Warming and increased precipitation enhance phenol oxidase activity in soil while warming induces drought stress in vegetation of an Arctic ecosystem

•We performed a warming and increased precipitation experiment in an arctic ecosystem.•Phenol oxidase activity was enhanced under warming with increased precipitation, but hydrolase activity was unaffected.•Warming appears to induce drought stress in plants and enzymes.

Global climate change models predict that surface temperature and precipitation will increase in the Polar Regions. Arctic tundra soils contain a large amount of carbon, which may be vulnerable to decomposition under potential climate change. However, mechanistic understanding of the decomposition process and the consequent changes remains lacking. In the present study, we conducted a manipulation experiment at an arctic soil system in Cambridge Bay, Canada, where temperature and precipitation were increased artificially by installing open top chambers and adding distilled water during growing seasons. After one and half year of environmental manipulation, we investigated extracellular enzyme activities, which are related to decomposition, and analyzed stable isotope signatures (δ13C and δ15N) in soils and plants, which are related to water and nitrogen availability. Hydrolase (β-d-glucosidase, cellobiase, N-acetyl-glucosidase and aminopeptidase) activity did not differ significantly under different treatments. However, phenol-oxidase showed higher activity under warming combined with increased precipitation than under other treatments. Stable isotope ratio (δ13C) in plants revealed that drought stress in vegetation was induced under warming. We concluded that in the long term, climate change may amplify the feedback of soil to climate change in arctic tundra soil.