Vegetation types: Major vegetation types in Iceland
Sparsely vegetated land
|Gravelly flats on the Biskupstunga rangeland. Photograph: Sigurður H. Magnússon.
Land where vegetation cover is 50% or less is often collectively referred to as sparsely vegetated land. Much of Iceland is non-vegetated or only sparsely vegetated, although many lowland regions are being slowly reclaimed. Sandy flats along major rivers and other alluvium account for a significant percentage of sparsely vegetated lowland areas. There is very little vegetation cover in much of the Icelandic highlands, which see little change even with the passage of time. Mosses and lichens are much more common in sparsely vegetated mountainous areas than in sparsely vegetated lowland areas.
Vegetation in these regions is thin and scattered and tends to grow in small tufts and tussocks in sandy or rocky soil. Gravel, stones, sand, clay or boulders cover the ground. The number of species and their composition varies depending on local conditions. Species frequently found in such areas include moss campion (Silene acaulis), thrift (Armeria maritima), alpine mouse-ear (Cerastium alpinum), common mouse-ear (Cerastium fontanum), sea campion (Silene uniflora), northern rock-cress (Arabidopsis petraea), slender bedstraw (Galium normanii), wild thyme (Thymus praecox ssp. arcticus), arctic riverbeauty (Chamerion latifolium), dwarf willow (Salix herbacea), woolly willow (Salix lanata), saxifrages (Saxifraga spp.), field horsetail (Equisetum arvense), lyme-grass (Leymus arenarius), fescues (Festuca spp.), wood-rushes (Luzula spp.) and bentgrasses (Agrostis spp.). Revegetation is being attempted on many gravelly flats and other sites where vegetation cover has been lost, either for exploitation purposes or in order to combat erosion.
Snowbed vegetation is found in hollows and depressions where snow collects in winter and takes a long time to melt, meaning that the growing season is very short. The most common vascular plants to grow in snowbeds are dwarf alpine willow (Salix herbacea), alpine arctic cudweed (Omalotheca supine), creeping sibbaldia (Sibbaldia procumbens), alpine willowherb (Epilobium anagallidifolium), alpine speedwell (Veronica alpina), hare's-foot sedge (Carex lachenalii) and mossy mountain-heather (Harrimanella hypnoides). A number of the hardiest grassland species also grow in snowbeds. The most common moss species are Racomitrium spp. and Polytrichum sexangulare. Anthelia liverworts are also common in snowbeds, where they are sometimes the dominant species, forming a continuous light grey carpet on the ground.
Moss heath vegetation
|Moss heath by the Skaftá River. Photograph: Borgþór Magnússon.|
Mosses account for more than half of all vegetation cover in Iceland and are particularly dominant in areas where there is little soil and growing conditions are unfavourable. Moss heath is common both in lava fields and at higher altitudes, where vascular plant growth is generally sparse. Vascular plant species found on moss heath include stiff sedge (Carex bigelowii), fescues (Festuca spp.), bentgrasses (Agrostis spp.), Bellard's kobresia (Kolbresia myosuroides), three-leaved rush (Juncus trifidus), willows (Salix spp. including Salix herbacea), crowberry (Empetrum nigrum), bog bilberry (Vaccinium uliginosum), heather (Calluna vulgaris), thrift (Armeria maritima) and alpine bistort (Bistorta vivipara).
|Lichens are clearly visible on this patch of heathland at Ölkelduháls in Southern Iceland. Photograph: Ásrún Elmarsdóttir.|
Heathland is dry and often hummocky, although hummocks can vary somewhat in size. A number of vascular plant species types can be dominant on heathland, for example grasses, heathers or dwarf shrubs. Vegetation is unevenly continuous. Common vascular plant species on Icelandic heathland include Bellard's kobresia (Kolbresia myosuroides), three-leaved rush (Juncus trifidus), stiff sedge (Carex bigelowii), mountain avens (Dryas octopetala), crowberry (Empetrum nigrum), bog bilberry (Vaccinium uliginosum), dwarf birch (Betula nana) and woolly willow (Salix lanata). Lichens can also be dominant on heathland.
