Excursies - Higher sandy soils - Drentsche Aa

13 important questions on Excursies - Higher sandy soils - Drentsche Aa

What does the Drenthe plateau consist of and when was this material deposited?

Boulder clay (keileem).
Deposited during the Saale glaciation, which is the one before the last ice age.

What material lays on top of the plateau and when was this deposited?

A layer of sand (dekzand).
From the most recent ice age (Weichselian glaciation).

Why is the esdorp landscape of Drenthe characterised by a relatively low density of villages?

Due to the presence of impermeable boulder clay in the subsoil, few locations were dry enough to build a village with a common arable field (es).
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Why are the villages located along the brook vallays?

Because there was access from the village to both the heathland on the plateau (collect turf sods) and the wet grasslands in the brook valleys.

What happened to the grasslands that were purchased by SBB?

Fertilisation has stopped and a grassland restoration method of mowing and removal of the hay (to remove excessive nutrients from the soil) was started.

What are the dominant and distictive plants under agricultural management?

1. Perennial ryegrass –Lolium perenne (Engels       raaigras)
2. Broad-leaved dock
   Rumex obtusifolius (Ridderzuring)

What are the dominant and distictive plants at sites with 30 years SBB management?

1. Sweet scented vernal grass - Anthoxanthum odoratum                  (Reukgras)
2. Woodrush -     Luzula campestris (Gewone veldbies)
3.  Broad-leaved marsh orchid
    Dactylorhiza majalis ssp majalis (Brede orchis) 
4. Sharp-flowered rush - Juncus acutiflorus (Veldrus)
    (partitions)
5. Common rush - Juncus effusus (Pitrus)
    (filled with marrow)

What does the grazing management (based on Frans Vera's ideas about natural park landscapes) lead to, and what are the ideas behind it?

It leads to open park landscapes, with some scurbs with thorns (that the herbivores don't eat).

The ideas behind it are rewilding and a more naturally dynamic landscape.

How were the drifting sands of the Gasteren dunes created?

By excessive sod removal on heathlands in the past, which allows the wind to erode the sandy subsoil at dry locations. The drifting sands are extremely poor in nutrients.

Where can drifting sands be found?

Drifting sand dunes usually lie;
1. on windblown sand deposits on the plateaus
, but here we also find them in
2. a former brook valley.

What are the differences between an upper course brook valley and a middle course brook valley?

Middle =
  • brook is broader
  • brook has more iron
  • higher groundwater level (due to high pressure from groundwater, end of keileem, it can escape)
  • richer and greener vegetation

What are seepage indicators?

1. Water sedge - Carex aquatilis (Noordse zegge)
2. Wood club-rush - Scirpus sylvaticus (Bosbies)

3. Marsh marigold - Caltha palustris (Dotterbloem)

What plant species are charactersitic of a brook valley grassland along a middle course?

1. Water horsetail - Equisetum fluviatile (Holpijp)
2. Marsh trefoil - Menyanthes trifoliata (Waterdrieblad)
3.  Ragged-Robin - Silene flos-cuculi
(Echte koekoeksbloem)

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