Warming of Arctic Meadow under Pollution Stress: Effects and Potential Adaptation

-Future warming and greenhouse gas release are expected to be the highest from arctic and boreal ecosystems exposed to climate warming. Artic agriculture, in the form of cultivated grasslands, is a unique and economically relevant feature of Northern Norway (e.g. Finnmark Province). The MeadoWarm project aimed 1) at determining the response of arctic agricultural ecosystem to increased temperature in terms of plant growth, soil organisms and GHG emissions, and 2) at studying the potential of biochar application to mitigating the warming impacts. The warming (3 °C) was carried out on a multispecies meadow during growing seasons of 2014-2016. We used infrared heaters at large plots for the first time in the arctic area. Our results clearly show that warmer climate will be beneficial for the agronomy in high latitudes. In this relatively short term study, warming significantly increased yields, mainly due to prolonged growing seasons. Warming also improved forage quality and greatly increased the clover content but also increased the amount of weeds. Warming had a relatively modest effect on greenhouse gas fluxes with no differences between warmed and control sites during the first study year. During the second year, carbon dioxide production was significantly increased at warmed sites. Biochar had no effect on the yield or on the greenhouse gas emissions. These results (increased clover content, increased weed content and increased respiration) highlight the need for adapting agronomic practices including fertilization and herbicide usage as well as the seed mixtures applied. Future mitigation options should be investigated given that warmer temperatures enhance soil respiration leading to break down of the valuable soil carbon stocks. Differences between studied years indicate that longer term experiments are crucially needed.

Boreal and arctic terrestrial ecosystems have become central to the climate change debate, notably because future warming is expected to be disproportionate as compared to world averages. Likewise, greenhouse gas release from terrestrial ecosystems expose d to climate warming is expected to be the largest in the arctic. Artic agriculture, in the form of cultivated grasslands, is a unique and economically relevant feature of Northern Norway (e.g. Finnmark Province). In Eastern Finnmark, these agro-ecosyste ms are under the additional stressor of heavy metal and sulphur pollution generated by metal smelters of NW Russia. Warming and its interaction with heavy metal dynamics will influence meadow productivity and species composition, and greenhouse gas emissi ons, as mediated by responses of soil microbial communities. Adaptation and mitigation measured will be needed. Biochar application, which immobilizes heavy metal, is a promising adaptation method to promote positive growth response in arctic meadows expo sed to a warming climate. In the MeadoWarm project we will conduct an ecosystem warming experiment combined to biochar adaptation treatments in the heavy-metal polluted meadows of Eastern Finnmark. In summary, the general objective of the presented projec t is twofold: 1) to determine the response of arctic agricultural ecosystems under environmental stress to increased temperatures, both in terms of plant growth, soil organisms and GHG emissions, and 2) to determine if biochar application can serve as a p ositive adaptation (plant growth) and mitigation (GHG emission) strategy for these ecosystems under warming conditions.