Some notes on the ecology of ranunculus hederaceus L

The ecology of the Ivy-leaved Water CrowfootRanunculus hederaceus was studied in the Netherlands, especially in the area of Schoorl. The species appears to be characteristic of contact zones between more elevated oligotrophic sandy soils and eutrophic (or polluted) small streams or small artificial running waters, or of stagnant waters strongly influenced by seepage phenomena, in which the periodic fluctuations in the water table do not exceed 2 dm. In the area studied, the species prefers a substratum consisting of a layer of sediment, one to several inches thick and rich in nitrogen, deposited on a sandy subsoil, in water that is usually only a few centimetres deep, remains rather cool in summer (its temperature not exceeding about 16° C) and only rarely freezes up in winter. This is in agreement with its eu-atlantic distribution.The opinion held by several workers that the Ranunculetum hederacei must be classified under the Montio-Cardaminetalia is, in my opinion, unfounded. The Ranunculetum hederacei is probably a vegetation type belonging to the Callitricho-Batrachion and fits very well into an ecological series of vegetation types that can be arranged according to a syndrome of ecological characteristics of which the fluctuation in the water table is the most important. The constant association withCallitriche platycarpa is presumably characteristic.