微地形对高寒草地土壤有机碳及氮含量的影响

目的]系统分析高寒草地不同微地形条件下土壤有机碳及氮含量的变化规律,为高寒地区合理利用草地提供理论参考。方法]在天祝高寒草地区选取7类不同微地形作为研究对象,测定其表层(0—30cm)土壤有机碳及氮含量。结果]随着土层深度的增加,位于坡底平地,土壤全氮和铵态氮含量呈减小的趋势,位于阴坡不同坡位,土壤全氮含量呈"V"型变化,土壤铵态氮呈减小的趋势,位于阳坡不同坡位,土壤全氮含量呈减小的趋势,土壤铵态氮含量呈先增大后减小的趋势;所有微地形中,随着土层深度的增加,土壤有机碳含量呈减小的趋势;随着土层深度的增加,坡底平地,中坡阳面和中坡阴面微地形中,土壤水解氮含量呈减小的趋势,下坡阳面和下坡阴面微地形中,土壤水解氮含量呈先减小后增大的趋势,上坡阳面和上坡阴面微地形中,土壤水解氮含量呈先增大后减小的趋势。土壤表层全氮、水解氮、有机碳的含量的变化为:下坡位上坡位中坡位,而铵态氮的含量呈现先减小后增大的趋势。结论]地形的微变化明显影响土壤氮有机碳和素的含量。

Effects of Micro-topography on Soil Organic Carbon and Nitrogen Content in Alpine Grassland

Objective] The study analyzed the variation of soil organic carbon (SOC) and nitrogen (N) content under different micro-topography in alpine grassland area in order to provide a theoretical basis for the reasonable use of grassland in alpine grassland.Methods] This study selected 7 different kinds of micro-topography in alpine grassland of Tianzhu to measure SOC and N in the land surface(0-30 cm).Results] With the increase of soil depths, the content of total N and NH₄-N decreased at the flat area of valley bottom. The content of soil total N showed a "V" trend and NH₄-N decreased in different position of north-facing slopes. In different position of south-facing slopes, the content of soil total N decreased, but soil content of NH₄-N showed an increase trend initially and decreased later. With the increase of soil depths, the content of SOC decreased in all micro-topography, while the content of soil hydrolyzable nitrogen decreased in terrace, middle and south-facing slope, middle and north-facing slope micro-topography. The content of hydrolyzable N decreased initially and then increased in bottom and south-facing slope and bottom and north-facing slope micro-topography, while increased initially and then decreased in top and south-facing slope and top and north-facing slope.Conclusion] The variation of total N, hydrolyzable N and SOC content at different topographic positions was ranked as:bottom slope > top slope > middle slope. The content of NH₄-N decreased initially and then increased. In conclusion, the variation in micro-topography impacts the content of SOC and N dramatically.