Birch Bog on Anthropogenically Transformed Raised Bogs. A Case Study from Pomerania (Poland) - MDPI
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Article
Birch Bog on Anthropogenically Transformed Raised
Bogs. A Case Study from Pomerania (Poland)
Zofia Sotek 1, *, Małgorzata Stasińska 1 , Ryszard Malinowski 2 , Renata Gamrat 3 and
Małgorzata Gałczyńska 4
1 Department of Botany and Natural Conservation, Faculty of Biology, University of Szczecin, Felczaka 3c,
PL-71-412 Szczecin, Poland; stasinsk@univ.szczecin.pl
2 Department of Soil Science, Grassland and Environmental Chemistry, West Pomeranian University of
Technology Szczecin, Słowackiego 17, PL-71-434 Szczecin, Poland; Ryszard.Malinowski@zut.edu.pl
3 Department of Ecology, Environmental Protection and Management, West Pomeranian University of
Technology Szczecin, Słowackiego 17, PL-71-434 Szczecin, Poland; Renata.Gamrat@zut.edu.pl
4 Department of Chemistry, Microbiology and Environmental Biotechnology, West Pomeranian University of
Technology Szczecin, Słowackiego 17, PL-71-434 Szczecin, Poland; Malgorzata.Galczynska@zut.edu.pl
* Correspondence: sotek@univ.szczecin.pl
Received: 1 April 2019; Accepted: 31 May 2019; Published: 12 June 2019
Abstract: Birch bog is formed on the margins of or within raised bogs, on secondary habitats.
The study aim was to understand the vegetation and mycological diversity of birch bog on the
background of habitat conditions on raised bogs subject to anthropogenic changes, including 15 areas
located on seven bogs. Two of the analyzed areas were located on a peat bog not subject to human
impact. Phytosociological and mycosociological relevés were taken and substrate analyses were
carried out (pH, humidity, N-NH4 , N-NO2 , N-NO3 and P-PO4 ). Based on habitat predictors, two area
groups were distinguished, differing primarily in humidity. More humid habitats were present on the
margins of bogs, and were characterized by lower acidity and higher N-NH4 and P-PO4 abundance.
Despite the fact they were enriched by runoffs from the neighboring arable fields, this was not always
reflected in the plant and fungi species richness. Quercus robur appeared on less humid habitats,
which may be a symptom of unfavorable changes toward habitat drying. In the majority of cases,
changes in the habitat independent of the birch patches located and the human impact type are not
yet reflected in the vegetation. However, they may be indicated by the fungal diversity, highest in
former peat extraction pits, and lowest in pristine peat.
Keywords: Vaccinio uliginosi-Betuletum pubescentis; peat bog plants; macrofungi; former peat extraction
pits; Betula pubescens; habitat predictors
1. Introduction
Bogs are among the most valuable ecosystems, not only due to the rare and valuable species
found therein, but also due to the fact that they are natural retention basins. They contain 10% of
the freshwater volume of the Earth [1]. Moreover, they are of key importance for the long-term
sequestration of atmospheric carbon [2]. It is estimated that peat contains circa 26% of all the terrestrial
carbon accumulated since the Last Glacial Maximum [3] thus they are among the largest terrestrial
carbon reservoirs. Close to 95% of all peat bogs around the world are located in the northern hemisphere
in a cold and at the same time humid temperate climate [4]. It is also here where the majority of
raised bogs are present, supplied solely by rainwater. Such ecosystems are highly susceptible not
only to natural factors, such as unfavourable climatic changes but above all hydrological disturbances
resulting from human activity [5].
Water 2019, 11, 1224; doi:10.3390/w11061224 www.mdpi.com/journal/water
Water 2019, 11, 1224 2 of 18
Globally, the human impact on wetlands has intensified in the last 200 years, and particularly
in the first half of the 20th century [1,6]. This phenomenon occurred at a high rate and extensively
primarily in industrialised countries, where the bog areas have been drastically reduced [7]. Wetlands,
including raised bogs, were frequently drained in order to use them in agriculture, forestry and to obtain
peat [8,9]. In Europe, almost all bog areas have been disturbed [6], whereas in Poland, close to 80% of
bog ecosystems have been subject to human interference [10]. In the majority of cases this has led to a
loss or degradation of those valuable habitats and, as a consequence, to changes or loss of vegetation
typical of bog ecosystems [11–13]. Plant species of raised bog communities are typically stenobionts; thus,
they are among the ecosystem elements that are most sensitive to habitat changes, including rapidly
expanding anthropogenic amendments, including drying and eutrophication [12,14]. Drying may trigger
peat decomposition processes, leading to C and CO2 loss, as well as to increased mineralisation of nutrients,
leading to internal eutrophication [15,16]. Processes occurring as a result of human impact may lead to a
rapid invasion of trees on open areas and development of forest communities. This is an unfavourable
phenomenon for raised bogs, as it leads to additional water drainage, increasing their degradation [17,18].
However, in the case of undisturbed bogs, tree invasion is inhibited, and their increasing share takes place
only under conditions typical of late stages of natural succession [19].
Among forest communities found on raised bogs, bog coniferous and deciduous forests are
distinguished, which are rare and valuable components of those ecosystems. They are included in
the Annex 1 to the Habitats Directive of the EU, as 91D0: natural habitats of Community interest
whose conservation requires the designation of special areas of conservation [20]. Birch bog (Vaccinio
uliginosi-Betuletum pubescentis) is one such community. It is a plant community with Atlantic
distribution type, occurring primarily in north-west Europe, including Austria [21], the Czech Republic [22],
Denmark [23], Germany [24,25], Hungary [26], Ireland [27], Slovakia [28], and in Ukraine [29]. In Poland, it
reaches its eastern boundary of geographic distribution. Patches of birch bog develop typically on drainless
terrain depressions with high groundwater level, on rather shallow, mesotrophic, acidic transition peats,
on acidic soils with the nature of stagnosol. It is the final stage of succession on transitional bogs, whereas it
occurs on the margins of raised bogs, as well as on the habitats with secondary genesis—in the areas where
intensive decomposition processes occur [30,31]. In many parts of Ireland, it develops on exploited and
drained peatlands, while raised bogs are mainly associated with areas enriched with nutrients, originating
from surface runoffs from surrounding areas [32].
Previous studies of swamp birch, both in north-western [23,27,32] and central [21,22] Europe,
were mainly focused on understanding the species composition of plants that build this community
and its structure. However, in general this aim was not a separate subject of consideration. Usually,
it was included in the study on plants colonising the examined bog [33–35]; sometimes, the selected
properties of the habitat were also taken into account [36]. Few reports concern the Holocene history
of birch bog woodlands [37–41]. They show that phases rich in Betula were already present in the early
Holocene or the Late Glacial in Central and Eastern Europe.
