L. W. Aarssen, Ecological Combining Ability and Competitive Combining Ability in Plants: Toward a General Evolutionary Theory of Coexistence in Systems of Competition, The American Naturalist, vol.122, issue.6, pp.707-731, 1983.
DOI : 10.1086/284167

J. P. Almeida, U. A. Hartwig, M. Frehner, J. Nösberger, and A. Lüscher, Evidence that P deficiency induces N feedback regulation of symbiotic N 2 fixation in white clover (Trifolium repens L.), Journal of Experimental Botany, vol.51, pp.1289-1297, 2000.

P. Annicchiarico and E. Piano, Response of white clover genotypes to intergenotypic and interspecific interference, The Journal of Agricultural Science, vol.128, issue.4, pp.431-437, 1997.
DOI : 10.1017/S0021859697004334

D. Arrouays, W. Deslais, and V. Badeau, The carbon content of topsoil and its geographical distribution in France, Soil Use and Management, vol.34, issue.1, pp.7-11, 2001.
DOI : 10.1111/j.1475-2743.2000.tb00162.x

I. Aydin and F. Uzun, Nitrogen and phosphorus fertilization of rangelands affects yield, forage quality and the botanical composition, European Journal of Agronomy, vol.23, issue.1, pp.8-14, 2005.
DOI : 10.1016/j.eja.2004.08.001

E. M. Baggs, R. M. Rees, K. A. Smith, and A. J. Vinten, Nitrous oxide emission from soils after incorporating crop residues, Soil Use and Management, vol.33, issue.2, pp.82-87, 2000.
DOI : 10.1111/j.1475-2743.1999.tb00088.x

C. Basset-mens, S. Ledgard, and A. Carran, First life cycle assessment of milk production from New Zealand dairy farm systems, AgResearch Limited, 2005.

C. Basset-mens, S. Ledgard, and M. Boyes, Eco-efficiency of intensification scenarios for milk production in New Zealand, Ecological Economics, vol.68, issue.6, pp.1615-1625, 2009.
DOI : 10.1016/j.ecolecon.2007.11.017

R. Baumont, J. Aufrere, V. Niderkorn, D. Andueza, F. Surault et al., Specific diversity in forages: its consequences on the feeding value, pp.189-206, 2008.

A. Besnard, A. Montarges-lellahi, and A. Hardy, Système de culture et nutrition azotée. Effets sur les émissions de GES et le bilan énergétique, Fourrages, vol.187, pp.311-320, 2006.

J. M. Blumenthal and M. P. Russelle, Subsoil Nitrate Uptake and Symbiotic Dinitrogen Fixation by Alfalfa, Agronomy Journal, vol.88, issue.6, pp.909-915, 1996.
DOI : 10.2134/agronj1996.00021962003600060010x

B. C. Boller and J. Nösberger, Symbiotically fixed nitrogen from field- grown white and red clover mixed with ryegrasses at low levels of15N-fertilization, Plant and Soil, vol.77, issue.2, pp.219-226, 1987.
DOI : 10.2135/cropsci1984.0011183X002400060020x

W. D. Bowman, J. C. Schardt, and S. K. Schmidt, Symbiotic N2-fixation in alpine tundra: ecosystem input and variation in fixation rates among communities, Oecologia, vol.16, issue.2, pp.345-350, 1996.
DOI : 10.2307/1551166

L. S. Brophy and G. H. Heichel, Nitrogen release from roots of alfalfa and soybean grown in sand culture, Plant and Soil, vol.80, issue.1, pp.77-84, 1989.
DOI : 10.1016/B978-0-444-41638-4.50010-8

L. Brown, D. Scholefield, E. C. Jewkes, N. Preedy, K. Wadge et al., The effect of sulphur application on the efficiency of nitrogen use in two contrasting grassland soils, The Journal of Agricultural Science, vol.135, issue.2, pp.131-138, 2000.
DOI : 10.1017/S0021859699008072

C. H. Carbonero, I. Mueller-harvey, T. A. Brown, and L. Smith, Sainfoin ( Onobrychis viciifolia): a beneficial forage legume, Plant Genetic Resources, vol.23, issue.01, pp.70-85, 2011.
DOI : 10.1017/S1742170507002049

B. J. Cardinale, J. P. Wrigh, M. W. Cadotte, I. T. Carroll, A. Hector et al., Impacts of plant diversity on biomass production increase through time because of species complementarity, Proceedings of the National Academy of Sciences, vol.411, issue.6838, pp.18123-18128, 2007.
DOI : 10.1038/35079573

G. Carlsson and K. Huss-danell, Nitrogen fixation in perennial forage legumes in the field, Plant and Soil, vol.253, issue.2, pp.353-372, 2003.
DOI : 10.1023/A:1024847017371

M. E. Castle, D. Reid, and J. N. Watson, Silage and milk production: studies with diets containing white clover silage, Grass and Forage Science, vol.34, issue.49, pp.193-200, 1983.
DOI : 10.1079/BJN19650046

J. H. Christensen, B. Hewitson, A. Busuioc, A. Chen, X. Gao et al., Regional climate projections Climate Change 2007: The Physical Science Basis, Contribution of Working group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, pp.847-940, 2007.

S. F. Christopher and R. Lal, Nitrogen Management Affects Carbon Sequestration in North American Cropland Soils, Critical Reviews in Plant Sciences, vol.15, issue.1, pp.45-64, 2007.
DOI : 10.1023/B:FRES.0000048479.30593.ea

R. P. Collins, J. Connolly, and C. Porqueddu, Effects of legume genetic diversity on the productivity of legume/grass mixtures -COST Action 852, Grassland Science in Europe, vol.9, pp.486-488, 2004.

