Vegetation on Svalbard
Plant life on Svalbard exists under marginal conditions, and it is here we find the most northerly types of Arctic tundra. A general trait of the vegetation is that the plants are low in height and often grow by creeping. Despite the challenging conditions, the vegetation exhibits large variation in form and function. Herbs, grasses, sedges, reeds, creeping dwarf shrubs, some ferns (such as horsetails) and mosses and lichens all grow here.
The plants on Svalbard differ in many of their characteristics; for example, they may be evergreen (Arctic bell-heather) or deciduous (polar willow), woody (Arctic bell-heather) or herbal (alpine bistort), and they may have roots (all vascular plants) or not (mosses and lichens). The plants' characteristic traits help determine the types of areas they grow best in, how they respond to growing conditions (impacts), and what types of disturbances they withstand (threats and vulnerability).
The some 160 plants species, 380 mosses and 600 lichens found on Svalbard exist in many different combinations, often referred to as vegetation types, or plant communities. The terrain, substrate type, humidity, exposure to wind and frost, summer temperatures, access to nutrients and how the area is used by grazing animals are among the most significant factors for determining the type of vegetation that grows at a given site. In addition, the plants also affect their own surroundings, and the interactions between plants contribute to the range of impact factors.
On mounds and ridges exposed to wind and frost, we find, for example, vegetation dominated by mountain avens, in community with purple saxifrage or lichens. On slopes, with somewhat more snow cover, we find Arctic bell-heather or grasslands with, for example, alpine meadow-grass. On flatlands and open plains with moderate snow cover, various types of moorland vegetation occur, composed of Arctic wood-rush, polar willow and mosses and lichen. Places where the snow lies longest are referred to as snowbeds, and such hollows are habitats for mosses and many herbs, such as mountain sorrel. On flat areas, with significant seepage, the mosses grow well. It is here that moss-dominated wetlands are created. On drier, slightly sloping substrates, we also find grasses (e.g. polar foxtail), and ferns (e.g. common horsetail), while sedge species, such as Hoppner's sedge and polar white cottongrass, are common on wetter flatlands. Another type of flat ground are salt meadows, where the salinity determines the prevalence of plants. Fertilizer creates large differences in productivity in Svalbard, notably below bird cliffs, where many different herbs and grasses grow and productivity reaches a high-arctic peak. The polar desert is found on upland terrain and in the north of Svalbard, featuring only sparse vegetation between stone and gravel.
Depending on the choice of spatial scale and methodology, vegetation can be divided into many types and configurations; field surveys and remote sensing  naturally yield somewhat different descriptions of the vegetation. The main differences, however, are independent of methodology and follow the overarching growing conditions.
One fascinating trait of the plants on Svalbard is that, even though they grow slowly and the individuals are long-lived (from several years to hundreds or even thousands of years, studies show that the plants are able to closely respond to the growing conditions.
Temperature is a decisive factor for high-arctic plants. The polar willow is one of the species that closely tracks summer temperatures, both in its annual secondary growth (through the creation of annual rings, like trees) and in its primary (shoot) growth. The other common plants' summer production also tracks July temperatures remarkably closely. It follows from this that, even if the annual growth is small, the plants have a potential to change over time.
Most of the plants are also important food sources for some of Svalbard's herbivorous animals. The Svalbard reindeer, Svalbard rock ptarmigan and different goose species enjoy a varied supply of new shoots and flowers in spring, and grass and herb stems in summer; and some, such as reindeer and geese, also eat mosses. The activity of the grazing animals also naturally affects the plants.
Some of the impacts of grazing on vegetation are relatively well-known; geese may grub up their favourite food (such as alpine bistort) by the roots, and this activity breaks up moss cover on the tundra in addition to removing plant material. In the first instance, this can result in a change from moss to grass- or sedge-dominated vegetation or clearings without vegetation, and in the most dramatic cases these patches appear to remain clear. The vegetation itself helps manage developments in the event of cessation of grazing: among the many vegetation types that are grazed by geese at different times, the most humid have the best resistance and regeneration. Likewise, changes in the main vegetation type have been described as a result of the impact of reindeer, including eating, trampling and fertilizing. For example, a single location, given fundamental growing conditions that are not overly different, can change from being dominated by woody plants to containing mostly grass. The grazing impact of ptarmigan has been little studied on Svalbard, but many plants (such as the alpine bistort in summer and buds and dry inflorescence in winter) are naturally an important resource for ptarmigan. We know less about the combined effects of the grazing animals, but it is conceivable that areas regularly grazed by several of the animals are subject to significantly different grazing impacts than places that are mostly used by only one of the grazers. In line with the plants' response to temperatures, vegetation responds to grazing from year to year, and fairly large changes in plant dominance may occur on an annual time scale.
It is well-known that the plants' proximity to each other is significant for the configuration of vegetation in general, for example, the mosses keep the ground moist and cool. This may benefit other species which grow well in damp places but, equally, dense moss cover can prevent new shoots from growing. The net effect of plant communities is a topic for present-day research, and may acquire even greater significance if the environment otherwise continues to change.
Six red-listed habitats have been described on Svalbard: Arctic permafrost-wetland, Arctic steppe, poor fen, bird cliffs, polar desert and hot spring , each of which has its own characteristic vegetation. Work is in progress to map and protect red-listed plant species, including moonwort and tundra birch. Most of the 54 red-listed vascular plants on Svalbard are herbs, grasses or sedges, whereas there are fewer woody plants. The natural explanation of this is that there are in general far fewer woody species growing on Svalbard than representatives from the other groups. Climate change, human traffic, random events such as landslides or floods and grazing are potential threats to red-listed plant species.
Svalbard's climate is in transition and climate change is considered to be one of the greatest threats to Svalbard's ecosystem in general. However, warmer temperatures alone rarely appear to be enough to increase plant growth dramatically, in contrast to research results from low-arctic areas where the tundra is locally being overgrown by shrubs. On the other hand, warming combined with better access to water and/or food may be expected to increase plant growth, to the extent that community-level changes in the vegetation may also be expected in the High North, even if this will happen more slowly. The plant groups which grow rapidly (herbs, grasses) may be expected to have greater potential to increase their dominance than the woody species currently established on Svalbard, since these have relatively slower growth rates. The impact of grazing animals on Svalbard may to some degree be expected to favour grasses, for example, which generally withstand grazing better than plants such as dwarf shrubs. The combined impacts of climate change and varying or altered grazing animal populations are, however, very difficult to predict.
Some vegetation types on Svalbard are locally vulnerable to trampling, and this applies in particular to the wettest types and slopes holding loose material. Since the growth rate is generally slow, trampled vegetation will have a very long regeneration period, and in some cases will not regrow. Human activity also brings with it plants not previously found on Svalbard, and there are a number of introduced species in limited locations. It is uncertain how quickly these new arrivals will find suitable conditions on the archipelago.
Long time series and other studies that seek to distinguish the effects on vegetation of climate, grazing animals and other impact factors, such as introduced species or trampling, are accorded high priority as tools for understanding vegetation patterns and changes by the many research bodies which are studying plants on Svalbard. Monitoring of vegetation is included in MOSJ (Environmental Monitoring of Svalbard and Jan Mayen) and COAT (Climate-Ecological Observatory for Arctic Tundra).
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