Regeneration by seeds in alpine meadow and heath vegetation in sub‐arctic Finland

Abstract

Abstract. This paper compares the regeneration by seeds of heath and meadow and studies relationships between the floristic composition of phases in the regeneration pathway. Seed densities in the seed rain and seed bank as well as the densities of emerged seedlings in gaps and in closed vegetation were greater in the meadow than in the heath. In the heath, environmental constraints hindered seedling emergence almost completely so seeds accumulated in the seed bank. In the meadow, the decrease in the seed bank was due to high seedling emergence. Within both plant communities, seedling emergence in gaps and in closed vegetation was comparable. In the meadow, the seed rain and seedling emergence in gaps, as well as the seed bank and seedling emergence in gaps were positively correlated. Differences in seed and adult plant sizes were reasons for the low correlation between the standing vegetation and the other phases. In DCA ordination the first axis separated the phase of seedling emergence in closed vegetation and seed bank. The second axis separated the standing vegetation from the other phases. The structure of the seed rain was more heterogeneous than that of other phases. In the heath, the standing vegetation and the seed rain were positively correlated. The ordination of these phases reflected the patchiness of standing vegetation and the ability of the diaspores of Betula nana to disperse over long distances.

Short‐ and long‐term effects of changes in reindeer grazing pressure on tundra heath vegetation

“…Seedling emergence rates are, however, low in established swards in tundra plant communities (Welling & Laine 2002). In this study, less than 1% of the dwarf shrub seeds germinated in intact swards, whereas between 10 and 20% germinated when swards were removed.…”

“…As tundra plants produce large numbers of seeds when weather conditions are suitable (Molau & Larson 2000) and seeds of B. nana disperse over long distances (Molau & Larson 2000;Welling & Laine 2002), B. nana seeds would be expected to reach graminoiddominated areas, at least in some years. Seedling emergence rates are, however, low in established swards in tundra plant communities (Welling & Laine 2002).…”

Functional traits predict relationship between plant abundance dynamic and long-term climate warming

“…Remarkably, addition of seed mass into the best model improved its predictive power, despite the fact that this parameter in itself was not a significant predictor of temperature-abundance slope (Table 1). Although many alpine vascular plant species feature clonal reproduction (18), reproduction by seeds remains important in the long-term, enabling long-distance dispersal and genetic flexibility of a population (19,20). The importance of seed mass as a predictive trait for the relationship between plant abundance and warming alerts to the potential for these processes to be affected by climate change.…”

Multiple Feedbacks Contribute to a Centennial Legacy of Reindeer on Tundra Vegetation

“…We consider it unlikely that seed dispersal limitation would be an important factor here, since seedproducing shrubs grow in close proximity to all HMGs. It is well documented that competition from dense grass swards prevents woody seedling establishment in grasslands in general (Kö chy and Wilson 2000), and also specifically in alpine grasslands (Welling and Laine 2002;Olofsson and Shams 2007;Klanderud 2010;Milbau and others 2013). Dense grass swards, aided by a high mineral N availability in the HMGs, probably efficiently prevent shrubs from establishing from seeds.…”