Abstract
Increases in shrub growth and canopy cover are well documented community responses to climate warming in the Arctic. An important consequence of larger deciduous shrubs is shading of prostrate plant species, many of which are important sources of nectar and berries. Here, we present the impact of a shading experiment on two prostrate shrubs, Vaccinium vitis-idaea L. and Arctous alpina L., in northern Alaska over two growing seasons. We implemented three levels of shading (no shade, 40% shade, and 80% shade) in dry heath and moist acidic tundra. Plots were monitored for soil moisture content, surface temperature, normalized difference vegetation index (NDVI), and flowering. Shading was shown to, on average, lower surface temperature (0.7 °C to 5.3 °C) and increase soil moisture content (0.5% to 5.6%) in both communities. Both species- and plot-level NDVI values were delayed in timing of peak values (7 to 13 days) and decreased at the highest shading. Flower abundance of both species was lower in shaded plots and peak flowering was delayed (3 to 8 days) compared with controls. Changes in timing may result in phenological mismatches and can impact other trophic levels in the Arctic as both the flowers and resulting berries are important food sources for animals.
Highlights
Warming in the Arctic has been accelerating in the past 50 years at higher rates compared to lower latitude regions (ACIA 2004, IPCC 2018)
Erect shrub expansion has been well documented as a consequence of warming temperatures and often results in shifts in the competitive landscape resulting in prostrate plants being out competed (Tape et al 2006, Myers-Smith et al 2011, Loranty and Goetz 2012, Tape et al 2012, Myers-Smith et al 2015)
We show here that shading alters the environmental conditions surrounding prostrate shrubs by increasing soil moisture levels and decreasing surface temperature
Summary
Warming in the Arctic has been accelerating in the past 50 years at higher rates compared to lower latitude regions (ACIA 2004, IPCC 2018). Erect shrub expansion has been well documented as a consequence of warming temperatures and often results in shifts in the competitive landscape resulting in prostrate plants being out competed (Tape et al 2006, Myers-Smith et al 2011, Loranty and Goetz 2012, Tape et al 2012, Myers-Smith et al 2015). The expansion of erect shrub cover may result in shading that adversely affects prostrate plants within the community. Past studies investigating the impact of shading on arctic plants have focused on plant growth and physiology
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