson et al. (2019). Typical dominants
on restored peatlands like Polytrichum strictum,
Calluna vulgaris and Eriophorum vaginatum
communities, which were abundant at the NR site, are
in the middle part of the pH and nutrient gradient
(Triisberg et al. 2014).
Different vascular plant PFTs had somewhat
different correlations with various peat nutrients. In
the current study, higher evergreen shrub cover was
on plots with higher P content similarly to Tuittila et
al. (2000). Also cover of the ombrotrophic sedge
E. vaginatum increased with peat P and C contents
similarly to Sottocornola et al. (2007). Deciduous
shrubs (represented by Vaccinium uliginosum) were
the only vascular plant PFT with a negative
correlation with nutrient contents of the peat. This
species is usually found in the NP conditions of bog
edges and bog forests (Krall et al. 2010).
The NR site had higher cover of plant litter, shrub
and sedges, and low cover of Sphagnum similarly to
mesotrophic peatland in the study by Renou-Wilson
et al. (2019) indicating that higher nutrient
concentrations in the upper peat layer of restored
peatlands lead the succession to vascular plant

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
10
dominated fen-like vegetation. PFT cover, especially
Sphagnum, shrub and forbs, is similar to raised bog
vegetation on rewetted NP milled peatlands (Zając et
al. 2018, Renou-Wilson et al. 2019) as in the current
study. This supports the previous studies relating
higher Sphagnum production with higher peat
moisture content (Potvin et al. 2015, Paal et al. 2016,
Purre & Ilomets 2018), while true mosses
(Sottocornola et al. 2007, Purre & Ilomets 2018) and
vascular plants (Berendse et al. 2001, Limpens et al.
2003, Malmer et al. 2000) benefit from higher
nutrient contents. Therefore, peat physical and
chemical properties should be determined prior to
restoration to ensure that a suitable approach is
chosen which takes into account the peat properties
of the site, and therefore whether the succession of the
restored peatland is likely to be towards a fen or bog
ecosystem.
Time since restoration
Abundances of various PFTs increased or decreased
with time since restoration. Time since restoration is
considered to be an important predictor of plant cover
in restored peatlands (Chirino et al. 2006, Karofeld et
al. 2015, Orru et al. 2016, Hancock et al. 2018,
Triisberg-Uljas et al. 2018), whereas in the study by
González et al. (2013) time since restoration
explained only about 4 % of variation in vegetation
composition. At our two sites, vascular plant cover
increased significantly with time following
restoration as also reported by González & Rochefort
(2014) and Karofeld et al. (2015).
According to Triisberg et al. (2014), recently
abandoned milled peatlands in Estonia are covered by
E. vaginatum, C. vulgaris and P. strictum which
evolve into communities that are characteristic to
transitional mires and raised bogs with time. This
coheres with our results from the NP site and another
nutrient-poor restoration site in Estonia (Karofeld et
al. 2015), while generalist species increased their
abundances throughout the study period in the NR
site.
Bryophyte cover increased at NP and decreased at
NR with time. Therefore, NR site differed from the
NP sites as described by Chirino et al. (2006),
Rochefort et al. (2013), González & Rochefort (2014)
in Canada and in Estonia by Karofeld et al. (2015).
Generally, cover of PFTs in our study remain in the
ranges of previous studies (González & Rochefort
2014, González et al. 2014a), while in some studies
(Chirino et al. 2006, Karofeld et al. 2015), higher
Sphagnum cover was obtained sooner after
restoration, whereas vascular plant cover remained
lower than in the current study.
In both study sites evergreen shrub cover, mainly
Calluna vulgaris, has increased with time since
restoration. The slower growth of shrubs than sedges
and herbs has been widely reported by previous
studies (Lavoie et al. 2005, Feldmeyer-Christe et al.
2011, Pouliot et al. 2012, González et al. 2013,
González & Rochefort 2014). As ericaceous shrubs
with mycorrhiza are characteristic of deeper
groundwater levels (Laine et al. 2012, Potvin et al.
2015), high and increasing cover of C. vulgaris
indicates the need for further restoration activities to
raise the water table.
Hummock Sphagnum species were absent from
NR, where they had not been actively dispersed
during restoration, whereas their cover increased
slowly but steadily at the NP site. González et al.