R. P. Collins, A. Helgadottir, B. E. Frankow-lindberg, L. Skot, C. Jones et al., Temporal changes in population genetic diversity and structure in red and white clover grown in three contrasting environments in northern Europe, Annals of Botany, vol.110, issue.6, pp.1341-1350, 2012.
DOI : 10.1093/aob/mcs058

J. Connolly, T. Bell, T. Bolger, C. Brophy, T. Carnus et al., An improved model to predict the effects of changing biodiversity levels on ecosystem function, Journal of Ecology, vol.458, issue.2, pp.344-355, 2013.
DOI : 10.1038/nature07840

H. T. Cralle and G. H. Heichel, Temperature and chilling sensitivity of nodule nitrogenase activity of unhardened alfalfa, Crop Science, vol.22, pp.300-304, 1982.

M. Daepp, J. Nösberger, and A. Lüscher, Nitrogen fertilization and developmental stage alter the response of Lolium perenne to elevated CO2, New Phytologist, vol.112, issue.2, pp.347-358, 2001.
DOI : 10.1007/s004420050278

H. De-kroon, ECOLOGY: How Do Roots Interact?, Science, vol.318, issue.5856, pp.1562-1563, 2007.
DOI : 10.1126/science.1150726

H. De-kroon, M. Hendriks, J. Van-ruijven, J. Ravenek, F. M. Padilla et al., Root responses to nutrients and soil biota: drivers of species coexistence and ecosystem productivity, Journal of Ecology, vol.82, issue.1, pp.6-15, 2012.
DOI : 10.1890/0012-9658(2001)082[3285:MOPSCR]2.0.CO;2

R. J. Dewhurst, L. Delaby, A. Moloney, T. Boland, and E. Lewis, Nutritive value of forage legumes used for grazing and silage, Irish Journal of Agricultural and Food Research, vol.48, pp.167-187, 2009.

J. Durand, J. E. Sheehy, and F. R. Minchin, Nitrogenase Activity, Photosynthesis and Nodule Water Potential in Soyabean Plants Experiencing Water Deprivation, Journal of Experimental Botany, vol.38, issue.2, pp.311-321, 1987.
DOI : 10.1093/jxb/38.2.311

. Ecoinvent-centre, The life cycle inventory data, v2.2. Swiss Centre for Life Cycle Inventories, 2010.

A. Elgersma and H. Schlepers, Performance of white clover/perennial ryegrass mixtures under cutting, Grass and Forage Science, vol.25, issue.2, pp.134-146, 1997.
DOI : 10.1038/311050a0

A. Elgersma, H. Schlepers, and M. Nassiri, Interactions between perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) under contrasting nitrogen availability: productivity, seasonal patterns of species composition, N 2 fixation, N transfer and N recovery, Plant and Soil, vol.221, issue.2, pp.281-299, 2000.
DOI : 10.1023/A:1004797106981

J. Eriksen, F. P. Vinther, and K. Soegaard, Nitrate leaching and N2-fixation in grasslands of different composition, age and management, The Journal of Agricultural Science, vol.142, issue.2, pp.141-151, 2004.
DOI : 10.1017/S0021859604003934

J. Eriksen, S. Ledgard, J. Luo, R. Schils, and J. Rasmussen, Environmental impacts of grazed pastures, Grassland Science in Europe, vol.15, pp.880-890, 2010.

D. R. Evans, J. Hill, T. A. Williams, and I. Rhodes, Effects of coexistence on the performance of white clover-perennial ryegrass mixtures, Oecologia, vol.67, issue.4, pp.536-539, 1985.
DOI : 10.1007/BF00379346

D. R. Evans, J. Hill, T. A. Williams, and I. Rhodes, Coexistence and the productivity of white clover-perennial ryegrass mixtures, Theoretical and Applied Genetics, vol.67, issue.1, pp.65-70, 1989.
DOI : 10.1007/BF00292317

J. A. Finn, L. Kirwan, J. Connolly, M. T. Sebastià, A. Helgadottir et al., Ecosystem function enhanced by combining four functional types of plant species in intensively managed grassland mixtures: a 3-year continental-scale field experiment, Journal of Applied Ecology, vol.406, issue.2, pp.365-375, 2013.
DOI : 10.1038/35021046

D. A. Fornara and D. Tilman, Plant functional composition influences rates of soil carbon and nitrogen accumulation, Journal of Ecology, vol.84, issue.2, pp.314-322, 2008.
DOI : 10.1641/0006-3568(2000)050[1089:EOGCOA]2.0.CO;2

J. Frame, The production and quality potential of four forage legumes sown alone and combined in various associations, Crop Research, vol.25, pp.103-122, 1986.

J. Frame, Herbage production and quality of a range of secondary grass species at five rates of fertilizer nitrogen application, Grass and Forage Science, vol.42, issue.30, pp.139-151, 1991.
DOI : 10.1111/j.1365-2494.1991.tb02216.x

B. E. Frankow-lindberg, Adaptation to Winter Stress in Nine White Clover Populations: Changes in Non-structural Carbohydrates During Exposure to Simulated Winter Conditions and ???Spring??? Regrowth Potential, Annals of Botany, vol.88, issue.suppl_1, pp.745-751, 2001.
DOI : 10.1093/annbot/88.suppl_1.745

B. E. Frankow-lindberg, C. Brophy, R. P. Collins, and J. Connolly, Biodiversity effects on yield and unsown species invasion in a temperate forage ecosystem, Annals of Botany, vol.103, issue.6, pp.913-921, 2009.
DOI : 10.1093/aob/mcp008

