1. Promoting sustainable land-use management: water, carbon and nutrient turnover
Dirk Hölscher &
Pak Soekisman

2. Objectives Present key results
Draw conclusions for agricultural and forest management

3. Land use types & land use gradients

4. Aboveground biomass, premontane natural forests
Hertel et al. 2009

5. Steffan-Dewenter et al., 2007
Tree cover (%)
Steffan-Dewenter et al., 2007

6. Meteorological flux tower in a montane rainforest, Bariri

7. Measured net ecosystem exchange flux Fc,
extrapolated respiration flux RE, and
the sum of both fluxes Pg (gross photosynthesis)
Ibrom et al., 2007

8. CO2 fluxes between the atmosphere: forest vs. cacao
Ibrom et al., 2007

9. Land use types and net ecosystem productivities:
scenarios
Olchev et al., 2008

10. Land use types and net ecosystem productivities:
model results
Olchev et al., 2008

11. Fluxes of sensible (H) and latent (E) energy: forest vs. cacao
Ibrom et al., 2007

12. Sap flux of cacao and shade trees
Köhler et al. 2009

13. Cacao tree water use vs. canopy gap fraction
Shade trees enhanced water use by cacao trees
(R2adj = 0.39, p = 0.043, n = 9)
Köhler et al. 2009

14. Gumbasa river watershed
Catchment size: km²
River discharge
R2 = 0.86
R²=0.83
automatic stage recorder
stage recorder – Forestry
climate station
climate station STORMA
main irrigation chanel
Lore Lindu National Park
Palu river watershed
Gerold & Leemhuis 2008
Gauging stations

15. Modeling discharge of the river discharge, Gumbasa watershed: effects of land cover change
Discharge (2003): status quo 2003: 590 mm
land use scenario A1: 838 mm + 42%  1200m annual crops
Land use scenario A2: 724 mm + 23%  1200m change into cacao
Gerold & Leemhuis 2008

16. Modeled run off components1 2 3 4 5 6 7 8
Discharge (mm d -1 )
Direct flow
Interflow
Base flow
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
2003
Kleinhans et al. 2004

17. Nutrient balance of maize and agroforest
Dechert et al., 2004

18. Summary land use types & land use gradients
High carbon storage in forests of Sulwesi
High carbon uptake by forest
Shade trees enhance transpiration from agrofrests
River discharge change with land cover change suggested
Agroforestry strongly benefits from nitrogen input by N fixing shade trees

19. Implications Very important to conserve remaining forests
Shade trees positively influence cacao cultivation

20. Drought experiments
Premontane rainforest
Cacao/Gliricidia agroforest

21. Cacao-Gliricidia agroforest

22. n=3 roof (treatment) plots, n=3 control plots
80% of plot area was covered by plastic panels (March 07- mid April 08);
n=3 roof (treatment) plots, n=3 control plots
M. Köhler
G Moser

23. Tree sap flux
Soil water content
Cacao bean yield
Litterfall

24. Moser et al. under review
Cacao yield
Roof closure
-55%, p<0.05
-10%, p>0.05
Moser et al. under review

25. Soil water storage (mm) Roof to control ratio
Soil water storage and cacao water use
Sap flux cacao
-11%, p>0.05
Roof closure
Soil water storage (mm) Roof to control ratio
Mean±SD, n=3
- 40%, p < 0.05)

26. Complementary use of soil water deuterium signalδ
Cacao
Gliricidia
Schwendenmann et al. 2009

27. Water uptake depth cacao and Glricidia
Schwendenmann, unpublished

28. Root water potential Cacao Gliricidia Osmotic adjustment in cacao
Control
Roof
Osmotic adjustment in cacao
Moser et al. under review

29. Van Straaten, unpublished
CO2 soil efflux
Period of roof closure
CO2 efflux (Mg C m-1 h-1)
Experiment period
If you are interested I can also give you an interpretation of what we believe took place in time….
i.e during and after the natural drought in Jan/Feb 2008 CO2 efflux remained consistently lower than control plot given drought stress in trees
Van Straaten, unpublished

30. CO2 efflux response to soil moisture
Volumetric water content (m3 m-3)
CO2 efflux (Mg C m-1 h-1)
Dirk: I can also give you a similar graph but instead with pF instead of VWC… But I guess for a general meeting it is easier to understand VWC.
(Adj R2 = 0.338, n = 94)
Van Straaten, unpublished

31. Summary cacao drought experiment
Cacao yield was little influenced for several months; a strong (~50%) reduction was observed at the end of the experiment
Little response of tree water use to drought
Cacao and Glriricidia trees use soil water resources complementary
Small effects of drought on soil CO2 efflux

32. Implications
Cacao is a suitable crop even where short dry spells occur
Shade trees: no negative effect on cacao tree performance

33. Forest

34. Soil moisture Köhler, unpublished 10 cm 40 cm 150 cm Roof closure
06/ / /2009

35. Sap flux: all trees
Schuldt, unpublished

36. Stem wood production (2nd year)
Moser, unpublished

37. Van Straaten, unpublished
CO2 soil efflux
CO2 efflux (Mg C m-1 h-1)
Experiment period
Period of roof closure
If you are interested I can also give you an interpretation of what we believe took place in time….
i.e during and after the natural drought in Jan/Feb 2008 CO2 efflux remained consistently lower than control plot given drought stress in trees
Van Straaten, unpublished

38. CO2 soil efflux vs. soil moisture
CO2 efflux (Mg C m-1 h-1)
(Adj R2 = 0.79, n = 93)
Van Straaten, unpublished

39. Summary forest drought experiment
Little response in tree sap flux to drought
Tree diameter growth was significantly reduced
Strong effect of drought on soil CO2 efflux

40. Overall summary Old-growth forest is to be conserved
Agroforestry is a promissing option in post-forest landscapes
Shade trees play a central role in cacao cultivation

41. Thank you for attention!