Populieren, brandnetels en natuurbehoud: omstreden positie van cultuurpopulieren onder de loep

Since World War II cultivars of poplar are planted on a large scale in valley ecosystems and alluvial forests in Flanders. These poplar plantations have a bad reputation in conservation. They are associated with destruction of valuable valley grasslands, and ruderalization of forest vegetation with nettles. This paper focuses on the processes behind the decline of the forest floor vegetation in poplar stands, and concludes that this decline is primarily linked with the historical background and practices in poplarplantation forestry, and not with the species itself. The dominance of nettles and the low frequency of forest plants in many poplar stands are related to the fact that it concerns recent plantations on former agricultural land (high soil phosphor and soil nitrogen content). In old, ecologically valuable alluvial forests it is intensive plantation forestry practice with very short rotation times, soil drainage and monospecific even-aged stands, that provokes the negative effects. Compared to the natural species of alluvial forests (Ash, Alder) poplars have very similar ecological characteristics (e.g. litter composition). In practice, this means that in newly established nature reserves, the cutting of present poplar stands is only recommended for the restoration of valuable valley grasslands or coppice forests. In all other circumstances, no interference is required, and even to be avoided. As Poplars do not rejuvenate naturally, and grow very fast, these stands will spontaneously develop towards valuable forest ecosystems, where other species will gradually take over.