M. Frehner, A. Lüscher, T. Hebeisen, S. Zanetti, F. Schubiger et al., Effects of elevated partial pressure of carbon dioxide and season of the year on forage quality and cyanide concentration of Trifolium repens L. from a FACE experiment, Acta Oecologica, vol.18, issue.3, pp.297-304, 1997.
DOI : 10.1016/S1146-609X(97)80018-5

D. Giambalvo, P. Ruisi, G. Di-miceli, A. S. Frenda, and G. Amato, Forage production, N uptake, N2 fixation, and N recovery of berseem clover grown in pure stand and in mixture with annual ryegrass under different managements, Plant and Soil, vol.164, issue.1-2, pp.379-391, 2011.
DOI : 10.1111/j.1439-037X.1990.tb00807.x

A. Guckert and R. K. Hay, The Overwintering, Spring Growth, and Yield in Mixed Species Swards, of White Clover in Europe, Annals of Botany, vol.88, issue.suppl_1, pp.667-668, 2001.
DOI : 10.1093/annbot/88.suppl_1.667

K. J. Hammond, J. L. Burke, J. P. Koolaard, S. Muetzel, C. S. Pinares-patino et al., Effects of feed intake on enteric methane emissions from sheep fed fresh white clover (Trifolium repens) and perennial ryegrass (Lolium perenne) forages, Animal Feed Science and Technology, vol.179, issue.1-4, pp.121-132, 2013.
DOI : 10.1016/j.anifeedsci.2012.11.004

D. A. Häring, D. Suter, N. Amrhein, and A. Lüscher, Biomass Allocation is an Important Determinant of the Tannin Concentration in Growing Plants, Annals of Botany, vol.99, issue.1, pp.111-120, 2007.
DOI : 10.1093/aob/mcl227

D. A. Häring, A. Scharenberg, F. Heckendorn, F. Dohme, A. Lüscher et al., Abstract, Renewable Agriculture and Food Systems, vol.78, issue.01, pp.19-29, 2008.
DOI : 10.2134/agronj2002.1059

U. A. Hartwig, The regulation of symbiotic N2 fixation: a conceptual model of N feedback from the ecosystem to the gene expression level, Perspectives in Plant Ecology, Evolution and Systematics, vol.1, issue.1, pp.92-120, 1998.
DOI : 10.1078/1433-8319-00054

T. Hebeisen, A. Lüscher, S. Zanetti, B. U. Fischer, U. A. Hartwig et al., Growth response of Trifolium repens L. and Lolium perenne L. as monocultures and bi-species mixture to free air CO2 enrichment and management, Global Change Biology, vol.3, issue.2, pp.149-160, 1997.
DOI : 10.1046/j.1365-2486.1997.00073.x

A. Hector, B. Schmid, C. Beierkuhnlein, M. C. Caldeira, M. Diemer et al., Plant Diversity and Productivity Experiments in European Grasslands, Science, vol.286, issue.5442, pp.1123-1127, 1999.
DOI : 10.1126/science.286.5442.1123

G. H. Henry and J. Svoboda, Dinitrogen Fixation (Acetylene Reduction) in High Arctic Sedge Meadow Communities, Arctic and Alpine Research, vol.18, issue.2, pp.181-187, 1986.
DOI : 10.2307/1551127

J. Hill, The three C's ? competition, coexistence and coevolution ? and their impact on the breeding of forage crop mixtures, Theoretical and Applied Genetics, vol.79, issue.2, pp.168-176, 1990.
DOI : 10.1007/BF00225947

J. Hille-ris-lambers, W. S. Harpole, D. Tilman, J. Knops, and P. B. Reich, Mechanisms responsible for the positive diversity-productivity relationship in Minnesota grasslands, Ecology Letters, vol.72, issue.8, pp.661-668, 2004.
DOI : 10.1126/science.1060391

H. Høgh-jensen, The Nitrogen Transfer Between Plants: An Important but Difficult Flux to Quantify, Plant and Soil, vol.71, issue.1-2, pp.1-5, 2006.
DOI : 10.1007/978-94-017-0776-3

H. Høgh-jensen and J. K. Schjoerring, Interactions between white clover and ryegrass under contrasting nitrogen availability: N 2 fixation, N fertilizer recovery, N transfer and water use efficiency, Plant and Soil, vol.197, issue.2, pp.187-199, 1997.
DOI : 10.1023/A:1004289512040

P. S. Hooda, M. Moynagh, I. F. Svoboda, and H. A. Anderson, A comparative study of nitrate leaching from intensively managed monoculture grass and grass???clover pastures, The Journal of Agricultural Science, vol.131, issue.3, pp.267-275, 1998.
DOI : 10.1017/S0021859698005863

D. U. Hooper and P. M. Vitousek, EFFECTS OF PLANT COMPOSITION AND DIVERSITY ON NUTRIENT CYCLING, Ecological Monographs, vol.68, issue.1, pp.121-149, 1998.
DOI : 10.2307/1940319

D. U. Hooper and J. S. Dukes, Overyielding among plant functional groups in a long-term experiment, Ecology Letters, vol.87, issue.2, pp.95-105, 2004.
DOI : 10.1046/j.1461-0248.2003.00555.x

D. U. Hooper, E. S. Chapin, . Iii, J. J. Ewel, A. Hector et al., EFFECTS OF BIODIVERSITY ON ECOSYSTEM FUNCTIONING: A CONSENSUS OF CURRENT KNOWLEDGE, Ecological Monographs, vol.75, issue.1, pp.3-35, 2005.
DOI : 10.1086/285824
URL : https://hal.archives-ouvertes.fr/hal-00188090