Apart from plants, fungi are important biotic factors for the formation and functioning of
phytocenoses because they are heterotrophic organisms they enter into a range of relationships with
plants as well as influence their habitat directly, causing organic matter decomposition. Macromycetes
of birch bog are sporadically included in research but they usually are only a single element of
wider, more comprehensive studies [42,43]. Certain macromycetes species are strictly associated
with peat ecosystems not to be found anywhere else [42,44,45]. Therefore, the condition of the plant
community can be reflected not only by plants, their species composition and share, but also the
diversity and composition of the mycobiota. These elements remain in a close relationship with the
habitat conditions. However, to date these three components were not considered together in the
aspect of anthropopression in birch bog. The aim of the study was to investigate the floristic and
mycological diversity of birch bog in regard to habitat conditions in raised bogs under anthropogenic
transformations. This objective was completed based on the answers to the following research
questions: (1) Did the research areas differ significantly in terms of selected physical and chemical
Water 2019, 11, 1224 3 of 18
properties of the soil, affecting the trophy of the habitat and, if so, whether this was influenced by the
type of anthropopression? (2) Are there any significant differences in composition of fungal biota and
plant species depending on the location of the research area and the type of anthropogenic impact?
(3) If a lower level of habitat predictors (soil properties) is found, is this reflected in both plants and
fungi or only in one of these components of the ecosystem? (4) Does the plant community have a
chance to preserve its individuality and biodiversity despite the presence of anthropopression?
2. Materials and Methods
The study was conducted in the period 2002–2004 and 2007–2009 in the area of seven raised bogs:
Niewiadowo, Roby, Mszar near Stara Dobrzyca, Stramniczka, Torfowisko Toporzyk, Zielone Bagno
and Ziemomyśl, located in north-west Poland. Two of the studied objects are mid-forest bogs, and
the other ones are located in the close vicinity of agricultural areas, used as arable fields or meadows.
This means that they are exposed to an inflow of biogens as a result of surface runoffs. Only Mszar near
Stara Dobrzyca was in the past and, is not exposed currently to any anthropogenic influences. Peat
exploitation was performed on five of the examined locations, and it was preceded by the dewatering
of deposits through a system of ditches that drained water from the peat bogs. However, the time
of excavation of the first drainage ditches and the beginning of exploitation is unknown it may be
concluded only on the basis of available historical maps. The oldest maps which show the network of
drainage ditches and indicate exploitation of the deposits come from 1921–1937 [46–49]. It suggests,
therefore, that peat was being obtained already before this period. The greatest intensity of exploitation
probably took place in the first few years after World War II, when peat was the cheapest fuel material.
Moreover, the documentation about the moment of finishing the exploitation is lacking. However,
reports of the locals show that it was completed in the late 1960s. Currently, peat forming regeneration
processes are taking place in the majority of the old excavations, leading to the formation of moss
or forest bog phytocenoses. However, dewatering of the peat deposit through the old overgrown
ditches continues. At present, with the exception for Ziemomyśl, these bogs are located within Natura
2000 sites and the majority of them are covered by reserves (Table 1).
Table 1. Characteristics of the analyzed bogs.
Geographical Area: Bog/ Kind of
Bog Name Dominant Communities
Coordinates Reserve (ha) Protection
Birch bog, willow thickets, Reserve;
54◦ 60 33.6” N community with Myrica gale and Natura 2000
Roby 96.25/84.40
15◦ 180 53.8” E Erica tetralix, moss community, PLH320017,
high sedge PLB320010
Reserve;
54◦ 90 1.6” N Boggy coniferous forests, birch
Stramniczka 94.49 Natura 2000
15◦ 410 25.2” E bog, moss community
PLH320017
Birch bog, community of
53◦ 110 33.7” N
Ziemomyśl 0.76 Eriophorum vaginatum-Sphagnum –
15◦ 180 39.7” E
fallax
Reserve;
Boggy coniferous forests, birch
53◦ 400 23.7” N Natura 2000
Zielone Bagna 55.38 bog, willow thickets,
16◦ 50 10.3” E PLH320039,
moss community
PLB320019
Reserve;
Mszar near Stara 53◦ 480 9.3” N Boggy coniferous forests, birch
11.17 Natura 2000
Dobrzyca * 15◦ 310 58.0” E bog, moss community
PLH320049
53◦ 390 25.20” N Boggy coniferous forests, birch Natura 2000
Niewiadowo * 42
14◦ 530 24.89” E bog, moss community PLH320013
Reserve;
Torfowisko 53◦ 420 40.2” N Boggy coniferous forests, birch
43.07 Natura 2000
Toporzyk 16◦ 30 3.8” E bog, moss community
PLB320019
*—mid-forest bogs; without stars—mid-field bogs.Water 2019, 11, 1224 4 of 18
For the purpose of the study, 15 patches of birch bog (Vaccinio uliginosi-Betuletum pubescentis)
representative of the aforementioned bogs were selected (Table 2). Two patches in Mszar near Stara
Dobrzyca were treated as reference points for the remaining surfaces due to the fact that they have not
been disturbed (no human impact present). The patch sizes were 400 m2 , with the exception of patch S2,
measuring 200 m2 . In order to determine the plant species diversity and their share in the community
structure, phytosociological relevés were taken using the Braun-Blanquet method. The patches also
constituted permanent plots for the observation of macromycetes. Systematic mycological observations
were carried out every 2–3 weeks on average; between 22 and 26 observations were carried out for each
plot. The share of fungi in the community was analyzed within bioecological groups: mycorrhizal
fungi and saprotrophic fungi (growing on peat and among mosses, litter-inhabiting).
Table 2. Characteristics of the research plots.
Starting Peat
Bog Name Plot Localization Comments
Extraction
middle part secondary habitat—former peat
N1
of the bog extraction pit
middle part
Niewiadowo before 1929 1 N2 habitat drying *
of the bog
middle part habitat drying *, secondary—former
N3
of the bog peat extraction pit
middle part habitat drying *, about 30 m from the
R1
of the bog former peat extraction pit
Roby middle part habitat drying *, about 20 m from the
before 1929 2 R2
of the bog former peat extraction pit
middle part
R3 habitat drying *
of the bog
plot in the immediate vicinity of
middle part
S1 overgrowing former extraction with a
of the bog
moss community
Stramniczka before 1929 3
middle part secondary habitat—former peat
S2
of the bog extraction pit
plot on the bog, not drained and not
SD1 bog margin exploited, in the depression of the
Mszar near Stara area, natural habitat
–
Dobrzyca plot on the bog, not drained and not
SD2 bog margin exploited, less hydrated, natural
habitat
plot in the depression of the area,
Torfowisko
before 1921 4 T1 bog margin exposed to surface runoff from the
Toporzyk
surrounding arable fields
plot on the bog, not drained and not
exploited, in the depression of the
Ziemomyśl – Z1 bog margin
area, exposed to surface runoff from
the surrounding arable fields
middle part secondary habitat—former peat
ZB1
of the bog extraction pit
Zielone Bagna middle part secondary habitat—former peat
before 1921 4 ZB2
of the bog extraction pit
middle part habitat drying *, secondary—former
ZB3
of the bog peat extraction pit
*—based on field observations (humidity and peat decomposition); 1 [49],2 [47],3 [48],4 [46].Water 2019, 11, 1224 5 of 18
The nomenclature of vascular plants is described in [50] and the nomenclature of mosses is according
to [51]. The nomenclature of fungi is given in [52]. The herbarium documentation is deposited in the
Herbarium of the Department of Botany and Nature Conservation, Szczecin University (SZUB-F).
