Journal
ECOLOGY AND EVOLUTION
Volume 3, Issue 11, Pages 3683-3700Publisher
WILEY
DOI: 10.1002/ece3.710
Keywords
Alpine; arctic; birch (Betula); carbon; litter; nitrogen; permafrost; plant-soil (belowground) interactions; soil respiration; willow (Salix)
Categories
Funding
- Canon National Parks Science Scholars Program
- Government of Canada International Polar Year Program
- Natural Sciences and Engineering Research Council of Canada
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Shrubs are the largest plant life form in tundra ecosystems; therefore, any changes in the abundance of shrubs will feedback to influence biodiversity, ecosystem function, and climate. The snow-shrub hypothesis asserts that shrub canopies trap snow and insulate soils in winter, increasing the rates of nutrient cycling to create a positive feedback to shrub expansion. However, previous work has not been able to separate the abiotic from the biotic influences of shrub canopies. We conducted a 3-year factorial experiment to determine the influences of canopies on soil temperatures and nutrient cycling parameters by removing similar to 0.5m high willow (Salix spp.) and birch (Betula glandulosa) shrubs, creating artificial shrub canopies and comparing these manipulations to nearby open tundra and shrub patches. Soil temperatures were 4-5 degrees C warmer in January, and 2 degrees C cooler in July under shrub cover. Natural shrub plots had 14-33cm more snow in January than adjacent open tundra plots. Snow cover and soil temperatures were similar in the manipulated plots when compared with the respective unmanipulated treatments, indicating that shrub canopy cover was a dominant factor influencing the soil thermal regime. Conversely, we found no strong evidence of increased soil decomposition, CO2 fluxes, or nitrate or ammonia adsorbtion under artificial shrub canopy treatments when compared with unmanipulated open tundra. Our results suggest that the abiotic influences of shrub canopy cover alone on nutrient dynamics are weaker than previously asserted.
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