P. Ineson, P. A. Coward, and U. A. Hartwig, Soil gas fluxes of N 2 O, CH 4 and CO 2 beneath Lolium perenne under elevated CO 2 : The Swiss free air carbon dioxide enrichment experiment, Plant and Soil, vol.198, issue.1, pp.89-95, 1998.
DOI : 10.1023/A:1004298309606

K. A. Jacot, A. Lüscher, J. Nösberger, and U. A. Hartwig, Symbiotic N2 fixation of various legume species along an altitudinal gradient in the Swiss Alps, Soil Biology and Biochemistry, vol.32, issue.8-9, pp.1043-1052, 2000.
DOI : 10.1016/S0038-0717(00)00012-2

K. A. Jacot, A. Lüscher, J. Nösberger, and U. A. Hartwig, The relative contribution of symbiotic N 2 fixation and other nitrogen sources to grassland ecosystems along an altitudinal gradient in the Alps, Plant and Soil, vol.225, issue.1/2, pp.201-211, 2000.
DOI : 10.1023/A:1026524212074

A. Jayanegara, F. Leiber, and M. Kreuzer, Meta-analysis of the relationship between dietary tannin level and methane formation in ruminants from in vivo and in vitro experiments, Journal of Animal Physiology and Animal Nutrition, vol.64, issue.124, pp.365-375, 2012.
DOI : 10.1016/j.anifeedsci.2007.03.013

E. S. Jensen, M. B. Peoples, R. M. Boddey, P. M. Gresshoff, H. Hauggaard-nielsen et al., Legumes for mitigation of climate change and the provision of feedstock for biofuels and biorefineries. A review, Agronomy for Sustainable Development, vol.41, issue.79, pp.329-364, 2012.
DOI : 10.1016/j.soilbio.2009.08.009
URL : https://hal.archives-ouvertes.fr/hal-00930531

M. Kaltschmitt and G. A. Reinhardt, Nachwachsende Energieträger -Grundlagen, Verfahren, ökologische Bilanzierung, 1997.

A. H. Kingston-smith, J. E. Edwards, S. A. Huws, E. J. Kim, and M. Abberton, Plant-based strategies towards minimising ???livestock's long shadow???, Proceedings of the Nutrition Society, pp.613-620, 2010.
DOI : 10.1017/S0029665110001953

C. A. Kirkby, J. A. Kirkegaard, A. E. Richardson, L. J. Wade, C. Blanchard et al., Stable soil organic matter: A comparison of C:N:P:S ratios in Australian and other world soils, Geoderma, vol.163, issue.3-4, pp.197-208, 2011.
DOI : 10.1016/j.geoderma.2011.04.010

L. Kirwan, A. Lüscher, M. T. Sebastia, J. A. Finn, R. P. Collins et al., Evenness drives consistent diversity effects in intensive grassland systems across 28 European sites, Journal of Ecology, vol.85, issue.3, pp.530-539, 2007.
DOI : 10.1007/s004420050278

O. Kitani, T. Jungbluth, R. M. Peath, and A. Ramdani, CIGR handbook of agricultural engineering, Energy & Biomass Engineering. American Society of Agricultural Engineers, vol.V, 1999.

K. Klumpp, J. M. Bloor, P. Ambus, and J. Soussana, Effects of clover density on N2O emissions and plant-soil N transfers in a fertilised upland pasture, Plant and Soil, vol.36, issue.1-2, pp.97-107, 2011.
DOI : 10.1016/j.soilbio.2003.09.009

J. H. Lambers, W. S. Harpole, D. Tilman, J. Knops, and P. B. Reich, Mechanisms responsible for the positive diversity-productivity relationship in Minnesota grasslands, Ecology Letters, vol.72, issue.8, pp.661-668, 2004.
DOI : 10.1126/science.1060391

L. Gall, A. Beguin, E. Dollé, J. B. Manneville, V. Pflimlin et al., Nouveaux compromis techniques pour concilier les impératifs d'efficacité économique et environnementale en élevage herbivore, Fourrages, vol.198, pp.131-152, 2009.

S. Ledgard, R. Schils, J. Eriksen, and J. Luo, Environmental impacts of grazed clover/grass pastures, Irish Journal of Agricultural and Food Research, vol.48, pp.209-226, 2009.

S. F. Ledgard and K. W. Steele, Biological nitrogen fixation in mixed legume/grass pastures, Plant and Soil, vol.78, issue.1-2, pp.137-153, 1992.
DOI : 10.1007/BF00011314

S. F. Ledgard, J. W. Penno, and M. S. Sprosen, Nitrogen inputs and losses from clover/grass pastures grazed by dairy cows, as affected by nitrogen fertilizer application, The Journal of Agricultural Science, vol.132, issue.2, pp.215-225, 1999.
DOI : 10.1017/S002185969800625X

S. F. Ledgard, M. S. Sprosen, J. W. Penno, and G. S. Rajendram, Nitrogen fixation by white clover in pastures grazed by dairy cows: Temporal variation and effects of nitrogen fertilization, Plant and Soil, vol.229, issue.2, pp.177-187, 2001.
DOI : 10.1023/A:1004833804002

P. Loiseau, P. Carrere, M. Lafarge, R. Delpy, and J. Dublanchet, Effect of soil-N and urine-N on nitrate leaching under pure grass, pure clover and mixed grass/clover swards, European Journal of Agronomy, vol.14, issue.2, pp.113-121, 2001.
DOI : 10.1016/S1161-0301(00)00084-8

M. Loreau and A. Hector, Partitioning selection and complementarity in biodiversity experiments, Nature, vol.88, issue.6842, pp.72-76, 2001.
DOI : 10.1046/j.1365-2745.2000.00470.x

