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

摘要

Characteristics of vegetation and soil inorganic nitrogen concentrations under different disturbed habi-tats (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 concen-trations 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 de-creasing 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 Au-gust and October.In October,NO3-N concentration increased in unfenced natural grassland.There were posi-tive correlations between aboveground biomass and NH4 +-N,NO3 --N under the three kinds of disturbed habi-tats .%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，0～10 cm与20～30 cm 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。