小流域内植被类型对土壤NO3-/NH4+空间变化的影响

流域内植被类型、地形地貌特征对土壤氮循环过程有重要的作用,是影响下游水体无机氮素来源以及富营养化的关键因子。通过比较小流域内4种植被类型(落叶松人工林、油松人工林、天然阔叶次生林和农田(玉米))对土壤NO3--N和NH4+-N含量空间变化的影响,揭示流域内不同立地条件下水源涵养林与土壤无机氮变化特征之间的关系。结果表明:4种植被类型土壤NO3--N和NH4+-N含量差异显著(P<0.05);由坡上到坡下土壤NO3--N和NH4+-N含量显著降低;在土壤表层NO3--N和NH4+-N含量最高,随着土层深度增加无机氮含量减少;与水源涵养林天然植被和人工林植被相比,农田土壤NO3--N含量最高(11.86mg·kg-1),有较高的氮流失风险。

Effects of vegetation type on the spatial variation of soil NO3——N and NH4+-N concentrations in a small watershed

As the key factors affecting the inorganic nitrogen sources and eutrophication of downstream aquatic system, the vegetation type and topographical feature in a watershed play an important role in soil nitrogen cycle. In this study, a comparison was made on the soil NO3--N and NH4+-N concentrations in Changbai larch plantation, Chinese pine plantation, broad-leaved forest, and maize land in a small watershed, aimed to approach the relations between the vegetation types and the characteristics of soil inorganic nitrogen within the watershed. Our results showed that the soil NO3--N and NH4+-N concentrations varied significantly with the vegetation types (P<0.05). From down-slope to up-slope, the soil NO3--N and NH4+-N concentrations decreased significantly from upper layer to lower layer, and the soil NO3--N concentration in maize land was the highest (11.86 mg·kg-1), with a higher risk of nitrogen leaching.