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Calliergon megalophyllum rediscovered in the Netherlands after 50 years: comparison to
Swedish habitats
Kooijman, A.; Hedenäs, L.; Mettrop, I.; Cusell, C.
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Kooijman, A., Hedenäs, L., Mettrop, I., & Cusell, C. (2015). Calliergon megalophyllum rediscovered in the
Netherlands after 50 years: comparison to Swedish habitats. Lindbergia, 38, 20-29.
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Download date: 19 Jun 2020
Lindbergia 38: 20–29, 2015
ISSN 2001-5909
Accepted 27 October 2015
Calliergon megalophyllum rediscovered in the Netherlands after
50 years: comparison to Swedish habitats
Annemieke Kooijman, Lars Hedenäs, Ivan Mettrop and Casper Cusell
A. M. Kooijman (a.m.kooijman@uva.nl) and I. Mettrop, Inst. for Biodiversity and Ecosystem Dynamics, Univ. of Amsterdam, Science
Park, PO Box 94062, NL-1090 GB Amsterdam, the Netherlands. IM also at: Dept of Aquatic Ecology and Environmental Biology, Inst.
for Water and Wetland Research, Radboud University Nijmegen, NL-6525 Nijmegen, the Netherlands. – L. Hedenäs, Dept of Botany,
Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden. – C. Cusell, Witteveen+Bos, PO Box 233, NL-7400
AE Deventer, the Netherlands.
The moss Calliergon megalophyllum is rediscovered in the Netherlands after approximately 50 years of absence, in
a location different from before: National Park Weerribben-Wieden. This is a Natura 2000 wetland area, and a
Dutch hotspot for rich-fen bryophytes. The species was growing in a fen pool. Plant species composition and water
chemistry were compared with Swedish samples collected throughout the country. Water chemistry of C. megalophyllum in Sweden was also compared with four other (semi-)aquatic species: C. giganteum, Scorpidium scorpioides,
Sarmentypnum trichophyllum and S. exannulatum. The species is characteristic for poorly buffered habitats, but has
nevertheless relatively high pH, which makes it sensitive to acidification, especially when atmospheric deposition is
high. In the Dutch locality, buffer capacity is maintained by input of base-rich ditch water through small channels
in the fen. The data further suggest that, like other Calliergon species, C. megalophyllum is growing in relatively
nutrient-rich habitats, especially with respect to P and K. In the Netherlands, plant nutrient concentrations suggest
that P is indeed not limiting, which may enhance survival of the species, as P-poor habitats in this country have
become very rare.
The (semi-)aquatic moss species Calliergon megalophyllum
Mikut. was rediscovered in the Netherlands after approximately 50 years of absence, in a location different from
before: a fen pool in National Park Weerribben-Wieden,
located in the northeastern part of the Holocene, peatland
part of the country. National Park Weerribben-Wieden is
a Natura 2000 wetland area, and a Dutch hotspot for richfen bryophytes (Kooijman 2012).
The last record of C. megalophyllum in the Netherlands was back in 1965. Calliergon megalophyllum has
been recognised as a distinct species for a long time in
Fennoscandia (Jensen 1939, Tuomikoski 1940, Nyholm
1965, Tuomikoski and Koponen 1979, Hedenäs 1993a,
b, 1997), and was even recognized in the Netherlands
(Karczmarz and Touw 1973). However, in the official revision of Rubers (1989), C. megalophyllum was included
in C. giganteum (Schimp.) Kindb., even though there are
hardly any problems with their separation, even in the
field. When one of us (L. Hedenäs) visited Rijksherbarium in Leiden, the holdings of C. giganteum were searched
for possible specimens of C. megalophyllum. The search
20
resulted in ten Dutch specimens of C. megalophyllum, all
from Groningen or Noord-Brabant, and all except one
from before 1950 (Appendix 1, van Tooren and Sparrius
2006). All specimens were found in aquatic habitats such
as pools and ditches. The species was considered extinct,
and when two of us (L. Hedenäs and A. M. Kooijman)
visited some of the former localities in 1992, we did indeed not find it.
