Download poster Warszawa 2013

A DORMANT FEN:
The underestimated value of dead organic matter metabolism
in
wetland
functioning
and
restoration
Wojciech Puchalski
A method of biogeochemical assessment
Pracownia Natury - The Nature Laboratory
ul. Sosnowa 8
PL-95-050 Konstantynów, POLAND
Introduction
The dormancy period in wetlands is usually considered unimportant in their metabolic balance
and system biogeochemistry, hence only few
research data exist and only data from the vegetation period are used for restoration planning.
In early spring flows of water between upland
areas, floodplain wetlands and rivers or lakes
often are at their peak intensities. The quality of
water from wetlands then affects algal blooms
and macrophytes in water bodies, and indirectly
other functions of the whole aquatic ecosystem.
Examples are given how local hydrologic cons
trains and plant species as a source of dead
organic matter influence processes of oxygen
consumption and nutrient uptake or release.
Results are important for decisions concerning
the water level and its dynamics.
1600
No add.
+PO4
+NH4
+NO3
+Corg
+CNP
1200
P-PO4 w
P-PO4 d
Contr.
A simple assessment method has been developed. It is based on exposition of freshly collected material (sediments,
algal/microbial mats, decaying plant debris) in water (preferably also taken from the site, or artificially prepared) in
stoppered bottles during one day. Different bottles with the same material may be amended with higher nutrient concentrations, or a concentration gradient can be prepared. Control bottles contain only water, without any solid material.
After exposition in temperature and light conditions resembling natural ones, nutrient uptake or release (negative
values) are calculated from differences in nutrient
amounts between sample and control bottles, divided by
exposed material weights and exposition time. In the
same set, differences in oxygen concentrations may be
measured with an oxygen probe, and its consumption
calculated. Also, by initial deoxygenation of water in
bottles, anoxic conditions can be established. A short,
one-day period of exposition produce no drastic changes
in function of microbial communities. This appeared to be
a rapid method of functional monitoring, suitable for
assessment of important biogeochemical processes,
where sediments, live plants or particular organic matter
are involved.
2400 N-NO3 w
N-NO3 d
2000
N-NH4 w
N-NH4 d
Examples of contrasting sediment types in a lowland floodplain
1200
800
1600
1200
800
400
800
400
400
0
s. fen imp.
sedge fen
Rn-A imp.
Rn-A
F-A imp.
F-A
s. fen imp.
sedge fen
Rn-A imp.
Rn-A
F-A imp.
F-A
0
s. fen imp.
sedge fen
Rn-A imp.
Rn-A
F-A imp.
F-A
0
Metabolic properties of sediments in different floodplain communities during early spring, in dry and wet years.
Uptake pf phosphate, ammonia and nitrate in Fraxino-Alnetum, Ribeso nigri-Alnetum and a sedge fen, in nonimpounded and impounded reaches of the Skotawa river, N. Poland.
250
600
P-PO4 consumption
200
400
April
June
150
700
N-NH4 consumption
600
June
200
500
June
400
300
0
-400
22-42
cattail, n+
reed, n-
cattail, n+
reed, n+
cattail, n-
reed, n-
1.5
coarse, n+
fine, n-
coarse, n-
coarse, n+
fine, n-
Do eutrophic conditions may advance the nutrient
release switch in spring?
Recalculated data from Robinson & Gessner (2000):
decay of alder (Alnus viridis) leaves
in an alpine headwater stream
The presence of emergent plant litter seems to be a necessary
condition for germination and early development of a rare aquatic fern, Salvinia natans. Accumulation of plant debris after
a flood enables abundant occurrence of this chaotic species.
14
14
14
birch
pine
oak
12
12
12
12
10
10
10
10
below reed belt
6
6
6
6
4
4
4
4
2
2
2
2
0
0
0
0
stems
leaves
reed stem prisms
wet reed floor
-20
-15
-10
-5
0
 g.g-1.d-1
5
w
0
50
100
150
g
k
l
w
p
60
g
k
l
p
60
alder
w
g
k
l
60
birch
w
p
40
40
40
40
reed stem prisms
reed stem prisms
20
20
20
20
wet leaf zone
wet leaf zone
0
0
0
0
w
stems
ref.:
stems
leaves
ref.:
g
k
l
p
w
g
k
l
p
w
g
k
l
k
l
p
pine
high water level
below reed belt
g
60
oak
high water level
below reed belt
water
22-42
below reed belt
ref.:
flooded
sedim.
