The effect of the seed mixture composition on the performance of target species and the resulting plant community in high-altitude grasslands
Creators: name: Kessler Rios, Margarita M.
Publisher: name: ZHAW Zürcher Hochschule für Angewandte Wissenschaften
Year: 2024
Subjects: Subalpine grassland
Restoration
Revegetation
Seed mixture
Plant-plant interaction
Germination
Survival
Growth
Establishment
Priority effect
Plant community
Arnica montana
Gentiana acaulis
Potentilla aurea
333.7: Landflächen, Naturerholungsgebiete
580: Pflanzen (Botanik)

description: High-altitude grasslands are complex and fragile habitats that are difficult to restore following disturbances or degradation. One of the most frequently used restoration interventions is sowing native site-appropriate multispecies seed mixtures to revegetate the affected areas and provide the site with conditions for further recovery. However, restored areas often fail to establish some of the species that previously occurred even though they are included in the seed mixtures. A possible way to enhance the establishment of such species is to consider the ecological mechanisms by which co-occurring plants interact in the early stages of revegetation. 
I evaluated the role of plant-plant interactions among species in the seed mixture in the performance of three target species: Arnica montana, Gentiana acaulis, and Potentilla aurea. The first two species are commonly absent or rare in revegetated areas, whereas the last one is very common. The performance of the target species was evaluated in terms of germination (rate and time), survival, and growth (biomass or plant cover) under monospecific, bispecific, and multispecific neighborhoods (seed mixtures) in controlled and field conditions. The effect of priority seeding and cover crops was also evaluated. Lastly, the effect of the seed mixture on the early established plant community was also assessed. 
The neighborhood significantly affected the germination and growth of the target species, but no significant effects on survival were detected. The target species performed poorly in the neighborhoods with strong competitors. However, their performance increased when the target species were given temporal priority (a growing season). The neighbors’ species response was species-specific. The results from the controlled experiment were not reflected in the field experiment since many other species colonized the plots, affecting the pairwise interactions observed in the greenhouse. The higher establishment of the target species was recorded in plots sown with seed mixtures containing seeds of the cover crop Secale cereale. 
Plant-plant interactions among species in the seed mixture play an important role in the target species' germination, growth, and likely survival. However, the effect of pairwise interaction from the greenhouse experiment was not necessarily a good predictor of the target species' performance in real plant communities. The potentially strong negative effects of competition between pairs of species were highly attenuated when the species interacted simultaneously with other plants in real plant communities. The field experiment highlighted the importance of micro-safe-site limitation that might be even more important than the competition at the early stage of community assembly in high-altitude grasslands.