V encuentro servicios ecosistemas lemaire

1. Grasslands and ecosystem services
within agro-ecosystems
Necessity for a multidisciplinary and multiscale approach
Gilles LEMAIRE
INRA, Lusignan France

2. New paradigms for grassland sciences
- Ecosystem services, the benefits human societies and
individual peoples can obtain from ecosystem
functioning: provisioning, regulating, cultural and
supporting
-Trade-offs between “grassland productivity” for
human food and fiber production and other “services”
- Grasslands have to be analysed not only as a source
for feeding domestic herbivores, but also as a way for
production “ecosystem services”.

3. Role and environmental impacts
of grassland areas
Direct effects:
Soil protection (erosion, SOM, biology, structure...)
Water quality (nitrate, phosphate, pesticides...)
Air quality (CO2 sequestration, N2O ?, NH3 ?)
Biodiversity (vegetation, soil fauna and flora, insects...)
Interactions with management systems

4. Scientific Objectives
Climate changes
Management
practices Herbivores
Greenhouse gases
Vegetation  CO2
 N2O
Soil Organic Matter  NOx
C, N, P cycles
C sequestration
Soil biology
SOM Biochemistry
Water Quality
 NO3-
Biodiversity
 DOC
 Pesticides...  Vegetation
 Microorganisms
 Micro-Meso-fauna

5. Fonctions of SOM
Agronomical impacts: Environnemental impacts:
Soil properties Greenhouse gases :
N2O, CO2
Soil Organic Matter CO2
Soil fertility
(SOM) sequestration
Regulation of C, N, P…cycles
Nitrate leaching

6. Inputs of fresh organic matter
within grassland ecosystem
Green litter
Brown litter
CO2
Dung
Input Soil organic matter
Chemical protection Labile SOM pool
Physical protection Intermediate SOM pool
Rhizodeposition Physicochemical protection Stable SOM pool
DOC

7. Coupling C and N Cycles
Soil organic matter represents 2/3rd of the total terrestrial carbon

8. 80
60
Net immobilisation
C:N
ratio 40
Net mineralisation
20
0
Time
During the decomposition of OM of residues there is a
decline in C:N ratio through CO2 losses…and then a phase
of net immobilisation followed by a phase of net
mineralisation of N depending on the C:N ratio of
residues at origin.

9. Comparison of N fluxes between
croping system and grassland
Gross Min. Gross Imm. Net Min.
4
N (kg/ha/j)
3
2
1
0
Annual crops Grasslands
Aita (1996) Loiseau et Thiéry (1992)

10. Leaf
litters
Root Plants
C/N 30
litters
C/N 40-50
N mineral
MOS Biomass
- Under grassland, there is a constant supply of litters with high C:N
- Then there is a high gross N immobilisation flux
- In the same time plants have a more or less continuous N
absorption rate all along the seasons…
- In consequence, NO3- cannot accumulate in soil > 3-5KgN.ha-1,
except after high level application of N fertilizer, and under urine
patches…
- Then losses of N by nitrate leaching is very low even in
winter…when stocking density remains not too high.

11. N leaching under grasslands
Grazing vs Cutting
300
Pâture Grazing:
Fauche
250
High increase in N
leaching when > 200
N lixivié (kg N /ha)
200
kgN/ha
150
Cutting:
100
Low N leaching
50 when < 400kgN/ha
0
0 200 Trade-off
400 600
Production vs Environment
fertilisation (kg N efficace/ha)

12. Effect of stocking density on N leaching
160
y = 8,77 e0,003x
140 r²=0.71
120
N lixivié (kg N/ha)
100
80
60
40 Simon et al, 1997 ;
Laurent et al.2000
Vertès et al, 2002
20
Benoit et al., 1995
0
0 200 400 600 800 1000 1200
chargement (UGB.JPE/ha)

13. CH4 N20
NOx
NH3
CO2
Herbivores
Photosynthesis
C-N-P
Vegetation
Soil
N
N absorption Feces
OM
Urine
Mineral N MIT
Microbes
C-N coupling
Nitrate
C-N decoupling

14. In grazing system C-N decoupling
/ C-N coupling depends on
stocking density
C-N decoupling C-N coupling
Above a threshold stocking density C-N decoupling excess
the capacity of C-N recoupling of vegetation and soil
microbes

15. Cutting system with indoor feeding and association with
cropping system through use of straw and efficient compost
production and recycling system could be highly intensified
with reduced environmental impacts
Hay-Silage
Control of GHG
Emission ?
Straw
Re-coupling C-N
Compost

