Individual study: The refuge role of beetle-banks and field margins for carabid beetles on UK arable farmland: densities, composition and relationships with vegetation
Thomas S.R. (2002) The refuge role of beetle-banks and field margins for carabid beetles on UK arable farmland: densities, composition and relationships with vegetation. How to Protect or What We Know About Carabid Beetles: from Knowledge to Application, from Wijster (1969) to Tuczno (2001), 2002 Conference, Warsaw, 185-199.
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Create beetle banks
A paired, replicated, controlled study on five arable estates in Hampshire and Wiltshire, UK (Thomas 2002) found that ground beetle (Carabidae) density and species diversity were higher on beetle banks than field margins in summer but not winter. In spring and summer, ground beetle density and species diversity were higher in beetle banks (averaging 75 individuals/m² in spring, 90 individuals/m² in summer) than field margins (45 and 60 individuals, respectively). In winter there was no difference in ground beetle density (approximately 200-300 individuals/m²), species richness (15-22 species) or diversity between beetle banks and field margins, but species richness increased with age in beetle banks. In summer, beetle banks had higher average cover of grass weeds but grass and broad-leaved weed cover was highly variable in both habitats. Ground beetles were surveyed on five beetle banks on one estate in January-February, May, August and February the following year. Vegetation was surveyed on 22 beetle banks (including those surveyed for beetles) on five estates in January-February (nine banks) and July (22 banks). Banks were 1-13 years old. Each bank was paired with a conventional permanent margin in the adjacent field. This study was part of the same experimental set-up as Thomas et al. 2000 and Thomas 2001.
Create beetle banks
A replicated, paired, controlled study on five conventional arable estates in Hampshire and Wiltshire, UK (Thomas 2002) found that ground beetle (Carabidae) population patterns and vegetation composition in beetle banks and field margins changed across seasons. In winter there was no difference in ground beetle density (range: about 200-300/m2), species richness (range: 15-22 species in total) or diversity between beetle banks and field margins, but species richness increased with age in beetle banks. Ground beetle density and species diversity was higher in beetle banks than field margins in both spring and summer (beetle banks had on average about 75 individuals/m2 in spring and ca. 90/m2 in summer while field margins had about 45 and 60/m2 in each season respectively). Only eight sites were included in the spring analysis. Ground beetle species composition was similar in the two habitats during winter and summer. The winter catches contained especially large proportions of Bembidion lampros. In spring the species composition was different with far fewer B. lampros and more larvae (not identified to species). Total plant cover was high in both habitats in both seasons but significantly higher in field margins during summer. However cover of tussocky grasses was higher in beetle banks in both seasons and did not decline with bank age. Field margins had higher species diversity in summer and higher species richness in both seasons compared with beetle banks. Both measures however increased with beetle bank age so that older banks had a similar number of species to margins. A total of 22 beetle banks were included in this study, ranging from < 1 to 14 years old, each paired with a conventional permanent margin in the adjacent field. Ground beetle populations were sampled in four periods (winter (January-February), spring (May), summer (August) and winter (February)) through destructive sampling (vacuum suction-sampling and digging up turf samples). Vegetation composition was investigated in winter (January-February) and summer (July) through quadrats placed on the ground. This study was part of the same experimental set-up as (Thomas et al. 2000, Thomas 2001, Thomas et al. 2001, Thomas et al. 2002).