1. Analysing seasonality of CO 2 on the basis of daily totals Bart Kruijt, Alessandro Araujo, Celso von Randow, Fabricio Zanchi, Renata Goncalvez, Jair Maia, Scott Saleska, Yadvidner Malhi, Antonio Manzi, Antonio Nobre, Javier Tomassella, Martin Hodnett WUR, VU, INPA, INPE, UNIR, Tuscon, Oxford, CEH

2. Outline Analysis of GPP on basis of daily total light response Understand seasonality from a minimum set of external controls Model variation of photosynthetic (GPP) capacity as function of production (NPP) itself

3. 3 sites (not four!) Tapajos K67 Manaus K34 Rebio Jaru Data from between 1999 and 2003; ‘Brasilflux’ date

4. Old stuff, searching for simple relationships…

5. Take a step back and see what is in daily totals Rebio Jaru

6. Manaus K34…

7. Tapajos K67

8. From NEE to GPP

9. Mean annual course of Gpp max, radiation and soil moisture

12. hypothesis “production of canopy photosynthetic capacity (LAI, enzymes) depends on canopy labile carbohydrate content.” Toy model: GPPmax(lab)CH 2 O Photosynthesis Construction Light Soil moisture breakdown respiration Credits to Olevi Kull †

13. Or, mathematically: dGpmax/dt = k1 Clab – k2 Gpmax dClab/dt = f(Gpm,Rad,sm) – k3 Clab k1, k2, k3 constants Asumed linear monthly light and soil moisture response Model behaves chaotically except for a finite set of parameter values Model is sensitive to initial values for Gpmax and Clab

14. Results…. Manaus K34 Tapajos K67

15. Rebio Jaru

16. Conclusions An approach to evaluate daily GPP insensitive to assumptions on nighttime losses The toy model qualitatively predicts delayed radiation and moisture response from ‘growth’ More work needed (get magnitudes and realism right) Model could be run for multiple years and possibly explain interannual variability Scope for inclusion in SVAT models?