Competition-free gaps are essential for the germination and recruitment of alpine species along an elevation gradient in the European Alps

Although the physiology and ecology of Alpine plants in the adult stage is well studied, surprisingly little is known about seedling recruitment, leading to a limited understanding of population dynamics in alpine systems. Here, we present the results of a seed-sowing experiment performed along an elevation gradient (2000-2900 m a.s.l.) in the European eastern Alps. We monitored the germination of seeds and seedling recruitment for two years, investigating effects of sites and home sites (seed origin), effects of gaps, and plant-plant interactions (competition, facilitation) in experimentally manipulated rings.

We found germination decreasing with increasing elevation, independent of the seed home site, but in line with the globally stated pattern for germination by warm cues for alpine species. Recruitment was, however, site-specific and high seedling mortalities were observed, especially at lower elevations. Sowing in above- and belowground competition-free gaps favoured recruitment, pointing out the important role of belowground competition and soil components for recruitment. In gaps with one neighbouring species, neutral plant-plant interactions occurred. However, considering the relative vegetation cover of each experimental site, high vegetation cover resulted in positive effects on recruitment at 2600-2900 m a.s.l., confirming positive interactions in this case.

This study provides important but rare data on alpine seedling recruitment studied in situ from seeds and discusses several key factors of reproduction in alpine systems.


Science Flash Margreiter1

(a) Experimental design. Seed collections at 2300 m and 2600 m a.s.l. represent the locations with optimal seed production of the target species, indicated in the theoretical diagram as their home sites. (b) The experiment was performed along an abiotic stress-gradient at four experiment sites. Germination and recruitment were monitored for two years. Seed sowing was done in experimentally created gaps. (c) The effects of experimental gaps on germination and recruitment were studied by including three gap types: ’gap+roots’: aboveground competition-free gap with belowground competition; ‘neighbor+roots’: only-one-central-plant-left aboveground gap; and ‘no-comp’: artificial gap (i.e., no competition and no interaction;). (d) Gap-type manipulations provided zero aboveground cover in ‘gaps+roots’ and ‘no-comp’, and 10.5% top cover in ‘neighbor+roots’ (d, upper panel). Gap-type manipulations were similar at each experiment site (d, lower panel).

Margreiter, V., Porro, F., Mondoni, A., and Erschbamer, B. (2022). Recruitment Traits Could Influence Species’ Geographical Range: A Case Study in the Genus Saxifraga (L.). Front. Plant Sci. 13:827330.

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