Abstract
The distribution of plant species and functional traits in alpine and arctic environments are determined by abiotic conditions, but also by biotic interactions. In this thesis, I investigate interactions among plants and herbivory effects on plant community composition and plant functional traits in three different regions: Swedish Lapland, Beringia (USA/Russia) and Finnmark (Norway). Reindeer grazing was found to be extensive in southern Lapland and had limited effects on plant community composition and seedling germination. However, reindeer presence was found to influence plant functional traits, particularly in the subalpine birch forest. Tall herbs were lower and had lower SLA when reindeer were present, while small herbs showed an opposite pattern. The contrasting effects on the two herb groups are probably explained by a competitive release for small herbs when the tall herbs are suppressed by reindeer. Rodents had the largest relative impact on plant community composition in southern Lapland and this is consistent with the study from Finnmark, where rodents heavily affected dwarf shrubs on predator-free islands. With no predators present, vole densities increased profoundly and almost depleted some dwarf shrub species. These results support the idea that small mammals in arctic and alpine tundra are controlled by predators (i.e. top-down). However, a decrease in the nutritional quality in a sedge after defoliation gives support for the idea that small mammals are regulated by plant quality (i.e. bottom-up). In Beringia, small and large herbivores differed in the relation to plant community composition, since large herbivores were related to species richness and small herbivores were related to plant abundance. Plant functional traits were related only to large herbivores and standing crop of vascular plants.
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Claims 15
Claim · model-written summary
Reindeer grazing in southern Lapland had limited effects on plant community composition and seedling germination.
- Taxon
- plant speciese0
- Treatment
- Reindeer grazinge1
- Outcome
- plant community composition and seedling germinatione1
- Direction
- no_changeinferrede1
Not reportedComparator
Verbatim
e0“The distribution of plant species and functional traits in alpine and arctic environments are determined by abiotic conditions, but also by biotic interactions”
e1“Reindeer grazing was found to be extensive in southern Lapland and had limited effects on plant community composition and seedling germination”
Claim · model-written summary
Reindeer presence influenced plant functional traits, particularly in the subalpine birch forest.
Not reportedDirection
Verbatim
e0“The distribution of plant species and functional traits in alpine and arctic environments are determined by abiotic conditions, but also by biotic interactions”
e2“reindeer presence was found to influence plant functional traits, particularly in the subalpine birch forest”
Claim · model-written summary
Tall herbs had lower SLA when reindeer were present.
Not reportedComparator
Verbatim
e3“Tall herbs were lower and had lower SLA when reindeer were present, while small herbs showed an opposite pattern”
Claim · model-written summary
Tall herbs were lower when reindeer were present.
Not reportedComparator
Verbatim
e3“Tall herbs were lower and had lower SLA when reindeer were present, while small herbs showed an opposite pattern”
Claim · model-written summary
Small herbs showed an opposite pattern to tall herbs in plant functional traits when reindeer were present.
Verbatim
e2“reindeer presence was found to influence plant functional traits, particularly in the subalpine birch forest”
e3“Tall herbs were lower and had lower SLA when reindeer were present, while small herbs showed an opposite pattern”
Claim · model-written summary
The contrasting effects on the two herb groups are probably explained by competitive release for small herbs when reindeer suppress tall herbs.
Verbatim
e4“The contrasting effects on the two herb groups are probably explained by a competitive release for small herbs when the tall herbs are suppressed by reindeer”
Claim · model-written summary
Rodents had the largest relative impact on plant community composition in southern Lapland.
Not reportedDirection
Verbatim
e0“The distribution of plant species and functional traits in alpine and arctic environments are determined by abiotic conditions, but also by biotic interactions”
e5“Rodents had the largest relative impact on plant community composition in southern Lapland”
Claim · model-written summary
On predator-free islands, rodents heavily affected dwarf shrubs.
Verbatim
e6“rodents heavily affected dwarf shrubs on predator-free islands”
Claim · model-written summary
With no predators present, vole densities increased.
- Taxon
- dwarf shrub speciese7
- Treatment
- no predators presente7
- Interactor
- volee7herbivore
- Outcome
- vole densitiese7
- Direction
- increasede7
Not reportedComparator
Verbatim
e7“With no predators present, vole densities increased profoundly and almost depleted some dwarf shrub species”
Claim · model-written summary
With no predators present, voles almost depleted some dwarf shrub species.
Verbatim
e7“With no predators present, vole densities increased profoundly and almost depleted some dwarf shrub species”
Claim · model-written summary
Small mammals in arctic and alpine tundra are probably controlled by predators (top-down).
Verbatim
e0“The distribution of plant species and functional traits in alpine and arctic environments are determined by abiotic conditions, but also by biotic interactions”
e4“These results support the idea that small mammals in arctic and alpine tundra are controlled by predators (i.e. top-down)”
Claim · model-written summary
Defoliation of a sedge decreased its nutritional quality.
Not reportedComparator
Verbatim
e5“a decrease in the nutritional quality in a sedge after defoliation gives support for the idea that small mammals are regulated by plant quality”
Claim · model-written summary
In Beringia, large herbivores were related to plant species richness.
Not reportedDirection
Verbatim
e0“The distribution of plant species and functional traits in alpine and arctic environments are determined by abiotic conditions, but also by biotic interactions”
e6“In Beringia, small and large herbivores differed in the relation to plant community composition, since large herbivores were related to species richness and small herbivores were related to plant abundance”
Claim · model-written summary
In Beringia, small herbivores were related to plant abundance.
Not reportedDirection
Verbatim
e0“The distribution of plant species and functional traits in alpine and arctic environments are determined by abiotic conditions, but also by biotic interactions”
e6“In Beringia, small and large herbivores differed in the relation to plant community composition, since large herbivores were related to species richness and small herbivores were related to plant abundance”
Claim · model-written summary
Plant functional traits in Beringia were related only to large herbivores and standing crop of vascular plants.
- Taxon
- vascular plantsTracheophytae7
- Interactor
- large herbivorese7herbivore
- Outcome
- plant functional traitse7
Not reportedDirection
Verbatim
e7“Plant functional traits were related only to large herbivores and standing crop of vascular plants”