Calliergon megalophyllum has a distinct northern hemisphere distribution pattern, occurring in a belt with a
latitude between approximately 60–70º, from Norway,
Sweden, Finland, Russia and Canada to the USA, usually
in pools and small rivers (GBIF 2015). In northern and
northeastern Europe, it is relatively frequent in many areas. However, the species has occasionally been found also
at lower latitudes, in Estonia, Latvia, Poland, Germany,
Czech Republic, Denmark (Hedenäs 2003, Meinunger
and Schröder 2007),
), and, as mentioned, in the Netherlands.
Although the species is widely distributed in the northern hemisphere, data on habitat conditions are scarce. In
© 2015 The Authors. This is an Open Access article.
this paper, we will characterize water chemistry and plant
species composition in the new Dutch locality of C. megalophyllum, and compare them to the general habitat conditions of the species in Sweden. To put this characterization in a wider perspective, the Swedish water samples
are also compared with four other semi-aquatic to aquatic
Calliergonaceae moss species, with which C. megalophyllum has either been confused in the Netherlands, or ones
that it sometimes grows together with in Sweden: the
closely related C. giganteum, and the species Scorpidium
scorpioides (Hedw.) Limpr., Sarmentypnum trichophyllum
(Warnst.) Hedenäs, and Sarmentypnum exannulatum
(Schimp.) Hedenäs. These species have partly similar, but
also slightly different habitats. With this information, we
will discuss the perspectives of survival of the species in
countries such as the Netherlands, with high environmental pressure.
Study sites and methods
Calliergon megalophyllum was found in October 2014 in a
fen pool in National Park Weerribben-Wieden (Fig. 1), a
wetland area known for its base-rich and transitional fens
belonging to the Natura 2000 habitattype H7140 (van
Wirdum 1991, Cusell 2014). The area is also a hotspot
for characteristic rich-fen bryophytes (Kooijman 2012).
The coordinates of the locality are: 52°42’54.1779’’N;
6°7’5.4821’’E, and a voucher is deposited in herbarium
S (reg. no. B211008). The fen itself consists of a peat
layer of approximately 60 cm thickness, formed on top
of cover sand from the last Ice age. The fen is mostly covered by Sphagnum spp. and Polytrichum commune Hedw.
Calliergon megalophyllum was found in a pool of 10 cm
depth in the central part of the fen, probably in remnants
of isolated former lakes that terrestrialized only in the
1960s. In the National Park, fens are mainly fed by rain
and surface water, as the wetland area is surrounded by
lower lying agricultural polders, blocking the influence
of groundwater seepage in the nature reserve itself (van
Wirdum 1991). In this particular C. megalophyllum fen,
the central parts are supplied with base-rich surface water
by small ditches which are connected to larger ditches
and channels.
After discovery of C. megalophyllum, all other plant
species in the habitat were recorded. Vascular plant names
are used according to van der Meijden (2005). Samples
of surface water and soil pore water were collected for
analysis of water chemistry. Soil samples and aboveground
vascular plant biomass were collected for their nutrient
composition. Depth profiles of the electrical conductivity
(EC) were recorded until the sandy bottom was reached
with a EC-prikstok, a sampling stick of 2 m which can
measure EC and temperature at different depths (van
Wirdum 1991). In addition, EC-values of the surface water were recorded with a field meter along a transect from
the C. megalophyllum pool, through the small channels,
to the ditch where the water originates from. This ditch
is located relatively far away from the main channel to
reduce nutrient input. EC in the main channel was also
measured, and water samples for chemical analysis were
collected in both ditch and channel.
Figure 1. Habitat of Calliergon megalophyllum at the newly found locality in National Park Weerribben-Wieden, the Netherlands,
with the species growing in the portions with open water (A), and close-up of C. megalophyllum in a locality in Medelpad, Sweden
(B). Photographs: L. Hedenäs.
21
To compare the Dutch C. megalophyllum habitat with
more general habitat characteristics of the species in Sweden, we used a part of the dataset of water chemistry and
plant species composition of 481 bryophyte localities
in wetlands and rich-poor fens throughout Sweden (L.
Hedenäs and A. M. Kooijman unpubl.). This survey was
centered on species of the Calliergonaceae and took place
in 1991–1997. Even though Sweden has a large population of C. megalophyllum, the species is also relatively
uncommon, and only 13 localities could be included (Appendix 1). Thus, to put the data for C. megalophyllum in
a wider perspective, the Swedish water samples were also
compared with four other semi-aquatic to aquatic Calliergonaceae moss species. The first one is the closely related C. giganteum (n = 21), with which C. megalophyllum
has been confused in the Netherlands. The other three
are Scorpidium scorpioides (Hedw.) Limpr. (n = 26), Sarmentypnum trichophyllum (Warnst.) Hedenäs (n = 6), and
S. exannulatum (Schimp.) Hedenäs (n = 24), which are
sometimes growing together with C. megalophyllum, and
have slightly different habitats.