(2014b) anticipate that more time since restoration is
needed for establishment of hummock Sphagnum if
they are not dispersed during restoration. However,
hummock Sphagnum species like Sphagnum fuscum
have good immigration potential (Campbell et al.
2003) and their absence at NR could also be explained
by unfavourable conditions at the restored site, such
as high nutrient contents and shading from vascular
plants in the later stages of succession.
Shannon diversity index increased over time
following restoration at NP similarly to results of
Tuittila et al. (2000) while being stable at NR. In
temperate peatlands, number of plant species tends to
decrease with succession in a longer time-scale after
the restoration from peat milling due to shading from
woody species (Prach et al. 2014). At the NR site,
increasing shading from vascular plants could be the
cause of a reduction in bryophyte PFTs such as true
mosses and lawn Sphagnum, and therefore a small
decrease in Shannon index in the end of the study
period. The difference between the sites could
originate from differences in nutrient richness, as
Kozlov et al. (2018) reported faster vegetation
succession at NR sites as in the current study.
Vascular plants and bryophytes
At the NP site, where vascular plant cover was
relatively low, it did not inhibit the development of
moss layer. Some results suggest that the presence of
vascular plants, especially E. vaginatum, could
improve Sphagnum regeneration on restored milled
peatlands by reducing frost heaving and improving
moisture conditions on milled peatlands (Ferland &
Rochefort 1997, Lavoie et al. 2003). The presence of
shrubs is positively related to moss surface height, so
supporting the development of microtopography on
revegetated milled peatlands (Pouliot et al. 2012).
At NR site higher vascular plant cover resulted in
lower Sphagnum and bryophyte cover. In case of high
shrub and tree abundance, the shading and litter from

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
11
vascular plants could reduce the abundance of
Sphagnum and change the species composition of the
moss layer (Paal et al. 2016). The negative impact of
higher vascular plant cover on Sphagnum is probably
site-specific (Limpens et al. 2004). Vascular plant
litter cover was higher at NR, so corroborating the
results of Berendse et al. (2001). High litter cover
(exceeding 20 %) reduces Sphagnum cover (Gaudig
et al. 2017), while in our study, average litter cover
did not exceed that limit at any of the sites throughout
the nine-year period of the study.
One possibility to decrease the negative effects of
vascular plants on development of moss layer could
be removal of vascular plants. Guêné-Nanchen et al.
(2017) showed that mowing of graminoids
(Eriophorum angustifolium) had no effect on
Sphagnum cover in a Sphagnum farm, while Gaudig
et al. (2017) found that mowing of vascular plants
was beneficial to Sphagnum productivity at
Sphagnum farming sites where several different
vascular PFTs were present. In our case, the main
vascular plants at the NP site were E. vaginatum,
which creates dense tussocks, and C. vulgaris, which
shades the moss layer. E. vaginatum has also been
reported to reduce the peat N and P contents
(Kaštovská et al. 2018), so creating unsuitable
conditions for other vascular plants. Initial removal of
shrubs can result in increased shrub cover through re-
sprouting, where there are relatively low water tables
(Tuittila et al. 2000), and similar results have been
found with birch (Betula pubescens, Betula pendula)
removal, although it resulted in a short-term increase
in the abundance of Sphagnum and other peatland
species (Czerepko et al. 2018). Therefore, the effect
of vascular plant removal is not uniform, and further
studies should be conducted.
The current study demonstrates the importance of
peat chemistry on restoration success on milled
peatlands. Applied restoration activities were
successful at the NP site where species composition
typical to oligotrophic peatlands and Sphagnum
carpet had formed. At the NR site, generalist vascular
plant species dominated and therefore further
restoration measures should be applied to support the
development of minerotrophic vegetation
composition. This is more in accordance with the
nutrient-rich peat chemistry conditions in the site than
oligotrophic peatland vegetation initially aimed at by
applying the MLTT. High abundance of shrubs at the
NR site indicates that the relatively deep water table
(about 20–30 cm) does not support the development
of (minerotrophic) peatland species, but communities
evolve in direction of generalist vascular plants. At
NR, if the main aim is to restore the bryophyte carpet,
repeated mowing of vascular plants until dense
bryophyte carpet has formed could have beneficial
effect on restoration outcomes and should be studied
further, simultaneously to applying additional
measures for raising the water table.
ACKNOWLEDGEMENTS
We thank Kairi Sepp and Raimo Pajula for the help
of preparing the study sites. We also thank AS Jiffy
Products Estonia for allowing us to use part of Ohtu
milled peatland as an experimental site.
