Snow-induced changes in dwarf birch chemistry increase moth larval growth rate and level of herbivory |
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Authors: | Mikaela Torp Johan Olofsson Johanna Witzell Robert Baxter |
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Institution: | 1. Department of Ecology and Environmental Science, Ume? University, 901 87, Ume?, Sweden 2. Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, P.O. Box 49, 230 53, Alnarp, Sweden 3. School of Biological and Biomedical Sciences, Institute of Ecosystem Science, University of Durham, Durham, DH1 3LE, UK
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Abstract: | 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. |
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