The pH and EC of the water samples were measured
immediately after collection. The Swedish water samples
were divided in two bottles, one acidified with HNO3
to prevent precipitation of Fe, and the other conserved
with chloroform to prevent biological changes. In the
Dutch sample, alkalinity (HCO3–) was also measured
directly after sampling, with titration to pH 4.2, using
0.01 M HCl. For all samples, NH4+, NO3–, PO43–, Cl
and SO42– concentrations were measured spectrophotometrically with a Skalar auto-analyzer (Westerman
1990). For the Swedish samples, concentrations of Na,
K, Ca, Mg, Fe, Al and HCO3– were also measured in
this way. For the Dutch samples, Na, K, Ca, Mg, Fe
and Al were measured with an ICP (Westerman 1990).
For the Swedish samples, ionic ratio, a proxy for the
relative contribution of groundwater versus rainwater
was calculated according van Wirdum (1991), based
on Ca- and Cl-concentrations. In the Dutch samples,
concentrations of Cl were unfortunately unreliable, as
they were 13–35 times lower than Na, while they are
normally more or less the same in the Dutch rich fens
(I. Mettrop unpubl.). To give at least some indication
of the ionic ratio of the Dutch sample, this was based
on Na rather than Cl. Soil material and aboveground
vascular plant tissue were dried and ground for CNSanalysis (Westerman 1990). P- and K-contents were determined after microwave-digestion with HNO3. Nutrient concentrations were measured with ICP.
As there was only one Dutch locality with C. megalophyllum, statistical testing of the habitat conditions was
not possible, but values generally fell within the Swedish range. Differences in habitat conditions between the
Swedish localities of C. megalophyllum, C. giganteum, S.
scorpioides and S. trichophyllum were tested with general
linear models, and post-hoc lsmeans tests.
22
Results
Plant species composition
In the new Dutch locality of Calliergon megalophyllum, accompanying bryophytes were S. scorpioides, Calliergonella
cuspidata (Hedw.) Loeske and Sphagnum contortum
Schultz, which point to relatively base-rich conditions
(Table 1). Vascular plant species included Carex lasiocarpa
Ehrh., Menyanthes trifoliata L., Pedicularis palustris L.,
Juncus subnodulosus Schrank and Ranunculus flammula L.,
which are also species of relatively base-rich fens. Other
vascular plant species of the Dutch locality also occurred
in the Swedish localities, such as Carex rostrata Stokes,
Comarum palustris (L.) Scop. and Nymphaea alba L., the
latter pointing to the former presence of open water. More
eutrophic species were also present, such as Lycopus europeus L. and Lythrum salicaria L. The Swedish localities
ranged from backwaters of rivers to small (ox-bow) lakes
and reed shores. Besides C. megalophyllum, the bryophyte
Sarmentypnum exannulatum (Schimp.) Hedenäs was
frequently found, which points to slightly lower buffer
capacity than in the Netherlands. Among the vascular
plants, Equisetum fluviatile L. and Carex aquatilis Wahlenb. frequently occurred. In many Swedish localities, at
least some relatively eutrophic species were present, such
as Caltha palustris L., Lysimachia vulgaris L., Epilobium
palustre L., Carex pseudocyperus L., Phalaris arundinacea
L., Typha latifolia L. and Lemna minor L. Typically northern (fen) species were generally absent, even in the north.
pH and buffer capacity
The Dutch locality of C. megalophyllum had a relatively
high pH of 6.4 (Table 2). However, buffer capacity was
relatively low. Electrical conductivity was only 138 µS
cm-1, and Ca and HCO3–concentration 289 µmol l-1 (7.6
mg l-1) and 560 µmol l-1 respectively. These values are 3–6
times lower than in the base-rich fens dominated by Scorpidium spp. in the area (Cusell et al. 2014). The pH in
the Dutch locality was comparable to the Swedish ones.