AUTHOR CONTRIBUTIONS
MI and LT designed and prepared the experimental
sites. AHP, LT and MI planned the study. LT and
AHP photographed the permanent plots throughout
the years and AHP analysed the plant cover and was
responsible for conducting and organising the peat
chemistry analysis. AHP did the statistical analyses
and prepared the manuscript with support of MI and
LT. All authors contributed to the final version of the
manuscript.
REFERENCES
Berendse, F., van Breemen, N., Rydin, H., Buttler, A.,
Heijmans, M., Hoosbeek, M.R., Lee, J.A.,
Mitchell, E., Saarinen, T., Vasander, H., Wallen,
B. (2001) Raised atmospheric CO2 levels and
increased N deposition cause shifts in plant
species composition and production in Sphagnum
bogs. Global Change Biology, 7, 591–598.
Beyer, C., Höper, H. (2015) Greenhouse gas
exchange of rewetted bog peat extraction sites and
a Sphagnum cultivation site in northwest
Germany. Biogeosciences, 12, 2101–2117.
Borcard, D., Legendre, P., Drapeau, P. (1992)
Partialling out the spatial component of ecological
variation. Ecology, 73, 1045–1055.
Campbell, D.R., Rochefort, L., Lavoie, C. (2003)
Determining the immigration potential of plants
colonizing disturbed environments: the case of
milled peatlands in Quebec. Journal of Applied
Ecology, 40, 78–91.
Chambers, F., Beilman, D., Yu, Z. (2011) Methods
for determining peat humification and for
quantifying peat bulk density, organic matter and
carbon content for palaeostudies of climate and
peatland carbon dynamics. Mires and Peat, 7, 07,
10 pp.
Chirino, C., Campeau, S., Rochefort, L. (2006)

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
12
Sphagnum establishment on bare peat: The
importance of climatic variability and Sphagnum
species richness. Applied Vegetation Science, 9,
285–294.
Clarke, D., Rieley, J. (2019) Strategy for Responsible
Peatland Management. Sixth edition,
International Peatland Society, Jyväskylä, 35 pp.
Czerepko, J., Boczoń, A., Wróbel, M., Gawryś, R.,
Sokołowski, K. (2018) Removal of birch as a
means of protecting raised bog mossy vegetation
Ledo-Sphagnetum magellanici. Wetlands Ecology
and Management, 26, 689–702.
Feldmeyer-Christe, E., Küchler, M., Wildi, O. (2011)
Patterns of early succession on bare peat in a Swiss
mire after a bog burst. Journal of Vegetation
Science, 22, 943–954.
Ferland, C., Rochefort, L. (1997) Restoration
techniques for Sphagnum-dominated peatlands.
Canadian Journal of Botany, 75, 1110–1118.
Fisher, R.A. (1928) The general sampling distribution
of the multiple correlation coefficient.
Proceedings of the Royal Society of London.
Series A, 121, 654–673.
Gagnon, F., Rochefort, L., Lavoie, C. (2018)
Spontaneous revegetation of a peatland in
Manitoba after peat extraction: diversity of plant
assemblages and restoration perspectives. Botany,
96, 779–791.
Gaudig, G., Krebs, M., Joosten, H. (2017) Sphagnum
farming on cut-over bog in NW Germany: Long-
term studies on Sphagnum growth. Mires and
Peat, 20, 1–19.
González, E., Rochefort, L. (2014) Drivers of success
in 53 cutover bogs restored by a moss layer
transfer technique. Ecological Engineering, 68,
279–290.
González, E., Rochefort, L., Boudreau, S., Hugron,
S., Groeneveld, E.V.G., Massé, A., Rochefort, L.
(2007) Polytrichum strictum as a nurse-plant in
peatland restoration. Restoration Ecology, 15,
709–719.
González, E., Henstra, S.W., Rochefort, L., Bradfield,
G.E., Poulin, M. (2014a) Is rewetting enough to
recover Sphagnum and associated peat-
accumulating species in traditionally exploited
bogs? Wetlands Ecology Management, 22, 49–62.
González, E., Rochefort, L., Boudreau, S., Poulin, M.
(2014b) Combining indicator species and key
environmental and management factors to predict
restoration success of degraded ecosystems.
