中文摘要：

以青海省3类典型高寒草甸为研究对象,分析土壤可溶性有机氮库和土壤氨基酸库种类、质量分数及其季节动态变化过程,确定牧草不同发育期土壤的供氮能力,为进一步研究高寒草甸植物吸收土壤氮素奠定基础.结果表明：高寒草甸土壤中最占优势个体游离氨基酸是苯丙氨酸和天冬氨酸,其次是亮氨酸、精氨酸、脯氨酸、组氨酸、谷氨酸、赖氨酸和甘氨酸,它们占总游离氨基酸的80%90%;藏嵩草草甸生长季土壤总游离氨基酸态氮平均质量分数为6.90×10（-6）,最高值出现在6月低.矮嵩草草甸生长季土壤总游离氨基酸态氮平均质量分数为7.44×10（-6）,随生长季土壤总游离氨基酸逐渐上升,到5月底达到最大值,随后逐渐下降.退化矮嵩草草甸土壤总氨基酸态氮季节变化不显著,平均质量分数为5.04×10（-6）;藏嵩草草甸土壤可溶性有机氮质量分数分别在4、9月初有2个高峰,分别为1.711×10（-5）、2.594×10（-5）,6月底达到最低值,仅为7.63×10（-6）;矮嵩草草甸土壤可溶性有机氮质量分数高峰分别在4月底和10月初,分别为2.36×10（-5）、2.036×10（-5）,6月底达到最低（1.1×10（-5））;退化矮嵩草草甸土壤可溶性有机氮质量分数季节动态与矮嵩草草甸相似,最高值出现在4月底,为1.582×10（-5）,最低值出现在6月（5.57×10（-6））;矮嵩草草甸土壤可溶性有机氮质量分数占土壤可溶性总氮的50.01%,土壤铵态氮占可溶性总氮的49.99%.土壤可溶性氨基酸态氮占土壤可溶性总氮的2 1.80%、占土壤可溶性有机氮的43.60%.与土壤无机氮比较,土壤可溶性有机氮库和可溶性氨基酸态氮库在高寒草甸土壤氮素中占有重要份额,这也是高寒植物可利用氮素的重要组成成分.

英文摘要：

The soil dissolved organic nitrogen （DON） content, soil amino acids species and their season dynam- ics were analyzed, and the soil N-supplying capacity of different time was determined on three type alpine meadows of Qinghai Province. This study would lay the foundation for alpine meadow plants to absorb soil ni- trogen. The results showed that the most dominant free amino acids in alpine meadow were phenylalanine andaspartic acid, followed by leucine, arginine, proline, histidine, glutamic acid, lysine and glycine, which make up 80%-90% of total free amino acid content. The average concentration of total free amino acids nitrogen was 6.90x10-6 dry soil for Kobresic tibetica meadow, reaching maximum at the end of June, and 7.44x10-6 dry soil for Kobresia humilis meadow, reaching maximum at the end of May, then gradually decrease with growth sea- son. The total amino acids nitrogen content of degarded Kobresia humilis meadow soil varies not phenomenally with seasons, whose average concentration was 5.04x 10-6. w（DON） ofKobresic tibetica meadow had two peaks of 1.711 x 10-5 and 2.594x 10-5 mg/kg, respectively in early April and September, and had the minimum, only 7.63 x 10-6 at the end of June. w（DON） ofKobresia humilis meadow has two peaks value, 2.36x 10 5 and 2.036x10-5, re- spectively by the end of April and in early October, reaching the minimum, only 1.1 x10-5, at the end of June. w （DON） of degraded Kobresia humilis meadow soil seasonal dynamic was as similar as Kobresia humilis mead- ow, the highest value was 1.582x 10 5 that appeared in the end of April, and the lowest value in the end of June was only 5.57x 10-6. w（DON） ofKobresia humilis meadows accounted for 50.01% of soil total dissolved nitro- gen, soil NI-L-N accounted for 49.99% of soil total dissolved nitrogen. Soil dissolved amino acids-N accounted for 21.80% of soil total dissolved nitrogen, soil dissolved amino acids-N accounted for 43.60% of DON in the soil. Research results showed that compared with soil inorganic nitroge