中文摘要：

为阐明黄土高原典型土壤全氮和微生物氮含量随土壤类型、土层和土地利用方式变化规律，研究了从北向南依次分布的干润砂质新成土（神木）、黄土正常新成土（延安）和土垫旱耕人为土（杨陵）等典型土壤的全氮和微生物氮含量的变化特征。结果表明，不同土壤类型、不同土层全氮和微生物氮含量存在显著差异。从南到北，全氮和微生物氮含量显著下降（P〈0．05）。对同一土壤类型，全氮和微生物氮含量在0—60cm随土层深度增加下降很明显，60-120cm有轻微下降，120cm以下低而稳定。微生物氮含量随土壤类型的变化趋势与全氮完全相同，其与土壤全氮、有机碳及微生物碳含量均存在极显著正相关关系（P〈0．01）。土壤微生物氮与全氮比值变化在0．42％～9．44％之间。虽然土地利用对土壤全氮和C／N比影响不显著，但却显著影响微生物氮含量和微生物氮与全氮的比值；与农田土壤相比，草地土壤微生物氮含量和微生物氮与全氮比值均明显增加。这一结果说明微生物氮含量和微生物氮与全氮比值更能有效、快速地反映土壤质量的变化。

英文摘要：

The soil total nitrogen, soil microbial biomass nitrogen and their relationship of three types of soils on the Loess Plateau （Ust-Sandiic Entisols at Shenmu, Los-Orthic-Entisol at Yan＇ an and Eum-Orthic Anthrosol at Yangling） were investigated to determine how they were affected by location and soil depth（0-200 cm） on the Loess Plateau. The results showed that the contents of soil total nitrogen and microbial biomass nitrogen were significantly different in different situations and soil depth. From south to north on Loess Plateau, the contents of soil total nitrogen and microbial biomass nitrogen decreased significantly. At the same location, the contents of soil total nitrogen and microbial biomass nitrogen in the profiles decreased remarkably within 0-60 cm, decreased slightly within 60-120 cm and remained at the lowest level under 120 cm. Soil microbial biomass nitrogen was significantly correlated with soil total nitrogen, soil organic carbon and soil microbial biomass carbon（ P 〈 0.01）. The range of soil microbial biomass nitrogen and soil total nitrogen ratio was 0.42 %-9.44 %. Land use was not closely related with the contents of soil total nitrogen and soil C/N （ P 〉 0.05） except soil microbial biomass nitrogen and the ratio of soil microbial biomass nitrogen over soil total nitrogen （ P 〈 0.05）.The contents of soil microbial biomass nitrogen and the ratio of soil microbial biomass nitrogen over soil total nitrogen in grassland soil was slightly higher compared with farmland. The results indicated that the soil microbial biomass nitrogen and the ratio of soil microbial biomass nitrogen over soil total nitrogen reflected the variation of soil quality more effectively.