N14C / JHI October 2012

Transcription

1 N14C / JHI October 212 N14C: a plant-soil nitrogen and carbon cycling model to simulate long-term ecosystem enrichment by atmospheric N deposition Ed Tipping EC Rowe CD Evans RTE Mills BA Emmett JS Chaplow JR Hall CEH Lancaster CEH Bangor CEH Bangor CEH Bangor + Bangor University CEH Bangor CEH Lancaster CEH Bangor

2 Background N enrichment Agriculture Fossil fuel burning N deposition To natural & seminatural ecosystems Concepts & processes N limitation N saturation Interactions of N with C Broad scale Effects Acidification Eutrophication Carbon sequestration Loss of biodiversity N 2 O emissions

3 AIMS OF THE N14C MODEL Simulate pools and fluxes of C and N in natural / seminatural terrestrial ecosystems over long time periods Parameterise with basic plot-scale data available for a range of sites representing different plant types, and with different N deposition rates Apply at national scale to account for contemporary survey data, and forecast responses to N dep change, climate change Adjust for individual sites with more data

4 DRIVERS MAT MAP N deposition, inc. history 14 C in atmosphere, inc. history Vegetation type INFORMED GUESSES Pristine N fixation NPP No / little land use change SITE OBSERVATIONS Soil C pool Soil N pool Soil CN ratio N inorg leaching flux DOC leaching flux DON leaching flux GENERIC OBSERVATIONS 14 C of bulk soil denitrification rates Parameterisation of N14C for 42 sites

5 N gas NPS dep CO 2 CO 2 hard soft Available NPS P weath CO 2 CO 2 Fast hard litter Slow Pass N14C (PS) leached inorg NPS DO C,N,P,S B-horizon DO C,N,P,S CO 2

6 Features of N14C Long-term simulations, annual timestep 13 BP to present, N dep from 18 Plant functional types: broadleaf, conifer, herbs, shrubs hard and soft plant components (roughly wood, not-wood) Vegetation 1 : high CN Vegetation 2 : low CN SOM pools: fast, slow, passive / constrained by 14 C Seasonality: Dormant Growth Dormant Simulates NPP, plant and soil C and N DOC, DON, NO 3 leaching denitrification, SO 14 C, DO 14 C Underlying assumption: the vegetation determines the soil

7 Values of optimised parameters broadleaf conifer herbs shrubs f fast a f slow f passive k immobn 1.88x x x x1-5 f gr,1.467 f gr,2.3 f DOC f DON.258 k denitr.484 ΔN immob2 1.35

8 Universal fit Simulated vs Observed soil C pools kg m -2 1 to 1 B C H S soil CN ratios g g soil N pools kg m -2 4 NO 3 g m

9 Site-specific fit Simulated vs Observed soil C pools kg m -2 1 to 1 B C H S soil CN ratios g g % 1 soil N pools kg m -2 4 NO 3 g m -2 k immobn f gr k denitr ΔN immob2 ΔN fix,pris

10 N14C simulations for Broadleaf, Conifer, Herbs, Shrubs MAT = 8 o C, MAP = 15 mm, Ndep(2) = 2 g m -2 NPP annual NPP gc m-2 C B S H soil C kg m Soil C S C H B soil N g m-2 4 soil C:N g g Soil N H B S C Soil C:N C S B H

11 N14C simulations for Broadleaf, Conifer, Herbs, Shrubs MAT = 8 o C, MAP = 15 mm, Ndep(2) = 2 g m annual DOC leaching gc m -2.4 annual DON leaching gn m -2 1 DOC leach S C B H.3.2 DON leach H S B C annual NO 3 leaching gn m NO 3 leach C S soil 14 C % modern Soil 14 C B,C H,S.2 H B

12 NO3 leaching g m B C H S observations N deposition (2) g m -2

13 NO3 leaching g m B C H S "universal" fit N deposition (2) g m -2

14 NO3 leaching g m B C H S site-specific fit N deposition (2) g m -2

15 NO3 leaching g m B C H S observations N deposition (2) g m -2

16 Annual NPP / upland grassland / N dep (2) = 2.25 gn m -2 a potential NPP NPP vegetation 1 NPP vegetation 2 NPP total actual

17 soil carbon g m passive 4 Upland grassland Ndep(2) = 2.25 gn m -2 a slow fast soil nitrogen g m -2 6 simulated soil C and N pools passive slow fast