Assessment of soil and water conditions was performed based on the analyses of cumulative soil
samples. Samples were collected in three consecutive years of the study, on three occasions in the
growing season: in spring, summer and autumn (they comprised replications in the statistical analysis),
from a depth of 0–20 cm. The following parameters were determined in the samples: ammonium
nitrogen content (N-NH4 )—via distillation, nitrite nitrogen content (N-NO2 )—via distillation, nitrate
nitrogen content (N-NO3 )—via colorimetry with Griess method, available phosphorus content
(P-PO4 )—via colorimetry with phosphomolybdate blue (Egner-Riehm method), pH—potentiometry,
humidity—by weight in a moisture balance. The analyses were performed at the Department of Soil
Sciences, Grassland and Environmental Chemistry of the West Pomeranian University of Technology.
The results concerning the parameters of soils were developed on the basis of the univariate
analysis of variance. Additionally, such factors as the place of occurrence of the raised bog, drying up
of the habitat, the influence of anthropopressure (surface runoff from agricultural fields and meadows)
and the location of the habitat were tested. The significance of differences was evaluated using the
Tuckey’s HSD (honestly significant difference) test at the significance level α = 0.05. Based on the
standardised physical-chemical data, the investigated soils were grouped by use of hierarchical cluster
analysis, Ward’s square Euclidean distance method [53]. This method consists in presenting similarities
between objects as a function of distance. The variables describing the object (in our case parameters
of soils) are more similar to one another when the distance between them is smaller.
Correlations between plants and fungi and habitat predictors and between plant predictors and
fungi were determined by calculating the Pearson’s correlation coefficient. In statistical analyses,
the vegetation cover in tree layer ‘a’ and shrub layer ‘b’ was considered jointly, as ‘a + b’, since both
layers played a similar role with regards to the group of mycorrhizal fungi and due to the correct
interpretation of results they should be analyzed jointly.
These statistical analyses presented in this paper were achieved using the statistical software
package for Windows (Statistica® v.12 PL, StatSoft, Szczecin, Poland).
3. Results
The upper layers of peat of all the analyzed areas were characterised by strongly acidic pH and
very low, although variable, value of available phosphorus (Table 3). The birch bog in Stramniczka and
Zielone Bagno encompasses large areas, forming on dykes and very dry areas, on a layer of humipeat
or in poorly hydrated, overgrown former peat extraction pits. In the Stramniczka bog, the upper layers
of peat of the S1 and S2 plot have similar humidity and higher amounts of N-NH4 and N-NO2 than
N-NO3 (Table 3). On the other hand, plots of the Zielone Bagno bog have variable humidity, yet on
ZB2 a significantly higher amount of N-NH4 was found. On Torfowisko Toporzyk, birch bog occurs
primarily in the western part of the bog, covered by transition peat deposit, and it remains in contact
with alder bog, growing on more eutrophic habitats. In this bog, the upper layer is characterised by
high humidity and higher amounts of N-NH4 and N-NO2 than N-NO3 . Birch bog on the Niewiadowo
bog was formed primarily in its southern and south-western part, creating extensive patches and from
the north, it is adjacent to coniferous bog forest. The upper layer of the bog indicates variability in
terms of humidity and nitrogen content (at N1 and N2—N-NO3 forms are predominant). The birch
bog in Mszar near Stara Dobrzyca covers small areas at the bog margins, indicating a high degree of
naturalness. The SD1 and SD2 plots differ significantly in terms of humidity but not soil composition.
They have a higher share of the N-NH4 and N-NO2 forms over N-NO3 . In the case of the Ziemomyśl,
birch bog grows over the majority of its surface, and it is characterised by good hydration of the upper
peat layer as well as a high share of the N-NH4 form. On the other hand, at Roby this community
occurs primarily on the margins and on slightly dried surfaces (R1-3), which do not exhibit significantWater 2019, 11, 1224 6 of 18
variability in terms of humidity and soil chemical composition. The dominance of the N-NO3 form
over N-NH4 and N-NO2 is worthy of noting (Table 3).
Table 3. Humidity and selected chemical properties of the top layer of peat soils.
N-NH4 N-NO3 N-NO2 P-PO4
Plot pHH2 O pHKCl Humidity %
mg/dm3 mg/dm3 mg/dm3 mg/dm3
Peat bog—Stramniczka
S1 3.25 abc 2.63 ab 0.062 abc 1.60 ab 4.16 cd 2.95 ab 86 abcd
S2 4.83 bcd 2.41 ab 0.058 abc 1.36 a 3.89 abc 2.84 ab 88 bcde
Peat bog—Zielone Bagno
ZB1 2.91 ab 2.29 ab 0.036 ab 1.06 a 4.02 bc 3.01 ab 90 de
ZB2 5.75 de 2.50 ab 0.054 ab 1.07 a 4.03 bc 2.97 ab 92 e
ZB3 3.23 abc 2.03 a 0.075 abc 1.22 a 3.78 abc 2.74 ab 84 abcd
Peat bog—Roby
R1 3.60 abcd 3.83 abc 0.088 abc 1.34 a 3.74 ab 2.82 ab 81 a
R2 3.64 abcd 3.78 abc 0.085 abc 1.33 a 3.70 ab 2.81 ab 81 a
R3 3.54 abcd 3.70 abc 0.078 abc 1.33 a 3.68 ab 2.73 ab 81 a
Peat bog—Niewiadowo
N1 3.62 abcd 4.02 bc 0.123 c 2.61 bc 4.42 de 3.03 b 90 de
N2 1.79 a 2.34 ab 0.025 a 0.80 a 3.60 a 2.76 ab 80 a
N3 5.37 cd 5.24 c 0.057 abc 0.65 a 3.77 ab 2.67 a 83 ab
Peat bog—Mszar near Stara Dobrzyca
SD1 4.22 bcd 3.80 adc 0.036 ab 1.19 a 4.60 e 3.61 c 92 e
SD2 2.94 ab 2.07 a 0.079 abc 1.329 a 4.49 de 3.53 c 84 abc
Peat bog—Toporzyk
T1 4.22 bcd 3.61 abc 0.034 ab 1.22 a 4.57 e 3.67 c 88 bcde
Peat bog—Ziemomyśl
Z1 7.74 e 2.98 ab 0.095 bc 2.80 c 4.03 bc 3.03 b 89 cde
Number of samples: N = 7; different letters (a, b, c, d, e—homogeneous groups) indicate significant difference at p < 0.05.