However, buffer capacity in the Dutch locality, albeit low
for Dutch standards, was on the highest part of the Swedish range. In the Swedish localities, mean EC values were
51 (± 32) µS cm-1, and Ca-concentrations 136 (± 110)
µmol l-1, which is approximately two times lower than in
the Dutch locality.
In the Swedish localities, pH values for C. megalophyllum were also relatively high, at least compared to the other moss species (Table 3). The pH values were comparable
to those of C. giganteum, but higher than for S. scorpioides,
and especially S. trichophyllum and S. exannulatum. Despite high pH, however, buffer capacity for C. megalophyllum was relatively low. Electrical conductivity, ionic ratio,
Table 1. Plant species composition in the only Calliergon megalophyllum locality in the Netherlands (NL) and 12 localities throughout
Sweden (samples 20–459). Nomenclature of bryophytes is according to van Tooren and Sparrius (2007), and of vascular plant species
according to van der Meijden (2005), except for Sarmentypnum tundrae (Arnell) Hedenäs, S. trichophyllum (Warnst.) Hedenäs, and
Carex juncella (Fr.) Th.Fr., which do not occur in the Netherlands.
NL
20
175
165
195
252
167
459
461
194
150
24
147
Calliergon megalophyllum
*
*
*
*
*
*
*
*
*
*
*
*
*
Sphagnum contortum
*
Scorpidium scorpioides
*
Calliergonella cuspidata
*
*
*
*
*
*
*
Drepanocladus aduncus
*
*
Climacium dendroides
*
Bryum pseudotriquetrum
*
*
*
*
Sarmentypnum exannulatum
*
*
Calliergon giganteum
*
Calliergon cordifolium
*
Sarmentypnum tundrae
*
Sphagnum squarrosum
*
Sphagnum riparium
*
*
Sarmentypnum trichophyllum
Carex lasiocarpa
*
Menyanthes trifoliata
*
Hydrocotyle vulgaris
*
Lythrum salicaria
*
Lycopus europeus
*
Pedicularis palustris
*
Thelypteris palustris
*
Juncus subnodulosus
*
Mentha aquatica
*
Ranunculus flammula
*
Utricularia minor
*
Carex rostrata
*
*
*
*
Comarum palustris
*
*
*
*
Galium palustre
*
*
*
Cardamine pratense
*
*
Nymphaea alba
*
Peucedanum palustre
*
*
Phragmites australis
*
*
Utricularia intermedia
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
Equisetum fluviatile
*
Utricularia vulgaris
*
Subularia aquatica
*
Sparganium sp.
*
*
*
*
*
*
Myrica gale
*
*
Lysimachia vulgaris
*
*
*
23
Table 1. Continued.
NL
20
175
Carex aquatilis
*
Carex vesicaria
*
Hydrochaeris morsus-rana
*
Myosotis scorpioides
*
Caltha palustris
*
165
195
252
167
459
461
194
*
*
*
*
*
*
*
Filipendula ulmaria
*
Juncus filiformis
*
Carex curta
*
Calamagrostis canescens
*
Carex juncella
*
*
Epilobium palustre
*
Equisetum palustre
*
Calla palustris
*
*
*
*
Cicuta virosa
*
Lysimachia thyrsiflora
*
Carex pseudocyperus
*
Scirpus lacustris
*
Carex elata
*
Carex diandra
*
Sparganium erectum
*
Nymphaea candida
*
Phalaris arundinacea
*
Veronica scutellata
*
*
Hippuris vulgaris
*
Ranunculus repens
*
Typha latifolia
*
*
Myosotis laxa
*
Rorippa palustris
*
Alisma plantago-aquatica
*
Sagittaria sagitifolius
*
Poa palustris
*
Lemna minor
*
Glyceria fluitans
*
Polygonum amfibium
*
Alopecuris geniculatus
*
Potamogeton sp.
24
24
*
Potamogeton natans
Sparganium minimum
150
*
*
147
Table 2. Chemical composition of the surface water in the only Calliergon megalophyllum locality in the Netherlands (NL) and 13
localities throughout Sweden (samples 20–459). * = ionic ratio (IR) in the Netherlands was based on Ca and Na, instead of Ca and Cl,
because Cl-concentration measurements were unreliable.
