Warming environmental conditions are credited with increasing Arctic shrub growth, yet it remains unclear how varying soil moisture regimes might impact plant productivity. To date, much of the Arctic shrub trait literature has focused on a few large research stations which are predominately found in coastal climates or in areas of moist tundra, so drier regions of the Arctic have been underrepresented in meta-analysis and modeling efforts. In certain Arctic regions increasing air temperatures could lead to drier soils due to evaporative losses and permafrost thaw drainage resulting in vegetation water stress, so the impacts of warming on the soil environment is an important covariate to consider. Therefore, to better understand the key differences in temperature variation and soil moisture availability on two dominant circumpolar deciduous shrubs, we utilized a natural landscape gradient in West Greenland. We asked which shrub traits are the most responsive to warmer temperatures and wetter soils, and whether shrubs growth could influence the microclimate of their habitats. To do this, we selected a suite of shrub trait data looking at quality and quantity plant traits and soils at 16 sites between the town of Kangerlussuaq and the margin of the Greenland Ice Sheet.
Results/Conclusions
The key results of our study found that both Salix glauca and Betula nana shrub growth was sensitive to variations in air temperature and soil moisture. For both species, increases in air temperature were positively correlated to greater shrub volume, with much of the additional growth due to an increase in secondary growth/woody biomass. Leaf biomass was best predicted by edaphic features including soil bulk density, extracted soil ammonium, and gravimetric soil moisture. Additionally, we found that variation in air temperature and soil temperature were slightly decoupled, with soil temperature also governed by soil moisture, soil bulk density, shrub leaf density, and total shrub volume. Warmer soils generally tended to be drier, suggesting that ongoing warming in the area could lead to significant water losses. These findings compliment previous dendrochronological research done in this area that shows evidence of shrub sensitivity to water availability and plant water stress. Therefore, our study demonstrates that Arctic plants are sensitive to soil water availability and recommend that variations in coupled temperature-moisture dynamics be considered when predicting if and where shrub expansion will occur.