Intra-annual patch stability Inter-annual patch stability Selective grazing, patch stability and vegetation dynamics in a rotationally-grazed pasture B. Dumont, P. Carrère, N. Rossignol, J. Chadoeuf, A. Farruggia, C. Ginane, F. Louault INRA, UR Herbivores, Ecosystème Prairial & Biostatistiques et Processus Spatiaux Lack of data on interactions between grazing intensity and livestock species  Difficulty to propose recommendations for the management of biodiversity and production in grassland ecosystems Study area: a productive grassland divided into 12 plots that were rotationally grazed by cattle at a high (Ca+) or a low (Ca-) stocking rate or by sheep at the same low stocking rate (Sh-) Measurements: diet selection and patch stability, we aim to relate to the initial direction of community changes in a long-term ecosystem manipulation experiment Forbs -1 -0.5 0.5 1 R1 R2 R3 R4 R5 Legumes Ca+ Ca- Sh- Jacobs’ Index Tall grasses Short grasses * * : missing data Diet selection Direct observation of bites For both sheep and cattle, Selection for legumes, forbs and short rather than tall grass patches, consistent with their higher nutritive value Avoidance of tall grasses increasing over the grazing season as grass becomes mature, especially after the 3rd rotation (R3) early July Intra-annual patch stability Fine-scale measurements on permanent grids Inter-annual patch stability Large-scale measurements (25 x 20m²) Respective proportions of vegetation types in stable 1.6 x 0.8 m² grids after the 3rd (Early July) and 4th (September) rotations of 2006 & 2007 Ca-: inter-annual stability of grazing patterns at the peak of biomass (R3; P < 0.05), but more ‘fluctuating’ patch boundaries in the autumn (R4) * Ca+: high degree of inter-annual patch stability after R4 (P < 0.001) due to repellent items Use of covariograms to assess the effect of local sward composition on patch stability over the grazing season Sh-: no inter-annual stability (R3: P = 0.83; R4: P = 0.23) Ca- Ca+ Sh- Vegetation dynamics Point quadrats Ca- & Sh-: positive link between the initial local abundance of legumes and forbs, and the stability of grazing patterns Ca- & Ca+: positive link between the initial abundance of reproductive grasses and the stability of ungrazed patches 2004 2006 2007 2008 Ca-  Greater effect of stocking rate than of grazer species in affecting the initial direction of community changes Sh- Ca+ Grasses Legumes Forbs Selective grazing at a fine scale can create relatively stable patches within the pasture Plots grazed by sheep showed some level of patch stability between the peak of biomass and the autumn, but no inter-annual stability. Grazing by cattle seems more likely to locally maintain relatively short cover over successive years, and would consequently favour functional vegetation diversity by creating relatively stable open patches enabling prostrate forbs and legumes to compete with tall grasses. In the long term, this could result in divergent vegetation dynamics within plots, and may lead to an effect of grazer species on sward botanical composition, beyond the strong effect of stocking rate INSTITUT NATIONAL DE LA RECHERCHE AGRONOMIQUE UR1213 Herbivores • F-63122 • Saint-Genès-Champanelle • France UR874 Ecosystème Prairial • F-63100 Clermont-Fd & UR546 Biostatistique et Processus Spatiaux • F-84914 Avignon A L I M E N T A T I O N A G R I C U L T U R E E N V I R O N N E M E N T