As a result of habitat predictor analysis based on the estimation of the distance between clusters
utilizing analysis of variance (Ward’s method), two major groups of the analyzed plots were obtained
(Figure 1). The first group included plots S1, S2, T1, ZB1, ZB2, N1, SD1 and Z1 which, with the
exception for T1 plot, were characterized by very high humidity. The second group included plots
R1, R2, R3, ZB3, N2, N3 and SD2, which, apart from SD2, were characterized by lower humidity in
comparison with the second group.
Both the less humid habitats (on the basis of the division with Ward’s method, Figure 1), as well
as human impacts (surface runoffs), indicated significant variability of soils in terms of humidity, pH,
ammonium nitrogen and orthophosphate (V) phosphorus. Such differences between soils were not
determined for the concentration of nitrate(V) and (III) nitrogen (Tables 4 and 5). Soils of the study areas
exposed to surface runoffs are enriched with N-NH4 and P-PO4 relative to natural and other areas.
Table 4. Characteristics of birch bog habitats varied in terms of humidity.
N-NO3 N-NO2 N-NH4 P-PO4
Habitat Humidity % pHH2 O pHKCl
mg/dm3 mg/dm3 mg/dm3 mg/dm3
Wet 82.08 b 3.82 b 2.86 b 3.28 0.070 3.44 b 1.14 b
Wetter 89.51 a 4.21 a 3.14 a 3.03 0.077 4.57 a 1.61 a
Number of samples: Nwet = 49 and Nwetter = 56; different letters (a, b) indicate significant difference at p < 0.05.Water 2019, 11, x FOR PEER REVIEW 7 of 18
ab abc a a de c abc
Peat bog—Toporzyk
4.22 3.61 0.034 1.22 4.57 3.67 88
T1
Water 2019, 11, 1224 bcd abc ab a e c bcde 7 of 18
Peat bog—Ziemomyśl
7.74 2.98 0.095 2.80 4.03 3.03 89
Z1
Table 5. Characteristics
e of peat soil research
ab areas bcon naturalc habitatsbc(SD1-2)b subjectedcde
to surface
runoffs (T1 and
Number Z1) and N
of samples: not subjected
= 7; different to surface
letters (a, b,runoff (S1-2, R1-3, ZB1-3,
c, d, e—homogeneous N1-3indicate
groups) and Z1).
significant
difference at P < 0.05.
N-NO3 N-NO2 N-NH4 P-PO4
Parameter Humidity % pHH2 O pHKCl
As a result of habitat predictor analysis based mg/dm3 ofmg/dm
on the estimation 3
the distance between
mg/dm 3 mg/dm3
clusters
utilizing analysis
Surface runoff of variance (Ward
88.87 a ’ s method),
4.30 a two major
3.35 b groups
3.30 of the analyzed
0.064 plots were
5.60 a obtained
2.01 a
(Figure 1). The first group88.12
Natural included
a plots
4.54 aS1, S2, T1,
3.57 a ZB1, 2.93ZB2, N1, SD1 0.058and Z13.58 which,
b with the
1.26 b
exception
Without for T1
surface plot, were
runoff characterized
85.15 b 3.88byb very high
2.84 c humidity.
3.15 The 0.080 second group 3.77included
b plots
1.31 b
R1, R2, R3,
Number ZB3, N2,
of samples: N3 and
N surface SD2,
runoff = 14,which,
N natural
apart
= 14 from
and N SD2, were characterized
without surface runoff = 77; by
different lower
letters humidity
(a, b, c) in
indicate
comparison
significant with the
difference < 0.05. group.
at psecond
Square Euclidean distance Ward's method
120
90
100*Distance/Distance max
Wetter Wet
60
30
0
SD1 Z1 S2 ZB1 Z1 S1 R3 T1 N2 R1 ZB3
ZB2 Z1 N1 ZB1 N1 R1 N3 N2 Z1 ZB3
Figure 1. Dendrogram of cluster analysis on the basis of soils parameters. Abbreviations: wet (R1, R2,
Figure 1. Dendrogram of cluster analysis on the basis of soils parameters. Abbreviations: wet (R1, R2,
R3, ZB3, N2, N3 and SD2), wetter (S1, S2, T1, ZB1, ZB2, N1, SD1 and Z1), other abbreviations are as in
R3, ZB3, N2, N3 and SD2), wetter (S1, S2, T1, ZB1, ZB2, N1, SD1 and Z1), other abbreviations are as
Tablein2.Table 2.
Taking into
Both theconsideration the habitat
less humid habitats (on thelocality, soils
basis of the of the with
division analyzed
Wardstudy areasFigure
’s method, differed statistically
1), as well
significantly
as humanonly in terms
impacts ofrunoffs),
(surface humidity, soil pH
indicated and concentration
significant variability ofof ammonium
soils in terms of nitrogen
humidity, (Table
pH, 6).
The middle
ammoniumpartsnitrogen
of the bogs are characterised
and orthophosphate (V) by higher soil
phosphorus. acidity
Such and lower
differences humidity
between andnot
soils were N-NH4
determined
and P-PO 4 for
abundance the concentration
than surfaces of
on nitrate(V)
the and
margins (III)
and nitrogen
in (Tables
former peat 4 and 5).
extraction Soils of
pits. the study
areas exposed to surface runoffs are enriched with N-NH4 and P-PO4 relative to natural and other
areas. 6. Characteristics of peat soil habitats depending on their location on the bog. Former peat
Table
extraction pits (S1-2, ZB1-3, N1 and N3), bog margin (T1, SD1-2 and Z1), middle part of the bog (R1-3
Table 4. Characteristics of birch bog habitats varied in terms of humidity.
and N2).
N-NO3 N-NO2 N-NH4 P-PO4
Plot Location Humidity % pHH2 O pHKCl
mg/dm3 mg/dm3 mg/dm3 mg/dm3
Peat extraction pits 87.59 a 4.01 b 2.89 b 3.01 0.083 4.14 ab 1.37
Bog margin 88.50 a 4.22 a 3.46 a 3.11 0.061 4.78 a 1.63
Middle part of the bog 80.89 b 3.68 c 2.77 b 3.41 0.069 3.14 b 1.20
Number of samples: N peat extraction pits = 49, N bog margin = 28 and N middle part of the bog = 28; different letters (a, b, c)
indicate significant difference at p < 0.05.Water 2019, 11, 1224 8 of 18
Soils of the analyzed study surfaces originating from mid-forest bogs were characterized by
significantly higher pHH2 O values than those located on mid-field bogs. The remaining physical and
chemical parameters of soil were similar (Table 7).