Forb meadow and grassland vegetation
|Forb meadow in Heiðmörk. Photograph: Sigurður H. Magnússon.|
Forb meadows and grasslands tend to be species-rich; dicots and grasses account for most plant life. This type of vegetation grows where the soil is fertile and sufficiently damp. In Iceland, such conditions are mainly found in hollows and depressions on sunny hillsides where vegetation is protected by snow over the winter. Grasses dominate grasslands, which may be quite flat and dry. Disused hayfields, where dandelions and buttercups abound in early summer, are an example of land where forbs and grasses are found in almost equal numbers.
A diverse range of grasses and flowering plants typify such areas, although dwarf shrubs and ferns are not uncommon. Forb meadow and grassland species include viviparous sheep's-fescue (Festuca vivipara), bentgrasses (Agrostis spp.), sweet vernal-grass (Anthoxanthum odoratum), tufted hair-grass (Deschampsia cespitosa), wood crane's-bill (Geranium sylvaticum), hairy lady's-mantle (Alchemilla filicaulis), meadowsweet (Filipendula ulmaria), meadow buttercup (Ranunculus acris), cow parsley (Anthriscus sylvestris), garden angelica (Angelica archangelica), creeping sibbaldia (Sibbaldia procumbens), alpine lady's-mantle (Alchemilla alpina), dwarf willow (Salix herbacea), arctic willow (Salix arctica), crowberry (Empetrum nigrum), bog bilberry (Vaccinium uliginosum) and male-fern (Dryopteris filix-mas). Numerous species often grow within a relatively small area. Moss species do not tend to be particularly diverse in forb meadows and grassland, although mosses can be quite noticeable under the herbage layer. Dog lichens (Peltigera canina) are the most common lichen species on grassland and in forb meadow.
Wood- and shrubland vegetation
|Understory vegetation in an old birch forest at Hallormsstaður in Eastern Iceland. Photograph: Ásrún Elmarsdóttir.|
Birch and tea-leaved willow are the main species of tree found in Icelandic woodlands and shrublands. Birch is the only species of tree to form continuous natural woodlands in Iceland, although the occasional rowan or aspen can be found growing in among the birch trees. Mosses and lichens often abound in forests, both as undergrowth and epiphytes growing on trees.
Understory vegetation varies greatly depending on growing conditions: how closely the trees grow together, how fertile and moist the soil is and how high above sea level the forest is situated. In Iceland, grazing sheep have also been an important factor in determining the nature of understory vegetation. Grasses and heathers often grow on the forest floor of a birch forest, sometimes joined by a mix of flowering plants. Where growing conditions are best, flowers, grasses and dwarf birches are typically dominant. The most common moss species in birch woodlands and shrublands are glittering wood-moss (Hylocomium splendens), springy turf-moss (Rhytidiadelphus squarrosus), shaggy moss (Rhytidiadelphus triquetrus) and Sanionia uncinata, while the most common lichens are dog lichens (Peltigera canina).
A fair number of alien tree species have been planted in Iceland, mainly in connection with reforestation efforts. Among these are the larch (Larix spp.), lodgepole pine (Pinus contorta var. latifolia), Sitka spruce (Picea sitchensis), mountain pine (Pinus mugo), black cottonwood (Populus trichocarpa) and feltleaf willow (Salix alaxensis). Understory vegetation often differs from that found in birch woodlands and is generally less species-rich – less light reaches the floor of a coniferous forest, where trees are taller and have a greater leaf area. By thinning out such forests, one can increase the amount of light that reaches the forest floor, which can in turn increase the species diversity of understory vegetation. Alien tree and bush species will certainly spread beyond planted forests in future; it remains to be seen how aggressive these species will prove in the wild.
|Fellaflói by Áfangafell on the Auðkúluheiði heath. Photograph: Borgþór Magnússon.|
Wetland vegetation grows in areas where soils are damp or water-saturated: fringes (moist land), sloping fens and level fens. Where the water level is high enough, one finds aquatic vegetation. Wetland species include narrow small-reed (Calamagrostis stricta), fescues (Festuca spp.), arctic rush (Juncus arcticus), common cottongrass (Eriophorum angustifolium), thread rush (Juncus filiformis), common sedge (Carex nigra), Lyngbye's sedge (Carex lyngbyei), bottle sedge (Carex rostrata), woolly willow (Salix lanata), arctic willow (Salix arctica) and marsh horsetail (Equisetum palustre).
