title: The impact of afforestation on soil organic carbon sequestration on the Qinghai Plateau, China.
abstract: Afforestation, the conversion of non-forested land into forest, is widespread in China. However, the dynamics of soil organic carbon (SOC) after afforestation are not well understood, especially in plateau climate zones. For a total of 48 shrub- and/or tree-dominated afforestation sites on the Qinghai Plateau, Northwestern China, post-afforestation changes in SOC, total nitrogen (TN), the carbon-to-nitrogen ratio (C/N) and soil bulk density (BD) were investigated to a soil depth of 60 cm using the paired-plots method. SOC and TN accumulated at rates of 138.2 g C m(-2) yr(-1) and 4.6 g N m(-2) yr(-1), respectively, in shrub-dominated afforestation sites and at rates of 113.3 g C m(-2) yr(-1) and 6.7 g N m(-2) yr(-1), respectively, in tree-dominated afforestation sites. Soil BD was slightly reduced in all layers in the shrub-dominated afforestation plots, and significantly reduced in soil layers from 0-40cm in the tree-dominated afforestation plots. The C/N ratio was higher in afforested sites relative to the reference sites. SOC accumulation was closely related to TN accumulation following afforestation, and the inclusion of N-fixing species in tree-dominated afforestation sites additionally increased the soil accumulation capacity for SOC (p < 0.05). Multiple regression models including the age of an afforestation plot and total number of plant species explained 75% of the variation in relative SOC content change at depth of 0-20 cm, in tree-dominated afforestation sites. We conclude that afforestation on the Qinghai Plateau is associated with great capability of SOC and TN sequestration. This study improves our understanding of the mechanisms underlying SOC and TN accumulation in a plateau climate, and provides evidence on the C sequestration potentials associated with forestry projects in China.
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100083, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China; College of Forestry, Northwest A&F University, Yangling, Shaanxi 712100, PR China.
authors.forename: Sheng-wei
authors.initials: SW
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100083, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
authors.forename: Peng-fei
authors.initials: PF
authors.lastname: Han
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100083, PR China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhang
authors.affiliation: University of Chinese Academy of Sciences, Beijing 100049, PR China; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Fan
authors.initials: F
authors.lastname: Ding
authors.affiliation: University of Chinese Academy of Sciences, Beijing 100049, PR China; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Cheng-lin
authors.initials: CL
authors.lastname: Ma
mesh_terms: D002244:Carbon / Q000032:analysis*; D057965:Carbon Sequestration; D002681:China; D065928:Forests; D009584:Nitrogen / Q000032:analysis; D012987:Soil / Q000737:chemistry*; D014197:Trees
chemical_list: D012987:Soil; D002244:Carbon; D009584:Nitrogen