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Using DayCent for estimating greenhouse gas emissions - Tamara Hochstrasser, UCD

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Using DayCent for estimating greenhouse gas emissions - Tamara Hochstrasser, UCD

  1. 1. Using DayCent for estimating greenhouse gas emissions Tamara Hochstrasser University College Dublin with help from: Steve del Grosso, Colorado StateUniversity, Catherine Watson, AFBI,Christoph Mueller, Florence Renou- Wilson
  2. 2. Outline UCD-soils group DayCent: some simulations of Irish grasslands Using DayCent for the whole of Ireland
  3. 3. UCD-soils group (Christoph Müller) Forests: Thomas Cummins Grasslands: Tamara Hochstrasser Peatlands: Florence Renou-Wilson, David Wilson Ibrahim Khalil Main aim: to develop a mechanistic understanding of organic matter dynamics and greenhouse gas emissions from Irish soils
  4. 4. Techniques Field gas measurements using closed chambers Stable isotope tracing techniques Modelling: statistical techniques, small process-specific mechanistic models, for grasslands: ecosystem model (DayCent)
  5. 5. Grassland DayCent modelling Aim: to provide greenhouse gas balance for agricultural grasslands under different management regimes in Ireland Two step approach: 1) Parameterisation of DayCent based on long-term (1989-99) dataset from experiment in Northern Ireland (Watson et al. 2007) 2) (planned) Extrapolation to different soil types and management regimes under a range of climates
  6. 6. Parameterisation for Irish grasslands Daily weather dataFertilizer Longitude and latitudeGrazing / cutting Grass/ CropManagement Growth rate Atmosphere C:N ratio Lignin content Root:shoot ratio (Whitehead, 1995) Soil texture Field capacity Bulk density Soil pH Flux of carbon/ nitrogen Control
  7. 7. Net Ecosystem ExchangeNEE component Units High N loam High N clay Low N loam Low N clayHarvested C gC/m2 293 (37) 331 (24) 212 (19) 232 (10)N2O g N2O/m2 0.45 (0.04) 0.77 (0.11) 0.18 (0.02) 0.27 (0.04)N2O eq g CO2/m2 133.5 (10.5) 230.6 (32.5) 52.7 (4.6) 81.9 (13.0)CH4 g CH4/m2 -0.21 (0.02) -0.12 (0.01) -0.21 (0.02) -0.12 (0.01)CH4eq g CO2/m2 -5.2 (0.4) -3.0 (0.2) -5.2 (0.4) -3.1 (0.2)CO2 g CO2/m2 380.9 (31.6) 444.9 (29.6) 329.2 (22.9) 373.1 (20.1)NEE tC/ha -1.5 -1.5 -1.1 -1.1 Hochstrasser et al. unpublished manuscript
  8. 8. Yield 16 16 14 14 12 12Yield (t/ha) Biomass Biomass 10 10 measured measured 8 8 6 6 4 4 Simulated Simulated biomass biomass 2 2 0 0 88 89 90 91 92 93 94 95 96 97 98 99 88 89 90 91 92 93 94 95 96 97 98 99 Time (Years) Time (Years) 100 kg N/ha/yr 500 kg N/ha/yr
  9. 9. Volumetric soil water content 1992 0.7 0.6 0.5 0.4 Simulated VSWC Actual 0.3 0.2 0.1 0 0 50 100 150 200 250 300 350 400 Time (days) Data from Hillsborough, NI
  10. 10. Soil Carbon 8000 7000 somtc 6000 Total C (with roots) 5000g/m2 rootC 4000 measured C 3000 2000 1000 0 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 year 100 kg N/ha/yr
  11. 11. Peatland Raised bog: Allen series, Co. Offaly. Picture by: Bob Hammond
  12. 12. What about peatlands?1) Soil moisture is usually evenly distributed which is not the case in peat soils2) Soil temperature vary differently to mineral soils, especially in the winter time3) Gas-diffusion processes are different in the peat matrix4) Processes of anaerobic biogeochemistry are also different to mineral soils5) Low pH Slide by: Florence Renou-Wilson
  13. 13. Preliminary conclusions DayCent is capturing the main processes in grasslands on mineral soils, but not peatlands Further improvement of model parameterisation may allow for a more realistic simulation of soils high in organic matter Long-term data are essential to develop an understanding of complex system dynamics
  14. 14. Extrapolation to Ireland? Will need: - climate (daily weather for 30+ years) - soil information - ‘typical’ management All existing combinations will have to be run separately and then a weighted (by area) average of the output values calculated Expensive, but has potential to show where large difference can be made
  15. 15. Conclusions An ecosystem model such as DayCent can be used to interpret data and enhance our understanding of soil organic matter dynamics If application for the whole of Ireland is envisaged, it is very important to change and develop the model so it is able to simulate organic soils In the longer term, if DayCent is used for greenhouse gas inventories, it is important to have the capacity to adapt the model as new insights are gained

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