Wetland vegetation is quite common in Iceland and is found in both highland and lowland regions. Wetlands are believed to have once accounted for around 8–10% of Iceland's surface area. Large swaths of lowland fen have been drained for cultivation purposes over the last several decades, however. In some areas, up to 30–40% of cultivatiable fens have been drained. Although highland wetlands have for the most part remained undisturbed, dams for large power plants have swallowed some of these wetlands.
Groundwater levels largely determine the nature of wetland vegetation, although altitude also has a part to play. Sedges, grasses and other monocots typically characterise wetlands, although arctic rush, bog billberry, willows and dwarf birches can dominate the wetland landscape in places. Other dicots do grow in wetlands, but these are rarely dominant. A number of mosses also thrive in wetlands. Lichens are seldom seen, however, with the exception of dog lichens on the tops of tussocks.
The boundaries between various types of wetland are often less than clear, and a number of different terms can be used to describe them: swamps, bogs, mires and marshes. In classifying wetlands, we make a simple distinction between sloping fen, where the terrain is gently sloping and water flows through the area but does not reach up to the turf, and level fen, where water is stagnant and reaches up to or flows over the turf. Tussocks are not common in level fens. Sloping fens, in contrast, are generally quite hummocky, and there is frequently a noticeable difference between the vegetation found on hummocks and that growing in between them. Quagmires, found mainly on mountain slopes where water springs up. They can often be seen from great distances, visible from afar as yellow-green patches of vegetation. While abundant in all wetlands, mosses are particularly noticeable in quagmires.
Mare's-tail and northern bur-reed in a pool at Seltún in the Krísuvík area. Photograph: Ásrún Elmarsdóttir.
Lake and pond vegetation in Iceland is somewhat unusual in that plant life is often abundant but made up of only a few species. Vegetation is found mainly in shallow water, for example sheltered inlets and coves. The most noticeable floating aquatic plants are often various pondweed species, such as red, broad-leaved and various-leaved pondweeds (Potamogeton alpinus, natans and gramineus). The leaves of these species float on the surface of the water, largely covering it, while flower spikes rise up into the air. The flower spikes of bur-reeds (Sparganium spp.), alternate water-millfoil (Myriophyllum alterniflorum), slender-leaved pondweed (Stuckenia filiformis), foxtail grasses (Alopecurus spp.) and some water-starworts (Callitriche spp.) often stand up above the water's surface, although the stems and leaves of these plants are submerged and form a tangled underwater mass. In large lakes such as Lake Mývatn, this vegetation often grows to be quite tall and dense. A continuous belt of tall plants often grows close to land; these plants include bottle sedge (Carex rostrata), Lyngbye's sedge (Carex lyngbyei), common spike-rush (Elocharis palustris), water horsetail (Equisetum fluviatile) and mare's-tail (Hippuris vulgaris). Thread-leaved water-crowfoot (Ranunculus confervoides), arctic buttercup (Ranunculus hyperboreus), common mudwort (Limosella aquatica), orange foxtail (Alopecurus aequalis) and whorl-grass (Catabrosa aquatica) tend to grow only in the shallows, although they do sometimes extend out to a depth where they are fully submerged. Here, they are joined by awlwort (Subularia aquatica), spring quillwort (Isoëtes echinospora), shoreweed (Littorella uniflora) and the rather unusual horned pondweed (Zannichellia palustris). This benthic growth often forms a continuous carpet that covers the bottom of the lake or pond. Aquatic mosses and green algae are also common in the benthos.
|Sea sandwort on Surtsey. Photograph: Erling Ólafsson.|
Coastal vegetation tends to be quite meagre and discontinuous, as there is generally little in the way of soil beyond gravel and sand. There are no proper beaches in areas where cliffs reach all the way to the sea, and ocean waves are in many places so aggressive that land plants have little opportunity to establish themselves on the few narrow strips of beach that are to be found. Coastal vegetation flourishes best in calmer fjords and bays.
