title: [Profile distribution of organic carbon and nitrogen in major soil types in the middle of Qilian Mountains].
abstract: This paper studied the distribution patterns of organic carbon (OC), total nitrogen (TN), NH4+ -N, and NO3- -N in the profiles of brown calcic soil, grey cinnamon soil, chestnut soil, and alpine meadow soil in the middle of Qilian Mountains. In all test soils, the contents of OC, TN, NH4+ -N, and NO3- -N decreased with increasing soil depth, and the accumulation and decomposition of OC and various N forms differed with soil types. The average content of OC in different soil profiles changed from 14.01 to 41.17 g x kg(-1), and was in the order of grey cinnamon soil > alpine meadow soil > chestnut soil > brown calcic soil; the average content of TN changed from 1.28 to 2.73 g x kg(-1), with a sequence of alpine meadow soil > grey cinnamon soil > chestnut soil > brown calcic soil. The C/N ratio was from 11.33 to 19.22, with the order of grey cinnamon soil > chestnut soil > alpine meadow soil > brown calcic soil. NH4+ -N content changed from 5.80 to 8.40 mg x kg(-1), and was in the order of brown calcic soil > alpine meadow soil > chestnut soil > grey cinnamon soil; NO3- -N content changed from 6.57 to 15.11 mg x kg(-1), being in the order of chestnut soil > alpine meadow soil > brown calcic soil > grey cinnamon soil. The ratio of NO3- -N to NH4+ -N was 1.00-2.69, with the sequence of grey cinnamon soil > chestnut soil > alpine meadow soil > brown calcic soil. The OC and N contents in the same soil types differed significantly with the conditions of climate, vegetation, and topography (e. g. , slope aspect and slope position). Correlation analysis showed that there were highly significant nositive correlations between OC, TN, and NH4+ -N, but these three items had no significant positive correlations with NO3- -N. Furthermore, there were highly significant positive correlations between available K, NH4+ -N, and NO3- -N and between available P and OC, significant positive correlations between available P, TN, and NH4+ -N, but no significant correlations between pH, total K, and total P and OC and N.
authors.affiliation: College of Resources and Environment, Northwest A & F University, Yangling 712100, Shaanxi, China. gengzengchao@126.com
authors.forename: Zeng-chao
authors.initials: ZC
authors.lastname: Geng
authors.forename: Lin
authors.initials: L
authors.lastname: Jiang
authors.forename: Shan-shan
authors.initials: SS
authors.lastname: Li
authors.forename: Diao
authors.initials: D
authors.lastname: She
authors.forename: Lei
authors.initials: L
authors.lastname: Hou
mesh_terms: D002244:Carbon / Q000032:analysis*; D002681:China; D017753:Ecosystem; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis*; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D012987:Soil / Q000032:analysis*
chemical_list: D009566:Nitrates; D009930:Organic Chemicals; D000644:Quaternary Ammonium Compounds; D012987:Soil; D002244:Carbon; D009584:Nitrogen