NL
20
175
165
195
252
167
459
461
194
150
24
147
332
pH
6.4
6.5
6.7
6.2
6.9
6.6
6.4
6.8
6.9
6.7
6.7
6.6
6.9
7.0
EC (µS cm-1)
138
44
37
52
23
98
28
43
75
54
33
14
37
130
0.34*
0.71
0.56
0.64
0.22
0.72
0.38
0.67
0.78
0.56
0.58
0.47
0.84
0.60
IR
water level (cm)
1
0
-4
4
-10
-10
3
-4
-4
-6
-20
0
0
6
Ca (µmol l-1)
289
103
67
103
15
214
53
116
206
98
78
38
295
391
HCO3– (µmol l-1)
560
344
394
393
196
412
98
301
572
377
230
49
246
659
Fe (µmol l )
-1
SO42– (µmol l-1)
4
7
5
6
3
4
3
14
17
4
5
10
4
4
115
31
57
52
41
121
31
49
53
56
31
31
10
94
NH4+ (µmol l-1)
0
0
12
16
36
0
4
14
14
0
18
2
10
4
NO3– (µmol l-1)
0.0
0.0
0.5
0.3
0.6
1.5
0.3
0.0
0.0
2.3
1.3
0.3
1.3
0.0
PO43– (µmol l-1)
0.30
0.00
0.32
0.63
0.21
116
0.11
0.42
0.63
0.53
0.21
0.00
0.32
0.11
72
23
14
23
72
7
54
24
21
36
18
3
10
18
K (µmol l-1)
Ca- and HCO3–-concentrations were significantly higher
for C. giganteum and S. scorpioides than for C. megalophyllum. Buffer capacity of the latter species was instead more
comparable to S. trichophyllum and especially S. exannulatum. All three species had relatively low values for EC, IR,
Ca and HCO3–, although lowest values were reached for
S. trichophyllum. These results support that the C. megalophyllum habitat has relatively high pH, but low buffer
capacity in both Sweden and the Netherlands.
In the Dutch locality, the C. megalophyllum pool was
located inside the fen, isolated from the surface water, except for the small ditches which presumably provide base-
rich water from the ditch. In the pool, EC-values were
below 150 µS cm-1 from the surface to a depth of 50 cm,
and EC-values lower down were hardly higher (Fig. 2).
In the small ditch system, EC values were around 231 µS
cm-1 in the ditch, and gradually decreased along the way to
138 µS cm-1 (Fig. 3). In the ditch, EC values were approximately two times lower than in the main channel, which
does not provide water to the fen and pool directly, due
to the long pathway before the water reaches the supplying ditch. This was also true for Ca-concentrations, which
were 989 and 559 µmol l-1 in the main channel and supplying ditch, respectively.
Table 3. Chemical composition of surface water in localities throughout Sweden for Calliergon megalophyllum (n = 13), compared to
three other (semi-)aquatic moss species Calliergon giganteum (n = 21), Scorpidium scorpioides (n = 26), Sarmentypnum trichophyllum
(n = 6) and Sarmentypnum exannulatum (n = 24). Values given are mean values and standard deviations. * = significant general effect
(p < 0.05); different letters indicate significant differences for a parameter between particular species.
C. megalophyllum
pH*
6.7 (0.2)
EC (µS cm-1)*
51 (32) a
Ionic ratio*
0.60 (0.17)
C. giganteum
6.7 (0.6)
c
a
S. scorpioides
6.3 (0.6)
c
S. trichophyllum
6.0 (0.7)
b
142 (102) b
111 (107) b
42 (24) a
0.76 (0.16)
0.74 (0.15)
0.46 (0.13)
Ca (µmol l )*
136 (110)
a
HCO3– (µmol l-1)*
328 (171) a
1034 (880) b
861 (841) b
164 (31) a
266 (236) a
7 (4)
10 (9)
18 (23)
b
8 (5)
23 (28) b
80 (74)
ab
82 (52)
Fe (µmol l )
-1
SO
2–
4
(µmol l )
-1
a
51 (30)
a
465 (447)
0.50 (0.16) a
–3.4 (7.0)
b
a
96 (67)
b
b
400 (443)
b
–6.8 (7.0)
60 (65) a
a
Water level (cm)*
b
1.5 (2.1)
b
a
-1
3.2 (1.5)
b
W. exannulatum
5.6 (0.6) a
ab
68 (28)
a
a
a
ab
2.0 (3.9) b
141 (168) a
72 (40) ab
NH4+ (µmol l-1)
10 (10) a
19 (35) a
11 (19) a
14 (17) a
5 (7) a
NO3– (µmol l-1)*
0.6 (0.7) a
1.5 (1.4) a
1.0 (1.4) a
5.9 (11.0) b
0.8 (0.9)
PO43– (µmol l-1)*
0.36 (0.32) b
0.26 (0.27) ab
0.12 (0.16) a
0.14 (0.05) a
0.14 (0.15) a
25 (19)
25 (40)
7 (9)
7 (8)
10 (10) a
K (µmol l )*
-1
b
b
a
a
25
Figure 2. EC-depth profile (µS cm-1) in the Dutch locality with
Calliergon megalophyllum, measured in october 2014.