Ecological Indicators, 46, 156–166.
Guêné-Nanchen, M., Pouliot, R., Hugron, S.,
Rochefort, L. (2017) Effect of repeated mowing to
reduce graminoid plant cover on the moss carpet
at a Sphagnum farm in North America. Mires and
Peat, 20, 06, 12 pp.
Hájková, P., Hájek, M. (2004) Bryophyte and
vascular plant responses to base-richness and
water level gradients in Western Carpathian
Sphagnum-rich mires. Folia Geobotanica, 39,
335–351.
Hancock, M.H., Klein, D., Andersen, R., Cowie, N.
(2018) Vegetation response to restoration
management of a blanket bog damaged by
drainage and afforestation. Applied Vegetation
Science, 21, 167–178.
Ilomets, M. (2017). Estonia. In: Joosten, H.,
Tanneberger, F., Moen, A. (eds.) Mires and
Peatlands of Europe: Status, Distribution and
Conservation. E. Schweizerbart, Stuttgart, 360–
371.
Järveoja, J., Peichl, M., Maddison, M., Soosaar, K.,
Vellak, K., Karofeld, E., Teemusk, A., Mander, Ü.
(2016) Impact of water table level on annual
carbon and greenhouse gas balances of a restored
peat extraction area. Biogeoscience, 13, 2637–
2651.
Joosten, H., Clarke, D. (2002) Wise Use of Mires and
Peatlands: Background and Principles Including
a Framework for Decision-Making. International
Mire Conservation Group and International Peat
Society, Saarijärvi, 307 pp.
Kannukene, L., Kask, M. (1982) A preliminary list of
bryophytes of Estonian peatlands. In: Masing, V.
(ed.) Peatland Ecosystems. Valgus, Tallinn, 34–
38.
Karofeld, E., Müür, M., Vellak, K. (2015) Factors
affecting re-vegetation dynamics of
experimentally restored extracted peatland in
Estonia. Environmental Science and Pollution
Research, 23, 13706–13717.
Karofeld, E., Jarašius, L., Priede, A., Sendžikaité, J.
(2016) On the after-use and restoration of
abandoned extracted peatlands in the Baltic
countries. Restoration Ecology, 25(2), 293–300.
Karofeld, E., Kaasik, A., Vellak, K. (2020) Growth
characteristics of three Sphagnum species in
restored extracted peatland. Restoration Ecology,
28(6), 1574–1583.
Kask, M. (1982) A list of vascular plants of Estonian
peatlands. In: Masing, V. (ed.) Peatland
Ecosystems, Valgus, Tallinn, 39–49.
Kaštovská, E., Straková, P., Edwards, K., Urbanová,
Z., Bárta, J., Mastný, J., Šantrůčková, H., Picek, T.
(2018) Cotton-grass and blueberry have opposite
effect on peat characteristics and nutrient
transformation in peatland. Ecosystems, 21(3),
443–458.
Kozlov, S.A., Lundin, L., Avetov, N.A. (2018)
Revegetation dynamics after 15 years of rewetting

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
13
in two extracted peatlands in Sweden. Mires and
Peat, 18, 05, 17 pp.
Krall, H., Kukk, T., Kull, T., Kuusk, V., Leht, M.,
Oja, T., Pihu, S., Reier, Ü., Zingel, H., Tuulik, T.
(2010) Eesti Taimede määraja (Estonian Plant
Identifier). Eesti Loodusfoto, Tartu, 448 pp. (in
Estonian).
Krebs, M., Gaudig, G., Matchutadze, I., Joosten, H.
(2017) Sphagnum regrowth after cutting. Mires
and Peat, 20, 12, 20 pp.
Kuiper, J.J., Mooij, W.M., Bragazza, L., Robroek,
B.J. (2014) Plant functional types define
magnitude of drought response in peatland CO2
exchange. Ecology, 95, 123–131.
Laine, A.M., Bubier, J., Riutta, T., Nilsson, M.B.,
Moore, T.R., Vasander, H., Tuittila, E.-S. (2012)
Abundance and composition of plant biomass as
potential controls for mire net ecosystem CO2
exchange. Botany, 90, 63–74.
Laine, A.M., Selänpää, T., Oksanen, J., Seväkivi, M.,
Tuittila, E.-S. (2018) Plant diversity and
functional trait composition during mire
development. Mires and Peat, 21, 02, 19 pp.
