Soil carbon sequestration by three perennial legume pastures is greater indeeper soil layers than in the surface soil

[摘要] Soil organic carbon (SOC) plays a vital role as both a sink for and sourceof atmospheric carbon. Revegetation of degraded arable land in China isexpected to increase soil carbon sequestration, but the role of perenniallegumes on soil carbon stocks in semiarid areas has not been quantified. Inthis study, we assessed the effect of alfalfa (Medicago sativa L.) and two locally adaptedforage legumes, bush clover (Lespedeza davurica S.) and milk vetch (Astragalus adsurgens Pall.) on the SOCconcentration and SOC stock accumulated annually over a 2 m soil profile.The results showed that the concentration of SOC in the bare soil decreasedslightly over the 7 years, while 7 years of legume growth substantiallyincreased the concentration of SOC over the 0–2.0 m soil depth. Over the7-year growth period the SOC stocks increased by 24.1, 19.9 and 14.6 Mg C ha⁻¹ under the alfalfa, bushclover and milk vetch stands, respectively, and decreased by 4.2 Mg C ha⁻¹ in the bare soil. The sequestration of SOC in the 1–2 m depth ofthe soil accounted for 79, 68 and 74 % of the SOC sequestered in the 2 mdeep soil profile under alfalfa, bush clover and milk vetch, respectively.Conversion of arable land to perennial legume pasture resulted in asignificant increase in SOC, particularly at soil depths below 1 m.

[学科分类] 地球化学与岩石