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Defense mechanisms against grazing: a study of trypsin inhibitor responses to simulated grazing by the sedge Carex bigelowii
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
2007 (English)In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 116, no 9, 1540-1546 p.Article in journal (Refereed) Published
Abstract [en]

Trypsin inhibitors have been suggested to constitute an inducible defense in the sedge Carex bigelowii, and some former studies suggest that this might be a cause for the cyclic population dynamics in many alpine and arctic small mammals, for example lemmings (Lemmus lemmus). We investigated this further by using a method of simulated grazing (clipping) at different intensities, in three different habitats with varying resource availability, with different harvest times (hours after clipping), and two different stages of ramets (reproductive/vegetative) in a study from the Swedish mountain range. Our results do not indicate that C. bigelowii has an inducible defense constituted by an increase in trypsin inhibitor activity (TIA), but rather that the amount of soluble plant proteins (SPP) is lowered in wounded plants. The responses were somewhat different in the three habitats, with ramets growing in the marsh showing the highest ratio of TIA to SPP, due to low amounts of SPP. We did not find any significant effects of harvest time, or of the stage of the ramet that could support the hypothesis of an inducible defense. To conclude, we could not find any evidence for an inducible defense consisting of trypsin inhibitors in Carex bigelowii ramets, but we did find variations in the amount of SPP that may have nutritional consequences for herbivores.

Place, publisher, year, edition, pages
2007. Vol. 116, no 9, 1540-1546 p.
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:su:diva-24188DOI: 10.1111/j.0030-1299.2007.15481.xOAI: oai:DiVA.org:su-24188DiVA: diva2:196972
Available from: 2007-03-29 Created: 2007-03-27 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Effects of herbivory on arctic and alpine vegetation
Open this publication in new window or tab >>Effects of herbivory on arctic and alpine vegetation
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: Botaniska institutionen, 2007. 38 p.
Keyword
herbivory, reindeer, rodents, functional traits, plant species composition, arctic, alpine, tundra, seed limitation, Carex bigelowii
National Category
Biological Sciences
Research subject
Plant Ecology
Identifiers
urn:nbn:se:su:diva-6746 (URN)91-7155-396-7 (ISBN)
Public defence
2007-04-20, föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 10:00
Opponent
Supervisors
Available from: 2007-03-29 Created: 2007-03-27Bibliographically approved

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