Of foxgloves, needles, and food (for thought)
By: Iris de Ronde
Our front garden faces north, so it gets little sun even in summer. Until a few years ago, I never watered here, not even in summer, as it was never really necessary. But after a hot dry summer, the result was that my ground-covering Geraniums died en masse. After winter, a kind of felling vegetation came in return: lots of Herb-Robbert, Wood Avens and Foxglove. The latter species, which some may know by its scientific as well as medical name Digitalis, immediately became my daughter's favourite plant. I also started seeing Foxglove more and more often. Was it a matter of a good year (after that drought), or a matter of never having noticed it before, but ─ fuelled by my daughter's enthusiasm ─ now suddenly being consciously observed by me?
Every now and then, if we happened to encounter it in the field, we would make vegetation relevés of foxglove vegetation. In Central Europe, this plantcommunity is assigned to an association not mentioned for the Netherlands. In recent years, however, the search became more structural, especially on the Veluwe where the species is frequently found. Our interest in this vegetation was regularly described as curious. Digitalis is such a common species after all, why would you want to study it!?
Foxglove is indeed common in the Netherlands, but this is actually quite a recent phenomenon (Figure 1). Over the last 50 years, the species has increased enormously in our country. Traditionally, the species is mentioned for Burgum and Heerenveen, the dunes near The Hague and Leiden, and along the southeastern border of our country: South Limburg, around Venlo, in the wide surroundings of Nijmegen, as far as Arnhem and Dieren, and the south of the Achterhoek as far as Winterswijk. On the Veluwe, Foxglove occurred along its southern edge and in the vicinity of Apeldoorn only.
Figure: 1 Foxglove in the Netherlands (Source: online distribution atlas)
On the Veluwe, we made many relevés with Foxglove in forest edges, on felling areas, in (road) verges and on dumping places of organic material (e.g. plaggen). The average species richness was 18 species in 21 square metres, including tree juveniles, mosses and lichens. Besides Foxglove, constant species were Common Bent, Sheep's sorrel and Climbing Corydalis. A big difference from relevés of felling areas from other countries is the absence of Rosebay Willowherbs, while this species is by no means rare in the Netherlands. In addition, Raspberry and Heath Groundsel are not common in our relevés, but they are common in relevés from Central Europe. Our relevés can be divided into several types (we will publish the classification and an extended version of this story in the Notizbücher der Kasseler Schule), but the most important conclusion is that we do have the felling vegetation mentioned for other countries, the Epilobio angustifolii-Digitalietum purpureae, in the Netherlands as well. This means that the association is therefore not limited to the colline and montane zone, as has been assumed so far!
What has caused Foxglove to increase so much in our country and why is it that a plant community known from the mountains is now found frequently on the Veluwe? The most frequently mentioned factor in shifts of species or vegetation between the lowlands and mountains is climate. If the climate changes, the vegetation zones in the mountains shift. But it does not make sense for a plant community to descend from the mountains to the lowlands in a warming climate: the zones shift upwards, not downwards. Another cause that recently is mentioned for all kinds of changes in the vegetation is the increase in nitrogen deposition, but this would mean that it would traditionally be more nitrogen-rich in the mountains than in the lowlands. But there is a much more obvious explanation if you understand the habitat of Foxglove and Foxglove vegetation.
At the beginning of the 20th century, a very large area of the Veluwe consisted of heathland, but after the end of the plaggen system, coniferous forests were planted over large areas. The remaining heathlands were infested by seeds from from the planted coniferous forests. As the forests grew, the Veluwe "heathland soil" slowly changed into a forest soil with lots of needle litter. Felling of the conifers created the ideal environment for the establishment for Foxglove and Climbing Corydalis and Epilobio-Digitalietum developed. This forestry system created an environment in the lowlands that occurs naturally in mountainous areas, and so Foxglove could descend into the lowlands. Thus, the occurrence of Foxglove vegetation on the Veluwe (and probably elsewhere in our country) is the result of the large-scale planting of forests some 150 years ago! Decay of the old farming system, rationalisation of agriculture and the release of land for coniferous forests thus have a striking and visible consequence in the mass occurrence of Foxglove. The strong grazing by red deer on the Veluwe not only prolongs the lifespan of this plant community ─ Foxglove is not eaten, but shrubs and tree seedlings are ─ but it also explains the low occurrence of Willowherb, Raspberry and Heath Groundsel that are eaten. Outside the Veluwe, these species are much more common in the vegetation recordings of the Epilobio-Digitalietum.
Just goes to show that something ordinary is not boring. In fact, there are no boring or uninteresting plants or vegetations at all. Every species or plant community has a story to tell about the place in question and can thus be a valuable source of knowledge about the landscape. The trick is only to "read" the story. Phytosociological vegetation science remains a very fascinating field of study!
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