Background information on the flora of Iceland

Any visitor of Iceland will admire the beauty of the rugged landscapes of Iceland. One may however, wonder why in so many regions of Iceland plant life is so poorly developed. Let me first explain what I mean with "poorly developed".
It means:
* The number of species is low;
* Practically no forests, shrubs stay low;
* Many desert-like regions.
It certainly does not mean that it is not interesting!

Low species numbers
The very first glacial period of the Pleistocene meant the end of conifer trees (except Juniper bush) on Iceland. Before the first glacial period they were present just like many broad-leaved tree species, suggesting that warmer climates than today existed before the glacial periods. The glacial periods has led to extinction of many plant species in Europe because (unlike in the America's) the main mountain ridges (Pyrenees, Alps, Carpathians) run east-west, meaning plants got trapped as vegetation zones had to move southward. After a glacial period it takes a while for plants to return. Islands of coarse can be difficult to reach for some species (depending on dispersal techniques). Iceland lies so far from both Europe and North America that resettlement after the last glacial period is one reason that the number of species is low. Some species have survived the glacial period in Iceland on what is believed to be Nunatak refuges. These are mountains which rise above the ice-cap. Today the Esjufjöll within the Vatnajökull is an example of such a refuge. It is believed that some 80 plant species can be found here. An example of a plant believed to have survived the glacial period is the Upright Lousewort ( Pedicularis flammea). Other plants made their return from the south. Pollen research for example show that the Dwarf Birch ( Betula nana) reached the Scottish north coast some 13 thousand years agobut reached Iceland some 10 thousand years ago.

Practically no forests, shrubs stay low
When the first Viking settlers came to Iceland they found an island that was covered for about 1/3 with birch woods. Today only 1 or 2 percent of the island's surface is covered by downy birch trees ( Betula pubescens). These birches are rarely higher than 2 meter tall, meaning one can hardly say they are trees (the specie is also present on the British isles and continental Europe where it generally grows up to 20 meter!) . The settlers were responsible for large scale felling of birches mainly for clearing for pastures and for fuel. They were however not aware that growing conditions on Iceland were far less favorable than in mainland Scandinavia and the soils far more susceptible to erosion. Today Icelanders are fully aware that Iceland needs to be reforested where possible. Many exotic species have been tested and some are used for forest planting. However, these plantations are still quite small. Erosion is still a major problem and other plants are used to try to tackle the problem. The two most used are the nootka lupine ( Lupinus nootkatensis) and Lyme grasses (Leymus spp). In the highlands, the latter seems to be the only specie that can bring some relief.

Many desert-like regions
There is not one reason why there are such vast areas of sparsely vegetated areas.
> Mountain screes: When traveling through Iceland one will see many mountain and hill slopes which are completely made up of coarse pebbles. These slopes can be quite steep but are completely void of plant life. These are the result of fast frost weathering where freezing water breaks up porous rock material.
> Aridity: It is hard to believe that Iceland suffers from arid conditions, being in the wet and stormy region of the north Atlantic. Yet this is in some regions a major factor. The reason is the geographical location of the ice caps and glacials. They are located off the south coast leaving either a small lowland fringe along the coast (under Vatnajökull and Mýrdallsjökull/Eyjafjallajökull) or a larger lowland area (south-western Iceland). Due to prevailing south-westerly's rain and snow flushes out in the south and on these ice caps (1500 or more mm per year) whilst north and northeast of the ice caps, esp . the huge Vatnajökull ice cap the air has become very dry (less than 400mm per year). No wonder that many desert-like regions can be found in the areas just north of Vatnajökull. A typical plant that generally grows all over Iceland in poor conditions but is quite conspicuous in these regions is the Moss campion ( Silene acaulis). The aridity also means that in many highlands during winter there is little snow cover. This can lead to freezing dust-storms which can be very harmful to plants trying to survive in these eroded areas. Where snow beds are formed in sheltered places plants can survive the winter conditions in the highlands. In the lowlands conditions are very different because winters here are exceptionally mild and wet (especially in the south) compared to regions in similar latitudes (like Siberia and Alaska).
> Volcanic activity: Volcanic activity is a major contributing factor why many regions appear like deserts. The volcanic ashes are extremely difficult for plants to settle in due to lack of some minerals, lack of organic substances and poor water retention. Given the problems of the winter climate (see above) only the hardiest individuals can survive. Wherever rocks are present the Tufted Saxifrage ( Saxifraga caespitosa) is one of those. On the sandy - ashes one can often find the Sea Campion ( Silene uniflora) growing in circular shapes over these grounds.

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