Lavoie, C., Grosvernier, P., Girard, M., Marcoux, K.
(2003) Spontaneous revegetation of mined
peatlands: An useful restoration tool? Wetlands
Ecology and Management, 11, 97–107.
Lavoie, C., Saint-Louis, A., Lachance D. (2005)
Vegetation dynamics on an abandoned vacuum-
mined peatland: 5 years of monitoring. Wetlands
Ecology and Management, 13, 621–633.
Limpens, J., Berendse, F., Klees, H. (2003) N
deposition affects N availability in interstitial
water, growth of Sphagnum and invasion of
vascular plants in bog vegetation. New
Phytologist, 157, 339–347.
Limpens, J., Berendse, F., Klees, H. (2004) How
phosphorus availability affects the impact of
nitrogen deposition on Sphagnum and vascular
plants in bogs. Ecosystems, 7, 793–804.
Malmer, N., Albinsson, C., Svensson, B.M., Wallén,
B. (2003) Interferences between Sphagnum and
vascular plants: effects on plant community
structure and peat formation. Oikos, 100, 469–
482.
Orru, M., Ots, K., Orru, H. (2016) Re-vegetation
processes in cutaway peat production fields in
Estonia in relation to peat quality and water
regime. Environmental Monitoring and
Assessment, 188, 655, 12 pp.
Paal, J., Jürjendal, I., Suija, A., Kull, A. (2016)
Impact of drainage on vegetation of transitional
mires in Estonia. Mires and Peat, 18, 02, 19 pp.
Parkinson, J.A., Allen, S.E. (1975) A wet oxidation
procedure suitable for the determination of
nitrogen and mineral nutrients in biological
material. Communications in Soil Science & Plant
Analysis, 6, 1–11
Potvin, L.R, Kane, E.S, Chimner, R.A., Kolka, R.K.,
Lilleskov, E.A. (2015) Effects of water table
position and plant functional group on plant
community, aboveground production, and peat
properties in a peatland mesocosm experiment
(PEATcosm). Plant and Soil, 387, 277–294.
Poulin, M., Andersen, R., Rochefort, L. (2013) A new
approach for tracking vegetation change after
restoration: A case study with peatlands.
Restoration Ecology, 21, 363–371.
Pouliot, R., Rochefort, L., Karofeld, E. (2012)
Initiation of microtopography in re-vegetated
cutover peatlands: evolution of plant species
composition. Applied Vegetation Science, 15,
369–382.
Prach, K., Řehounková, K., Lencová, K., Jírová, A.,
Konvalinková, P., Mudrák, O., Študent, V.,
Vanĕček, Z., Tichŷ, L., Petřík, P., Šmilauer, P.,
Pyšek, P. (2014) Vegetation succession in
restoration of disturbed sites in Central Europe:
the direction of succession and species richness
across 19 seres. Applied Vegetation Science, 17,
193–200.
Purre, A-H., Ilomets, M. (2018) Relationships
between bryophyte production and substrate
properties in restored milled peatlands.
Restoration Ecology, 26, 858–864.
Purre, A-H., Pajula, R., Ilomets, M. (2019) Carbon
dioxide sink function in restored milled peatlands
– The significance of weather and vegetation.
Geoderma, 346, 30–42.
Purre, A-H., Ilomets, M., Truus, L., Pajula, R., Sepp,
K. (2020) The effect of different treatments of
moss layer transfer technique on plant functional
types biomass in revegetated milled peatlands.
Restoration Ecology, 28(6), 1584–1595.
Renou-Wilson, F., Moser, G., Fallon, D., Farrell,
C.A., Müller, C., Wilson, D. (2019) Rewetting
degraded peatlands for climate and biodiversity
benefits: Results from two raised bogs. Ecological
Engineering, 127, 547–560.
Rochefort, L. (2000) Sphagnum – A keystone genus
in habitat restoration. The Bryologist, 103, 503–
508.
Rochefort, L., Quinty, F., Campeau, S., Johnson, K.,
Malterer, T. (2003) North American approach to
the restoration of Sphagnum dominated peatlands.
Wetlands Ecology and Management, 11, 3–20.
Rochefort, L., Isselin-Nondedeu, F., Boudreau, S.,
Poulin, M. (2013) Comparing survey methods for
monitoring vegetation change through time in a
restored peatland. Wetlands Ecology and

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
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Management, 21, 71–85.
