Factors influencing butterfly diversity in a long-term experiment differing in grazing intensity

Reducing grazing intensity offers opportunities for maintaining and enhancing biodiversity. By creating a heterogeneous mosaic of patches differing in sward height and vegetation composition, extensive grazing provides good opportunities for diverse butterfly assemblages. Here, we report long-term effects of three grazing intensities (adjusted by target compressed sward heights: 6 cm and 12 cm since 2002 and additionally 18 cm since 2005) arranged in a randomized block design with three replicates, on a continuously stocked pasture grazed by cattle in the Solling Uplands, Germany. Data on butterfly species richness and abundance were collected from 2003 and 2004 and again in 2010 and 2011 on three 50 m-transects per paddock on three occasions in summer. Results suggest a lenient grazing intensity to be most advantageous for butterflies. The findings are presented in relation to abundance of flower heads as well as to sward surface height and its heterogeneity.