The impact of conifer plantation forestry on the Chydoridae communities of blanket bog lakes
description
Transcript of The impact of conifer plantation forestry on the Chydoridae communities of blanket bog lakes
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
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
To investigate how conifer plantation forestry operations affect blanket bog lakes in terms of:
1) Their hydrochemical status
2) Their Chydoridae (Cladocera) communities
Aims
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’)
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
Blanket bog lake:catchment containing only undisturbed blanket bog
Mature plantation lake: catchment dominated by closed-canopy conifer plantation
Clearfell lake: catchment containing mature conifer plantation with recently (within 2 – 5 years) clearfelled areas
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
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
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
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
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
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
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
• 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
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
• 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
• 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