Table 7. Characteristics of peat soils of mid-field and mid-forest bogs. Mid-forest bogs (N1-3 and
SD1-2), mid-field bogs (S1-2, T1, R1-3, ZB1-3 and Z1).
N-NO3 N-NO2 N-NH4 P-PO4
Parameter Humidity % pHH2 O pHKCl
mg/dm3 mg/dm3 mg/dm3 mg/dm3
Mid-field bogs 85.86 3.96 b 2.96 2.97 0.066 4.27 1.43
Mid-forest bogs 86.14 4.18 a 3.12 3.49 0.087 3.59 1.31
Number of samples: N mid-forest bogs = 35 and N mid-field bogs = 70; different letters (a, b) indicate significant difference
at p < 0.05.
A total of 78 plant taxa were found in birch bog, and in individual patches from 14 to 34 species
were recorded (Figure 2). Class Vaccinio-Picetea, in which this community is included, is represented
depending on the patch from 2 to 12 species, and moss species from the class Oxycocco-Sphagnetea from
0 to 7. The vegetation cover in certain layers of the examined patches was occasionally variable (Figure 3).
This is visible, e.g., in the layers of the tree and shrub stand on Roby bog (R1-3), as compared with the
Water 2019, 11, x FOR PEER REVIEW 9 of 18
remaining objects. The tree stand of all the analyzed patches is dominated by Betula pubescens, frequently
accompanied
comparedby Pinus
with thesylvestris
remaining (sometimes
objects. Therather common—N2
tree stand and SD1),
of all the analyzed and less
patches commonlyby
is dominated Sorbus
acuparia
Betula Betula pendula.
andpubescens, Theaccompanied
frequently shrub layer is bypredominantly
Pinus sylvestris formed
(sometimesby Betula
rather pubescens
common—N2 Frangula
and and
alnusSD1), and less commonly
undergrowth, sometimesSorbus acuparia
with and Betula pendula.
an admixture of SalixThespp.shrub layer is
In some predominantly
patches (R1, S2 formed
and SD1-2),
by Betula pubescens and Frangula alnus undergrowth, sometimes with an
the herbal layer is frequented by species of open moss area from class Oxycocco-Sphagnetea, admixture of Salix spp. In
including
some patches (R1, S2 and SD1-2), the herbal layer is frequented by species of open
Erica tetralix, Eriophorum vaginatum and Oxycoccus palustris. The contribution of Sphagnum is marked in moss area from
class Oxycocco-Sphagnetea, including Erica tetralix, Eriophorum vaginatum and Oxycoccus palustris.
the moss layer, and in some areas (SD1-2, S1-2 and T1) abundance of Sphagnum fallax, Sph. palustre
The contribution of Sphagnum is marked in the moss layer, and in some areas (SD1-2, S1-2 and T1)
and Sph. squarosum, and among brown mosses, Pleurozium schreberi (ZB2 and N1-3) and Aulacomnium
abundance of Sphagnum fallax, Sph. palustre and Sph. squarosum, and among brown mosses, Pleurozium
palustre (SD2 and
schreberi (ZB2R1-2)
and was recorded.
N1-3) Sphagnumpalustre
and Aulacomnium magellanicum
(SD2 andwas R1-2)
rare, and
waswas recorded
recorded. only on the
Sphagnum
preserved habitatwas
magellanicum (SD1-2). The was
rare, and presence of Lycopodium
recorded only on theannotinum—a
preserved habitatspecies regionally
(SD1-2). characteristic
The presence of
of birch bog wasannotinum—a
Lycopodium found on T1, N2-3 regionally
species and ZB1-3. Encroachment
characteristic of Phragmites
of birch bog was found australis—a species
on T1, N2-3 and with
wideZB1-3.
ecological scale—was
Encroachment recordedaustralis—a
of Phragmites in patchesspecies
R2, S2withandwide
Z1, ecological
and a considerable contribution
scale—was recorded in of
patches
Molinia R2, S2
cearulea andand
in R1 Z1, R3,
and with
a considerable contribution
the concomitant of Moliniaofcearulea
appearance juvenilein R1 and R3,
Quercus with whereas
robur, the
Picea concomitant appearance
abies was growing of juvenile
singularly onlyQuercus
in T1. robur, whereas Picea abies was growing singularly only
in T1.
Figure 2. 2.Number
Figure Numberof
of plant speciesininthe
plant species thepatches.
patches.Water 2019, 11, 1224 9 of 18
Figure 2. Number of plant species in the patches.
FigureFigure 3. The
3. The vegetation
vegetation cover
cover inin layersofofthe
layers thepatches.
patches. Abbreviations:
Abbreviations: ‘a+b’—cover of tree
‘a+b’—cover and shrub
of tree and shrub
layer,layer, c—cover
c—cover of herb
of herb layer,
layer, d—cover
d—cover ofofmoss
mosslayer.
layer.
A total
Water of11,144
2019, macromycetes
x FOR PEER REVIEW species were recorded on the permanent plots of birch bog, 10and
of 18 from
33 to 74 species were found on particular plots. As a rule, the highest number of species was found
A total of 144 macromycetes species were recorded on the permanent plots of birch bog, and
on plots located in former peat extraction pits, and the lowest on bog margins (with the exception of
from 33 to 74 species were found on particular plots. As a rule, the highest number of species was
the T1 plot). The share of fungi in the selected ecological groups was variable (Figure 4). Cortinarius
found on plots located in former peat extraction pits, and the lowest on bog margins (with the
flexipes, Laccariaofproxima,
exception Lactarius
the T1 plot). tabidus,
The share Russula
of fungi betularum
in the and R. claroflava
selected ecological groups were distinguished
was variable (Figure 4).among
mycorrhizal fungi
Cortinarius (46 species)
flexipes, Laccaria in terms Lactarius
proxima, of the frequency of occurrence
tabidus, Russula betularum and
andabundance.
