Investigating the mechanisms by which arctic shrubs influence nitrogen availability and feedback to increased shrub growth

Jennie DeMarco, University of Florida, jennied@ufl.edu (Presenter)
Michelle Cailin Mack, University of Florida, mcmack@ufl.edu
Syndonia Bret-Harte, University of Alaska, Fairbanks, msbretharte@alaska.edu

Climate warming in the arctic may shift vegetation from graminoids to deciduous shrub dominance, potentially altering the structure and function of the ecosystem through influences on the abiotic and biotic controls over carbon (C) and nitrogen (N) cycling. Shrubs may influence the soil microclimate and litter inputs to the soil, altering the rate at which nutrients are cycled back to soil and available to plants. In arctic tundra near Toolik Lake, Alaska, we experimentally manipulated snow depth across three arctic plant communities that varied in their initial shrub abundance to test whether the snow that accumulates around arctic deciduous shrubs alters the soil microclimate enough to increase soil N availability and nutrient turnover. Specifically, we tested whether the addition of snow altered N mineralization and litter decomposition. In addition we investigated the influence of soil organic matter (SOM) and litter quality on N availability and nutrient turnover. We found that winter snow addition increased soil N availability in the summer only through increased rates of N mineralization but had no effect on litter decomposition rates. In addition, SOM quality was greatest in the plant community with the highest abundance of shrubs resulting in faster turnover and greater N availability. In contrast, litter decomposition rates were slower in shrub dominant communities resulting in slower nutrient turnover and higher retention of N on the litter. We conclude, that on a short time scale shrub interactions with snow increase N availability, at least in the summer, at a time when plants are more active. In addition, our study suggests that a transition to a shrubbier arctic could lead to retention of N in the litter layer and an increase in N availability in the soil potentially leading to a positive feedback to increased shrub growth.

Presentation Type:  Poster

Session:  Global Change Impact & Vulnerability   (Tue 11:30 AM)

Associated Project(s): 

• Related Activity

Poster Location ID: 151