In flat areas water circulates along winding streams and soaks the earth along their banks, creating a marshy area known as wetlands.
Phreatic water or rainwater?
The wetlands of the Pyrenees are usually fed by phreatic water that seeps into them from springs and streams. However, in mountainous Atlantic climates where it rains very often, wetlands formed by rainwater can also be found.
Wetlands that create mosaics
The environments of the wetlands are very heterogeneous, which means that different natural communities grow there, creating a mosaic effect that changes from one place to another. The vegetation communities differ depending on a set of ecological factors that include the flooding regime, the acidity and the nutrients in the water.
Peat bogs that reach the pyrenees
In the wetlands of very rainy places the soil is cleaned frequently and is always waterlogged. Leaves and roots have difficulty decomposing in these environments and so they accumulate in the form of peat. In some places in the north of Europe the peat can be several metres thick and the deposits they make are called peat bogs. These are extremely unusual, however, in the Pyrenees.
Mosaic of valley bottom mires of a small lake (communities of Carex rostrata, C. limosa, populations of Scirpus cespitosus acidophiles, cotton plants, etc.) conditioned by the depth of the water table.
Photo: A. Ferré
Black pines are often found in wetlands but rarely do they manage to form bog woodlands like the ones in the Trescuro lakes.
Photo: E. Carrillo
The calcium-rich wetlands of deergrass (Scirpus Cespitosus)
Easy to identify due to the high abundance of deergrass and the frequent occurrence of bird’s-eye primrose (Primula farinosa), German Asphodel (Toﬁeldia calyculata) and large-flowered butterwort (Pinguicula grandiﬂora), which carpet the banks of the wetland streams, always in places where calcium-rich water circulates. It is very common in the Pyrenees.
The cross-leaved heath
This grows in the less saturated areas of the wetlands and is easily visible when the cross-leaved heath (Erica tetralix) blooms. In the Pyrenees it only occurs in the western part in very rainy climates and in Catalonia it is only found in the Molières valley.
The sphagnum hummocks
These cushions of peat moss (a type of moss that can retain water like a sponge) rise above the flat wetlands. Plants typical of less saturated areas like common sundew (Drosera rotundifolia), a small insectivorous grass, may grow on the top of the peat moss.
How to survive up to your neck in water and with few nutrients
The soil of the wetlands is always soaked with water, which makes it difficult for roots to breathe. The plants that thrive in these environments have a spongy texture that allows gases to circulate around their leaves, roots and rhizomes.
Common sedge (Carex nigra) and a piece of common sedge root with empty spaces that carry air.
Peat moss (Sphagnum) and a close-up of large, dead cells full of water (white), which ensure that the live cells (green) around them do not dry out.
The wetlands are very poor in nutrients, so some of the plants that grow there have viscous leaves to trap small insects and obtain nitrogenated nutrients.
Drosera longifolia, with glandular hairs that trap and digest small animals.
Photo: C. Pedrocchi