排水沟渠影响下的高原泥炭地土壤氮空间分布特征

Spatial distribution of soil nitrogen under the influence of drainage gully on alpine peatlands

通过分析排水沟渠影响下的泥炭地土壤氮空间分布特征,阐明全球变化背景下排水沟壑对高原泥炭地退化的影响,为若尔盖高原退化湿地区的生态恢复提供决策支持。将若尔盖湿地自然保护区内的一条排水沟渠作为研究区,在11个垂直于沟渠的断面上,通过环刀法在沟渠两侧取样,分析排水沟渠对阶地沼泽土壤全氮和碱解氮的影响。结果表明:土壤全氮含量0.34~21.86 g·kg^-1,平均值为11.26±6.22 g·kg^-1;土壤碱解氮含量28.35~1965.60 mg·kg^-1,平均值为889.53±470.31 mg·kg^-1;纵向上,以高海拔和靠近河流的含量较低,碱解氮与全氮的比值与高程呈正相关;横向上,与沟渠不同距离间存在差异,越靠近沟渠的样点,其全氮含量越高,但统计上不显著(P>0.05),高程更低的左岸碱解氮含量低于右岸;表层土壤的碱解氮以靠近沟渠1 m的距离最低(P<0.05),左、右岸的碱解氮/全氮比值均呈"V"型变化,与沟渠的距离增加先降低再升高;垂向上,土壤全氮和碱解氮以表层最高,随着深度增加而降低;阶地沼泽连续地块上的土壤氮分布受高程影响大,随着海拔升高而降低;表层土壤氮含量最高,随着深度增加其垂向变化趋势不一致;排水沟壑对泥炭地土壤氮的时空分布格局产生影响,对靠近沟渠的影响最大,且显著降低表层的土壤氮含量。

The spatial distribution characteristics of nitrogen in peatland soil around a drainage gully were analyzed to clarify the impacts of drainage gully on alpine peatland under the background of global change.The results would provide decision support for ecological restoration of degraded peatlands in Zoige plateau.A drainage gully was selected in the Zoige Wetland Nature Reserve as study area.Soil samples were collected on both sides of the drainage gully by ring knife.The contents of total nitrogen and alkali-hydrolyzable nitrogen in the soil were measured.The results showed that soil total nitrogen content was 0.34-21.86 g·kg^-1,with an average of11.26±6.22 g·kg^-1.Soil alkali-hydrolyzable nitrogen content was 28.35-1965.60 mg·kg^-1,with an average of 889.53±470.31 mg·kg^-1.Soil nitrogen content was lower at higher altitudes and decreased along the direction of water flow in gully.The ratio of alkali-hydrolyzable nitrogen to total nitrogen was positively correlated with elevation.There were differences in nitrogen content between different distances in the direction perpendicular to the gully.The total nitrogen content was higher at sampling sites close to the gully,but with no statistical significance(P>0.05).The alkali-hydrolyzable nitrogen content on the left bank with lower elevation was smaller than that on the right bank.The alkali-hydrolyzable nitrogen in the surface soil near the ditch was the lowest(P<0.05).The ratio of alkali-hydrolyzable nitrogen to total nitrogen showed a"V"shape on both banks,decreasing first and then increasing with the distance from the gully.Both soil total nitrogen and alkali-hydrolyzable nitrogen were the highest in the surface layer and decreased with the soil depth.The distribution of soil nitrogen on the continuous block of terrace swamp decreased with the elevation.The surface soil nitrogen content was the highest,and the vertical change trend was inconsistent with the soil depth.Generally,drainage gully significantly reduced soil nitrogen content in the surface layer in the peatland.The impact of drainage gully on spatial distribution pattern of soil nitrogen in peatland varied with the distance from gully.