9-22
8
-25
15
0-9
8
-1
m.salv.dried
days
from start
8
-1
20
N uptake / release
8
g.g .d
m.salv.lake
0
wet leaf zone
wet reed floor
25
5
wet leaf zone
reed stem prisms
no.salv.dried
0.5
alder
reed stem prisms
stems
leaves
30
10
20.00
10.00
0.00
-10.00
-20.00
-30.00
-40.00
-50.00
-60.00
high water level
ref.:
35
no.salv.lake
1
14
reed stem prisms
2
dry reed wet reed wet reed
wet
seepage unflood.
unflood. Glyceria sedim.
sedim.
Late spring: the switch from nutrient uptake to releasedepends on plant species and trophic conditions.
(N- low trophy, n+ eutrophic conditions) The litter of emergent macrophytes, after its initial leaching in autumn, appears
to be an important consumer of dissolved nutrients during early spring, when live plants are still dormant and nutrientrich waters of upland origin enter the floodplain. Dissolved nutrients are assimilated by decomposing microorganisms,
as C:N and C:P ratios in plant debris are extremely high. With the progress of decomposition in late spring, previously
absorbed nutrients become partially released, but this occurs during period of intensive development of macrophyte
stands, which may use this available nutrient supply for their growth. Mechanical removal of plant litter during the end
of nutrient uptake period in spring might serve as more effective way of exporting surplus nutrient load then removal
of mowed sedge hay in summer.
high water level
40
A250 lake
0
0
cattail, n+
reed, n+
cattail, n-
reed, n-
-2.00
coarse, n-
100
-800
45
A250 dried
9-22
no
release
reed, n+
release
-150
plant litter added
2.5
-1.00
release
-600
-100
0-9
50
fine sediments
added
-4.00
cattail, n-
-50
200
3
-3.00
50
-200
3.5
days
from start
0.00
100
0
P uptake / release
1.00
April
Sulfur purple bacterial mat - highly reductive,
denitrification, Fe and SO4 = reduction present
Decomposing plant debris in spring
2.00
N-NO3 consumption
April
Diatom mat- oxidative,
P-consuming, enabling nitrification
w
p
-20
-20
-20
-20
-40
-40
-40
g
k
l
p
leaves
reed stem prisms
reed stem prisms
-40
wet reed floor
wet reed floor
12
-1
-1
g.g .d
-1
-30
-20
-10
0
-1
g.g .d
10
forest bog
10
-50
0
50
100
Phosphate (upper graphs) and ammonia (lower graphs) uptake/release by reed litter in early spring, under low (left)
and high (right) nutrient content, in littoral reed stands of Lake Kwiecko, N. Poland, characterized by frequent
water level changes.
forest ecot.
8
6
forest stream
4
agric. ecot.
2
0
w
200
150
C[P-PO4]
+PO4
C[N-NO3]
C[N-NH4]
+NH4+
+DOM
100
150
C[P-PO4]
100
N upta ke
P-PO 4 upt ake
50
50
0
0
2
4
6
8
10
12
14
16
-1
-50
-1
Oxygen consumption, mgO2.g .d
0
2
4
6
8
10
12
14
16
Oxygen consumption, mgO 2.g -1.d-1
agric.
streaml
k
p
Natural floodplains of rivers are characterized by a well developed mosaic of patches, where various redox values create conditions for different biogeochemical
reactions and microbial processes. Distribution of such patches and intensity of their functions are much more stable than in low-order streams.
This, in turn, create conditions for development of various plant species and communities, according to their specific environmental demands.
-50
-100
0
g
Oxygen consumption (upper graphs) and phosphate uptake (+)
or release (-) (lower graphs) between autumn (fallout of leaves)
and late summer next year.
Differences are related not only to tree species, but also to
aquatic habitat type where the decomposition of fallen leaves
does occur.
Mosaic floodplain structure enables a greater complexity of
metabolic processes where coarse allochthonous organic
matter is involved.
-150
-200
Relationships between P, N and oxygen uptake
P-PO4 uptake related to O2 consumption, intensities depend on availability of P and DOM.
No clear pattern for nitrogen (both ammonia and nitrate) metabolizm
Biogeochemical constrains should be considered in floodplain restoration or protection projects, when the maintenance or reintroduction of particular plant
communities is desired.
Also, these floodplain processes are important in nutrient transformations, their entrapment and storage or release to river water, thus regulating trophic conditions
in the river channel and lakes or seas receiving riverine inflows.
In low trophic conditions, nutrients are available from decomposition of last year's plant litter, which was enriched with nutrients during cold season.
Optimising plant litter decay in spring may lead to establishment of healthy and stable emergent plant communities in floodplains.