Clad oct09 jdawson
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  • UK, Nth America and Europe

Clad oct09 jdawson Presentation Transcript

  • 1. Overview of competing theories for increases in freshwater DOC concentrations Julian Dawson Northern Rivers Institute School of Geosciences, University of Aberdeen 20th October 2009
  • 2. Long-term DOC data Allt a’Mharcaidh (Data from Marine Scotland) [DOC] = 0.15 mg L-1 yr-1 DOC Flux = 1.17 kg C ha-1 yr-1
  • 3. Seasonality Increasing variability of seasonal DOC concentrations
  • 4. Spatial differences across UK, N. Europe & N America  (Monteith et al., 2007) Changes in [DOC] variable  315 records, 216, 55  (Worrall & Burt, 2007)
  • 5. Competing Hypothesis Increased temperatures Decreasing soil acidity/ionic strength  reduction in sulphate/marine salt deposition Changing hydrology  precipitation/discharge/flow paths Land management changes Eutrophication  increasing N-deposition CO2 fertilization Increased mobilisation of soil carbon stores
  • 6. Uncertainties Drivers not mutually exclusive, potential combination of factors. No one individual contributory factor across spatially variable sites. Difficult to isolate mechanisms based on monitoring data alone. Certain mechanisms may predominate in different study environments (soil-type, land-use) Different drivers across temporal scales from daily to decadal and longer….
  • 7. Acknowledgements Iain Malcolm (Marine Scotland) Chris Soulsby, Doerthe Tetzlaff, Markus Hrachowitz (Northern Rivers Institute)