(Above): Central parts of the aapamires are wet and often rather fertil, because the water in aapamire is minerotrophic - getting from the mineralsoil. This mire is however rather poor.
At the edges of aapa the peat is usually more dry and poor (pine mires). In this mire there are some small-scale hummock ridges.
The long hummock ridges and wide water ponds (= flarks) are common
in the northern aapas (Peräpohjola and Forest Lapland area).
Meltingwater has a great significance determining the formation and location of hummock ridges and flarks.
On the early winter - when the snowcver is thin - fhe strings jump out evidently.
The mean plant here on the strins is dwarf birch (Betula nana). - Savukoski 15.11.09.
At present the eutrophic mires are rare in North Finland (see eutrophic areas!).
They are drained for growing of forests. - There are many rare plant species in the calcareous fens.
Above): a computer "constructed" aapa with different types of mires (pine mires and flark areas with open fens).
Some typical mire plants growing at the front (from the left): marsh tea (Ledum palustre),
arctic cloudberry (Rubus chamaemorus) and bog rosemary (Andromeda polifolia).
On the edge of the flark bogbean (Menyanthes trifoliata) and cotton grass (Eriophorum vaginatum).
Subarctic flarkmire (belongs to aapamires) in Paatsjoki-river valley (Norway).
In the mire you can see the stones (peatlayer is thin!)
and small water
ponds (=flarks). Domiinant plant speciea is cotton grass (Eriophorum angustifolium).
The palsa bogs (palsa hummocs) are found between tundra and boreal zone all over
the northern regions, especially in the mountainbirchforest zone.
Winter frosts have a great significance in the formation of palsa hummocks: wind sweeps the snow off
from a small bog hummock, allowing ice formation in deeper peat layers, too. In summer the frozen hummock
does not melt entirely, (peat has a good insulation capacity...). The following winters the ice core continues to grow.
The vegetation on a palsa hummock is poor: dwarf shrubs and mire mosses.
The lower parts are often moister and richer in nutrients (sedge-dominated vegetation and flarks).
As time goes on - when palsa hummock is growing high enough - it begins to decay: peatclods on fringes split downward.
In this way the all hummock can defrost. The palsahummock on picture (above) has thawed in last summers (also in 2004)
because the blocks have rather abrupt sides. Is this indicating the greenhouse effect? Compare with another palsa picture!
