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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 . Background.

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slide1

The impact of conifer plantation forestry on the Chydoridaecommunities of blanket bog lakes

Tom J. Drinan, Conor T. Graham, John O’Halloran and Simon S.C. Harrison

HYDROFOR Project

slide2

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
slide3

Aims

  • To investigate how conifer plantation forestry operations affect blanket bog lakes in terms of:
      • Their hydrochemical status
      • 2) Their Chydoridae(Cladocera) communities
slide4

Study design

Sedimentary (Sandstone) Geology

Igneous (Granite) 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’)
  • 7 lakes non-forested (‘blanket bog’)
  • 7 lakes afforested:
    • 4 lakes surrounded by mature conifer forests (‘mature plantation’)
    • 3 lakes surrounded by clearfelling (‘clearfell’)
slide5

Study lakes

  • 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

GB1

GM1

SB1

SB3

GM2

GB2

SB2

SB4

SM1

GM3

GB3

SB5

GB4

GM4

SM2

SB6

SM3

GC1

GB5

SC1

GC2

GB6

SC2

GB7

GC3

SC3

slide6

Blanket bog lake:

catchment containing only undisturbed blanket bog

slide8

Clearfell lake:

catchment containing mature conifer plantation with recently (within 2 – 5 years) clearfelled areas

water chemistry

Methodology

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
slide10

a)

Results – water chemistry

Water Chemistry PCA

  • Higher plant nutrients, TDOC, major ions, heavy metals, and reduced dissolved oxygen concentrations in lakes with forestry

b)

  • Sandstone blanket bog
  • Granite blanket bog
  • lSandstone mature plantation
  • pGranite mature plantation

lSandstone clearfell

pGraniteclearfell

slide11

Results – water chemistry

Total Nitrogen

Ammonia

Soluble Reactive Phosphorus

Granite

Sandstone

Chlorophyll a

slide12

Results – water chemistry

Total monomeric aluminium

pH

Dissolved oxygen

Dissolved organic carbon

Granite

Sandstone

slide13

Discussion of 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 autotrophicand heterotrophic production
  • Reduced dissolved oxygen concentrations
  • Elevated heavy metal concentrations.
slide14

Results – chydorids

Chydorid community nMDS

  • Sandstone blanket bog
  • Granite blanket bog
  • lSandstone mature plantation
  • pGranite mature plantation

lSandstone clearfell

pGraniteclearfell

slide15

Results – chydorids

Chydorussphaericus

Alonopsis elongata

Alonellaexcisa

Alonella nana

Granite

Sandstone

slide16

Results – chydorids

  • Alonopsiselongatadominant in blanket bog lakes and Chydorussphaericus, Alonellanana and Alonellaexcisadominant in clearfelland mature plantation lakes
  • Only two individuals of a single species (Alonaguttata) were recorded from a recently clearfelled lake underlain by granite. This lake also contained the highest concentrations of Al & Fe
  • Alonellaexcisawas more abundant in sandsone lakes
slide17

Discussion of chydorids

  • Increased autotrophy and heterotrophy leads to a reductionin size of the dominant food particles available A. elongata feeds on larger food particles, C.sphaericus, A. nana and A. excisafeed 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
slide18

Conclusions

  • Chydorid community change is consistent with conifer plantation forestry exerting a trophic, rather than an acidic or toxic effect on lake ecosystems
  • 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
slide19

Acknowledgements

  • 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