黄土高原南北主要类型土壤氮组分相关关系研究

Relationship of Components of Soil Nitrogen for Typical Soils from North to South on the Loess Plateau

黄土高原作为典型生态脆弱区，不同植被覆盖下土壤氮组分分布特征及相关关系研究一直受到学术界的广泛关注。本研究采集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（杨凌）等典型土壤剖面0～200cm土层土样，分析了土壤全氮及酸解有机氮含量、酸解有机氮主要组分与微生物生物量氮之间的相关性，以期阐明黄土高原典型土壤主要氮组分之间的相关性及其特点。结果表明：黄土高原从北到南典型土壤全氮与微生物生物量氮、固定态铵及酸解有机氮各组分含量之间的相关性均达到极显著水平（P〈0．01），微生物生物量氮除了与固定态铵及酸解氨基糖态氮没有显著相关性外，与其余氮组分均达到极显著线性相关水平（P〈0．01），且酸解氨基酸态氮是微生物生物量氮的主要贡献者。

The Loess Plateau is characterized by highly erodible soils, steep slopes and low vegetation coverage due to excess exploitation of land resource and improper land use, and the characteristics of soil nitrogen and its components have been the concern in the recent years. In order to clarify the distribution characteristics of typical soil total nitrogen, soil organic nitrogen and the correlation among the components of soil organic nitrogen from north to south on the Loess Plateau, based on different soil types and land-use patterns, the layers of 0-10 cm, 10-20 em, 20-40 cm, 40-60 cm, 60-80 cm, 80-100 cm, 100- 120 cm, 120-140 cm, 140-160 cm, 160-180 cm and 180-200 cm of typical soils of Ust-Sandiic Entisols （Shenmu）, Los-Orthic- Entisol （Yan＇an） and Eum-Orthic Anthrosol （Yangling） were collected and the contents of soil organic nitrogen and the correlations among soil total nitrogen, soil organic nitrogen, microbial biomass nitrogen, soil fixed ammonium, amino acid nitrogen, ammonia nitrogen and amino sugar nitrogen were analyzed. The results showed that the contents of soil total nitrogen and soil organic nitrogen were different under different soil types and soil depths. In the same location, the contents of soil total nitrogen and organic nitrogen in the profiles decreased remarkably within 040 em, decreased slightly within 40-80 cm and remained low and stable under 80 cm soil depth. From south to north, the contents of soil total nitrogen and organic nitrogen decreased significantly. There were highly significant correlations （P〈0.01） among soil total nitrogen, soil organic nitrogen and its components, microbial biomass nitrogen and soil fixed ammonium. Soil microbial biomass nitrogen had significant （P〈0.05） or extremely significant （P〈0.01） linear correlations with the contents of soil total nitrogen, soil organic nitrogen and most of components of soil nitrogen, but no linear correlation with amino sugar nitrogen and fixed ammonium nitrogen contents. Amino acid nitrogen was the important contributor to soil microbial biomass nitrogen.