作 者 ：杨绒,严德翼,周建斌,汪文霞,马勤安
期 刊 ：生态学报 2007年 27卷 4期 页码：1397~1403
关键词：可溶性有机氮；游离氨基酸；全氮；土壤类型；土壤养分；
Keywords:soluble organic nitrogen (SON), free amino acid (FAA), total nitrogen, soil types, soil nutrients,
摘 要 ：测定了黄土高原地区不同生态系统土壤中可溶性有机氮( SON )和游离氨基酸的含量，并分析了其与土壤其他性质之间的关系。结果表明，黑垆土、红油土和淋溶褐土中SON的平均含量分别为24.75、39.10mg/kg和41.80mg/kg，占可溶性总氮( TSN )的51.25%、68.28%和68.57%，分别为土壤全氮的2.54%、3.75%和4.00%；土壤游离氨基酸的含量分别为7.18、7.42mg/kg和7.41mg/kg，分别占SON的30.53%、19.23%和17.50%，占全氮的0.74%、0.71%和0.71%.方差分析结果表明，土壤类型对土壤SON含量及其在TSN和全氮中所占的比例、游离氨基酸在SON中所占的比例有显著影响，而对游离氨基酸的含量及其占土壤全氮比例的影响未达显著水平。枯枝落叶层中SON含量( 248.26 mg/kg )为农田土壤( 24.75 mg/kg)的10倍左右，且林地土壤0～20 cm土层SON含量( 31.03 mg/kg )显著的高于当地农田，两种生态系统0～20 cm土层土壤中游离氨基酸含量( 7.18～7.32 mg/kg )相当，但均极显著低于枯枝落叶层中游离氨基酸平均含量( 18.57 mg/kg )。相关分析结果表明，TSN、SON以及游离氨基酸与全氮、硝态氮、铵态氮、有机质等各养分之间均有极显著的相关性。
Abstract:Soluble organic nitrogen (SON) is defined as organic N that can be extracted from soil by water or salt solutions. The dynamics of SON in soil are different from the dynamics of mineral N and insoluble organic N. SON is a potential source of dissolved organic nitrogen (DON), which is considered to be one of the main forms of N lost from forest ecosystems. In addition, SON is also one of the labile N forms in soil that is available to plants and microorganisms. Therefore, SON plays a vital role in N cycling in forest ecosystems. Recently, researchers found that the SON content of some arable soils in England was as high as the mineral N content. Based on this finding, the scientists concluded that SON was an important pool in the N cycle. But, little is known about the amount of SON or its cycling dynamics in soils on the Loess Plateau of China.
In this study, 15 soil samples (0-20 cm) were collected from three sites on the Loess Plateau with different climate and soil types. The soil types were Typ-Cal-Ustic Isohumisols at Yongshou, Typ-Eum-Orthic Anthrosols at Yangling, and Typic Hapli-Ustic Argosols at Zhouzhi. We extracted SON and free amino acid (FAA) from soil samples with 1M KCl. The correlation coefficients between SON and FAA with various soil properties were also determined.
The average SON content in the Isohumisol was 24.75 mg/kg compared to 39.10 mg/kg in the Anthrosol and 41.80 mg/kg in the Argosol. On a percentage basis, SON comprised 51.25% of the total soluble N (TSN) and 2.54% of the total soil N in the Isohumisol. In comparison, SON comprised 68.28% of the TSN and 3.75% of the total soil N in the Anthrosol and 68.57% of the TSN and 4.00% of total soil N in the Argosol. The average FAA concentration was 7.18 mgN/kg in the Isohumisol, compared to 7.42 mgN/kg in the Anthrosol and 7.41 mgN/kg in the Argosol. In the Isohumisol, FAA accounted for 30.53% of the TSN and 0.74% of the total soil N. In comparison, FAA made up 19.23% of the TSN and 0.71% of the total soil N in the Anthrosol and 17.50% of the TSN and 0.71% of the total soil N in the Argosol. Soil type had a significant effect on the SON content as well as the SON:TSN, SON:total soil N and FAA:SON ratios, but had no significant effect on the FAA concentration or the FAA: total soil N ratios.
In forest areas, the SON concentration was 248.26 mg/kg in the litter and 31.03 mg/kg in the 0-20 cm soil layer. These values were significantly higher than for arable soils in the same area (24.75 mg/kg). The SON concentration in the litter layer of forest soil was 10-fold higher than in the arable soils. The FAA concentrations were similar in the 0-20 cm layer of the arable and forest soils (7.18-7.32 mgN/kg), but significantly lower than in the litter layer (18.57mgN/kg) of the forest. Correlation analysis showed that TSN, SON and FAA were significantly correlated with total soil N, NO-3-N, NH+4-N, organic matter, available K and available P, indicating the important role of SON and FAA in the supply of N in these soils.