18 sim N g m -2 sim C kg m C obs C kg m -2 N obs N g m -2 sim C:N g g -1 NI-CA broadleaf (5) NI-CA conifer (6) CS broadleaf (91) CS conifer (124) CS neutral grassland (231) CS acid grassland (96) CS heath (15) CS bog (159) 1 to Independent data Predicted vs observed soil C & N C:N obs C:N g g -1 MAT MAP N dep 2 Veg type

19 Preliminary predictions / outputs Most of the studied conifer sites are N-saturated - other sites are still N-limited NO 3 leaching responds quickly to changes in N deposition Soil N cycling responds more slowly C sequestration (vegetation + soil) due to N deposition trees ~ 2-4 g g -1 herbs & shrubs ~ 1-15 g g -1 Increased temperature tends to reduce NO 3 leaching - via faster soil cycling, increased NPP

20 Conclusions Can approximately account for C and N cycling as f(vegetation type, MAT, MAP, Ndep) N14C is a useful tool to understand interactions Testing so far is promising, but need more Additional factors : P, acidity, O 3, trace elements, soil moisture, erosion, grazing, fire, disease, history N14C simulates changes in productivity potential link to plant biodiversity Funded by Defra and NERC

21 LTLS NERC Macronutrient Cycles Programme Consortium Grant LTLS Analysis and simulation of the Long-Term / Large-Scale interactions of C, N and P in UK land, freshwater and atmosphere E Tipping CEH JF Boyle U Liverpool J Quinton Lancaster U ME Stuart BGS AP Whitmore Roth Res RC Helliwell JHI* NL Rose UCL S Ullah U Keele CL Bryant NERC RCF * Funded by the Scottish Government

22 LTLS questions Over the last 2 years, what have been the temporal responses of soil C, N and P pools in different UK catchments to nutrient enrichment? What have been the consequent effects on C, N and P transfers from land to the atmosphere, freshwaters and estuaries? How have terrestrial and freshwater biodiversity responded to increases in ecosystem productivity engendered by nutrient enrichment at different locations? Answered by: integrated modelling analysis, aimed at accounting for observable present element pools and fluxes in different UK catchments in terms of their nutrient enrichment histories

23 LTLS scope & approach Long-term processes 18-present 2, BP 18 All UK catchments to the tidal limit + water directly entering estuaries & sea Existing data New gapfilling data Integrated modelling

24 LTLS focus period 18-2 human beings are now carrying out a large scale geophysical experiment Revelle & Suess, 1956 the UK s long-term, spatiallydistributed, biogeochemical experiment in nutrient enrichment LTLS proposal 211

25 LTLS joined-up models Atmospheric N deposition Natural terrestrial ecosystems Erosion & leaching Agricultural ecosystems Rivers Lakes Groundwater G2G Biodiversity plants, headwaters, lakes

26 LTLS outputs & benefits Integrated model - spatially distributed, long-term description of UK macronutrient pools, fluxes and interactions - feasibility of joining up simple models - large-scale / long-term implications for biog and biod Platform for incorporating more detailed / site-specific / short-term knowledge Policy national-scale description, multiple effects, scenario analysis Capacity-building upscaling, model linkage

27 The end

28 Plant functional types broadleaf conifer herb shrub C:N hard C:N soft low nutrient C:N soft high nutrient f hard f soft f hard,litter f soft,litter f Nretained low nutrient high nutrient

29 Summary of field sites units Broadleaf Conifer Herbs Shrubs n MAT o C MAP mm a N deposition g m -2 a topsoil depth cm topsoil C pool kg m topsoil N pool g m topsoil C:N g g N inorg leaching g m -2 a DOC leaching a g m -2 a DON leaching a g m -2 a NPP max b g m -2 a DE 5 GB 1 NL 4 DE 1 DK 2 NL 1 NO 5 SE 6 GB 4 NO 1 DK 7 GB 1 NL 2 NO

30 2 Net Primary Production - maximum values estimated by quantile regression (9%) NPP gc m -2 a MAP mm NPP gc m -2 a MAT o C

31 N fixation Pristine.3 gn m -2 a -1 Based on sparse literature Key to pre-industrial ecosystem N and C Down-regulated by N deposition (DeLuca et al)

32 Preliminary estimates of C sequestration due to N dep 4 C / Ndep g g Broad Conifer Herbs Shrub N deposition in 2 g m -2