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

Judith M Sarneel,Maja K Sundqvist,Ulf Molau,Mats P Björkman,Juha M Alatalo

doi:10.1016/j.scitotenv.2020.138304

Judith M Sarneel, Maja K Sundqvist + Show 3 more

Open Access

https://doi.org/10.1016/j.scitotenv.2020.138304

Copy DOI

Abstract

AimsLitter 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. MethodsIn 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. ResultsInitial 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. ConclusionsWhile 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.

Highlights

Almost half of the terrestrial carbon resource is bound in high latitude tundra soils (Tarnocai et al, 2009)
We found that the microbially driven initial decomposition rate across six vegetation types in the Arctic was decreased by the direct effects of experimental warming
Stabilization (STBI) of litter material during the second phase of microbially driven decomposition decreased upon experimental warming, but significant differences were found between vegetation type, which could be correlated to differences in soil moisture and its interaction with temperature

Summary

Introduction

Almost half of the terrestrial carbon resource is bound in high latitude tundra soils (Tarnocai et al, 2009). If climate change enhances decomposition of this 1672 Pg. carbon, this could significantly change nutrient cycling (Hobbie, 1996) and release considerable amounts of greenhouse gases into the atmosphere (Lu et al, 2013; Melillo et al, 2017; Tarnocai et al, 2009). This positive feedback mechanism could further enhance global warming and stimulate more decomposition. Since global warming is more pronounced in Arctic regions (IPCC, 2013), and since decomposition greatly depends on temperature and soil chemistry (Hobbie, 1996; Lu et al, 2013), it is crucial to improve our understanding of how climate warming affects carbon cycling and litter decomposition across the Arctic

Methods

Results

Discussion

Conclusion