M. Loreau, S. Naeem, P. Inchausti, J. Bengtsson, J. P. Grime et al., Biodiversity and Ecosystem Functioning: Current Knowledge and Future Challenges, Science, vol.294, issue.5543, pp.804-808, 2001.
DOI : 10.1126/science.1064088

J. A. Lory, M. P. Russelle, and G. H. Heichel, Quantification of Symbiotically Fixed Nitrogen in Soil Surrounding Alfalfa Roots and Nodules, Agronomy Journal, vol.84, issue.6, pp.1033-1040, 1992.
DOI : 10.2134/agronj1992.00021962008400060024x

A. Lüscher, J. Connolly, and P. Jacquard, Neighbour specificity between Lolium perenne and Trifolium repens from a natural pasture, Oecologia, vol.67, issue.3, pp.404-409, 1992.
DOI : 10.2307/2259348

A. Lüscher, J. Fuhrer, and P. C. Newton, Global atmospheric change and its effect on managed grassland systems Grassland: A Global Resource, pp.251-264, 2005.

A. Lüscher, J. F. Soussana, and O. Huguenin-elie, Role and impacts of legumes in grasslands for high productivity and N gain from symbiotic N 2 fixation, pp.101-107, 2011.

A. Lüscher, M. Daepp, H. Blum, U. A. Hartwig, and J. Nösberger, Fertile temperate grassland under elevated atmospheric CO2???role of feed-back mechanisms and availability of growth resources, European Journal of Agronomy, vol.21, issue.3, pp.379-398, 2004.
DOI : 10.1016/j.eja.2003.10.009

A. Lüscher, I. Mueller-harvey, J. F. Soussana, R. M. Rees, and J. L. Peyraud, Potential of legume-based grassland-livestock systems in, Europe. Grassland Science in Europe, vol.18, pp.3-29, 2013.

E. Marquard, A. Weigelt, V. M. Temperton, C. Roscher, J. Schumacher et al., Plant species richness and functional composition drive overyielding in a six-year grassland experiment, Ecology, vol.11, issue.12, pp.3290-3302, 2009.
DOI : 10.1016/j.actao.2007.05.003

A. H. Marshall, T. A. Williams, M. T. Abberton, T. P. Michaelson-yeates, P. Olyott et al., Forage quality of white clover (Trifolium repens L.) x Caucasian clover (T. ambiguum M. Bieb.) hybrids and their grass companion when grown over three harvest years, Grass and Forage Science, vol.16, issue.1, pp.91-99, 2004.
DOI : 10.1080/0028825X.1978.10426878

W. P. Mccaughey, K. Wittenberg, and D. Corrigan, Impact of pasture type on methane production by lactating beef cows, Canadian Journal of Animal Science, vol.79, issue.2, pp.221-226, 1999.
DOI : 10.4141/A98-107

R. B. Mckane, D. F. Grigal, and M. P. Russelle, Spatiotemporal Differences in 15N Uptake and the Organization of an Old-Field Plant Community, Ecology, vol.71, issue.3, pp.1126-1132, 1990.
DOI : 10.2307/1937380

L. Mommer, J. Van-ruijven, H. De-caluwe, A. E. Smit-tiekstra, C. A. Wagemaker et al., Unveiling below-ground species abundance in a biodiversity experiment: a test of vertical niche differentiation among grassland species, Journal of Ecology, vol.82, issue.5, pp.1117-1127, 2010.
DOI : 10.1111/j.1755-0998.2008.02130.x

M. C. Mortenson, G. E. Schuman, and L. J. Ingram, Carbon Sequestration in Rangelands Interseeded with Yellow-Flowering Alfalfa (Medicago sativa ssp. falcata), Environmental Management, vol.33, issue.S1, pp.475-481, 2004.
DOI : 10.1007/s00267-003-9155-9

M. Nassiri and A. Elgersma, Effects of nitrogen on leaves, dry matter allocation and regrowth dynamics in Trifolium repens L. and Lolium perenne L. in pure and mixed swards, Plant and Soil, vol.246, issue.1, pp.107-121, 2002.
DOI : 10.1023/A:1021528732218

L. Nesheim and B. C. Boller, Nitrogen fixation by white clover when competing with grasses at moderately low temperatures, Plant and Soil, vol.77, issue.1, pp.47-56, 1991.
DOI : 10.1007/BF00011898

D. Nyfeler, Productivity and nitrogen utilization in productive grassland: effect of species combinations, species proportions and nitrogen fertilization, 2009.

D. Nyfeler, O. Huguenin-elie, M. Suter, E. Frossard, and A. Lüscher, Grass???legume mixtures can yield more nitrogen than legume pure stands due to mutual stimulation of nitrogen uptake from symbiotic and non-symbiotic sources, Agriculture, Ecosystems & Environment, vol.140, issue.1-2, pp.155-163, 2011.
DOI : 10.1016/j.agee.2010.11.022

D. Nyfeler, O. Huguenin-elie, M. Suter, E. Frossard, J. Connolly et al., Strong mixture effects among four species in fertilized agricultural grassland led to persistent and consistent transgressive overyielding, Journal of Applied Ecology, vol.112, issue.3, pp.683-691, 2009.
DOI : 10.1002/9781118204221

A. Oberson, E. Frossard, C. Bühlmann, J. Mayer, P. Mäder et al., Nitrogen fixation and transfer in grass-clover leys under organic and conventional cropping systems, Plant and Soil, vol.112, issue.1-2, pp.237-255, 2013.
DOI : 10.1007/s004420050278

Y. Oelmann, N. Buchmann, G. Gleixner, M. Habekost, C. Roscher et al., Plant diversity effects on aboveground and belowground N pools in temperate grassland ecosystems: Development in the first 5 years after establishment, Global Biogeochemical Cycles, vol.84, issue.12, p.10, 1029.
DOI : 10.1890/02-0433

