Grasslands and ecosystem services within agro-ecosystemsNecessity for a multidisciplinary and multiscale approach Gilles LEMAIRE INRA, Lusignan France
New paradigms for grassland sciences- Ecosystem services, the benefits human societies andindividual peoples can obtain from ecosystemfunctioning: provisioning, regulating, cultural andsupporting-Trade-offs between “grassland productivity” forhuman food and fiber production and other “services”- Grasslands have to be analysed not only as a sourcefor feeding domestic herbivores, but also as a way forproduction “ecosystem services”.
Role and environmental impacts of grassland areasDirect 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
Scientific Objectives Climate changesManagement 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
Fonctions of SOMAgronomical 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
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
Coupling C and N CyclesSoil organic matter represents 2/3rd of the total terrestrial carbon
80 60 Net immobilisation C:N ratio 40 Net mineralisation 20 0 TimeDuring the decomposition of OM of residues there is adecline in C:N ratio through CO2 losses…and then a phaseof net immobilisation followed by a phase of netmineralisation of N depending on the C:N ratio ofresidues at origin.
Comparison of N fluxes between croping system and grassland Gross Min. Gross Imm. Net Min. 4N (kg/ha/j) 3 2 1 0 Annual crops Grasslands Aita (1996) Loiseau et Thiéry (1992)
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.
N leaching under grasslands Grazing vs Cutting 300 Pâture Grazing: Fauche 250 High increase in N leaching when > 200N 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)
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)
CH4 N20 NOx NH3 CO2 HerbivoresPhotosynthesis C-N-P Vegetation Soil NN absorption Feces OM Urine Mineral N MIT Microbes C-N coupling Nitrate C-N decoupling
In grazing system C-N decoupling / C-N coupling depends on stocking densityC-N decoupling C-N couplingAbove a threshold stocking density C-N decoupling excess the capacity of C-N recoupling of vegetation and soil microbes
Cutting system with indoor feeding and association withcropping 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
1. Permanent vegetation and soil microbes couple strongly C-N cycles2. Grazing animals decouple C-N cycles and then provoke C and N emissions3. Intensification at grazing reaches a limit beyond which environmental fluxes become too important according to stocking density4. 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 management6. Comparison between grazing and cutting must be done at whole system level and not only at field or paddock level…
Role and environmental impacts of grassland areasIndirect 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;
Multi-function and multi-scale approachSpatial integrationLand use system mosaïc TerritoriesCatchmentLandscape Ecology and biodiversityInteractions between farms Landscape Farms Production systemsConception-Evaluation of innovativesystems Ingeneering Forage systemsEnvironnemental balance SystemsMulti function evaluation Cropping systemsBiogeochemical CyclesEnvironnemental Fluxes LocalBiodiversité ProcessesExpérimentation, Monitoring Soil-vegetationModelisation
Spatial interactions between grassland areas and cropping areas Flux of foods Grasslands OM Stocks minerals Livestock Concentrates system Exportations Grassland area Croping area
Integration of grasslands within cropping systems Grassland Flux foods OMPreceding mineralseffect Stocks LivestockFollowing systemeffect GrasslandExportations Grains
Agro-Ecology IngeneeringField 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
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 …
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
Effects of grasslands on biodiversity at landscape level
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
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
Effect of reintroduction of grasslands on LittleBustard 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
Conclusions1- Grasslands through soil-vegetation interactions allow a strong C-N coupling leading to very conservative C and N cycles and reducedfluxes to atmosphere and hydrosphere.2- But grazing herbivores decouple greatly C and N, leading toincreasing emission of GHG and nitrate leaching with stockingdensity.3- Trade-off exists between grassland intensification andenvironment impacts.4- Grassland areas can contribute to mitigate environmental impactsof intensive cropping system at landscape and regional levels5- Mixed farming between arable crops and livestock productionsystems based on grasslands could help to reconcile high foodproduction systems with high level of ecosystem services
Necessity of structuring the scientificcommunity on continental ecosystem across EuropeScientific community on continental ecosystem is veryfragmented across a high variety of ecosystem types and a highvariety 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 andforecasting the impacts of climate change and land use change oncontinental scale-ecology and to answer society questions.Answering environmental questions requires coupling more thansophisticating analysis of individual elementary processes.
…, 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?
Thank you for your attention and for invitation
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