Shrub shading moderates the effects of weather on arthropod activity in arctic tundra |
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| Authors: | Ashley L Asmus Helen E Chmura Toke T Høye Jesse S Krause Shannan K Sweet Jonathan H Perez Natalie T Boelman John C Wingfield Laura Gough |
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| Affiliation: | 1. Department of Biology, University of Texas at Arlington, Arlington, Texas, U.S.A.;2. Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, U.S.A.;3. Department of Neurobiology, Physiology and Behavior, University of California, Davis, California, U.S.A.;4. Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska, U.S.A.;5. Department of Bioscience and Arctic Research Centre, Aarhus University, R?nde, Denmark;6. College of Agriculture and Life Sciences, School of Integrated Plant Science, Cornell University, Ithaca, New York, U.S.A.;7. Lamont‐Doherty Earth Observatory and Department of Earth and Environmental Sciences, Columbia University, Palisades, New York, U.S.A.;8. College of Life Sciences and Medicine, University of Aberdeen, Aberdeen, U.K.;9. Department of Biological Sciences, Towson University, Towson, Maryland, U.S.A. |
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| Abstract: | 1. Rapid warming has facilitated an increase in deciduous shrub cover in arctic tundra. Because shrubs create a cooler microclimate during the growing season, shrub cover could modulate the effects of global warming on the phenology and activity of ectotherms, including arthropods. This possibility was explored here using two dominant arthropod groups (flies and wolf spiders) in Alaskan tundra. 2. We monitored arthropods with pitfall traps over five summers at four sites that differed in shrub abundance, and used generalised additive mixed models (GAMMs) to separate the two underlying components of pitfall trap catch: the seasonal trend in arthropod density and the effects of short‐term weather variation (air temperature, wind speed, rainfall, solar radiation) on arthropod activity. 3. We found that shrub cover significantly altered the seasonal trend in the abundance of flies by reducing early‐season pitfall catch, in line with observed later snowmelt in shrub‐dominated plots at these sites. 4. Additionally, shrub cover modulated the effects of many weather variables on arthropod activity: shrub cover shifted wolf spiders' temperature–activity relationship, dampened the positive effect of solar radiation on the activity of arthropods in total, and ameliorated the negative effect of wind on the activity of flies. 5. Thus, these results indicate that shrub encroachment will probably be accompanied by altered arthropod responses to warming and other key weather variables. Because the rate of key ecological processes – herbivory, decomposition, predation – are controlled by activity at the organismal level, these effects on arthropods will have long‐term ecosystem‐level consequences. |
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| Keywords: | Climate change ectotherms microhabitat phenology pitfall trap |
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