Soil organic carbon sequestration and its stability after vegetation restoration in the Loess Hilly Region, China

Abstract

AbstractVegetation restoration is widely recognized as a way to improve soil organic carbon (SOC) stock. However, whether these recovered carbons are stable is yet largely uncertain. Thus, we determined the sequestration and stability of SOC in soils with three different types (Caragana korshinskii (CA) aged for 10, 20, 36, and 47 years, Hippophae rhamnoides (HR) aged for 5, 10, 20, and 30 years, and Robinia pseudoacacia (RP) aged for 5, 10, 20, 37, and 56 years) to compare their SOC sequestration and stability in different depths in this study. The SOC content, SOC stock, very labile fraction of oxidizable carbon (C1), labile fraction of oxidizable carbon (C2), and carbon management index (CMI) in 0–30 cm depths of the three types increased over the chronosequence. The SOC stocks increased by 1.40–3.19 Mg ha−1 in CA during the 47‐year restoration, by 5.76–10.01 Mg ha−1 in HR during the 30‐year restoration and by 1.88–8.93 Mg ha−1 in RP during the 56‐year restoration, respectively, in 0–30 cm depths. The carbon stability index (SI) in 0–10 cm depth of CA, 0–30 cm depths of HR, and 0–50 cm depths of RP decreased with recovery time. Over the recovery time, SOC content, SOC stock, CMI, and SI were lower than those of nature forest (NF aged more than 100 years) in all restored sites at the later stage of recovery. SOC sequestration decreased, but its stability increased, with the soil depths. Overall, HR had a higher SOC sequestration rate and lower SI (0–30 cm) than CA and RP. Our results revealed that although the SOC sequestration appears enhanced over the restoration, but the SOC stability becomes lower, so that the recovery of these site to the level of NF may meet difficulties in this semiarid Loess Hilly Region.