Are the climatic factors combined with reindeer grazing affecting the soil CO2 emissions in subarctic boreal pine forest?

- Reindeer grazing had only small effect on soil CO2 efflux.
- Soil water content had no effect on soil CO2 efflux.
- Soil temperatures were higher on grazed areas.
- Soil temperature had an effect on soil CO2 efflux.
- Negative correlation between soil water content and soil temperature

In this work, we investigated how the reindeer grazing in subarctic boreal Scots pine forests and climate (air temperature and the amount of precipitation) affects soil temperature, soil water content, and ultimately the CO2 efflux from forest soils. The study was carried out in years 2013 and 2014, where 2013 was an extremely dry year (especially the summer), while 2014 was a “normal” year. Our work showed that in subarctic mature pine forests, soil temperatures were higher, and soil water content was fluctuating more on grazed areas compared to non-grazed areas in both years. On both years, the soil water content on the grazed area was higher in June and the situation changed in the second half of July when the moisture content in the non-grazed area remained higher. There was a negative correlation between soil water content and soil temperature. The soil CO2 effluxes were mostly affected by the year of measurement, time of measurement (different months through growing season), soil temperature and also by the management (grazed or non-grazed) resulting in higher CO2 emissions on the grazed areas. Soil moisture content was not affecting the soil CO2 efflux. The average soil CO2 efflux values were significantly higher in the year 2014 compared to the year 2013 mainly due to differences in soil temperature at the beginning of season.