Evidence for non-steady-state carbon emissions from snow-scoured alpine tundra

John F Knowles,Peter D Blanken,Mark W Williams,Corey R Lawrence

doi:10.1038/s41467-019-09149-2

Abstract

High-latitude warming is capable of accelerating permafrost degradation and the decomposition of previously frozen carbon. The existence of an analogous high-altitude feedback, however, has yet to be directly evaluated. We address this knowledge gap by coupling a radiocarbon-based model to 7 years (2008–2014) of continuous eddy covariance data from a snow-scoured alpine tundra meadow in Colorado, USA, where solifluction lobes are associated with discontinuous permafrost. On average, the ecosystem was a net annual source of 232 ± 54 g C m−2 (mean ± 1 standard deviation) to the atmosphere, and respiration of relatively radiocarbon-depleted (i.e., older) substrate contributes to carbon emissions during the winter. Given that alpine soils with permafrost occupy 3.6 × 106 km2 land area and are estimated to contain 66.3 Pg of soil organic carbon (4.5% of the global pool), this scenario has global implications for the mountain carbon balance and corresponding resource allocation to lower elevations.

Highlights

High-latitude warming is capable of accelerating permafrost degradation and the decomposition of previously frozen carbon
Recent work has shown that a variety of alpine shrubland and meadow ecosystems are net annual sources of carbon to the atmosphere[7,8,9,10], and there is evidence of permafrost degradation in mountain ranges around the world that function as indicator systems and source areas of water and nutrients to lower elevations[11,12,13,14]
Since lower temperature soils are more sensitive to warming[15,16], climate change could have a disproportionate impact on high-altitude soil organic matter (SOM) reserves, but ecosystem response to permafrost degradation is complicated by changes in plant-soil interactions, hydrology, and nutrient fluxes that operate on dissimilar timescales[10,17,18,19,20]

Summary

Introduction

High-latitude warming is capable of accelerating permafrost degradation and the decomposition of previously frozen carbon. We used the data to parameterize a multi-pool soil carbon model in order to calculate the relative contribution of these carbon sources to the measured radiocarbon content of carbon dioxide (14CO2) from a long-term alpine tundra research site on Niwot Ridge, Colorado, USA.

Results

Conclusion