Plant recruitment in the High Arctic: Seed bank and seedling emergence on Svalbard

Abstract

. Composition and density of the soil seed banks, together with seedling emergence in the field, were examined on Svalbard. 1213 soil samples were collected from six drymesic habitats in three regions representing various stages of colonization from bare moraines to full vegetation cover and spanning a range of typical nutrient and thermal regimes. Of the 165 vascular plant species native to Svalbard, 72 were present as mature plants at the study sites and of these 70% germinated seed. Proglacial soil had 12 seedlings per m2, disturbed Dryas heath 131, intact Dryas heath 91, polar heath 715, thermophilic heath 3113, and a bird cliff 10437 seedlings. Highest seed bank species richness was at the thermophilic heath (26 species). Seedlings of 27 species emerged in the field, with fewer seedlings in disturbed habitats (60 seedlings per m2) than in intact Dryas heath (142), suggesting that an absence of ‘safe sites’ limited seedling establishment in disturbed habitats. Measurement of seedling emergence in the field increased awareness of which species are able to germinate naturally. This may be underestimated by up to 31% if greenhouse trials alone are used, owing partly to unsuitability of greenhouse conditions for germination of some species and also to practical limitations of amount of soil sampled. Most thermophilic species failed to germinate and some species present at several sites only germinated from the thermophilic heath seed bank, suggesting that climate constrains recruitment from seeds in the High Arctic.

Germinating seeds or bulbils in 87 of 113 tested Arctic species indicate potential for ex situ seed bank storage

“…richardsonii, Minuartia biflora, Pedicularis dasyantha var. dasyantha, and Saxifraga platysepala, germinated to low percentages from seeds or seed banks in other studies from Svalbard (Eurola 1972;Cooper et al 2004;Müller et al 2011), indicating that the lack of ripe seeds or germination in our study may be due to, for example, annual variation. Similarly, for Arctophila fulva, Cardamine polemonioides, and Saxifraga aizoides, lack of ripe seeds can also be a result of annual variation, although we are not aware of any other germination tests of these species from Svalbard.…”

“…Rare and thermophilous species also do not germinate from natural Arctic seed banks (Cooper et al 2004). However, germinability may vary strongly among years (Laine et al 1995), and sexual reproduction may occur only in infrequent, favourable years, as indicated by the levels of genetic diversity found in some rare, thermophilous species (Alsos et al 2002).…”

Tree and Shrub Expansion Over the Past 34 Years at the Tree-Line Near Abisko, Sweden

“…The increase of shrub growth maybe related to higher air temperature (Cooper et al 2004;Walker et al 2006). A study based on experiments from 11 sites across the Pan-Arctic area revealed that climate warming might cause an increased growth of shrub species (Walker et al 2006).…”

Plant co-existence patterns and High-Arctic vegetation composition in three common plant communities in north-east Greenland

“…Grau et al clear negative effect on small-scale plant richness and co-existence in the fell-field. We found that the negative impact of Dryas on plant co-existence can occur in High-Arctic ecosystems depending on the environmental constraints, even though it has been commonly described as a facilitator low shrub in northern latitudes (Chapin et al 1994;Cooper et al 2004). Klanderud & Totland (2004) predicted Dryas would have a negative impact on alpine, but not on High-Arctic, community diversity.…”