The impact of conifer plantation forestry on the Chydoridae communities of blanket bog lakes

1. 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

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 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

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

4. 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’)

5. 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

6. Blanket bog lake: catchment containing only undisturbed blanket bog

7. Mature plantation lake: catchment dominated by closed-canopy conifer plantation

8. Clearfell lake: catchment containing mature conifer plantation with recently (within 2 – 5 years) clearfelled areas

9. 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

10. 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

11. Results – water chemistry Total Nitrogen Ammonia Soluble Reactive Phosphorus Granite Sandstone Chlorophyll a

12. Results – water chemistry Total monomeric aluminium pH Dissolved oxygen Dissolved organic carbon Granite Sandstone

13. 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.

14. Results – chydorids Chydorid community nMDS • Sandstone blanket bog • Granite blanket bog • lSandstone mature plantation • pGranite mature plantation lSandstone clearfell pGraniteclearfell

15. Results – chydorids Chydorussphaericus Alonopsis elongata Alonellaexcisa Alonella nana Granite Sandstone

16. 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

17. 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

18. 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

19. 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