Has botanical enhancement of broad-leaved plantations in Milton Keynes, United Kingdom, resulted in more woodland-like insect assemblages?

Abstract

Methods of invertebrate sampling were used to determine how the deliberate introduction of field layer vegetation to broad-leaved plantations influenced the associated insect assemblages. Enclosed pitfall traps and tent-like emergence traps were employed at (1) 25-year-old plantations where botanical enhancement had taken place a decade previously; (2) "nonenhanced" plantations of a similar age; and (3) local ancient woods, all in Milton Keynes, Buckinghamshire, United Kingdom. The aim was to discover whether enhancement had produced a community intermediate to nonenhanced plantations and naturally established woodland. Enhancement had not successfully created plantations botanically more woodland-like and plantation types were not constant; however, plant species richness had increased. This was also true of the insect assemblages (Coleoptera, Diptera and Hemiptera), which showed more variation in composition, though woodland communities could still be distinguished. However, those insect species present in the naturally established woods did have a significantly greater frequency and abundance in the enhanced plantations compared to the nonenhanced plantations, especially so with "woodland edge" species. Mantel tests showed significant correlations between the plant species present and insect assemblages taken by both sampling types. Although insect species richness was not significantly higher in the enhanced plantations, this correlated strongly with plant species richness and a measure of vegetation volume. The overall findings suggest that the enhancement had created plantations only subtly more like the local woodlands, though the insect assemblages had responded. However, relative to the time scale of woodland development, it is still early days.