Reindeer grazing in northern boreal forests – effects on greenhouse gas emissions from forest floor.

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) Kajar Köster (University of Helsinki, Finland), Egle Köster (University of Helsinki, Finland), Frank Berninger (University of Helsinki, Finland), Jussi Heinonsalo (University of Helsinki, Finland), Jukka Pumpanen (University of Eastern Finland, Finland)
Abstract text

Reindeer (Rangifer tarandus L.) are the most important large mammalian herbivores in the northern ecosystems, strongly affecting Arctic lichen dominated ecosystems. Changes caused by reindeer in vegetation have indirect effects on physical features of the soil.  

In a field experiment in northern boreal subarctic coniferous forests in Finnish Lapland, we investigated the influence of reindeer grazing on soil GHG (CO2, CH4 and N2O) fluxes, ground vegetation coverage and biomass, soil temperature and water content. We established the experiment as a split plot experiment with 2 blocks and 5 sub-plots per treatment that were divided into grazed and non-grazed parts, separated with a fence.

Our study showed that grazing by reindeer significantly affected lichen and moss biomasses. Lichen biomass was significantly lower in the grazed areas. We also observed that when lichens were removed, mosses were quickly overtaking the areas and moss biomass was significantly higher in grazed areas. Our results indicated that grazing by reindeer in the northern boreal subarctic forests affects the GHG emissions from the forest floor and these emissions largely depend on changes in vegetation composition. Soil was always a source of CO2, and soil CO2 emissions were significantly smaller in non-grazed areas. The soils in our study areas were CH4 sinks through entire measurement period, and grazed areas consumed more CH4 compared to non-grazed areas. Non-grazed areas with lower moss biomass and soil temperature were a small sink of N2O while the total fluxes remained around zero in the grazed areas.

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