Nutrient availability
As already indicated, almost all Dutch and Swedish
relevés contained at least some eutrophic species. Ammonium and nitrate seemed less important, but in both the
Dutch and Swedish localities of C. megalophyllum, phosphate concentrations in the water were relatively high,
with (mean) values of around 0.3 µmol l-1. In the Swedish localities, phosphate concentrations were also significantly higher for C. megalophyllum than for S. scorpioides,
S. trichophyllum and S. exannulatum, with intermediate
values for the closely related C. giganteum. More or less
the same was true for K-concentrations, with higher values for the two Calliergon species. Because Fe and SO42–
may both affect P-availability, they were measured as well.
However, concentrations were low in general, and did not
generally differ between moss species. In the Dutch locality with C. megalophyllum, concentrations of N and K in
vascular plant tissue showed values of 16.5 and 15.3 mg
g-1 (Table 4), which are not elevated or very low. However,
P-concentrations were relatively high, and showed values
of 1.2 mg g-1. Also, the N:P ratio of 13.8 was relatively
low (Koerselman and Meuleman 1996).
Discussion and conclusions
Based on the available information, the results suggest that
the habitat conditions in the new Dutch locality of Calliergon megalophyllum fit well within the range described
for Sweden. Also, comparison of Swedish localities for
C. megalophyllum and the closely related C. giganteum
makes clear that the two species have actually different
habitats, especially with respect to buffer capacity. For
C. giganteum, buffer capacity was approximately three
Figure 3. EC-surface profile (µS cm-1) in the dutch locality with
Calliergon megalophyllum, from the ditch where the water comes
from, through a series of small ditches inside the fen, to the pool
were the species was found. EC-values were measured in October 2014. The mean EC-value in the main canal, which is not
directly connected to fen and pool, is also given.
times higher than for C. megalophyllum. These habitat
differences further supports that they are really different
species (Jensen 1939, Tuomikoski 1940, Nyholm 1965,
Tuomikoski and Koponen 1979, Hedenäs 1993a, b), in
contrast to what was assumed by Rubers (1989).
High pH and low buffer capacity
Calliergon megalophyllum is characteristic for habitats with
a high pH of 6.4–7.0, but nevertheless low buffer capacity. This is a difficult combination, as low buffer capacity
may be advantageous to photosynthesis under water, but
more difficult to combat acidification of the habitat. Low
buffer capacity may to some extent help photosynthesis
of submerged mosses. Under water, CO2 supply may be a
problem due to low rates of diffusion, but is also chemically limited at high pH, when the main carbon form is
HCO3–. Many aquatic macrophytes can use bicarbonate
as alternative carbon source (Madsen and Sand-Jensen
1991), but there is no evidence that bryophytes can do
this, except perhaps Fontinalis antipyretica Hedw. (Glime
and Vitt 1984, Penuelas 1985). When buffer capacity is
low at relatively high pH, submerged mosses may be able
to capture at least some CO2 from the water. This may
Table 4. Nutrient concentrations in (g kg-1) and ratios in plant and soil in the Dutch locality with Calliergon megalophyllum.
N
P
K
C:N ratio
N:P ratio
Plant biomass
16.5
1.2
15.3
28.7
13.8
1.1
Soil material
14.8
0.6
1.2
34.4
24.7
12.1
26
N:K ratio
be a reason why S. trichophyllum, which has lower pH
and slightly lower buffer capacity than C. megalophyllum,
is growing completely submerged, while the latter was
found at or above the water surface in 50% of the cases.
When buffer capacity becomes too high, such as for, e.g.
C. giganteum and S. scorpioides, growing above the water
may be a better option.
