The temperature sensitivity of soil organic carbon decomposition is greater in subsoil than in topsoil during laboratory incubation

Dong Yan,Changming Fang,Jinquan Li,Junmin Pei,Jun Cui,Ming Nie

doi:10.1038/s41598-017-05293-1

Dong Yan, Changming Fang + Show 4 more

Open Access

https://doi.org/10.1038/s41598-017-05293-1

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Journal: Scientific Reports	Publication Date: Jul 12, 2017
Citations: 45	License type: open-access

Affiliation: Fudan University

Abstract

The turnover of soil organic carbon (SOC) in cropland plays an important role in terrestrial carbon cycling, but little is known about the temperature sensitivity (Q10) of SOC decomposition below the topsoil layer of arable soil. Here, samples of topsoil (0–20 cm) and subsoil (20–40 cm) layers were obtained from paddy fields and upland croplands in two regions of China. Using a sequential temperature changing method, soil respiration rates were calculated at different temperatures (8 °C to 28 °C) and fitted to an exponential equation to estimate Q10 values. The average SOC decomposition rate was 59% to 282% higher in the topsoil than in the subsoil layer because of higher labile carbon levels in the topsoil. However, Q10 values in the topsoil layer (5.29 ± 1.47) were significantly lower than those in the subsoil layer (7.52 ± 1.84). The pattern of Q10 values between the topsoil and subsoil was significantly negative to labile carbon content, which is consistent with the carbon quality-temperature hypothesis. These results suggest that the high temperature sensitivity of SOC decomposition in the subsoil layer needs to be considered in soil C models to better predict the responses of agricultural SOC pools to global warming.

Highlights

Soils contain approximately 1,500 Pg organic carbon (C) in the global upper 100 cm, which is about three times the amount stored in terrestrial vegetation (550 Pg) and twice that stored in the atmosphere (750 Pg)[1, 2]
soil organic carbon (SOC) content was significantly higher in the TL than in the subsoil layers (SL)
Permanganate oxidizable C (POXC) as an index of soil labile C was significantly higher in the TL than in the SL for both paddy field and upland soil (Table 1; P < 0.05), suggesting that SOC had a higher quality in the TL than in the SL

Summary

Introduction

Soils contain approximately 1,500 Pg organic carbon (C) in the global upper 100 cm, which is about three times the amount stored in terrestrial vegetation (550 Pg) and twice that stored in the atmosphere (750 Pg)[1, 2]. The soil organic carbon (SOC) pool plays important roles in the cycling and balance of global C3. The global storage of SOC in cropland is about 128–165 Pg C4, which is approximately 8% to 10% of the terrestrial SOC pool[5, 6]. In addition to being an important part of global SOC storage, SOC in cropland is the most active SOC pool among terrestrial ecosystems[7]. Understanding the Q10 of SOC decomposition in cropland is important for understanding global C cycling. The TL is often disturbed by ploughing and other agricultural activities[22] and is characterized by a porous soil structure with high permeability[23], rapid changes in moisture and temperature[24] and abundant nutrients and organic materials from crop root turnover and exudation[25]. SOC pools, decomposition, and dynamics may differ between TL and SL30, 31

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