Grazing intensity affects insect diversity via sward structure and heterogeneity in a long-term experiment

Published source details Jerrentrup J.S., Wrage-Mönnig N., Röver K. & Isselstein J. (2014) Grazing intensity affects insect diversity via sward structure and heterogeneity in a long-term experiment. Journal of Applied Ecology, 51, 968-977.
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This study is summarised as evidence for the following.

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	Reduce grazing intensity on grassland by reducing stocking density Action Link

Reduce grazing intensity on grassland by reducing stocking density

A replicated, randomized, paired, controlled study in 2002–2011 in a grassland in Lower Saxony, Germany (Jerrentrup et al. 2014) found that grassland grazed at reduced cattle density had a higher species richness and abundance of butterflies than grassland grazed at moderate density, but there was no additional benefit of more recent very low density grazing. After 8–9 years, plots grazed at reduced density had a higher abundance (18.7–30.6 individuals/transect) and species richness (6.0–8.4 species/transect) of butterflies than plots grazed at moderate density (abundance: 8.1–20.0 individuals/transect, richness: 3.3–5.3 species/transect). However, on plots grazed at very low density butterfly abundance (16.3–34.1 individuals/transect) and species richness (5.4–7.8 species/transect) were similar to the reduced density plots. Over nine years, the abundance of marbled white Melanargia galathea increased more on reduced density plots (2002: 0–1 individuals; 2011: 4–12 individuals) than on moderate density plots (2002: 0–1 individuals; 2011: 1–5 individuals). From 2002–2011, three 3-ha paddocks were each divided into three treatments, each grazed annually from April–October: moderate density (3–6 cattle/ha, target sward height 6 cm), reduced density (1–3 cattle/ha, 12 cm sward) and very low density (2 cattle/ha, 18 cm sward, from 2005 only). Target sward heights were maintained by varying numbers of Simmental cattle in each paddock following biweekly sward height measurements. From July–September 2002–2004 and 2010–2011, butterflies were recorded biweekly on three 50-m transects/treatment.

(Summarised by: Andrew Bladon)