Fens
What (over)lives in the nutrient-poor fens?
Especially in the central heathland area of the Grenspark, there are many beautiful fens such as Stappersven, Groote en Kleine Meer, Putse Moer and Drielingvennen. These fens arise when rainwater remains in bomb craters or on an impermeable layer in wind-blown dune pits. All the ponds in the Grenspark are fed exclusively by rainwater: you can read about the consequences this has for the flora and fauna below.
Due to the high altitude of the fens compared to the surroundings, no water flows into the area and rainwater is the only 'nourishment' of these fens. The water in the fens is therefore nutrient-poor and acidic. This has major consequences for plants and animals: only 'specialists' can live in them. The unique character of the fens in the Grenspark is cherished, but safeguarding it is no easy task. The biggest challenges are desiccation and nitrogen deposition.
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Flora
From peat moss to multi-stemmed water reeds: these plants can be found in the fens of the Grenspark.
Peat moss, knolrus and the many-stemmed water rush are the pioneers that manage to survive in the fens. They are well adapted to the acid and nutrient-poor environment and even thrive in it. Peat moss can also be found along the wet banks, often together with white and brown beakwort, little or round sundew and sometimes the rare marsh woad. Peat moss beautifully represents the transition from banks to the wet heath around the fens.
Different types of fens, different vegetation
There are different types of fens. There are ponds with a bare sandy bottom, such as the Groote Meer. Water lobelia, floating water plantain, shore weed, submerged marsh fern and rush fern grow here. They are all plants of the rare shore weed alliance as this group of plants - which often live near each other - is also called. They deteriorated due to drying out, acidification and enrichment of the fens with (too) nutrient-rich water. When these fens become dry for a longer period of time, this vegetation disappears and other, more common species take its place.
Fauna
The water of the fens offers a unique habitat for small aquatic animals and various birds.
Rare amphibians and 30 species of dragonflies
All kinds of aquatic animals live along the fens. In the case of the bog swimmer, this is perhaps not so surprising, but you can also see the yellow-billed water beetle here, as well as water spiders. A number of rare amphibians can also be spotted here, such as the moor frog, the natterjack toad and the finned newt. For them, the fens are excellent breeding grounds. Visiting the Grenspark on a beautiful summer's day? Then chances are you will see dragonflies and damselflies hovering above the water surface, ready to reproduce. Did you know that there are many species of dragonflies? Almost 30 different species are already found in the Grenspark, such as the moon damselfly, coral damselfly, tawny armoured damselfly, four-spot, black haired dragonfly and spotted damselfly. How many different species do you manage to spot?
Flying buffet
Birds also stay in the fens. Many duck species - common teal, common teal, tufted duck, shoveler and shelduck - find an excellent resting or nesting place in the fens. Waders can be seen here looking for food on the dried-up banks. Coming in August? Chances are you will spot swallows then. Hundreds of them come to the Grenspark to feed on mosquitoes before migrating to Africa. During migration or in the winter period, you will also see other birds: goldeneyes, pintails, gadwall and widgeons, for example. Occasionally, you will also see a black-necked grebe or little grebe in the fens of the Grenspark. These breeding birds are less common here and depend on slightly nutrient-rich water to raise their offspring: it is precisely these ponds that often dry up in summer.
Fens management
A number of heathland ponds with bare sandy bottoms used to have rich vegetation with valuable fen vegetation, including the species of the bankweed alliance mentioned above. As described earlier, these plants got more difficult in recent decades. Enrichment with too nutrient-rich water is a cause, as is desiccation, acidification or a combination of these causes. The aim is to bring back the original rare flora of these fens, but this sometimes requires drastic measures.
Wasven
The Wasven at Kortenhoeff used to be used to wash the sheep before shearing, hence the name. It was also used to wash clothes, bedding and wool. As a result, the naturally nutrient-poor water regularly became (limitedly) 'polluted'. Thus, the water became slightly enriched, less acidic and plants of the shore weed association grew. Later, however, the estate was intensively farmed and as a result - due to enrichment and acidification - these typical plants disappeared completely. The desired nutrient-poor situation was restored in 1989 by ploughing down the fen banks and cleaning up the fen. Since then, they have been showing up on the banks again: sundew, marsh deer hay, meadow hogweed, water purslane and, occasionally, the rare pondweed.