高寒生态脆弱区不同扰动生境草地植被及土壤无机氮变化特征

Characteristics of vegetation and soil inorganic nitrogen concentrations under different disturbed habitats in a weak alpine ecosystem

为了解不同干扰生境下高寒生态脆弱区草地植被、土壤无机氮素含量变化特征,以天祝高寒草地为对象,选取3种干扰生境（围栏内天然草地、围栏外天然草地以及牧道）,测定和分析不同季节、不同土壤深度铵态氮和硝态氮含量变化特征。结果表明,不同干扰生境,地上植物种类、盖度、高度及生物量等变化明显;相同土层深度,铵态氮、硝态氮含量表现为围栏内〉围栏外〉牧道。相同干扰生境土壤铵态氮、硝态氮含量随土层深度增加而降低,且变化幅度较大,0-10cm与20-30cm土层间差异显著;土壤铵态氮、硝态氮含量从4月到10月呈现先增加后减少的趋势,并在8月出现峰值,围栏内土壤铵态氮含量8月与10月无显著差异,围栏外土壤硝态氮含量10月升高。3种干扰生境下铵态氮、硝态氮同地上生物量之间均呈正相关关系。

Characteristics of vegetation and soil inorganic nitrogen concentrations under different disturbed habitats（fenced natural grassland,unfenced natural grassland and driveways）were determined and analyzed in a weak alpine grassland ecosystem of Tianzhu.Characteristics were based on field survey for vegetation and the indophenol blue colorimetric method and dual wavelength spectrophotometry for NH4^＋-N and NO3^--N concentrations respectively.There was an obvious change between the different degrees of grassland degradation in ground plant species,coverage,height,biomass,and NO3-N and NH4^＋-N concentrations which showed a decreasing tendency in the sequence fenced natural grassland〉unfenced natural grassland〉driveway at the same soil depth.NO3^--N and NH4^＋-N concentrations decreased with soil depth in comparable disturbed habitats.From April to October NO3^--N and NH4^＋-N concentrations initially increased but then decreased and had a peak value in August.There was no significant difference in fenced soil NH4^＋-N concentrations between August and October.In October,NO3-N concentration increased in unfenced natural grassland.There were positive correlations between aboveground biomass and NH4^＋-N,NO3^--N under the three kinds of disturbed habitats.