Heikoop, J.E., L.B. Sparrius & W. Revet. Dragonfly and vascular plant diversity along ecologically designed ditch banks in Gouda. Brachytron 7(2): 35-42 A comparative survey of plant and dragonfly biodiversity and numbers between traditional and ecologically designed ditch banks on peaty soils in the suburban town of Gouda (The Netherlands, province of Zuid-Holland) was carried out by volunteers of the Dutch Butterfly Conservation. Three common dragonfly species (Coenagrion pulchellum, Ischnura elegans and Orthetrum cancellatum) and many plants were significantly more abundant in ecologically designed ditch banks. Species numbers and densities were both about a factor two higher along ecological ditches, independent of meteorological conditions during counting. However, in most ditches either the number of plant species doubled or the number of dragonfly species doubled, the latter, therefore, with a lower increase of plant species. This can be related to the design of the ditch side. The most important, positive factors for dragonfly diversity are 1) presence of a gently sloping ditch bank, 2) not too shallow or deep water in the middle of the ditch width and 3) a sheltered riparian vegetation with for instance Iris pseudacoris, Phragmites australis and Typha latifolia. For vascular plant diversity the most important factors are 1) a gently sloping ditch bank and 2) sunlight. A combination of these factors, preferable with some variation within a short distance, may yield optimal conditions for both species groups. Considering these results, we conclude that ecologically designed ditch banks in suburban surroundings can strongly stimulate both plant and dragonfly diversity.

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Brachytron

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Nederlandse Vereniging voor Libellenstudie

Lisette J.E. Heikoop, Laurens B. Sparrius, & Wim Revet. (2003). Libellen en planten langs natuurvriendelijke oevers in Gouda. Brachytron, 7(2), 35–42.