人为活动对云南纳帕海湿地土壤碳氮变化的影响

以纳帕海湿地原生沼泽作为参照 ,选择人为干扰下的沼泽化草甸 ,草甸和排干湿地开垦的耕地作为研究对象 ,研究人为干扰对纳帕海湿地土壤碳氮变化的影响。两年的定位研究结果表明 :沼泽土壤C/N值较高 ;人为干扰下纳帕海湿地土壤空间结构上土壤有机质 0～ 2 0cm表层与 2 0～ 4 0cm下层相差 4倍 ,水平分布上则随人为干扰加强、沼泽化过程减弱而降低 ,下降幅度高达 2 2 .92 %～ 6 9.6 4 %;土壤全氮及其空间分布呈现与有机质相同趋势 ,两者相关系数r=0 .98;NH 4 N、NO-3 N与全氮和水解氮相关系数分别为r=- 0 .74、r=- 0 .6 5 ,r=- 0 .81、r=- 0 .76。表明了纳帕海湿地沼泽土壤较低的矿化量和对碳的固定及较大的氮累积量 ,以及人为活动干扰后湿地土壤碳氮养分的释放变化。

IMPACTS OF HUMAN DISTURBANCES ON ORGANIC CARBON AND NITROGEN IN NAPAHAI WETLANDS, NORTHWEST YUNNAN

Dynamics of organic carbon and total nitrogen under different types of land use in Napahai marsh wetland,northwest Yunnan was studied with the sequential coring and in-situ exposure method.The results show that soil organic carbon and total N varied significantly both vertically and horizontally.The content of organic matter was 110.67 g kg^-1 in the primary marsh soil,85.30 g kg^-1 in the swampy meadow topsoil and only 22.66 g kg^-1 in the deep soil layer,and decreased horizontally from primary marsh to swampy meadow,meadow and to cropland by 22.92%~69.64%.Total N followed organic matter in the same trend in spatial distribution,showing a significant correlation coefficient vert ically (r_(top)=0.93,r_(deep)=0.96).But it had a low correlation coefficient horizontally with NH₄⁺-N(r=-0.74) and NO₃^--N (r=-0.65).Besides,a significantly negative correlation was observed between NH₄⁺-N (NO₃^--N) and hydrolysable N (r=-0.81,r=-0.76).The C/N was high (average 23.69) in the primary marsh,showing that primary marsh in Napahai wetland had low mineralization rate,a high nitro-gen accumulation rate and a carbon fixation rate,which also explains that soil organic carbon and total N in Napahai wetland are degrading with human disturbances.