Hof et al (2010b) hedgehog grassy field margins macro-invertebrates

Title: The impact of grassy field margins on macro-invertebrate abundance in adjacent arable fields, Agriculture, Ecosystems and Environment 139; 280-283. 2010

Authors: A. R. Hof & P. W. Bright

Country: UK

Background to study

An investigation into the value of grassy field margins for macro-invertebrate communities and their predators. 

Method

• 32 arable fields, sown with wheat, were sampled for invertebrate abundance in May to July 2009.
• All fields were bounded by >2 m wide hedgerows and half of the fields had an additional 4-6 m wide grassy field margins, managed through an agri-environment scheme.  
• Fields with and without field margins were paired and were similar in management, field size, soil type, were located on the same farm and were sampled on the same day to avoid impacts of environmental differences other than field margin.
• Earthworm abundance (total number and biomass) was measured by sieving for worms from 15 soil cores (15 cm diameter and depth), gastropod (>5 mm) abundance (total number and biomass) was estimated visually at night by spot sampling 0.5 m² quadrangles and the species richness and abundance of carabids was measured using pitfall traps (8 cm diameter, 14 cm depth), half filled with anti-freeze and placed 1 cm below the surface for 72 hrs. Five samples using each method was undertaken at <1 m, 10 m and 20 m from hedgerows within each field and on the same side of the hedgerow for each pair of fields.
• Differences in invertebrate abundance and richness were compared between fields with and without field margins.

Key results

• The mean number of earthworms at 0 to 20 m distances from the field edge was significantly higher in fields with a grassy margin than those without. At 0 m distance from the field edge, the mean biomass of earthworms was also significantly higher in fields with grassy margins compared with those without.
• The mean number and biomass of earthworms was significantly higher at 0 m distance from the edge of fields, than at 10 m and 20 m distances from the edge in fields with and without a grassy margin.
• The mean number of gastropods was significantly lower on fields with compared to fields without grassy margins at 0 and 10 m from the edge, as was the mean biomass, but only at 0 m from the field edge.
• A significantly higher mean number, but not biomass, of gastropods were found closest to the edge in fields with and without grassy margins and the mean biomass and number of gastropods were significantly higher at 0 m from the edge of the field compared with areas further from the edge.
• Of 18 species of carabids recorded, 72% were predators, 22% were phytophagous species and 6% were detrivores. More species of carabids were found in fields without, than in fields with grassy margins and no significant differences were observed between samples taken at different distances from the edge.
• The mean number carabids, but not species, found in pitfall traps was significantly higher in fields with, than fields without grassy margins and the mean number of individuals and of carabid species did not vary at different distances from the edges of fields.

Key messages to landowners and managers derived from these results

• Agri-environment schemes that (re)create hedgerows and establish grassy field margins are recommended for hedgehog conservation, particularly in intensively farmed arable landscapes where food availability is low.