Download - The impact of conifer plantation forestry on the Chydoridae communities of blanket bog lakes
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The impact of conifer plantation forestry on the Chydoridae communities of blanket bog
lakes
Tom J. Drinan, Conor T. Graham, John O’Halloran and Simon S.C. Harrison
HYDROFOR Project
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Background
• Plantation forests cover an estimated 10% of the Irish land surface area. Many of these plantations are on peat soils
• Extensive afforestation of peat soils has taken place since the 1950’s – this crop is now reaching harvestable age
• Previous studies have demonstrated a high risk of plant nutrient and sediment run-off to receiving waters from afforested catchments, particularly on peat soils
• There is a clear risk to the ecological status of high conservation value peatland water bodies from catchment forestry operations
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To investigate how conifer plantation forestry operations affect blanket bog lakes in terms of:
1) Their hydrochemical status
2) Their Chydoridae (Cladocera) communities
Aims
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Study design
Igneous (Granite) Geology
7 lakes non-forested (‘blanket bog’)
7 lakes afforested:
4 lakes surrounded by mature conifer forests (‘mature plantation’)
3 lakes surrounded by clearfelling (‘clearfell’)
Sedimentary (Sandstone) Geology
6 lakes non-forested (‘blanket bog’)
6 lakes afforested:
3 lakes surrounded by mature conifer forests (‘mature plantation’)
3 lakes surrounded by clearfelling (‘clearfell’)
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Study lakes
GB1GB2
GM1GM2
GB3GB4
GM3GM4
GB5 GC1GB6 GC2GB7 GC3
SB3SB4SB5SB6SC1SC2SC3
SB1SB2SM1SM2SM3
• The lakes underlain by granite are located at lower altitude and in closer proximity to the coast than the lakes underlain by sandstone
S = SandstoneG = Granite
B = Blanket bogM = Mature plantation C = Clearfell
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Blanket bog lake:catchment containing only undisturbed blanket bog
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Mature plantation lake: catchment dominated by closed-canopy conifer plantation
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Clearfell lake: catchment containing mature conifer plantation with recently (within 2 – 5 years) clearfelled areas
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Water Chemistry
• Dip samples (a single sample from the water column) were taken every two months from each lake, beginning March 2009
• We measured pH, conductivity, temperature, dissolved oxygen, colour, alkalinity, TDOC, TP, SRP, TN, TON, ammonia, SO4, Ca, Na, Cl, Mg, Al, Mn and Fe
Chydoridae
• Semi-quantitative method: slowly sweeping a hand-held sweep net (100 μm mesh, 0.15 m diameter frame) horizontally both inside and outside a stand of vegetation for 30 seconds in the littoral zone of each lake
Methodology
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Results – water chemistry
-0.4 0.4
-0.6
0.4
pHConductivity
Temperature
Chlorophyll a
TDOCTP
SRPTN
TON
CaK
MnFe
b)
Water Chemistry PCA
• Higher plant nutrients, TDOC, major ions, heavy metals, and reduced dissolved oxygen concentrations in lakes with forestry
-10 4
-4
4
PC 1
PC 2
a)
Sandstone blanket bog
Granite blanket bog
l Sandstone mature plantation
p Granite mature plantation
l Sandstone clearfell
p Granite clearfell
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Blanket bog Mature plan-tation
Clearfell0.00
0.05
0.10
0.15
0.20
(mg
l -1)
Ammonia
Blanket bog Mature plan-tation
Clearfell0.000
0.008
0.016
0.024
(mg
l -1)
Soluble Reactive Phosphorus
Sandstone Granite
Blanket bog Mature plan-tation
Clearfell0
0.4
0.8
1.2
(mg
l -1)
Total Nitrogen
Results – water chemistry
Blanket bog Mature plan-tation
Clearfell0
7
14
21
28
(μg
l -1)
Chlorophyll a
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Blanket bog Mature plan-tation
Clearfell6
8
10
12(m
g l -
1)
Dissolved oxygen
Blanket bog Mature plantation
Clearfell0
6
12
18
24
(mg
l -1)
Dissolved organic carbon
Blanket bog Mature plan-tation
Clearfell0
2
4
6
8pH
Blanket bog Mature plan-tation
Clearfell0
60
120
180
240
(μg
l -1)
Total monomeric aluminium
Sandstone Granite
Results – water chemistry
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Likely sources of forestry inputs include:
• Decomposition of the clearfell residue (brash, foliage etc.)
• Decomposition of peat soil
• Artificial fertilisers applied during the forest crop cycle
Potential impacts of forestry-mediated hydrochemical change:
• Enhanced autotrophic and heterotrophic production
• Reduced dissolved oxygen concentrations
• Elevated heavy metal concentrations.
Discussion of water chemistry
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Chydorid community nMDS
Stress: 0.15
Sandstone blanket bog
Granite blanket bog
l Sandstone mature plantation
p Granite mature plantation
l Sandstone clearfell
p Granite clearfell
Results – chydorids
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Sandstone Granite
Alonopsis elongata
Blanket bog Mature plantation Clearfell0
150
300
450
600
750
Mea
n ab
unda
nce
Chydorus sphaericus
Blanket bog Mature plantation Clearfell0
250
500
750
1000
Mea
n ab
unda
nce
Alonella nana
Blanket bog Mature plantation Clearfell0
90
180
270
360
Mea
n ab
unda
nce
Alonella excisa
Blanket bog Mature plantation Clearfell0
50
100
150
200
Mea
n ab
unda
nce
Results – chydorids
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• Alonopsis elongata dominant in blanket bog lakes and Chydorus sphaericus, Alonella nana and Alonella excisa dominant in clearfell and mature plantation lakes
• Only two individuals of a single species (Alona guttata) were recorded from a recently clearfelled lake underlain by granite. This lake also contained the highest concentrations of Al & Fe
• Alonella excisa was more abundant in sandsone lakes
Results – chydorids
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Discussion of chydorids
• Increased autotrophy and heterotrophy leads to a reduction in size of the dominant food particles available A. elongata feeds on larger food particles, C. sphaericus, A. nana and A. excisa feed on smaller food particles
• C. sphaericus is more tolerant to the general decline in lake water quality
• Toxicity from heavy metals only important following recent extensive catchment clearfelling
• The higher pH and base cation concentration, driven primarily by marine sea-spray deposition, may account for geological effects on chydorids
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• Chydorid community change is consistent with conifer plantation forestry exerting a trophic, rather than an acidic or toxic effect on lake ecosystems
Conclusions
• Plantation forestry effect was consistent across geologies and regions, indicating that the anthropogenic effect overrides any effect of catchment geology, altitude and proximity to sea
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• This study was funded by the HYDROFOR project which is co-funded by
the Department of Agriculture, Fisheries and Food, and Environmental
Protection Agency (EPA) under the STRIVE Programme 2007–2013
• We thank Dr. Elvira de Eyto for her help with zooplankton identification
and various aspects of the research
Acknowledgements