newtheoryfornutrientcompeon,$ plant$traits,$and$improved

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New  Theory  for  Nutrient  Compe22on,  Plant  Traits,  and  Improved  Advec2on  

Improves  ALM   W.J.  Riley,  B.  Ghimire,  Q.  Zhu,  J.Y.  Tang,  C.D.  Koven  

•  N  and  P  are  important  controllers  of  terrestrial  C-­‐climate  feedbacks    

•  Current  representaHons  in  ALM  are  poorly  tested  and  numerically  problemaHc  

•  Here,  we  synthesize  results  from  three  recently  submiOed  ACME-­‐supported  publicaHons:  

•  Using  a  new  method  to  represent  mulH-­‐nutrient  and  mulH-­‐consumer  interacHons  (ECA)  

•  PrognosHc  leaf  traits  that  control  photosynthesis  •  Plant  root  nutrient  uptake  traits  •  Improved  advecHve  flux  calculaHons    

•  These  advances  lead  to  improved  esHmates  of  global  carbon  exchanges,  NO3

-­‐  leaching,  and  N2O  gas  emissions.  

Objective

•  Equilibrium Chemistry Approximation application for nutrient constraints (Tang and Riley 2013)

•  Comparison with experimental manipulations and global observations using ILAMB

•  Improved advective transport calculation

Approach

•  Global  GPP  biases  reduced  by  65%    •  Improved  ALM  captures  N  and  P  

addiHon  experiments  •  The  parHHoning  of  ecosystem  N  losses  

to  N2O  and  NO3-­‐  has  been  dramaHcally  

improved    •  Improvements  depend  on  improved  

representaHons  of  nutrient  compeHHon  and  advecHve  fluxes  

Impact

Ghimire,  B.,  W.  J.  Riley,  and  C.  D.  Koven  (2015a),  submi&ed  Biogeosciences.  Zhu,  Q.,  and  W.  J.  Riley  (2015),  submi&ed  Nature  Climate  Change.  Zhu,  Q.,  W.  J.  Riley,  J.  Y.  Tang,  and  C.  D.  Koven  (2015),  Biogeosciences  Discussion,  12,  

4057-­‐4106.  

Figure.  Global  GPP  bias  reduced  by  65%.  Energy  and  water  variables  also  improved  (Ghimire  et  al.,  submi@ed  Biogeosciences).  

Figure.  N  losses  in  CLM4  and  CLM4.5  shown  to  be  poorly  predicted  by  Houlton  et  al.  (2015).  Improved  compeLLon  and  advecLon  dramaLcally  improves  N  loss  predicLons  (Zhu  and  Riley,  submi@ed  Nature  Climate  Change).  

Figure.  ECA  accurately  predicts  N  and  P  ferLlizaLon  responses  in  tropical  systems  (Zhu  et  al.  2015,  Biogeosciences  D)