While low buffer capacity may be an advantage for
photosynthesis in aquatic bryophytes, it is a problem to
maintain a relatively high pH, especialy in areas with high
atmospheric deposition. In the Netherlands, weakly buffered habitats with S. scorpioides in the Pleistocene, sandy
part of the country were still present in the 1960s (Kooijman and Westhoff 1985, Arts 1990). However, the species
has disappeared from this region, probably due to high
atmospheric deposition. In the Netherlands, approximately 1.5 times higher amounts of buffer components
are needed to maintain the pH in the habitat around 6.5
compared to less polluted areas in e.g. Sweden (Kooijman
2012). It is not unlikely that C. megalophyllum has disappeared from part of the former Dutch localities by acidification in a similar way.
In the new Dutch locality, it is not clear whether C.
megalophyllum is really new to the area, or whether it has
been there for a long time. In any case, the buffer capacity is relatively high compared to Sweden, albeit low
compared to real rich-fen habitats in the National Park
dominated by Scorpidium spp. (Cusell et al. 2014). Buffer
capacity is presumably maintained by input of relatively
base-rich ditch water into the small channel system during high water levels in the National Park. In other parts
of the National Park, similar channels, with higher buffer
capacity, have led to an increase of rich-fen bryophytes
such as S. scorpioides, S. cossoni (Schimp.) Hedenäs and
Hamatocaulis vernicosus (Mitt.) Hedenäs (A. M. Koijman,
L. Hedenäs, I. Mettrop and C. Cusell unpubl.). More
systematic research is needed, but it is very likely that occasional flooding with base-rich, relatively nutrient-poor
water can mitigate at least some of the adverse effects of
high atmospheric deposition.
Nutrient availability
Calliergon megalophyllum seems to prefer intermediate to
nutrient-rich habitats. In both Sweden and the Netherlands, phosphate concentrations in the water were relatively high, and eutrophic plant species occurred in almost
all relevés. In at least some of the old Dutch localities,
where C. megalophyllum has disappeared, eutrophic species were also present, such as Glyceria maxima (Hartm.)
Holmb. and Lycopus europeus in the Belversven in 1947
(Appendix 1). Also, plant N:P ratios in the present locality suggest that P is not a limiting factor. Other Calliergon
species are also growing in relatively nutrient-rich habitats,
such as C. cordifolium and to some extent C. giganteum.
This may be an inherent habitat trait of the genus, inherited from ancestors during the evolution of the Calliergonaeceae (Hedenäs and Kooijman 1996).
Growing under relatively nutrient-rich conditions may
be an advantage in the Netherlands, where eutrophication in wetlands is a real problem (Lamers et al. 2014).
In the National Park, approximately 79% of the annual
P-input comes from adjacent agricultural polders, especially in winter (Cusell 2014). Nevertheless, values around
0.3 µmol P l-1 in the water are not really high, and C.
megalophyllum would probably not survive hypertrophic
conditions. In some of the old Dutch localities, C. megalophyllum may have disappeared due to eutrophication of
the water, such as in former ditches. In the National Park
Weerribben-Wieden, its present locality, however, nutrient levels have decreased in the National Park over the past
decades. Although total P did not decrease, phosphate levels in the main channels of the National Park have clearly
dropped to values around 0.1 µmol l-1 (Cusell 2014). In
one of the best rich-fen complexes in the area, eutrophic
bryophytes such as C. cuspidata have been replaced along
the shoreline by characteristic species such as S. scorpioides, while aboveground vascular biomass decreased from
approximately 1000 to 250 g m-2. A further decrease in
P-input is much more difficult to achieve, but there is no
reason to say that the present conditions are not suitable
for C. megalophyllum, especially when buffer capacity in
the habitat is maintained the way it is.
Concluding remarks
It is unknown why C. megalophyllum has disappeared
from the Netherlands in the past. However, the particular
habitat conditions of high pH, but low buffer capacity
suggest that acidification has played at least some role,
similar to the disappearance of weakly buffered habitats
with S. scorpioides (Kooijman and Westhoff 1995). In addition, pollution of surface waters in the 1960s may have
led to local extinction, although C. megalophyllum is a
relatively eutrophic species and can at least stand slightly
elevated nutrient levels, such as in the new Dutch locality.
