神农架不同坡位3种林型土壤碳氮比分布特征

Distribution of Soil C:N Ratio in Three Forest Types on Different Slope Positions in Mt.Shennongjia,China

以神农架林区落叶阔叶林、针阔混交林、针叶林为研究对象,以人工林和草丛为对照组,探讨不同林型和坡位条件下土壤碳、氮及土壤C/N的分布特征。结果表明：（1）林型和坡位对土壤有机碳（SOC）和全氮（TN）均有显著（P〈0.05）影响,SOC和TN含量以及贮量均呈现出在同一森林类型上坡位〈中坡位〈下坡位,在同一坡位针叶林〉落叶阔叶林〉针阔混交林的趋势。（2）土壤C/N在针阔混交林、落叶阔叶林和对照组草丛均呈现出：下坡位高于上坡位,中坡位在二者间徘徊,在针叶林表现出中坡位〉上坡位〉下坡位的趋势;落叶阔叶林条件下坡位的土壤C/N为18.03,是上坡位（13.36）的1.35倍,是中坡位（12.72）的1.41倍。（3）上坡位和中坡位条件下,土壤C/N均是针叶林最高,落叶阔叶林和针阔混交林次之,草丛最低;下坡位则是落叶阔叶林〉针阔混交林=针叶林〉草丛〉人工林。（4）同一林型或坡位条件下,土壤C/N均呈现表层大于深层的趋势,A层和B层的土壤C/N分别是C层土壤C/N的1.07∽2.12倍和1.02∽1.81倍。

Taking the deciduous broadleaved forest, coniferous forest and mixed conifer and deciduous broad- leaved forest as the research object and the tussock and Larix kaempferi artificial forest as contrasts, to dis- cuss the characteristics of soil organic carbon, total nitrogen and soil C - N ratio on different slope positions and forest types. The results showed that the concentrations and contents of soil organic carbon and total nitrogen were significantly （P〈0.05） affected by slope positions and forest types. They increased in the order the upper slop〈the mid slope〈the lower slope in the same forest type, and decreased in the order coniferous forest〈deciduous broadleaved forest〉mixed conifer and deciduous broadleaved forest in the same slope position. The soil C ： N radios of deciduous broadleaved forest, mixed conifer and deciduous broadleaved forest and tussock showed that the lower slope were higher than the upper slope, and the mid slope lined between them, while the soil C ： N ratio of coniferous forest decreased in the order the mid slope〉the upper slop〉 the lower slope, in deciduous broadleaved forest, the soil C ： N ratio of the lower slope （18.03） was 1.35 times of that in the upper slope （13.36） and was 1.41 times of that in the mid slope （12.72）. In the upper slope and mid slope, the soil C ： N radios of coniferous forest were the highest, followed by deciduous broadleaved forest and mixed conifer and deciduous broadleaved forest, and the soil C ：N radios of tussock were the lowest, in the lower slope, the soil C ： N radios decreased in the order deciduous broadleaved forest）co- niferous forest=mixed conifer and deciduous In the same forest type or slope position, the broadleaved forest）tussock〉Larix kaempferi artificial forest. soil C ： N radio was larger in the surface layer than that in the deep layer, the soil C： N radios in A layer and B layer were 1.07--2.12 and 1.02--1.81 times that of those in C layer.