Designing seed mixtures for restoration on alpine soils: who should your neighbours be?

Abstract

Questions: (1) When alpine vegetation is actively restored by seeding, how is vegetation cover influenced by seeding treatments and soil conditions? (2) How does the cover of species differ when they are seeded in a mixture and how is their response influenced by soil conditions? (3) Do individual species perform better or worse in a mixture than when sown separately?Location: Hjerkinn, Dovrefjell, Norway.Methods: In a factorial, randomized field experiment, we recorded the percentage cover of Festuca ovina, Luzula multiflora subsp. frigida and Poa alpina seeded in four different soil types for 3 yr after seeding. We seeded the three species separately and in a mixture in organic topsoil, peat soil, mineral fine soil and mineral coarse soil. We also recorded seedling emergence in a greenhouse experiment, using the same seeding treatments.Results: In the field experiment, vegetation cover established fastest when F. ovina was sown in monoculture, followed by the seed mixture. After 3 yr, mean cover of F. ovina was 1.4 times higher than mean P. alpina cover and more than three times higher than mean L. multiflora cover for single species treatments, and four (P. alpina) and 15 (L. multiflora) times higher when the species were seeded together. L. multiflora germinated slowly in the greenhouse experiment, which could partly explain its poor field performance. In the field experiment, establishment was faster in organic soils than mineral soils for all seeding treatments. The largest difference between F. ovina and L. multiflora performance in the mixture treatment was found in the organic soil types, where overall cover was larger than in the mineral soils. In the organic soils, F. ovina was slightly facilitated in the mixture treatment, while the opposite was found for L. multiflora.Conclusion: When the restoration goal is to quickly establish a vegetation cover, seeding monocultures of rapidly establishing species may be more effective than seeding mixtures, even in alpine sites, where interspecific facilitation may prevail.

Alpine restoration: planting and seeding of native species facilitate vegetation recovery

“…Seeding of F. ovina did not have negative effects on vascular plant species richness or Salix recruitment and thereby provides more promising results than the commercially available Festuca rubra that impeded the establishment of native species in previous studies in the Hjerkinn firing range (see Hagen & Evju 2013; Hagen et al 2014). Our findings, in combination with those of Rydgren et al (2017), suggest that seeding of native grass species could be an effective method to increase vegetation cover in early stages of restoration projects without hindering the natural recovery of vascular plant species richness. The fact that neither performance of the Salix plantings nor Salix recruitment was negatively affected by F. ovina , combined with the finding that field layer cover (existing largely of F. ovina ) was not negatively affected by Salix plantings, suggests that planting and seeding can be used simultaneously.…”

“…However, results from controlled greenhouse experiments cannot be directly translated to a field setting, where environmental conditions are more dynamic (Verdú & Traveset 2005; Rydgren et al 2017). Field studies with F. ovina in alpine areas have shown that the grass rapidly provides a vegetation cover when seeded as a monoculture (Rydgren et al 2017) and that seed mixtures including F. ovina can develop into large, persistent populations (Rydgren et al 2011; Rydgren et al 2016). However, examinations of the effects of seeded F. ovina monocultures on species richness have not yet been performed.…”

Advancing restoration ecology: A new approach to predict time to recovery

“…If, however, control plots undergo systematic changes in species composition during the restoration process, for example, due to climate change (Hobbs & Cramer, ; Timpane‐Padgham, Beechie, & Klinger, ), use of control plots analysed at a latest possible time point should be considered. But since restoration projects seldom are planned experiments (see McKay, Christian, Harrison, & Rice, ; Rydgren, Hagen, Rosef, Pedersen, & Aradottir, ) restoration targets may be difficult to define precisely in terms of species composition. An important point is that the variation along major environmental gradients (and hence species composition) among reference plots must match the restoration plots for the two datasets to be comparable (Rydgren et al., ).…”

Fix‐it Felix: advances in testing plant facilitation as a restoration tool

“…Rydgren et al. (), in this issue of Applied Vegetation Science , explore all dimensions of the Fix‐it Felix effect perfectly, highlighting a modern facilitation perspective by empirically incorporating plant facilitation as a restoration tool.…”

“…Rydgren et al. () clearly examine the role that net interactions, competition and facilitation play in mediating the outcome of restoration in a high‐stress, arctic‐alpine ecosystem. The experimental design is fully randomized and orthogonal testing mixture/monoculture by substrate type both in the field and in a greenhouse via seed addition for three different species common to the region.…”