1. Reduction of grazing intensity favours biodiversity as a result of increased pasture heterogeneity. There is a clear lack of data on the impact of grazing horses which differ by their digestive system and which strongly prefer short lawns. Mesophile grassland, central France (430m a.s.l.) Continuous grazing (April-November); horses were removed from pastures in August to prevent animals being limited in their intake in highly grazed plots. Liveweight change: 3horses/plot when animals entered and left their pastures Species richness and abundance:  This study (2006-2009): Analysis of the effects of continuously grazing horses at a high or a moderate stocking rate (SR) on both animal performance and the diversity of vascular plants, ground beetles and grasshoppers in a hill-range pasture. Ménard et al. 2002. J. Appl.Ecol. 39,120-133; Wallis de Vries et al. 2007. Grass For. Sci. 62,185-197; Dumont et al. 2009. Grass For. Sci. 64, 92-105 - Vascular plants (25 fixed 50×50cm quadrats/plot) ; June 2006 & 2009 - Ground beetles (Carabidae) (18 pitfall traps/plot); each year in June - Grasshoppers (Orthoptera) (3 fixed 50×2m transects/plot); each year in July & Sept MATERIALS AND METHODS Moderate SR (1.1LU.ha -1 ) 3 saddle horses/2.7ha ×3 replicates High SR (1.8LU.ha -1 ) 5 saddle horses/2.7ha 1LU=600kg.ha -1 Stocking rateYear ModerateHighs.e.P2006200720082009s.e.P Gr. beetles Species richness22.421.20.03NS28.3 a 18.7 c 16.7 c 23.5 b 0.02*** Log N individuals2.132.030.04†2.18 a 2.17 a 1.87 b 2.10 a 0.06*** Short grassland (<10cm)0.810.840.13NS1.13 a 0.96 a,b 0.49 c 0.71 b,c 0.18* Tall grassland (>10cm)1.831.720.04*1.751.821.661.860.09NS Table 1. Species richness and abundance of ground beetles (log N individuals / plot) and grasshoppers (log N+1 individuals / plot in July)  The reduction of SR did not affect horse performance per ha (April-July: 617g.ha -1.d- 1, Sept-Nov: 331g.ha -1.d -1 )  Plant species richness (28 species/plot) was unaffected by SR. The creation of relatively stable short patches by horses (Ménard et al. 2002) enabled legumes to compete with tall grasses: legume abundance increased under the high SR (0.042 to 0.157 of plot area) while it remained stable (0.082 of plot area) under the moderate SR (SR×year p=0.024).  Species richness of ground-beetles and grasshoppers were unaffected by SR. Reduction in grazing intensity benefited ground beetles and grasshoppers, especially those species asociated with tall swards (Table 1). Consistent with observations made in ruminants (Wallis de Vries et al. 2007, Dumont et al. 2009)  greater number of ecological niches, higher availability of food resources, more favourable microclimate, lower levels of disturbance from livestock in moderately grazed pastures. NS not significant; † P<0.1; *P<0.05, **P<0.01, ***P<0.001 Within each row, mean values with different superscripts are significantly different at P<0.05 MATERIAL AND METHODS RESULTS & DISCUSSION Grasshoppers Species richness8.67.70.04NS10.7 a 5.8 c 8.7 b 7.3 b,c 0.04*** Log N+1 individuals1.791.750.04NS2.30 a 0.96 c 2.00 b 1.81 b 0.09*** Short grassland (<10cm)0.861.090.17NS1.64 a 0.56 c 0.96 b 0.73 b,c 0.21*** Tall grassland (>10cm)1.731.560.07*2.18 a 0.69 c 1.94 b 1.76 b 0.10*** How does stocking rate influence biodiversity in a hill-range pasture continuously grazed by horses? G. Fleurance 1,2, B. Dumont 2, A. Farruggia 2 1 IFCE, Arnac-Pompadour, France. 2 INRA, UR1213 Herbivores, Theix, France. geraldine.fleurance@clermont.inra.fr