Strategies of Survival in Plants of the Fenoscandian Tundra

Abstract

Many arctic species originated outside the Arctic and some of their physiological responses are similar to those in temperate latitudes. Unique adaptations to the Arctic have rarely been found. The recent influx of other species has, however, broken down reproductive barriers and gene flow has been stimulated. In extreme arctic environments, selection forces driving evolution are mainly of the physical environment and plant interactions are positive. Elsewhere, biotic factors, such as herbivory, are important and plant interactions become negative through competition. Physical selective forces operate in winter and summer. Low winter temperatures rarely affect arctic plants, but snow depth and duration influence species distributions. Deep and persistent snow deforms plants and limits the period of resource acquisition. Cryptogams are common in such snow beds. Little or no snow cover exposes plants to abrasion by wind-blown particles and desiccation. In such fell-field sites, deciduous species and xerophytes, such as evergreen cushion plants, are common. Arctic summers are short and developmental processes are extended beyond one growing season, with perennials predominating. Cushion plants efficiently increase their temperatures above ambient, while evergreen and deciduous ericaceous dwarf shrubs coexist and have complementary strategies for intercepting radiation in a low canopy. "hndra soils are generally infertile and may be disturbed by freezehhaw cycles. Nutrients are conserved by recycling within shoots and between ramets within clones. Vegetative proliferation enhances the survival of young ramets, while physiological integration between ramets enables young ramets to forage across patchy environments. Negative plant-animal relationships are particularly important in the Subarctic. Periodic infestations of moth caterpillars defoliate large areas of mountain birch and stimulate increases in populations of their predators. Periodic population peaks of small rodents graze or kill much vegetation and they may moderate the dynamic structure of plant communities, as the plant species have different abilities to regenerate.

Transition zones between vegetation patches in a heterogeneous Arctic landscape: how plant growth and photosynthesis change with abundance at small scales

“…Similarly, the thick, long-lived, low-N leaves of E. hermaphroditum, with enclosed stomata leading to low transpiration and high WUE, are well adapted to dry, nutrient-poor sites experiencing winter abrasion and freezing desiccation (Shaver and Chapin 1991;Sonesson and Callaghan 1991), consistent with its relative abundance in patches with greater exposure and increased potential water and nutrient stress.…”

“…Our sampling of soil moisture was undertaken on a single date, several days after signiWcant rainfall, and so a much smaller gradient of moisture may occur at other times throughout the growing season. An alternative limitation to growth may instead be winter exposure damage, which was not possible to quantify in our study (Sonesson and Callaghan 1991).…”

“…nana patches could therefore be partially due to the positive eVects of shelter outweighing the negative eVects of shading in taller vegetation, as well as the increase in water and nutrient availability. Presumably, the decline in growth in forb and V. uliginosum patches would then indicate the part of the transect where positive eVects of shelter no longer outweigh the negative eVects of shading; this is consistent with net positive eVects of facilitation being uncommon where increased competition within a closed canopy cancels out facilitation (Sonesson and Callaghan 1991;Totland and Esaete 2002).…”

Variability of polar scurvygrass Cochlearia groenlandica individual traits along a seabird influenced gradient across Spitsbergen tundra

“…data). It is therefore possible that persistent snow cover may have deformed plants and/or shortened the growing season and limited the period of resource acquisition (Sonesson and Callaghan 1991). Nonetheless, no snowrelated changes in vegetation morphology were seen within the topographically similar area that was situated along Gnålberget slope away from the colony.…”

Comparative analysis of annual rings of perennial forbs in the Loess Plateau, China

“…Under stressful growing conditions, plants are usually compelled to extend individual life spans as a result of the reduced growing rate (Sonesson and Callaghan, 1991;Molau, 1997). The growth of forbs species in the Loess Plateaus is strictly limited by the lower level of resource availability, including water resources, organic carbon and total nitrogen and phosphorus stocks (Wang et al, 2010;Liu et al, 2013).…”