玛曲高寒草地不同利用方式下土壤氮素含量特征

Characteristics of nitrogen contents under different land use conditions in Alpine grassland of Maqu

在玛曲高寒草地,选取不同利用方式下的围封5年的草地、轻度退化与人工修复草地、中度退化草地、重度退化黑土滩型草地、沙化草地以及栽培的燕麦草地为研究对象,分析其土壤氮素含量特征。结果表明,草地的开垦与退化使得可供植物利用的有机碳(SOC)、全氮、无机氮(NH4+-N+NO3--N)与铵态氮含量明显降低,轻度退化与人工修复草地的SOC、无机氮及铵态氮含量均最高,分别为8.78 g/kg,49.44 mg/kg,42.71 mg/kg;重度退化黑土滩型草地中硝态氮含量最高,达13.21 mg/kg。土壤全氮及无机氮与有机碳之间呈显著正相关(P<0.01),土壤硝态氮及铵态氮与土壤全氮之间也均呈显著正相关(P<0.01),且均表现为线性关系;SOC是影响玛曲不同利用方式下草地土壤氮素含量的重要因素。

We studied six land use types（grassland fenced for 5 years,lightly degraded and human-induced restoration grassland,medium degraded grassland,heavily degraded ＂black soil patch＂ grassland,sandy grassland,and oat artificial grassland） in Alpine Grassland of Maqu and analyzed their characteristic organic carbon and nitrogen contents.The organic carbon,inorganic nitrogen（NH4＋-N＋NO3——N） and ammonium nitrogen contents were all highest in lightly degraded and human-induced restoration grassland soil with concentrations of 8.78,49.44,42.71 mg/kg respectively.However,nitrate nitrogen was the highest in heavily degraded ＂black soil patch＂ grassland where it reached 13.21 mg/kg.The reclamation and degradation depleted soil the organic carbon,inorganic nitrogen and ammonium nitrogen content.The soil total nitrogen showed a significant linear relationship with nitrate nitrogen and ammonium nitrogen.Both total nitrogen and ammonium nitrogen had a significant（P〈0.01） positive linear correlation with organic carbon.The total nitrogen and inorganic nitrogen content in soil was found to be positively related to organic matter（P〈0.01）,suggesting that the decrease of organic matter due to reclamation and degradation might be the main cause of the decrease in nitrogen content of the soils.