Soil carbon sequestration and its potential by grassland ecosystems in China

Human activities,such as lowering grazing intensity,enclosure restoration,can improve the accumulation of carbon in grassland soils and sequester carbon.China has large area of grassland,which accounts for more than 30% of China′s total area.Carbon sequestration through grassland management has drawn a great attention.In this study,the grassland of China was divided into three types: typical grassland,desert grassland and alpine meadow.Based on long-term station experimental data,the carbon sequestration rates of enclosure,taming,degraded grassland restoring,aerial seeding and returning farm to grassland were estimated by calculating the average carbon sequestration rates or potential;when data was available,estimation was made in typical grassland,desert grassland and alpine meadow respectively.The carbon sequestration rate of enclosure in typical grassland was 0.47t·hm-2·a-1,while in desert grassland and alpine meadow;the carbon sequestration rate was 0.28 t·hm-2·a-1.The carbon sequestration rates of taming,degraded grassland restoring,aerial seeding and returning farm to grassland were 1.09,0.9,0.9 t·hm-2·a-1 and 0.5 t·hm-2·a-1 respectively.The carbon sequestration potential of degraded grassland recovery was defined as the loss of grassland degradation.The carbon loss(also the carbon sequestration potential) in unit area of typical grassland was 31.58t·hm-2,while in desert and alpine grassland,the carbon sequestration potential was 34.26 t·hm-2 according to the average value in relevant long-term experiments.The results of carbon sequestration were shown as follows:(1) On the assumption that 55% of the grassland in Inner Mongolia,Xinjiang,Qingyhai,Nixia,Gansu,Shaanxi and Tibet was degraded due to over grazing,then by degraded grassland recovery,the carbon storage in grassland soils could increase by 4561.62Tg,and this increase was mainly located in Inner Mongolia,Tibet and Xinjiang.(2) According to the statistics of the area of each grassland type and the grassland management,carbon sequestration potential of non-grazing restoration,taming and returning farms to grassland was 12.01,1.46Tg·a-1 and 25.59Tg·a-1 respectively.(3) The extra carbon sequestration ability by managements was 9.17Tg·a-1 in 2004 when more investments were given to grassland management,the extra carbon sequestration potential of non-grazing restoration,taming and returning farms to grassland was 3.09、0.38Tg·a-1 and 5.70 Tg·a-1 respectively.