M. C. Patto, B. Skiba, E. C. Pang, S. J. Ochatt, F. Lambein et al., Lathyrus improvement for resistance against biotic and abiotic stresses: From classical breeding to marker assisted selection, Euphytica, vol.163, issue.39, pp.133-147, 2006.
DOI : 10.1270/jsbbs1951.34.273

M. B. Peoples, J. Brockwell, D. F. Herridge, I. J. Rochester, B. J. Alves et al., The contributions of nitrogen-fixing crop legumes to the productivity of agricultural systems, Symbiosis, vol.79, issue.1-3, pp.1-17, 2009.
DOI : 10.1007/BF02149818

P. R. Peterson, C. C. Sheaffer, R. M. Jordan, and C. J. Christians, Responses of Kura Clover to Sheep Grazing and Clipping: I. Yield and Forage Quality, Agronomy Journal, vol.86, issue.4, pp.655-660, 1994.
DOI : 10.2134/agronj1994.00021962008600040013x

J. L. Peyraud, L. Gall, A. Lüscher, and A. , Potential food production from forage legumebased-systems in Europe: an overview, Irish Journal of Agricultural and Food Research, vol.48, pp.115-135, 2009.

K. Pirhofer-walzl, J. Rasmussen, H. Høgh-jensen, J. Eriksen, K. Soegaard et al., Nitrogen transfer from forage legumes to nine neighbouring plants in a multi-species grassland, Plant and Soil, vol.40, issue.1-2, pp.71-84, 2012.
DOI : 10.1016/j.soilbio.2007.08.010

J. Rasmussen, K. Soegaard, K. Pirhofer-walzl, and J. Eriksen, N2-fixation and residual N effect of four legume species and four companion grass species, European Journal of Agronomy, vol.36, issue.1, pp.66-74, 2012.
DOI : 10.1016/j.eja.2011.09.003

P. Rochette and H. H. Janzen, Towards a Revised Coefficient for Estimating N2O Emissions from Legumes, Nutrient Cycling in Agroecosystems, vol.82, issue.102, pp.171-179, 2005.
DOI : 10.4141/S02-008

J. Rockström, W. Steffen, K. Noone, A. Persson, F. S. Chapin et al., A safe operating space for humanity, Nature, vol.16, issue.7263, pp.472-475, 2009.
DOI : 10.1029/2003JD004462

C. Roscher, S. Thein, B. Schmid, and M. Scherer-lorenzen, Complementary nitrogen use among potentially dominant species in a biodiversity experiment varies between two years, Journal of Ecology, vol.142, issue.3, pp.477-488, 2008.
DOI : 10.1017/CBO9780511623523

C. Roscher, J. Schumacher, J. Baade, W. Wilcke, G. Gleixner et al., The role of biodiversity for element cycling and trophic interactions: an experimental approach in a grassland community, Basic and Applied Ecology, vol.5, issue.2, pp.107-121, 2004.
DOI : 10.1078/1439-1791-00216

C. Roscher, V. M. Temperton, M. Scherer-lorenzen, M. Schmitz, J. Schumacher et al., Overyielding in experimental grassland communities - irrespective of species pool or spatial scale, Ecology Letters, vol.306, issue.4, pp.419-429, 2005.
DOI : 10.1126/science.1060391

R. J. Roughley and P. J. Dart, Strain, Journal of Experimental Botany, vol.21, issue.3, pp.776-786, 1970.
DOI : 10.1093/jxb/21.3.776

P. Rowlinson, M. Steele, and A. Nefzaoui, Livestock and Global Climate Change, 2008.

M. P. Russelle, J. F. Lamb, N. B. Turyk, B. H. Shaw, and B. Pearson, Managing Nitrogen Contaminated Soils, Agronomy Journal, vol.99, issue.3, pp.738-746, 2007.
DOI : 10.2134/agronj2005.0325

M. P. Russelle, J. F. Lamb, B. R. Montgomery, D. W. Elsenheimer, B. S. Miller et al., Alfalfa Rapidly Remediates Excess Inorganic Nitrogen at a Fertilizer Spill Site, Journal of Environment Quality, vol.30, issue.1, pp.30-36, 2001.
DOI : 10.2134/jeq2001.30130x

U. R. Sangakkara, U. A. Hartwig, and J. Nösberger, Soil moisture and potassium affect the performance of symbiotic nitrogen fixation in faba bean and common bean, Plant and Soil, vol.11, issue.1, pp.123-130, 1996.
DOI : 10.1007/BF00029282

M. Scherer-lorenzen, C. Palmborg, A. Prinz, and E. D. Schulze, THE ROLE OF PLANT DIVERSITY AND COMPOSITION FOR NITRATE LEACHING IN GRASSLANDS, Ecology, vol.84, issue.6, pp.1539-1552, 2003.
DOI : 10.1111/j.1365-2389.1993.tb00433.x

R. L. Schils, Nitrate losses from grazed grass and grass/clover pastures on clay soils, Meststoffen, pp.78-84, 1994.

R. L. Schils, A. Verhagen, H. F. Aarts, and L. B. Sebek, A farm level approach to define successful mitigation strategies for GHG emissions from ruminant livestock systems, Nutrient Cycling in Agroecosystems, vol.8, issue.2, pp.163-175, 2005.
DOI : 10.1002/jpln.1996.3581590513

B. Schmid, A. Hector, P. Saha, and M. Loreau, Biodiversity effects and transgressive overyielding, Journal of Plant Ecology, vol.1, issue.2, pp.95-102, 2008.
DOI : 10.1093/jpe/rtn011