R. claroflavaThis
were group
was most frequently
distinguished amongrepresented
mycorrhizalon the
fungiplots in former
(46 species) in peat
termsextraction pits, and
of the frequency least frequently
of occurrence and on
abundance.
bog margins. This group fungi
Lignicolous was most(47)frequently representedamong
were predominant on the plots in former fungi
saprotrophic peat extraction
(90), andpits,
some of
and least frequently on bog margins. Lignicolous fungi (47) were predominant
them form permanent, annual or several-year-old fruiting bodies, including Daedaleopsis among saprotrophic
confragosa,
fungi (90),
Diatrypella and some
favacea, Fomesoffomentarius,
them form permanent, annual or
Inonotus obliquus andseveral-year-old fruiting The
Fomitopsis betulina. bodies, including
second group of
Daedaleopsis confragosa, Diatrypella favacea, Fomes fomentarius, Inonotus obliquus and Fomitopsis betulina.
saprotrophic fungi in terms of abundance, including a considerably lower number of species, consisted
The second group of saprotrophic fungi in terms of abundance, including a considerably lower
of peat-growing fungi (15), such as Gymnopus dryophilus, Rhodocollybia maculata, Entoloma cetratum and
number of species, consisted of peat-growing fungi (15), such as Gymnopus dryophilus, Rhodocollybia
E. sericatum.
maculata,Their contribution
Entoloma cetratum andwasE.variable between
sericatum. individual plots;
Their contribution however,
was variable it wasindividual
between lowest on the
peat bog margins.
plots; however,Bryophilous
it was lowestfungi
on the(12)
peatwere
bog represented by, among
margins. Bryophilous others,
fungi Bogbodia
(12) were uda, Hypholoma
represented by,
elongatum Galerina tibiicystis, and litter-growing fungi (13) by e.g., Mycena
among others, Bogbodia uda, Hypholoma elongatum and Galerina tibiicystis, and litter-growingand
and galopus Gymnopus
fungi (13)
androsaceus. The presence
by e.g., Mycena galopus andof representatives of bothThe
Gymnopus androsaceus. groups on individual
presence plots was
of representatives variable.
of both groups on
individual plots was variable.
Figure 4. Contribution
Figure of bioecological
4. Contribution groups
of bioecological of fungi
groups of in the patches.
fungi Abbreviations:
in the patches. M—mycorrhizal
Abbreviations: M—
fungi,mycorrhizal
Sh—fungifungi,
on peat, Sm—fungi
Sh—fungi among
on peat, mosses,
Sm—fungi Sl—litter-inhabiting
among fungi.
mosses, Sl—litter-inhabiting fungi.
The results of Pearson’s correlation (R) used to determine the type of correlation between plants
and fungi and the selected habitat parameters of birch bog indicate the existence of significant
relationships between the group of species of class Vaccinio-Picetea, the total number of fungi, M, Sh
and Sl fungi groups, and substrate pHKCl, and N-NO3, N-NO2, N-NH4 and P-PO4 content (Table 8).
Moreover, the M fungal group exhibited a positive correlation with substrate pHH2O and humidity (R
= 0.62, R = 0.64, p < 0.05, respectively). A positive correlation with pHH2O was also found for vegetationWater 2019, 11, 1224 10 of 18
The results of Pearson’s correlation (R) used to determine the type of correlation between plants and
fungi and the selected habitat parameters of birch bog indicate the existence of significant relationships
between the group of species of class Vaccinio-Picetea, the total number of fungi, M, Sh and Sl fungi
groups, and substrate pHKCl , and N-NO3, N-NO2, N-NH4 and P-PO4 content (Table 8). Moreover,
the M fungal group exhibited a positive correlation with substrate pHH2 O and humidity (R = 0.62,
R = 0.64, p < 0.05, respectively). A positive correlation with pHH2 O was also found for vegetation cover
in ‘a + b’ and ‘d’ layers (R = 0.51, R = 0.56, p < 0.05, respectively). Furthermore, a positive significant
relationship occurred between humidity and certain vegetation parameters and the total number of
fungi species (Table 9). Moreover, a negative correlation was only found between the species group
from class Oxycocco-Sphagnetea, and substrate pHKCl (R = −0.53, p < 0.05).
The existing relationships between fungi and plant predictors are presented in Table 8. A significant
positive correlation was obtained between class Vaccinio-Picetea species group, and the total number of
fungi species and M, Sh and Sl fungi groups (R = 0.87, R = 0.67, R = 0.72, R = 0.78, p < 0.05, respectively).
A significant negative correlation was obtained between class Oxycocco-Sphagnetea species group and
the total number of fungi species and Sh fungi group (R = −0.60, R = −0.61, p < 0.05, respectively).
Furthermore, the Sh group was negatively correlated with the plant cover of the ‘d’ layer (R = −0.59,
p < 0.05, respectively).
Table 8. Pearson correlation (R - coefficient) between plants, macromycetes and habitat parameters.
Abbreviations: NP—total number of plant specis in relevé, Vac-Pic—species of Vaccinio-Picetea,
Ox-Sph— species of Oxycocco-Sphagnetea, a + b—cover of tree and shrub layer (%), c—cover of herb
layer (%), d—cover of moss layer (%), NF—total of fungi species, M—mycorrhizal fungi, Sh—fungi on
peat, Sm—fungi among mosses, Sl—fungi on litter.
Parameter Humidity pHH2 O pHKCl P-PO4 N-NH4 N-NO3 N-NO2
NP 0.60 * 0.31 0.29 0.33 0.35 0.35 0.35
Vac-Pic 0.52 * 0.49 0.82 * 0.73 * 0.72 * 0.68 * 0.72 *
Ox-Sph −0.42 −0.30 −0.53 * −0.44 −0.48 −0.43 −0.48
a+b 0.56 * 0.51 * 0.42 0.45 0.47 0.47 0.47
c 0.54 * −0.12 0.24 0.21 0.25 0.20 0.25
d 0.19 0.56 * −0.17 0.02 0.09 0.18 0.09
NF 0.57 * 0.48 0.94 * 0.83 * 0.80 * 0.73 * 0.80 *
M 0.64 * 0.67 * 0.92 * 0.92 * 0.84 * 0.83 * 0.84 *
Sh 0.44 0.19 0.73 * 0.58 * 0.58 * 0.48 0.58 *
Sm −0.24 0.01 −0.41 −0.26 −0.23 −0.14 −0.23
Sl 0.50 0.39 0.82 * 0.73 * 0.73 * 0.67 * 0.73 *
0.60 *—significant by p < 0.05, N = 15.
Table 9. Pearson correlation (R-coefficient) between plant predictors and macromycetes.
Parameter NP Vac-Pic Ox-Sph a+b c d
NF 0.21 0.87 * −0.60 * 0.34 0.25 −0.43
M 0.24 0.67 * −0.30 0.37 0.11 −0.14
Sh 0.19 0.72 * −0.61 * 0.22 0.43 −0.59 *
Sm −0.31 −0.49 0.44 −0.40 −0.39 0.50
Sl 0.05 0.78 * −0.46 0.26 0.27 −0.42
0.87 *—significant by p < 0.05, N = 15.