16. 1. Permanent vegetation and soil microbes couple strongly C-N cycles
2. Grazing animals decouple C-N cycles and then provoke C and N
emissions
3. Intensification at grazing reaches a limit beyond which
environmental fluxes become too important according to stocking
density
4. Cutting management is a way for a higher intensification of
grassland…but high cost!!!
5. Decoupling C-N by animals indoor need to be acompanied by a re-
coupling C-N within a coherent animal manure management
6. Comparison between grazing and cutting must be done at whole
system level and not only at field or paddock level…

17. Role and environmental impacts of
grassland areas
Indirect effects on cropping systems:
Control of weed communities and reduction of herbicide use;
Control of pests and diseases and reduction of pesticide use;
Recycling of nutrients and reduction of fertilizer use;
Improved soil structure and reduction of fuel energy use;
Heterogeneity of habitats and diversity of trophic chains;

18. Multi-function and multi-scale approach
Spatial integration
Land use system mosaïc
Territories
Catchment
Landscape Ecology and biodiversity
Interactions between farms Landscape
Farms
Production systems
Conception-Evaluation of innovative
systems Ingeneering Forage systems
Environnemental balance Systems
Multi function evaluation
Cropping systems
Biogeochemical Cycles
Environnemental Fluxes Local
Biodiversité Processes
Expérimentation, Monitoring Soil-vegetation
Modelisation

19. Spatial interactions between grassland areas
and cropping areas
Flux of foods
Grasslands OM Stocks
minerals
Livestock Concentrates
system
Exportations
Grassland area Croping area

20. Integration of grasslands within
cropping systems
Grassland Flux foods
OM
Preceding minerals
effect
Stocks
Livestock
Following system
effect
Grassland
Exportations
Grains

21. Agro-Ecology Ingeneering
Field
Analyse of local processes and Environment x
Management interaction, What if ?
Cropping system
Conception and evaluation of cropping and
forage systems, What is necessary for...?
Forage system
Conception and evaluation of livestock systems
from socio-economic and environment
Livestock system perspectives

22. G. Paillard-INRA C. Maitre-INRA
Interactions between cereal farms and livestock
farms within a territory
- Fluxes of organic matter and nutriments among specialised farms
and possibilities for more conservative biogeochemical fluxes by
coupling more strongly C and N…
- Diversification of land use and management systems through:
- common crop rotation systems
- exchanges of field
- production and sell of hays …

23. Contribution of Grasslands to Landscape Ecology
Farm Atmosphere Environment
Crops GHG emission Climate
Grasslands CO2 balance Soil
Livestock Topography
Biodiversity
Land use
Habitat diversity
Trophic networks
Catchment
Water quality
Flux

24. Effects of grasslands on biodiversity
at landscape level

25. The decline of biodiversity
within European agriculture plains
*Cultivated areas with high diversity of crops host the richest diversdity
*>250 species of birds whose 173 prioritaries et 118 in danger
From BirdLife 2004
CNRS Chizé

26. During the last 30 years:
decrease of livestock production
decrease of grassland areas
specialization for cereal production systems
increase in field size
reduction of the complexity of the landscape mosaïc
1958 1990

27. Effect of reintroduction of grasslands on Little
Bustard population within a cereal cropping area
CNRS Chizé
4,4
clutch size
3,9
3,4
2,9
2,4
1,9
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
60
50
40
30
20
10
0
95
96
97
98
99
00
01
02
03
04
05
06
07
19
19
19
19
19
20
20
20
20
20
20
20
20

28. Conclusions
1- Grasslands through soil-vegetation interactions allow a strong C-
N coupling leading to very conservative C and N cycles and reduced
fluxes to atmosphere and hydrosphere.
2- But grazing herbivores decouple greatly C and N, leading to
increasing emission of GHG and nitrate leaching with stocking
density.
3- Trade-off exists between grassland intensification and
environment impacts.
4- Grassland areas can contribute to mitigate environmental impacts
of intensive cropping system at landscape and regional levels
5- Mixed farming between arable crops and livestock production
systems based on grasslands could help to reconcile high food
production systems with high level of ecosystem services

29. Necessity of structuring the scientific
community on continental ecosystem across
Europe
Scientific community on continental ecosystem is very
fragmented across a high variety of ecosystem types and a high
variety of scientific disciplines;
Most of the environmental problems (water quality, air quality,
soils quality, climatic changes, pollutant, biodiversity problems…)
require interdisciplinary approaches and long term observations,
experimentations and data collection to enable simulation and
forecasting the impacts of climate change and land use change on
continental scale-ecology and to answer society questions.
Answering environmental questions requires coupling more than
sophisticating analysis of individual elementary processes.

30. …, continue…
Research infrastructures implementation in experimental ecology,
is a prerequisite for structuring research on continental
ecosystems, enabling understanding of ecosystem responses to
disturbance, providing pertinent knowledge for managing
anthropogenic ecosystems in a sustainable way.
…and then… opportunities to merge European research projects
with South American ones within a wider international network?

31. Thank you for your attention
and
for invitation