The impact of conifer plantation forestry on the Chydoridae
communities of blanket bog lakes Tom J. Drinan, Conor T. Graham,
John OHalloran and Simon S.C. Harrison HYDROFOR Project
Slide 2
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 1950s 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
Slide 3
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 lakes GB1 GB2 GM1 GM2 GB3 GB4 GM3 GM4 GB5GC1 GB6GC2
GB7GC3 SB3 SB4 SB5 SB6 SC1 SC2 SC3 SB1 SB2 SM1 SM2 SM3 The lakes
underlain by granite are located at lower altitude and in closer
proximity to the coast than the lakes underlain by sandstone S =
Sandstone G = Granite B = Blanket bog M = Mature plantation C =
Clearfell
Slide 6
Blanket bog lake: catchment containing only undisturbed blanket
bog
Slide 7
Mature plantation lake: catchment dominated by closed- canopy
conifer plantation
Slide 8
Clearfell lake: catchment containing mature conifer plantation
with recently (within 2 5 years) clearfelled areas
Slide 9
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, SO 4, Ca, Na,
Cl, Mg, Al, Mn and Fe Chydoridae Semi-quantitative method: slowly
sweeping a hand-held sweep net (100 m 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
Slide 10
Results water chemistry b) Water Chemistry PCA Higher plant
nutrients, TDOC, major ions, heavy metals, and reduced dissolved
oxygen concentrations in lakes with forestry a) Sandstone blanket
bog Granite blanket bog Sandstone mature plantation Granite mature
plantation Sandstone clearfell Granite clearfell
Slide 11
Ammonia Soluble Reactive Phosphorus Sandstone Granite Total
Nitrogen Results water chemistry Chlorophyll a
Slide 12
Dissolved oxygen Dissolved organic carbonpH Total monomeric
aluminium Sandstone Granite Results water chemistry
Slide 13
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
Slide 14
Chydorid community nMDS Sandstone blanket bog Granite blanket
bog Sandstone mature plantation Granite mature plantation Sandstone
clearfell Granite clearfell 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
Slide 17
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
Slide 18
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
Slide 19
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
20072013 We thank Dr. Elvira de Eyto for her help with zooplankton
identification and various aspects of the research
Acknowledgements