不同生态系统土壤氨基酸氮的组成及含量

Constituent and Amount of Amino Acid in Different Ecological System Soils

采集于内蒙古白音锡牧场、陕西澄城、杨凌、宜川和太白山等地不同生态系统的 1 2个土样 ,用 6 mol/ L HCl水解 ,经 H型酸性阴离子交换树脂柱纯化后 ,用 Beckman 1 2 1 MB型氨基酸分析仪测定了 1 7种常见氨基酸。测定结果表明 ,不同生态系统土壤酸解氨基酸含量有很大差异 ,表现为草甸土壤 (氨基酸含量为 2 2 83.9μg N/ g) >森林土壤 ( 1 733.6μg N/g) >草原土壤 ( 85 6 .3μg N/ g) >农田土壤 (平均为 2 4 8.5± 37.8μg N/ g) ,并且氨基酸氮与土壤全氮有极显著的正相关关系 ( p<0 .0 1 ) ;在氨基酸中以中性氨基酸所占比例最大 ,平均为 5 3.99% ,其次为碱性和酸性氨基酸 ,分别为 2 4 .94 %和2 0 .5 9% ,含硫氨基酸最少 ,仅为 0 .4 8% .游离氨基酸以草甸土壤最高 ,为 1 4 .5 8μg N/ g,其它土壤在 1 .1 4～ 8.6 7μg N/ g之间 ,大部分在 2～ 3μg N/ g。游离氨基酸不仅数量低 ,而且种类也比酸解氨基酸少。不管是酸解氨基酸 ,还是游离氨基酸 ,在 0～ 2 0 cm土层的含量均大于 2 0～ 4 0 cm土层 ,从不同土壤样品的平均结果看 ,对酸解氨基酸 ,0～ 2 0 cm土层为96 0 .9μg N/ g,2 0～ 4 0 cm土层为 5 2 8.9μg N/ g ;对游离氨基酸氮 ,0～ 2 0 cm土层 6 .2 8μg N / g,2 0～ 4 0 cm土层 2 .2 2μgN/ g。

The twelve soil samples used in the experiment were collected from Baiyin Xi, Inner Mongolia, Taibai Mountains, Chengcheng, Yichuan, and Yangling, Shaanxi, representing different ecological systems, such as pasture, forest, meadow and arable lands The air dried soils were hydrolyzed with 6 mol/L HCl for 20h. After the hydrolysates were purified with the column of H type acidic anion exchangeable resin, seventeen amino acids were determined on Beckman 121 MB amino acid analyzer. The results show that the amounts of acidic hydrolyzable amino acids varied significantly among the soils in different ecological systems with 2283 9μg N/g in meadow soil, 1 733 6μg N/g in forest soil, 856 3μg N/g in steppe soil and 248 5±37 8μg N/g in arable soil, respectively. There was a very significant positive correlation between hydrolyzable amino acid and total nitrogen (significant at p =0 01). The amount of lysine, glycine, aspartic acid and alanine was higher among seventeen amino acids. These four amino acid nitrogen accounted for 45 5% of total amino acid nitrogen. The content of cysteine, methionine, tyrosine, phenylalanine, isoleucine, proline and serine was lower, accounted for 16 13% of total amino acid nitrogen, other amino acids, such as glutamic acid, arginine, valine, threonine, leucine and histidine was medium, constituted 38 39% of total amino acid nitrogen. A little of cysteine was found in forest soil, pasture soil and meadow soil, while it was undetected in arable soils. In the four kinds of acidic hydrolyzable amino acids, neutral amino acid nitrogen, basic amino acid nitrogen, acidic amino acid nitrogen and sulfur containing amino acid nitrogen accounted for 53 99%, 24 94%, 20 59% and 0 48% of total amino acid nitrogen, respectively. Free amino acid content was higher in meadow soil (14 58μg N/g ), and it ranged from 1 14μg N/g to 8 67μg N/g in other soils. Most of soils had 2～3μg N/g. The results indicated that not only the amount of the free amino acid was lower, but also the kind of the free amino acid was fewer compared with acidic hydrolyzable amino acid. Only 4～6 kinds of free amino acid were detected in most of soils. The amount of glutamic acid was the highest among free amino acid with a average of 1 58 μg N/g, and aspartic acid followed with a average of 0 66μg N/g. The amount of free acidic amino acid, free neutral amino acid and free basic amino acid was 2 24μg N/g, 1 67 μg N/g and 0 42μg N/g, and their percentage to total amount free amino acid was 51 8%, 38 6% and 9 6%, respectively. The free sulfur containing amino acid was not detected in any soil, and the successive order about four kinds of free amino acid was not similar with acidic hydrolyzable amino acid. Both of acidic hydrolyzable amino acid and free amino acid content in 0～20cm layer were higher than that in 20～40cm layer. The average content of amount of acidic hydrolyzable amino acid of all soil samples in 0～20cm layer and 20～40cm layer was 960 9μg N/g and 528 9μg N/g, respectively, and free amino acid in corresponding layer was 6 28μg N/g and 2 22μg N/g, respectively. After continuous supplying of nitrogen fertilizer, acidic hydrolyzable amino acid increased 16 3μg N/g for red manual loessial soil and 56 6μg N/g for manual loessial soil, respectively, compared to no application of nitrogen fertilizer. The increased amino acid was mainly neutral amino acid in red loessial soil and mainly basic amino acid in manual loessial soil, indicating that the effect of nitrogen fertilizer on the acidic hydrolyzable amino acid of different soils was not same. Application of nitrogen fertilizer increased the percentage of acidic hydrolyzable amino acid to total nitrogen in soil compared with no application of nitrogen fertilizer, but the difference was small (average 1 85%). Free amino acid content in soils with nitrogen fertilizer applied was increased by 3 28μg N/g, compared to that of soils without application of nitrogen fertilizer. These facts indicated that the nitrogen ferti