O. Schwank, H. Blum, and J. Nösberger, The Influence of Irradiance Distribution on the Growth of White Clover (Trifolium repens L.) in Differently Managed Canopies of Permanent Grassland, Annals of Botany, vol.57, issue.2, pp.273-281, 1986.
DOI : 10.1093/oxfordjournals.aob.a087107

S. Schwinning and A. J. Parsons, Analysis of the Coexistence Mechanisms for Grasses and Legumes in Grazing Systems, The Journal of Ecology, vol.84, issue.6, pp.799-813, 1996.
DOI : 10.2307/2960553

S. Schwinning and A. J. Parsons, A Spatially Explicit Population Model of Stoloniferous N-Fixing Legumes in Mixed Pasture with Grass, The Journal of Ecology, vol.84, issue.6, pp.815-826, 1996.
DOI : 10.2307/2960554

R. Serraj, T. R. Sinclair, and L. C. Purcell, Symbiotic N2 fixation response to drought, Journal of Experimental Botany, vol.50, issue.331, pp.143-155, 1999.
DOI : 10.1093/jxb/50.331.143

J. C. Simon, F. Vertès, M. L. Decau, and L. Le-corre, Nitrogen flows in grazed pastures. 1- Balances on the farm scale and nitrate leaching under pastures, Fourrages, vol.151, pp.249-262, 1997.

B. Sleugh, K. J. Moore, J. R. George, and E. C. Brummer, Binary Legume???Grass Mixtures Improve Forage Yield, Quality, and Seasonal Distribution, Agronomy Journal, vol.92, issue.1, pp.24-29, 2000.
DOI : 10.2134/agronj2000.92124x

J. Soussana and T. Tallec, Can we understand and predict the regulation of biological N2 fixation in grassland ecosystems?, Nutrient Cycling in Agroecosystems, vol.112, issue.2, pp.197-213, 2010.
DOI : 10.1104/pp.112.2.575

J. F. Soussana and M. Lafarge, Competition for resources between neighbouring species and patch scale vegetation dynamics in temperate grasslands, Annales de Zootechnie, vol.47, issue.5-6, pp.371-382, 1998.
DOI : 10.1051/animres:19980505
URL : https://hal.archives-ouvertes.fr/hal-00889738

J. F. Soussana, T. Tallec, and V. Blanfort, Mitigating the greenhouse gas balance of ruminant production systems through carbon sequestration in grasslands, animal, vol.11, issue.03, pp.334-350, 2010.
DOI : 10.2136/sssaj2002.1981

J. F. Soussana, F. R. Minchin, J. H. Macduff, N. Raistrick, M. T. Abberton et al., A Simple Model of Feedback Regulation for Nitrate Uptake and N2 Fixation in Contrasting Phenotypes of White Clover, Annals of Botany, vol.90, issue.1, pp.139-147, 2002.
DOI : 10.1093/aob/mcf161

J. F. Soussana, P. Loiseau, N. Vuichard, E. Ceschia, J. Balesdent et al., Carbon cycling and sequestration opportunities in temperate grasslands, Soil Use and Management, vol.55, issue.2, pp.219-230, 2004.
DOI : 10.1007/978-3-642-60684-7_1

S. D. Sparrow, V. L. Cochran, and E. B. Sparrow, Dinitrogen Fixation by Seven Legume Crops in Alaska, Agronomy Journal, vol.87, issue.1, pp.34-41, 1995.
DOI : 10.2134/agronj1995.00021962008700010007x

E. M. Spehn, L. M. Scherer, B. Schmid, A. Hector, M. C. Caldeira et al., The role of legumes as a component of biodiversity in a cross-European study of grassland biomass nitrogen, Oikos, vol.84, issue.2, pp.205-218, 2002.
DOI : 10.1002/(SICI)1097-0231(19990715)13:13<1237::AID-RCM633>3.0.CO;2-C

P. J. Squillace, J. C. Scott, M. J. Moran, B. T. Nolan, and D. W. Kolpin, VOCs, Pesticides, Nitrate, and Their Mixtures in Groundwater Used for Drinking Water in the United States, Environmental Science & Technology, vol.36, issue.9, pp.1923-1930, 2002.
DOI : 10.1021/es015591n

E. Sturludóttir, C. Brophy, G. Bélanger, A. Gustavsson, M. Jørgensen et al., Benefits of mixing grasses and legumes for herbage yield and nutritive value in Northern Europe and Canada. Grass and Forage Science, 2013.

F. Surault, B. Julier, and P. Barre, Agricultural values of perennial ryegrass pastures constituted by one or several cultivars, Fourrages, vol.204, pp.255-262, 2010.

D. Suter, H. U. Briner, and A. Lüscher, Effect of Lolium perenne L. variety on the botanical composition of grass-clover mixtures, Grassland Science in Europe, vol.12, pp.417-420, 2007.

D. Suter, O. Huguenin-elie, D. Nyfeler, and A. Lüscher, Agronomically improved grasslegume mixtures: higher dry matter yields and more persistent legume proportions, Grassland Science in Europe, vol.15, pp.761-763, 2010.

D. Suter, E. Rosenberg, E. Mosimann, and R. Frick, Standardmischungen für den Futterbau -Revision 2013-2016, Agrarforschung Schweiz, vol.3, pp.1-12, 2012.

M. Suter, J. Connolly, J. A. Finn, Á. Helgadóttir, P. Golinski et al., Grass-legume mixtures enhance yield of total nitrogen and uptake from symbiotic N 2 fixation: Evidence from a threeyear multisite experiment, Grassland Science in Europe, vol.18, pp.76-78, 2013.