Whether it will survive there probably mainly depends on
the buffer capacity, which is maintained by input of baserich surface water through small channels. Whether the
species can expand in the Netherlands is more difficult to
say, since weakly buffered habitats with relatively high pH
have become very rare.
Acknowledgements – We would like to thank Leo Hoitinga, Leen
de Lange and Peter Serné for their laboratory assistance, and Vereniging tot behoud van Natuurmonumenten for the boat and
access to the place. This research was further funded by Kennisnetwerk Ontwikkeling en Beheer Natuurkwaliteit (O+BN)
of the Dutch Ministry of Economic Affairs, Agriculture and Innovation.
27
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Appendix 1. Site description of Calliergon megalophyllum localities in NL (present and extinct) and Sweden (only localities sampled in
this paper). The general position of the extinct Dutch localities is indicated on the map in van Tooren and Sparrius (2006).
Sample
Year
Site description
The Netherlands
NL
2014
small pool in fen, National Park Weerribben-Wieden, 52°42’54.17’’N; 6°70’54.82’’E
NL
1864
Haren, Groningen; among Fontinalis antipyretica, together with C. giganteum
NL
1898
ditch, den Bosch, Noord-Brabant
NL
1898
ditch, Nieuwkuijk, Noord-Brabant
NL
1935
mill canal, Harendermolen, Groningen
NL
1943
in river Rosep, Oisterwijk, Noord-Brabant
NL
1947
shallow lake, Belversven, Noord-Brabant; with Phragmites australis, Schoenoplectis lacustris, Glyceria
maxima, Nymphaea alba, Menyanthes trifoliata, Carex rostrata, Comarum palustris, Peucedanum palustre,
Mentha aquatica, Galium palustre, Carex curta, Lysimachia vulgaris, Lysimachia thyrsiflora, Lycopus
europeus, Cicuta virosa, Scutellaria galericulatum, Rumex hydrolapathum
NL
1948
shallow lake. Belversven, Noord-Brabant
NL
1948
shallow lake, Belversven, Noord-Brabant
NL
1948
shallow lake with Phragmitetum, Belversven, Noord-Brabant
NL
1965
partly terrestrialized shallow lake, Moerputten Vlijmen, Noord-Brabant; with Comarum palustris
S20
1991
backwater (ava) Stenselestryckan in River Vindelälven, Björksele, Lycksele Lappmark, 65°01’04.62’’N,
18°45’47.25’’E
S24
1991
backwater, Vindelgransele, Björksele, Lycksele Lappmark, 65°10’32.64’’N, 18°29,95.83,,E
S147
1991
backwaters of River Umeälven, Kattisavan, Lycksele, Lycksele Lappmark, 64°75’75.45’’N, 18°16’29.71’’E
S150
1991
backwaters of River Umeälven, Kattisavan, Lycksele, Lycksele Lappmark, 64°75’75.45’’N, 18°16’29.71’’E
S165
1991
old backwater (ava), 2 km ESE of Strandåker, Vindeln, Västerbotten, 64°27’81.26’’N, 19°24’57.76’’’E
S167
1991
old backwater (ava), W shore of Vindelälven opposite Renfors, Vindeln, Västerbotten, 64°21’77.69’’N,
19°70’13.40’’E
S175
1993
shore of the dammed River Dalälven, the island Kvarnön, W side, Söderfors, Uppland, 60°41’35.33’’N,
17°20’46.70’’E
S194
1993
small pond near Filadelfia church, Djurås, Gagnef, Dalarna, 60°55’59.58’’N, 15°12’01.53’’E
S195
1993
Lake Gallsjön, Överbacka, Gagnef, Dalarna, 60°56’49.46’’N, 15°10’94.24’’E
S252
1993
reed belt at S shore of Lake Mindalssjön, Turinge, Södermanland, 59°19’76.38’’N, 17°49’33.76’’E
S332
1996
reed belt at S shore of Lake Hacksjön, Botkyrka, Södermanland, 59V17’76.70’’N, 17°94’59.05’’E
S459
1997
ox-bow lakes W of the River Dammån, ca 1 km S of Lillstavallen, Mattmar, Jämtland, 63°23’50.51’’N,
13°88’19.91’’E
S461
1997
ox-bow lakes W of the River Dammån, ca 1.25 km S of Lillstavallen, Mattmar, Jämtland, 63°23’30.60’’N,
13°88’68.05’’E
Sweden
29