The effect of decreasing permafrost stability on ecosystem carbon in the northeastern margin of the Qinghai\u2013Tibet Plateau

Wenjie Liu,Shichang Kang,Shengyun Chen,Xiang Qin,Jiawen Ren,Junyi Liang,Dahe Qin

doi:10.1038/s41598-018-22468-6

Abstract

The objective of this study is to investigate the effect of decreased permafrost stability on carbon storage of the alpine ecosystems in the northeastern margin of the Qinghai–Tibet Plateau. During July and August 2013, we selected 18 sites in five types of permafrost (stable, substable, transitional, unstable, and extremely unstable) regions. We measured aboveground phytomass carbon (APC) and soil respiration (SR), soil inorganic carbon (SIC), soil organic carbon (SOC), belowground phytomass carbon, and soil properties down to 50 cm at same types of soils and grasslands. The results indicated that ecosystem carbon in cold calcic soils first decreased and then increased as the permafrost stability declined. Overall, decreasing permafrost stability was expected to reduce ecosystem carbon in meadows, but it was not obvious in swamp meadows and steppes. APC decreased significantly, but SIC and SOC in steppes first decreased and then increased with declining permafrost stability. Soil clay fraction and soil moisture were the controls for site variations of ecosystem carbon. The spatial variations in SR were possibly controlled by soil moisture and precipitation. This meant that alpine ecosystems carbon reduction was strongly affected by permafrost degradation in meadows, but the effects were complex in swamp meadows and steppes.

Highlights

Permafrost plays a fundamental role in alpine ecosystems, and permafrost degradation has been shown to have significant consequences for these ecosystems[1,2,3]
Cold calcic soil was distributed in five different permafrost stability zones (Table S1), which were selected to evaluate the effects of permafrost degradation on different forms of carbon
There was no significant difference in ecosystem carbon (EC) between the substable and transitional permafrost zones

Summary

Introduction

Permafrost plays a fundamental role in alpine ecosystems, and permafrost degradation has been shown to have significant consequences for these ecosystems[1,2,3]. Arctic and subarctic climate warming has significantly enhanced permafrost degradation[4,5,6,7,8,9], expansion of shrub vegetation communities, hydrological cycles, and CO2 and CH4 emissions These are associated with the loss of large amounts of soil carbon stored in permafrost soils at high-latitudes in the Northern Hemisphere[4,10,11,12,13]. More than 90% of belowground biomass in alpine grasslands has been shown to be concentrated in the top 30 cm of soil[37], and SOC is concentrated in topsoil and correlates well with BPC in this area[38] For those reasons, ecosystem carbon above ground and below ground at a 0–50 cm depth range, like soil carbon in permafrost, were influenced by permafrost degradation. We selected several sites in different permafrost zones with the same soil or grassland vegetation types to conduct a systematic investigation of SR, vegetation, and soil properties at a depth of 0–50 cm

Objectives

Methods

Results

Discussion

Conclusion