Soil carbon sequestration by three perennial legume pastures is greater in deeper soil layers than in the surface soil
- 1Collaborative Innovation Center of Henan Grain Crops, Agronomy College of Henan Agricultural University, Zhengzhou, Henan 450002, China
- 2State Key Laboratory of Grassland Agro-Ecosystem, Institute of Arid Agroecology, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
- 3The UWA Institute of Agriculture and Centre for Plant Genetics and Breeding, The University of Western Australia, M080, Perth, WA 6009, Australia
- 4Medical College of Northwest University for Nationalities, Lanzhou 730030, China
Abstract. Soil organic carbon (SOC) plays a vital role as both a sink for and source of atmospheric carbon. Revegetation of degraded arable land in China is expected to increase soil carbon sequestration, but the role of perennial legumes on soil carbon stocks in semiarid areas has not been quantified. In this study, we assessed the effect of alfalfa (Medicago sativa L.) and two locally adapted forage legumes, bush clover (Lespedeza davurica S.) and milk vetch (Astragalus adsurgens Pall.) on the SOC concentration and SOC stock accumulated annually over a 2 m soil profile. The results showed that the concentration of SOC in the bare soil decreased slightly over the 7 years, while 7 years of legume growth substantially increased the concentration of SOC over the 0–2.0 m soil depth. Over the 7-year growth period the SOC stocks increased by 24.1, 19.9 and 14.6 Mg C ha−1 under the alfalfa, bush clover 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 of the soil accounted for 79, 68 and 74 % of the SOC sequestered in the 2 m deep soil profile under alfalfa, bush clover and milk vetch, respectively. Conversion of arable land to perennial legume pasture resulted in a significant increase in SOC, particularly at soil depths below 1 m.