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Snow-induced changes in dwarf birch chemistry increase moth larval growth rate and level of herbivory
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Arcum)
Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, P.O. Box 49, 230 53 Alnarp, Sweden.
School of Biological and Biomedical Sciences, Institute of Ecosystem Science, University of Durham, Durham, DH1 3LE, UK.
2010 (English)In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 33, no 5, 693-702 p.Article in journal (Refereed) Published
Abstract [en]

Changes in snow cover might influence arctic ecosystems to the same extent as increased temperatures. Although the duration of snow cover is generally expected to decrease in the future as a result of global warming, the amounts of snow might increase in arctic areas where much of the elevated precipitation will fall as snow. We examined the effects of an increased snow cover, as a result of a snow fence treatment, on soil nitrogen mineralization, plant phenology, plant chemistry (nitrogen and potential defense compounds), the level of invertebrate herbivory, and performance of invertebrate herbivores in an arctic ecosystem, using dwarf birch (Betula nana) and the autumnal moth (Epirrita autumnata) as study organisms. An enhanced and prolonged snow cover increased the level of herbivory on dwarf birch leaves. Larvae feeding on plants that had experienced enhanced snow cover grew faster and pupated earlier than larvae fed with plant material from control plots, indicating that plants from enhanced snow-lie plots produce higher-quality food to herbivores. The increased larval growth rate was strongly correlated with higher leaf nitrogen concentration in plants subjected to snow manipulation, and also to certain phenolic acids. Snow manipulation did not change net nitrogen mineralization rates in the soil or total carbon concentration in leaves, but it altered the within-season fluctuating pattern of leaf phenolic compounds. This study demonstrates a positive relationship between increased snow cover and level of herbivory on deciduous shrubs, thus proposing a negative feedback on the climate-induced dwarf shrub expansion in arctic areas.

Place, publisher, year, edition, pages
Springer, 2010. Vol. 33, no 5, 693-702 p.
Keyword [en]
Climate change, Snow fence, Plant phenology, Nitrogen, Epirrita autumnata, Betula nana
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:umu:diva-30414DOI: 10.1007/s00300-009-0744-9ISI: 000276615400013OAI: oai:DiVA.org:umu-30414DiVA: diva2:282798
Available from: 2009-12-22 Created: 2009-12-21 Last updated: 2017-12-12Bibliographically approved
In thesis
1. The Effect of Snow on Plants and Their Interactions with Herbivores.
Open this publication in new window or tab >>The Effect of Snow on Plants and Their Interactions with Herbivores.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The ongoing climate changes are predicted to accelerate fast in arctic regions with increases in both temperatures and precipitation. Although the duration of snow cover is generally expected to decrease in the future, snow depth may paradoxically increase in those areas where a large amount of the elevated precipitation will fall as snow. The annual distribution and duration of snow are important features in arctic ecosystems, influencing plant traits and species interactions in various ways. In this thesis, I investigated the effect of snow on plants and their interactions with herbivores by experimentally increasing the snow cover by snow fences in three different habitats along an environmental gradient in Abisko, northern Sweden.

I found that the snow cover mattered for plant quality as food for herbivores and herbivore performance. An enhanced and prolonged snow cover increased the level of insect herbivory on dwarf birch leaves under field conditions. Autumnal moth larvae feeding on leaves that had experienced increased snow-lie grew faster and pupated earlier than larvae fed with leaves from control plots. These findings indicated that plants from snow-rich plots produced higher-quality food for herbivores. My studies showed that differences in snow-lie explained parts of the within-year spatial and seasonal variation in plant chemistry and patterns of herbivory in this arctic landscape. The relationship between leaf nitrogen concentration and plant phenology was consistent between treatments and habitats, indicating that snow per se, via a delayed phenology, was controlling the nitrogen concentration. The relationship between leaf age and level of herbivory was positive in the beginning of the growing season, but negative in the end of the growing season, indicating an increasing importance of plant palatability and a decreasing importance of exposure time in determining the level of herbivory throughout the growing season. The concentrations of phenolics varied among habitats, treatments and sampling occasions, suggesting that these plants were able to retain a mosaic of secondary chemical quality despite altered snow conditions. Furthermore, the nutrient limiting plant growth, according to N:P ratio thresholds, appeared to shift from nitrogen to phosphorus along the topographic gradient from snow-poor ridges to more snow-rich heathlands and fens. Snow addition had, however, no significant effect on other nutrient concentrations than nitrogen and no significant effect on the leaf N:P ratio, indicating that differences in snow cover could not explain the variation in plant nutrient concentrations among habitats. In a five-year study, I found opposing inter-annual effects of increased snow on plant chemistry. In contrast to earlier results, the effect of snow-lie on plant nitrogen concentration was predominantly negative. However, the effect of increased snow cover on the level of herbivory remained predominantly positive. The strong within-year relationship between snow-melt date (via plant phenology) and plant nitrogen concentration and level of herbivory could not predict inter-annual variation in the effect of snow manipulation. I did not find any conclusive evidence for a single factor causing the inter-annual opposing effect of snow addition, but the results indicated that interactions with summer and winter temperatures might be important.

In conclusion, this thesis showed that climate-induced changes in snow conditions will have strong effects on plant traits and plant-herbivore interactions. However, alterations in snow cover do not influence all plant traits and the effect may vary in time and space.

Place, publisher, year, edition, pages
Umeå: Print&Media, 2010. 59 p.
Keyword
Snow, arctic ecosystem, plant-herbivore interactions, phenology, nitrogen, phenolics, experimental manipulation, natural gradient, inter-annual variability
National Category
Biological Sciences
Identifiers
urn:nbn:se:umu:diva-30444 (URN)978-91-7264-923-1 (ISBN)
Public defence
2010-01-22, Lilla Hörsalen (KB3A9), KBC-huset, Umeå, 10:00 (English)
Opponent
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Available from: 2009-12-29 Created: 2009-12-22 Last updated: 2009-12-29Bibliographically approved

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Torp, MikaelaOlofsson, Johan

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