4. Discussion
In Poland, birch bog is a rather rare community, restricted to the north-west part of the country.
Its mature phytocenoses occupy the habitat with the total area of only 8.75 km2 [30]. Typically, this
community is species-poor, which has been observed both in Ireland [27], as well as in Poland, where
normally about 20 plant species are found in one patch [30]. Among the birch bog patches we analyzed,Water 2019, 11, 1224 11 of 18
2/3 contained less than 20 plant species (Figure 2), and their low numbers were found not only on
the undisturbed peat bog (SD2), but also on certain bog areas subject to human pressure (e.g., N2).
Consequently, the low species diversity cannot be linked solely to natural habitats.
Ward’s analysis of birch bog distinguished two habitat groups, less and more humid. The more
humid habitats were characterised by lower acidity and were more ammonium nitrogen and phosphorus
rich. They were located primarily on the best-hydrated bog margins, which were accessed by runoffs
from neighbouring, more nutrient-rich minerotrophic areas. These runoffs often contained biogens
from arable lands adjacent to bogs. The patch with the highest floristic diversity (T1, 34 species) was
formed on such a habitat. This may suggest that substrate biogen abundance and high humidity play
a significant role in both the species richness and composition of the community. However, this was
not always reflected by soil richness, for example on Z1—a patch characterised by the highest biogen
abundance and high humidity—only 16 plant species were determined on bog margin. Correlation
analysis results suggest that the total number of plant species in a community patch is significantly
associated only with humidity (Table 8). On the other hand, nutrients such as N-NH4 , N-NO3 , N-NO2
and P-PO4 , may have a positive impact on the abundance of class Vaccinio-Picetea species, in which
the discussed community is included. The type of phytocenoses neighboring birch bog significantly
influences the number of species found therein. In the case of T1, the neighboring alder bog, rushes and
minerotrophic forests resulted in the patch being enriched with plants which penetrated from those
habitats, including Peucedanum palustre, Picea abies and Galium palustre. On the other hand, the species
poverty of the Z1patch, which was the most biogen-rich, may be associated with i.a. the vicinity of
a moss area, which comprises oligotrophic species, exhibiting the lower capacity to penetrate more
nutrient-rich habitats. The appearance of Sphagnum magellanicum—a species strictly associated with
raised bog habitats, in the SD1-2 patches, located on bog margins and not subject to human pressure,
also resulted from the direct vicinity of moss area with birch bog. The negative correlation between
the number of species from class Oxycocco-Sphagnetea, and pHKCl (Table 8) is typically explained by
the considerable share of Sphagnum spp., as they additionally impact habitat acidification, by binding
cations (Ca and Mg) present in the environment and the release of hydrogen ions [54]. However,
at Roby (lowest pH) this correlation can be linked with slightly higher (with regards to the majority of
the remaining study objects) number of herbaceous plant species included in this class, and not with
Sphagnum spp., as those mosses grew there only at low amounts. Typically, the share of raised bog
species in birch bog is low [30].
Less humid habitats were mostly located within the bogs. The least humid birch bog patches were
located in Roby (R1-3) and Niewiadów (N2). They were richer in N-NO3 than N-NH4 , which could be
a symptom of unfavourable changes toward habitat drying [55–57]. This phenomenon may be also
suggested by the presence of single juvenile Quercus robur individuals [58] recorded in patches R1 and
R3, where moor grass was also found, as well as in R2. Moreover, in the vegetation structure of R2,
a high share of shrub ‘b’ layer was recorded, sometimes higher than trees ‘a’, this could have stemmed
from the lower habitat humidity, which may have promoted numerous appearances of Betula pubescens
in the understory which was definitely predominant here.
The spatial structure of birch bog was in some cases otherwise, e.g., by comparing herbs layer
‘c’ and moss layer ‘d’ on extracted bogs with undisturbed bog (Mszar near Stara Dobrzyca). In bog
patches subject to human change, the ‘c’ cover was usually higher than the ‘d’. A reverse relationships
were found in Betuletum pubescentis on the previously exploited peatlands in Ireland [27], as well as
in a similar community described as bogged birch forest with peat located on similar disturbed habitats
in Siberia [42]. Former peat extraction pits, in which birch bog (S1-2, ZB1-3, N1 and N3) was formed,
were characterised by similar humidity and slightly lower acidity in comparison with areas on the bog
margins. However, the vegetation did not demonstrate considerable differences with relation to this
community patches located on other sites. In these sites, birch bog was typically well-developed, which
was also indicated by the presence of Lycopodium annotinum in half of these patches, a characteristic
species for this community, as well as common Pleurozium schreberi, which had a considerable share inWater 2019, 11, 1224 12 of 18
some patches. Former peat extraction pits constitute secondary habitat for birch bog and it may thrive
in them only when the high water level is not maintained in this habitat, otherwise Betula pubescens
will gradually wither, and under favorable conditions succession may have the direction of moss
community restoration. Expansion of forest vegetation is determined by the groundwater level in the
bog and the air availability in the upper peat layer [57,59]. For the normal development of the root
system, trees require more than a 10% share of peat pores to be filled with air [59]. The analyzed bogs,
independently of the study area location (middle, margin, former peat extraction pits), fulfilled this
condition, only on peat bog not subject to human impact, the study area SD1 had pores filled with air
in 8% and with water in 92%. Furthermore, trees require a nutrient supply for normal development.
Birch requires considerably higher amounts of nutrients than pine [60]. On no disturbed peat bogs has
the development of trees been inhibited primarily by the excessive humidity and bog growth, and to a
lesser degree by the nutrient deficiency [61,62].
Molinia cearulea is a common element of birch bog and its share in this community may vary.
In Austria, apart from Vaccinium uliginosum, it is a common predominant plant species of the herbs
layer of this community [21]. In patches R1 and R3, where moor grass was most common, it was
observed that peat mosses were characterised by lower cover percentage. Competition between these
plants for light could be one of the causes of this phenomenon. The importance of this factor was
indicated by Hogg et al. [63], who observed that cutting back M. coerulea restricts its competitiveness
for light, having a positive impact on the development of peat mosses. On the other hand, Limmper [64]
determined that the high share of herbaceous plants on peat bogs may have a negative impact on the
development of these mosses. The shadow effect by vascular plants has been indicated to be a cause
for this state by Hayward and Clymo [65] and by Heijmans et al. [66]. In turn, the living layer of peat
moss may inhibit the growth of vascular plants by binding large amounts of nitrogen [64,67].
Birch and moor grass may appear on ombrotrophic bogs not only on their natural habitats, that
is the margins of raised bog, but also on moss areas. It is a highly unfavourable phenomenon as the
increase of their total cover and expansion of other vascular plants stimulates evapotranspiration [67,68].