Shannon, C.E. (1948) A mathematical theory of
communication. Bell System Technical Journal,
27, 379–423.
Smolders, A.J.P., Tomassen, H.B.M., van Mullekom,
M., Lamers, L.P.M., Roelofs, J.G.M. (2003)
Mechanisms involved in the re-establishment of
Sphagnum-dominated vegetation in rewetted bog
remnants. Wetlands Ecology and Management,
11, 403–418.
Soini, P., Riutta, T., Yli-Petäys, M., Vasander, H.
(2010) Comparison of vegetation and CO2
dynamics between a restored cut-away peatland
and a pristine fen: evaluation of the restoration
success. Restoration Ecology, 18, 894–903.
Sottocornola, M., Boudreau, S., Rochefort, L. (2007)
Peat bog restoration: Effect of phosphorus on
plant re-establishment. Ecological Engineering,
31, 29–40.
Taylor, N.G., Grillas, P., Sutherland W.J. (2019)
Peatland conservation. In: Sutherland, W.J.,
Dicks, L.V., Ockendon, N., Petrovan, S.O., Smith,
R.K. (eds.) What Works in Conservation 2019,
Open Book Publishers, Cambridge, UK, 375–438.
Triisberg, T., Karofeld, E., Liira, J., Orru, M., Ramst,
R., Paal, J. (2014) Microtopography and the
properties of residual peat are convenient
indicators for restoration planning of abandoned
extracted peatlands. Restoration Ecology, 22, 31–
39.
Triisberg-Uljas, T., Vellak, K., Karofeld, E. (2018)
Application of oil-shale ash and straw mulch
promotes the revegetation of extracted peatlands.
Ecological Engineering, 110, 99–106.
Tuittila, E-S., Komulainen, V-M., Vasander, H.,
Laine, J. (1999) Restored cut-away peatland as a
sink for atmospheric CO2. Oecologia, 120, 563–
574.
Tuittila, E-S., Vasander, H., Laine, J. (2000) Impact
of rewetting on the vegetation of a cut-away
peatland. Applied Vegetation Science, 3, 205–212.
Tuittila, E-S., Vasander, H., Laine, J. (2004)
Sensitivity of C sequestration in reintroduced
Sphagnum to water-level variation in a cutaway
peatland. Restoration Ecology, 12, 483–493.
Wang, M., Moore, T.R. (2014) Carbon, nitrogen,
phosphorus, and potassium stoichiometry in an
ombrotrophic peatland reflects plant functional
type. Ecosystems, 17, 673–684.
Ward, S.E., Bardgett, R.D., McNamara, N.P., Ostle,
N.J. (2009) Plant functional group identity
influences short-term peatland ecosystem carbon
flux: evidence from a plant removal experiment.
Functional Ecology, 23, 454–462.
Wilson, D., Tuittila, E-S., Alm, J., Laine, J., Farrell,
E.P., Byrne, K.A. (2007) Carbon dioxide
dynamics of a restored maritime peatland.
Ecoscience, 14, 71–80.
Wilson, D., Farrell, C.A., Fallon, D., Moser, G.,
Müller, C., Renou-Wilson, F. (2016) Multiyear
greenhouse gas balances at a rewetted temperate
peatland. Global Change Biology, 22, 4080–4095.
Zając, E., Zarzycki, J., Ryczek, M. (2018) Substrate
quality and spontaneous revegetation of extracted
peatland: case study of an abandoned Polish
mountain bog. Mires and Peat, 21, 12, 14 pp.
Submitted 22 Dec 2019, final revision 12 Nov 2020
Editor: Bartłomiej Glina
Assistant Editor: Thomas Kelly
_______________________________________________________________________________________
Author for correspondence:
Anna-Helena Purre, School of Natural Sciences and Health, Tallinn University, Narva Road 29, 10120 Tallinn,
Estonia. Tel: +372 55 695 978; E-mail: annahele@tlu.ee

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
15
Appendix
Table A1. Standardised regression coefficients according to RDA between plant functional type cover and peat chemistry at both study sites in 2015. * indicates p <
0.05; ** p < 0.01. Ombrotrophic forbs and minerotrophic sedges were not present on plots where peat chemistry samples were collected and were therefore omitted
from the analysis.
