title: [Contribution of wheat rhizosphere respiration to soil respiration under elevated atmospheric CO2 and nitrogen application].
abstract: With the support of free-air carbon dioxide enrichment (FACE) system and by using isotope 13C technique, and through planting wheat (Triticum aestivum L., C3 crop) on a soil having been planted with maize (Zea mays L., C4 crop) for many years, this paper studied the effects of elevated atmospheric CO2 and nitrogen application on the delta 13C value of soil emitted CO2 and the wheat rhizosphere respiration. With the growth of wheat, the delta 13C value of soil emitted CO2 had a gradual decrease. Elevated atmospheric CO2 concentration (200 micromol mol(-1)) decreased the delta 13C value of emitted CO2 at booting and heading stages significantly when the nitrogen application rate was 250 kg hm(-2) (HN), and at jointing and booting stages significantly when the nitrogen application rate was 150 kg hm(-2) (LN). Nevertheless, the elevated atmospheric CO2 promoted the proportions of wheat rhizosphere respiration to soil respiration at booting and heading stages significantly. From jointing stage to maturing stage, the proportions of wheat rhizosphere respiration to soil respiration were 24%-48% (HN) and 21%-48% (LN) under elevated atmospheric CO2, and 20%-36% (HN) and 19%-32% (LN) under ambient atmospheric CO2. Under both elevated and ambient atmospheric CO2 concentrations, the delta 13C value of emitted CO2 and the rhizosphere respiration had different responses to the increased nitrogen application rate, and there was a significant interactive effect of atmospheric CO2 concentration and nitrogen application rate on the wheat rhizosphere respiration at jointing stage.
authors.affiliation: College of Agronomy, Henan University of Science and Technology, Luoyang 471003, Henan, China. tjkou@yahoo.com.cn
authors.forename: Tai-ji
authors.initials: TJ
authors.lastname: Kou
authors.forename: Xiao-feng
authors.initials: XF
authors.lastname: Xu
authors.forename: Jian-guo
authors.initials: JG
authors.lastname: Zhu
authors.forename: Zu-bin
authors.initials: ZB
authors.lastname: Xie
authors.forename: Da-yong
authors.initials: DY
authors.lastname: Guo
authors.forename: Yan-fang
authors.initials: YF
authors.lastname: Miao
mesh_terms: D001272:Atmosphere / Q000032:analysis*; D002245:Carbon Dioxide / Q000032:analysis*; D005308:Fertilizers; D009584:Nitrogen / Q000737:chemistry*; D058441:Rhizosphere; D012987:Soil / Q000737:chemistry; D014908:Triticum / Q000378:metabolism* / Q000502:physiology
chemical_list: D005308:Fertilizers; D012987:Soil; D002245:Carbon Dioxide; D009584:Nitrogen