T. Tallec, S. Diquelou, J. Avice, F. Lesuffleur, S. Lemauviel-lavenant et al., Availability of N and S affect nutrient acquisition efficiencies differently by Trifolium repens and Lolium perenne when grown in monoculture or in mixture, Environmental and Experimental Botany, vol.66, issue.2, pp.309-316, 2009.
DOI : 10.1016/j.envexpbot.2009.02.002

S. Tamminga, A. Bannink, J. Dijkstra, and R. Zom, Feeding strategies to reduce methane loss in cattle, Animal Science Group, 2007.

R. J. Thomas, The role of the legume in the nitrogen cycle of productive and sustainable pastures, Grass and Forage Science, vol.64, issue.2, pp.133-142, 1992.
DOI : 10.1007/978-94-009-7529-3_1

K. Thompson, A. P. Askew, J. P. Grime, N. P. Dunnett, and A. J. Willis, Biodiversity, ecosystem function and plant traits in mature and immature plant communities, Functional Ecology, vol.2, issue.2, pp.355-358, 2005.
DOI : 10.1126/science.1060391

D. Tilman, The Ecological Consequences of Changes in Biodiversity: A Search for General Principles, Ecology, vol.80, issue.5, pp.1455-1474, 1999.
DOI : 10.2307/176540

B. R. Trenbath, Biomass productivity of mixtures Advances in Agronomy, pp.177-210, 1974.

R. Turkington, The Growth, Distribution and Neighbour Relationships of Trifolium Repens in a Permanent Pasture. V. The Coevolution of Competitors, The Journal of Ecology, vol.77, issue.3, pp.717-733, 1989.
DOI : 10.2307/2260981

H. A. Van-dorland, H. R. Wettstein, H. Leuenberger, and M. Kreuzer, Effect of supplementation of fresh and ensiled clovers to ryegrass on nitrogen loss and methane emission of dairy cows, Livestock Science, vol.111, issue.1-2, pp.57-69, 2007.
DOI : 10.1016/j.livsci.2006.11.015

J. Van-ruijven and F. Berendse, Positive effects of plant species diversity on productivity in the absence of legumes, Ecology Letters, vol.81, issue.3, pp.170-175, 2003.
DOI : 10.1007/s003740000271

F. Vertès, J. C. Simon, L. Le-corre, and M. L. Decau, Nitrogen flows in grazed pastures. II. Study of flows and their effects on leaching, Fourrages, vol.151, pp.263-280, 1997.

F. P. Vinther and E. S. Jensen, Estimating legume N2 fixation in grass-clover mixtures of a grazed organic cropping system using two 15N methods, Agriculture, Ecosystems & Environment, vol.78, issue.2, pp.139-147, 2000.
DOI : 10.1016/S0167-8809(99)00124-3

M. Wachendorf, R. P. Collins, A. Elgersma, M. Fothergill, B. E. Frankow-lindberg et al., Overwintering and Growing Season Dynamics of Trifolium repens L. in Mixture with Lolium perenne L.: A Model Approach to Plant-environment Interactions, Annals of Botany, vol.88, issue.suppl_1, pp.683-702, 2001.
DOI : 10.1093/annbot/88.suppl_1.683

G. Waghorn, Beneficial and detrimental effects of dietary condensed tannins for sustainable sheep and goat production???Progress and challenges, Animal Feed Science and Technology, vol.147, issue.1-3, pp.116-139, 2008.
DOI : 10.1016/j.anifeedsci.2007.09.013

G. C. Waghorn and R. S. Hegarty, Lowering ruminant methane emissions through improved feed conversion efficiency, Animal Feed Science and Technology, vol.166, issue.167, pp.291-301, 2011.
DOI : 10.1016/j.anifeedsci.2011.04.019

Y. Y. Wen and H. F. Jiang, Cutting effects on growth characteristics, yield composition, and population relationships of perennial ryegrass and white clover in mixed pasture, New Zealand Journal of Agricultural Research, vol.9, issue.4, pp.349-358, 2005.
DOI : 10.2135/cropsci1983.0011183X002300040028x

T. A. Williams, M. T. Abberton, and I. Rhodes, Performance of white clover varieties combined in blends and alone when grown with perennial ryegrass under sheep and cattle grazing, Grass and Forage Science, vol.52, issue.1, pp.90-93, 2003.
DOI : 10.1007/BF00225891

J. Woledge, Competition between grass and clover in spring as affected by nitrogen fertiliser, Annals of Applied Biology, vol.57, issue.6, pp.175-186, 1988.
DOI : 10.1111/j.1365-2494.1985.tb01756.x

S. L. Woodward, G. C. Waghorn, and P. G. Laboyrie, Condensed tannins in birdsfoot trefoil (Lotus corniculatus) reduce methane emissions from dairy cows, Proceedings of New Zealand Society of Animal Production, vol.64, pp.160-164, 2004.

S. L. Woodward, G. C. Waghorn, K. R. Lassey, G. , and L. P. , Does feeding sulla (Hedysarum coronarium) reduce methane emissions from dairy cows? Proceedings of New Zealand Society of, Animal Production, vol.62, pp.227-230, 2002.

L. Wu and M. B. Megechan, Simulation of nitrogen uptake, fixation and leaching in a grass/white clover mixture, Grass and Forage Science, vol.14, issue.1, pp.30-41, 1999.
DOI : 10.1111/j.1475-2743.1998.tb00145.x

S. Zanetti, U. A. Hartwig, C. Van-kessel, A. Lüscher, T. Hebeisen et al., Does nitrogen nutrition restrict the CO 2 response of fertile grassland lacking legumes?, Oecologia, vol.112, issue.1, pp.17-25, 1997.
DOI : 10.1007/s004420050278