title: Effects of land use change on soil gross nitrogen transformation rates in subtropical acid soils of Southwest China.
abstract: Land use change affects soil gross nitrogen (N) transformations, but such information is particularly lacking under subtropical conditions. A study was carried out to investigate the potential gross N transformation rates in forest and agricultural (converted from the forest) soils in subtropical China. The simultaneously occurring gross N transformations in soil were quantified by a (15)N tracing study under aerobic conditions. The results showed that change of land use types substantially altered most gross N transformation rates. The gross ammonification and nitrification rates were significantly higher in the agricultural soils than in the forest soils, while the reverse was true for the gross N immobilization rates. The higher total carbon (C) concentrations and C / N ratio in the forest soils relative to the agricultural soils were related to the greater gross N immobilization rates in the forest soils. The lower gross ammonification combined with negligible gross nitrification rates, but much higher gross N immobilization rates in the forest soils than in the agricultural soils suggest that this may be a mechanism to effectively conserve available mineral N in the forest soils through increasing microbial biomass N, the relatively labile organic N. The greater gross nitrification rates and lower gross N immobilization rates in the agricultural soils suggest that conversion of forests to agricultural soils may exert more negative effects on the environment by N loss through NO3 (-) leaching or denitrification (when conditions for denitrification exist).
authors.affiliation: Yunnan Agricultural University, Kunming, 650201, China, xuyongboxx@163.com.
authors.forename: Yongbo
authors.initials: Y
authors.lastname: Xu
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Xu
mesh_terms: D000383:Agriculture; D001673:Biodegradation, Environmental; D002681:China; D058440:Denitrification; D065928:Forests; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D058465:Nitrification; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D009566:Nitrates; D012987:Soil