title: [Effects of land use change on soil active organic carbon in deep soils in Hilly Loess Plateau region of Northwest China].
abstract: Response of soil active organic carbon to land-use change has become a hot topic in current soil carbon and nutrient cycling study. Soil active organic carbon distribution characteristics in soil profile under four land-use types were investigated in Ziwuling forest zone of the Hilly Loess Plateau region. The four types of land-use changes included natural woodland converted into artificial woodland, natural woodland converted into cropland, natural shrubland converted into cropland and natural shrubland converted into revegetated grassland. Effects of land-use changes on soil active organic carbon in deep soil layers (60-200 cm) were explored by comparison with the shallow soil layers (0-60 cm). The results showed that: (1) The labile organic carbon ( LOC) and microbial carbon (MBC) content were mainly concentrated in the shallow 0-60 cm soil, which accounted for 49%-66% and 71%-84% of soil active organic carbon in the profile (0-200 cm) under different land-use types. Soil active organic carbon content in shallow soil was significantly varied for the land-use changes types, while no obvious difference was observed in soil active organic carbon in deep soil layer. (2) Land-use changes exerted significant influence on soil active organic carbon, the active organic carbon in shallow soil was more sensitive than that in deep soil. The four types of land-use changes, including natural woodland to planted woodland, natural woodland to cropland, natural shrubland to revegetated grassland and natural shrubland to cropland, LOC in shallow soil was reduced by 10%, 60%, 29%, 40% and LOC in the deep layer was decreased by 9%, 21%, 12%, 1%, respectively. MBC in the shallow soil was reduced by 24% 73%, 23%, 56%, and that in the deep layer was decreased by 25%, 18%, 8% and 11%, respectively. (Land-use changes altered the distribution ratio of active organic carbon in soil profile. The ratio between LOC and SOC in shallow soil increased when natural woodland and shrubland were converted into farmland, but no obvious difference was observed in deep soil. The ratio of MBC/SOC in shallow soil decreased when natural shrubland was converted into farmland, also, no significant difference was detected in the ratio of MBC/SOC for other land-use change types. The results suggested that land-use change exerted significant influence on soil active organic carbon content and distribution proportion in soil profile. Soil organic carbon in deep soil was more stable than that in shallow soil.
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhang
authors.forename: Ming-Xiang
authors.initials: MX
authors.lastname: Xu
authors.forename: Ya-Feng
authors.initials: YF
authors.lastname: Zhang
authors.forename: Chao-Hua
authors.initials: CH
authors.lastname: Wang
authors.forename: Gai
authors.initials: G
authors.lastname: Chen
mesh_terms: D000383:Agriculture; D002244:Carbon / Q000032:analysis*; D002681:China; D065928:Forests; D065948:Grassland; D012987:Soil / Q000737:chemistry*
chemical_list: D012987:Soil; D002244:Carbon