Shrub-induced snowpack variability alters wintertime soil respiration across a simulated tundra landscape

ABSTRACT

Across the arctic tundra, the expansion of tall shrubs is expected to alter soil microbial activity in winter through shrub effects on snow redistribution. Tall shrubs act as a windbreak, trapping deep snowdrifts that insulate the ground from extreme cold and elevate soil respiration within shrub patches. However, this windbreak effect may reduce both snow cover and soil respiration in open tundra areas outside shrub patches. The net impact of increasing shrub cover on soil respiration across landscapes with heterogeneous vegetation cover and snow depths remains unknown. Here, I use a set of tundra landscape simulations to address this knowledge gap. The simulations vary shrub cover, mean snow depth and the strength of shrub windbreak effect. I show that for mean snowfall depths 40 cm or greater, increasing shrub cover usually reduced landscape-level soil respiration due to greater heterogeneity in snow depth. These simulations suggest that there is no overarching positive relationship between shrub density and wintertime soil respiration on a landscape scale. Hypotheses generated from these simulations may be tested empirically to improve the representation of tundra vegetation and snow dynamics in Earth System Models.

KEYWORDS:

• Arctic
• carbon cycle
• shrub expansion
• snow
• winter ecology
• soil respiration

Acknowledgements

I thank Dr Ken Tape, Dr Patrick Sullivan and two anonymous reviewers for their thoughtful feedback on the ideas presented here. This project was inspired by discussions in the 2017 Arctic Winter Ecology course at the University Centre in Svalbard, led by Dr Ingibjörg Svala Jónsdóttir.

Disclosure statement

No potential conflict of interest was reported by the author.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

Financial support was generously provided by the National Science Foundation Graduate Research Fellowships Program (grant no. 00039202) and the University of Minnesota Department of Ecology, Evolution, and Behavior; National Science Foundation (00039202).