Decomposition rate and stabilization across six tundra vegetation types exposed to >20 years of warming

© 2020 The Authors Aims: Litter decomposition is an important driver of soil carbon and nutrient cycling in nutrient-limited Arctic ecosystems. However, climate change is expected to induce changes that directly or indirectly affect decomposition. We examined the direct effects of long-term warming relative to differences in soil abiotic properties associated with vegetation type on litter decomposition across six subarctic vegetation types. Methods: In six vegetation types, rooibos and green tea bags were buried for 70–75 days at 8 cm depth inside warmed (by open-top chambers) and control plots that had been in place for 20–25 years. Standardized initial decomposition rate and stabilization of the labile material fraction of tea (into less decomposable material) were calculated from tea mass losses. Soil moisture and temperature were measured bi-weekly during summer and plant-available nutrients were measured with resin probes. Results: Initial decomposition rate was decreased by the warming treatment. Stabilization was less affected by warming and determined by vegetation type and soil moisture. Soil metal concentrations impeded both initial decomposition rate and stabilization. Conclusions: While a warmer Arctic climate will likely have direct effects on initial litter decomposition rates in tundra, stabilization of organic matter was more affected by vegetation type and soil parameters and less prone to be affected by direct effects of warming.This study was supported by Carl Tryggers stiftelse för vetenskaplig forskning and a grant by Qatar Petroleum to J.M.A., by BECC - Biodiversity and Ecosystem services in a Changing Climate as well as from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 657627 to M.P.B., and by Formas to M.K.S (No: 2013-533) and M.P.B (No: 2016-01187). J.M.S. conducted the work within the strategic theme Sustainability at Utrecht University, subtheme Water, Climate, and Ecosystems, and was funded by the Swedish Research Council VR (No: 2014-04270). The authors thank the staff of Abisko Scientific Research Station for their help and hospitality, and Matthias Molau, Thomas Stålhandske, and Linus Hedh for assistance in the field. TBI data is available under number 119 in the TBI database that will be published online on www.teatime4science.org after publication of the meta-analysis. Until publication on this platform, the data can be obtained by emailing tbi@decolab.org. G. F. Veen is acknowledged for reviewing the manuscript before submission and D. B. Metcalfe for language editing