This may contribute to habitat drying, which is very sensitive to changes in water relations, and in such
cases susceptible to invasion of Picea abies, which is an alien species in terms of habitat and geography.
However, no such phenomenon has been observed on the analyzed patches located in the middle of
the bogs. The presence of singular individuals of spruce was recorded only in T1, located in a more
nutrient-rich bog margin.
Birch bog is one of the bog forest communities least known in mycological terms. Fungi constitute
its important, integral structural element, as they enter into a series of interactions with different plant
species and they influence not only the maintenance but also the habitat transformation [69]. They also
play the dominant role among decomposer organisms in acidic peat ecosystems [44]. The majority of
them are saprotrophs, participating in the decomposition of organic matter [70,71]. Birch bog, other
than for plants, is typically rich in macroscopic fungi species, which has been determined in both the
Słowiński National Park (78 species, [72]) as well as in the Goleniów Forest (85 species, [73]). Among
the analyzed plots, ZB1-2 and N1 (61-74 species) are the richest in fungi species, and are located in
former peat extraction pits. In turn, the SD1-2 plots not subject to human pressure turned out to be
the least rich in fungi species (33–39). The contribution of peat mosses could be one of the factors
restricting the number of fungi species on an undisturbed habitat, as it was here highest among all the
analyzed plots. The locally compact layer of peat mosses typically inhibited the development of fungi
growing on a different substrate, including peat, which is further suggested by the negative correlation,
whereas it favored the occurrence of a small group of fungi associated with moss areas, e.g., Galerina
paludosa, G. tibiicystis and Sphagnurus paluster. The role of these moss species is confirmed by the
obtained negative correlation between the total number of fungi species per plot, and the number of
plant species from class Oxycocco-Sphagnetea. An analysis of Pearson’s correlation indicates that both
the total number of species of fungi found within one surface and the number of mycorrhoidal species
were significantly and positively correlated with the number of plant species from the Vaccinio-PiceteaWater 2019, 11, 1224 13 of 18
class. This relationship stems from the community structure in which the Vaccinio-Picetea class
plant species are among its basic elements, and in particular B. pubescens and its accompanying trees
interacting with fungi. Numerous fungi species, including mycorrhizal species, are specific for given
tree species [74], which is reflected by the biota of macromycetes of the given community. Plots N2
(in the middle of the bog) and SD1 (bog margin) are examples here, where the considerable share of
pine resulted in the appearance of fungi associated with them, including Russula emetica, Lactarius rufus
and Auriscalpium vulgare.
The fungal species diversity of birch bog does not only depend on the multi-plane relationships
between these specific organisms and plants but also on chemical properties of the soil. Results
presented in this study indicate the existence of significant relationships between the occurrence of
fungi species and selected environmental factors, i.a. humidity and soil pH. In birch bog, all the
study areas were characterised by more or less acidic soil. The determined positive correlation
between the number of fungi and certain bioecological fungi groups, and pH suggests that excessively
acidic soil may have a negative impact on the diversity of macromycetes. Numerous fungi species
prefer determined values of pH and react differently to its change [75,76]. A similar situation
occurs in the case of phosphorus and nitrogen compound content in soil, as many fungi species
e.g., ectomycorrhizal, exhibit different tolerance to the high or low content of nitrogen in soil [77].
Moreover, the availability of different nitrogen forms plays a significant role in the production of
fruiting bodies [76] and formation of ectomycorrhiza [78]. Based on the obtained positive correlation
between the total number of macromycetes on the given plot and certain bioecological groups of fungi,
as well as the content of phosphorus and various nitrogen forms in the soil it can be expected that
with their increase macromycetes diversity will increase. Trees growing on humid peat soils largely
depend on ectomycorrhizal symbionts which facilitate their absorption of nutrients and participate in
capturing P [79,80]. In the case of Betula pubescens saplings [67], it was determined that the presence of
ectomycorrhizal symbionts did not guarantee trees growth, which could stem from inhibition of the
activity of those symbionts by acidic conditions. The correct content of nitrogen and phosphorus in the
soil is of particular importance for the development of birch [11,67], given that birch is incapable of
fully utilising nitrogen in the event of the absence of P in soil [81].
5. Conclusions
Changes occurring in the habitat of Vaccinio uliginosi-Batuletum pubescentis birch bog regardless
of (1) location of bog patches, (2) anthropopression type (drainage, peat exploitation, surface runoff),
(3) time of anthropogenic impact (peat exploitation - lasted about 40 years, completed approx. 60 years
ago, dewatering—started a few years before exploitation of peat, lasts with lower intensity to today)
and (4) intensity of human impact, in most cases are not yet reflected in the vegetation, as found on the
basis of a comparison with birch growing in a peat bog not disturbed by humans. Plant species, e.g.,
Quercus robur, started to appear only in singular areas, but in the case of their greater share they may
have indicate ongoing transformations of these habitats. Habitat conditions enable the presence of only
a strictly limited number of widely distributed plant species, such as Phragmites austrialis. However,
the slow rate of change is demonstrated by the high diversity of fungi species, which was highest
in the areas of former peat extraction pits, whereas lowest on bog margins, and particularly on the
undisturbed bog. On the other hand, the considerable presence of fungi that are strictly associated
with bogs constitutes an indicator for the still good preservation state of the studied objects.
When birch bog appears on secondary habitats in the middle of a bog, a dilemma arises as to
whether humans should allow for its further development. In the case where birch bog would threaten
the existence of a moss area on an ombrogenic peat bog, activities aiming toward its eradication for the
advantage of the moss area should be undertaken by using e.g., long-term submerging of the area where
birch bog is found. However, if this community is well developed, which would be demonstrated
by, i.a. presence of its characteristic species, and its state, based on the accepted indicators, can be
evaluated as good [58], then such a community should be protected also on secondary habitats, as it isWater 2019, 11, 1224 14 of 18
rare and has priority among Natura 2000 habitats. It is a permanent community in stable hydrological
conditions. Despite the fact that the majority of the studied birch bog habitats have been and still are
being mostly subject to different types of human impact, their physicochemical properties, including
humidity, enable further development of this community. The majority of the analyzed birch bog
patches are located on protected areas, thus granting them a higher chance of survival.
Author Contributions: Z.S. and M.S. designed, conducted the research, partly analyzed the data, and wrote the
paper; R.M. carried out laboratory analyzes, partly analyzed the data and participated in writing; R.G. participated
in fieldwork and reviewed the final draft of the manuscript; M.G. partly analyzed the data and reviewed the final
draft of the manuscript. All authors read and approved the final manuscript.
Funding: Studies supported financially in part by the Ministry of Science and Higher Education (Poland), grant
N N305 2617 33.
Conflicts of Interest: The authors declare no conflict of interest.
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