1. Biogeochemical Causes and Consequences of Land Use Change
Christoph Müller, Alberte Bondeau, Hermann Lotze-Campen, Dieter Gerten, Wolfgang Lucht, Pascalle Smith, Sönke Zaehle

2. Outline Introduction LPJ-DGVM Causes of land use change
Consequences of land use change
Outlook

3. Causes and Consequences
Biogeochemical causes
Climate
Atmospheric CO2 concentration
Water availability
Soil fertility
Biogeochemical consequences
Impacts on water cycle
Impacts on carbon cycle

4. LPJ-DGVM space and time loops competition differentiation climate CO2
AET
COi
space and time loops
metabolism
soil water supply
mean structure
of an individual
yearly NPP
allometric
conditions
old
structure
new
crown area
height
fine roots
leaves
LAI
sapwood
heartwood
0-50 cm cm
stem
diameter
biochemistry
functional
relationships
differentiation
allometry
competition
APAR =
PAR · [1  exp( k · LAI )]
LPJ-DGVM
climate
CO2
soil
C budget
H20 budget
biogeography

5. Crops in LPJ Better representation of biogeochemical stocks and fluxes
Assessment of agricultural production in global change context
Climate change
Socioeconomic changes
just fine
too dry
too wet

6. Crops in LPJ
Adaptation of LPJ to simulate the carbon and water fluxes for crops: each CFT on a distinct stand with access to a separate soil water pool
Sowing date estimation:
for 4 temperate CFTs = f(T), for 4 tropical CFTs = f(P)
Adaptation of heat sum and vernalization requirement
Oct
Jul
LAI, ~ 6
Total biomass, ~ 20 tDM/ha
Grain harvested, ~ 6 tDM/ha
Daily coupled growth and development simulation:
Phenology, LAI change, carbon allocation to leaves, roots, storage organs, ... Estimation of the harvesting period
Winter wheat
New input needed: Land Use
For grasses, several cuts (f(LAI)), or regular grazing
No water stress for irrigated crops, computation of the water requirement and of the effective irrigation
Possibility of multiple cropping (e.g. rice)
Grass during the intercrop season
Harvested biomass removed, residues sent to the litter pool or removed (fodder, biofuel, ...)

7. Crops in LPJ Phenological variations for the European temperate zone
[10°W-32°E; 34°N-72°N] period

8. Biogeochemical Causes of Land Use Change
Causes: Climate
< >3.5
Changed yield potentials due to climate change
+2°C -10% prec.
Biogeochemical Causes of Land Use Change

9. Causes: Socio-economy
Drivers of world food demand
Population
Dietary habits
World GDP growth ( ) 2.8 % p.a. (per capita: 1.4 % p.a.)
Income
Causes: Socio-economy

10. Mind games: Settings Demography: 5.6 billion vs. 12 billion
Lifestyles: diet of 1995 vs. meat*2 vs. meat/2
Market structures: perfect global market

11. Mind games: Land Use Patterns
Early 1990s
Leff et al. 2004
Mind games: Land Use Patterns
Scenario pop12, meat*2

12. Consequences of Land Use Change
80-100%
60-80%
45-60%
30-45%
20-30%
10-20%
0-10%
Harvested NPP/NPP
Biogeochemical Consequences of Land Use Change

13. Consequences of Land Use Change

14. Consequences of Land Use Change
Difference in transpiration (mm yr–1) 1961–90
without irrigation
yr–1
<
Global totals (change):
Transpiration: – 7.3 %
Runoff: %
Gerten et al. (2004)

15. Mind games: Consequences
Agricultural area (b)
Harvested crop biomass (c)
(a)

16. Outlook: MAgPIE Generating Land Use Patterns for LPJ
Optimization algorithm (Linear Programming)
Minimize total costs of production, subject to economic and environmental constraints
Other model outputs
total crop & livestock production
total input use (labor, fertilizer)
shadow prices (land, water)
Model structure (global)
[i] economic regions (~ )
[j] spatial cells ( ~ LPJ resolution)
[k] activities (~20): crops, livestock, irrigation, biofuels
[m] constraints: physical limits, rotational, internal balances
Biophysical constraints (LPJ)
land, water
Socio-economic constraints (GTAP, FAO)
demand, cost structures, prices
Crop yields (LPJ)
Land use shares in LPJ cells (%)
Cereals
Oilseeds
Pulses
Sugar beets
Generating Land Use Patterns for LPJ

17. Thank you for your attention.