Do changes in winter snow conditions and their effects on climate feedback processes depend on prior reindeer grazing history?

Theme 1. Environmental protection
Session Name 1.11 Reindeer & caribou in the Arctic system: Interactions between environmental, social and biophysical processes
Presentation Type Oral
Author(s) Jeffrey Welker (UArctic, Univ of Oulu & Univ of Alaska, Finland), Maria Väisänen (University of Oulu, Finland), Riku Paavola (Oulanka Research Station, Finland), Otso Suominen (Kevo SubArctic Research Station, Finland)
Abstract text

Northern ecosystems are experiencing many changes including shifts in snowfall with important ecosystem feedback consequences. For instance, deeper snowpack insulates soils from cold that may directly enhance winter soil CO2 emissions but also carry-over to summer CO2 exchange thus adding to climate forcing. However, across boreal-arctic ecosystems, reindeer grazing is prevalent and has modified vegetation and soil. These reindeer-induced shifts may subsequently modify the degree to which changes in snowpack alter CO2 fluxes. For instance, some levels of grazing may accentuate C fixation and net C sequestration or, to the contrary, accentuate CO2 losses.  The net effect between winter climate changes and reindeer grazing as they affect trace gas feedbacks are complex and today poorly known.

We are using long-term (20 & 50 years) reindeer exclusions with corresponding grazed areas in the boreal (Oulanka) and sub-arctic (Kevo) ecosystems in northern Finland as the fundamental infrastructure for this EU-EcoClimate program. At both ecosystems and grazing treatments, we will manipulate wintertime snowpack (increases, decreases & ambient levels) beginning in the fall of 2018. We will measure, how different snow conditions affect the net ecosystem CO2 exchange – plant photosynthetic C uptake and plant and soil respiratory C release, including continuous measuring of winter CO2 emissions. In addition, the treatment effects on vegetation, soil nutrient status and energy balance will be monitored. Here, we will present preliminary results showing how the decadal exclusion of reindeer grazing has affected vegetation, soil nutrients and ecosystem CO2 balance using data collected over the 2018 growing season.

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