The most common coastal species include sea sandwort (Honckenya peploides), oyster plant (Mertensia maritima), oraches (Atriplex spp.) and lyme-grass (Leymus arenarius). Scots lovage (Ligusticum scoticum) and sea rocket (Cakile maritima) favour the southern and western coasts. Sea cliffs and boulders are home to a number of plant species, including northern saltmarsh-grass (Puccinellia coarctata), common scurvygrass (Cochlearia officinalis), sea plantain (Plantago maritima), roseroot (Rhodiola rosea) and garden angelica (Angelica archangelica). Green algae grow at the tide line or right by the water's edge. Brown algae are more common where there are boulders, these being mainly wrack species such as bladderwrack (Fucus vesiculosus) and Fucus distichus. In the zone extending from the low tide line down to a depth of 20–30 m, one finds both red and larger brown algae: sugar sea belt (Laminaria saccharina), fingered tangle (Laminaria saccharina) and dabberlocks (Alaria esculenta). These species often form whole forests of algae on the ocean floor. These forests peter out below 30 m. Most species growing at these depths are red algae.
Vegetation in flat coastal areas, such as lowlying marshland, where the ocean generally reaches at high tide, is often continuous – unique communities of vascular plants where northern saltmarsh-grass, creeping bent (Agrostis stolonifera), lesser saltmarsh sedge (Carex glareosa), Hoppner's sedge (Carex subspathacea) and Mackenzie's sedge (Carex mackenziei) tend to be the dominant species, along with a number of dicots such as sea plantain, sea arrowgrass (Triglochin maritima) and saltmarsh stitchwort (Stellaria humifusa). The one vascular plant species in Iceland that grows submerged in the sea or below the tide is eelgrass (Zostera angustifolia), found at a number of locations in Iceland, although it is most common not far off shore on the clay seabed of Breiðafjörður Fjord.
|Clumps of moss at a geothermal area on the Reykjanes Peninsula. Photograph: Ásrún Elmarsdóttir.|
The species composition of vegetation in geothermal areas often differs from that which grows in areas where the ground is cold. Such vegetation is typically referred to as hot spring or geothermal vegetation, i.e., plant communities where their composition, structure or production are shaped by geothermal heat or related factors. Where geothermal heat is carried to the surface, low acidity tends to characterise the soil, and the concentration of minerals and other chemical compounds and elements is different from that of other ecosystems.
A number of “geothermal” species have been identified in Iceland, i.e., species that thrive only in geothermal areas. Some of these species are very rare. Examples of vascular plant species that grow only in geothermal areas include small adder's-tongue (Ophioglossum azoricum), marsh cudweed (Gnaphalium uliginosum), water speedwell (Veronica anagallis-aquatica), jointed rush (Juncus articulatus), water mint (Mentha aquatica), water pygmyweed (Tillaea aquatica) and marsh pennywort (Hydrocotyle vulgaris). A number of other species can grow both in non-geothermal vegetative communities and in the unique conditions created by geothermal heat: wild thyme (Thymus praecox ssp. arcticus), creeping bent (Agrostis stolonifera), frog rush (Juncus ranarius), chickweed willowherb (Epilobium alsinifolium), greater plantain (Plantago major), procumbent pearlwort (Sagina procumbens) and autumn hawkbit (Leontodon autumnalis). Mosses are often common in geothermal areas, particularly the geothermal species Archidium alternifolium, Riccia beyrichiana, Campylopus flexuosus, Campylopus introflexus and Atrichum angustatum. Geothermal vegetation can vary significantly from site to site and is influenced by factors such as altitude.
Sources: Eyþór Einarsson. 2005. Flóra og gróður Íslands. In ÍSLANDSATLAS (pp. 18-23). Reykjavík: Edda.
Hörður Kristinsson. 2010. A Guide to the flowering plants and ferns of Iceland. Reykjavík: Mál og menning.