Capeat
Npeat
Ppeat
Kpeat
P-PO4, peat
ASHpeat
Moisturepeat
pHpeat
Decompositionpeat
R2
Evergreen shrubs
0.44**
0.41**
-0.11
-0.28
-0.03
0.14
-0.32*
-0.22
0.02
0.55
Deciduous shrubs
-0.15
-0.37*
0.16
0.37*
-0.05
-0.21
0.11
0.39*
0.02
0.11
Minerotrophic forbs
-0.48**
0.16
-0.19
-0.18
0.54**
0.16
0.24
0.72**
-0.18
0.67
Minerotrophic grasses
0.46**
0.49**
-0.04
-0.02
0.18
-0.17
0.33*
-0.38*
0.03
0.22
Ombrotrophic sedge
0.24
0.05
0.15
0.13
0.00
-0.30
-0.11
0.23
0.00
0.23
Evergreen trees
-0.07
-0.67**
0.40*
0.11
-0.53**
-0.11
-0.17
0.19
0.03
0.71
Deciduous trees
-0.18
0.44**
-0.39*
-0.12
0.34*
-0.08
-0.04
0.49**
-0.16
0.40
True mosses
-0.10
0.23
-0.13
-0.09
0.37*
0.57**
0.43**
-0.55**
0.05
0.20
Hummock Sphagna
-0.03
-0.29
0.23
0.08
0.11
-0.11
0.44**
-0.04
0.06
0.29
Lawn Sphagna
-0.13
0.15
-0.40
0.02
-0.06
-0.04
0.01
-0.06
0.01
0.19

A.-H. Purre et al. A DECADE OF VEGETATION DEVELOPMENT ON TWO MILLED PEATLANDS
Mires and Peat, Volume 27 (2021), Article 02, 16 pp., http://www.mires-and-peat.net/, ISSN 1819-754X
International Mire Conservation Group and International Peatland Society, DOI: 10.19189/MaP.2019.BG.StA.1928
16
Table A2. Spearman correlation coefficients between plant functional type, species and its group, and year
since restoration. - indicates that species is absent from the site. * indicates p < 0.05; ** – p < 0.01.
Nutrient-rich site
Nutrient-poor site
Hummock Sphagna
-0.09
0.20**
S. fuscum
-0.09
0.21**
S. rubellum
-
0.15**
Lawn Sphagna
-0.18**
0.06
S. angustifolium
-0.12*
-0.06
S. magellanicum
-0.31**
-0.15**
S. capillifolium
0.03
0.04
Sphagnum
-0.19**
0.30**
True moss
-0.47**
0.26**
Polytrichum strictum
-0.59**
0.24**
Aulacomnium palustre
-0.28**
0.05
Pleurozium schreberi
0.05
-0.02
Dicranum polysetum
-0.02
0.12*
Evergreen shrub
0.64**
0.65**
Vaccinium oxycoccus
0.24**
0.28**
Calluna vulgaris
0.58**
0.59**
Andromeda polifolia
-0.11*
0.23**
Empetrum nigrum
0.12*
-0.01
Rhododendron tomentosum
0.01
0.08
Deciduous shrub (Vaccinium uliginosum)
0.01
0.13*
Ombrotrophic forb (Drosera rotundifolia)
-
0.14*
Minerotrophic forb
0.01
-
Epilobium angustifolium
0.14*
-
Dianthus sp.
-0.11*
-
Thelypteris palustris
-0.11*
-
Potentilla palustris
0.01
-
Minerotrophic grasses
-0.22**
-
Phragmites australis
-0.03
-
Dactylis glomerata
-0.31*
-
Ombrotrophic sedge (Eriophorum vaginatum)
0.28**
0.35**
Minerotrophic sedge (Carex spp.)
-0.03
-
Evergreen tree (Pinus sylvestris)
0.28**
0.24**
Deciduous tree
0.34**
0.08
Betula pendula
0.35**
0.08
Salix spp.
0.02
-
Populus tremula
0.09
-
Alnus glutinosa
-0.01
-
Lichen
-0.08
0.25**
Litter
-0.25**
0.24**
Bare peat
-0.44**
0.07
Mulch
-0.26*
-0.83**
Oligotrophic peatland species (%)
-0.19**
0.43**
Minerotrophic peatland species (%)
-0.24**
0.05
Generalist species (%)
0.64**
0.61**
Mineral soil species (%)
0.15**
0.08