中文摘要：

【目的】分析不同季节和退化程度的山地草甸土壤氮素含量,为退化草甸区域的植被恢复提供理论依据。【方法】于2014年6月和11月,分别按0-20 cm和20-40 cm的土层深度分层多点采集江西省武功山草甸中未退化（CK）草甸区（植被盖度〉90%）、轻度退化（LD）草甸区（60%〈植被盖度〈75%）、中度退化（MD）草甸区（30%〈植被盖度〈45%）、重度退化（HD）草甸区（植被盖度〈10%）等4个样地土壤样品,测定其全氮和碱解氮含量。【结果】武功山草甸6月的全氮含量在各退化阶段中均高于11月。上层（0-20 cm）土壤中,6月时LD样地土壤全氮含量最高,为5226.22 mg/kg,极显著高于其他样地（P〈0.01,下同）;11月时CK样地土壤全氮含量最高,为4237.57 mg/kg,显著高于其他样地（P〈0.05,下同）。下层（20-40 cm）土壤中,6月时LD样地土壤全氮含量最高,为4358.69 mg/kg,显著高于其他样地;11月时CK样地土壤全氮含量最高,为3011.86 mg/kg,显著高于除LD样地外的其他样地。CK、LD、MD和HD样地中,6-11月上层土全氮含量减少量分别为7.31%、23.65%、20.87%和2.45%;下层土全氮含量减少量分别为16.94%、32.57%、28.30%和5.27%。同一样地中同时期上层土全氮含量均高于下层土。另外,6月全氮含量随着退化的加剧呈先增加再减少的变化趋势,在轻度退化阶段达到最高值,而在11月呈持续减少趋势。土壤碱解氮的变化趋势与全氮相似。土壤全氮、碱解氮在未退化、轻度退化和中度退化阶段均具有显著正相关性,但在重度退化阶段相关性不显著（P〉0.05）。【结论】山地草甸植物生长所需的氮素大多来源于土壤,但人为干扰最终会导致土壤氮素流失,因而易导致草甸退化。

英文摘要：

【Objective】The effects of different seasons and degradation degrees on soil N in the mountain meadows were studied in order to provide theoretical references for restoring vegetation of degraded meadow. 【Method】The stratified soils at different depths（0-20 cm and 20-40 cm） were collected from different meadows in Wugong mountain of Xiangxi province in June and November 2014,. And these meadows were divided into four types viz., undegraded meadow（CK,vegetation coverage〉90%）, light-degraded meadow（LD, 60%〈vegetation coverage〈75%）, moderate-degraded meadow（MD, 30%〈vegetation coverage〈45%）, heavy-degraded meadow（HD, vegetation coverage 〈10%） based on degradation degrees of meadow. Then the contents of total N and alkali-hydrolyzale N in the different stratified soils were determined.【Result】The results showed that, in the different degraded meadows of Wugong mountain, the content of total N in June was higher than that in November. In the topsoil（0-20 cm）, the total N content of LD was the highest（5226.22 mg/kg） in June, which was extremely significantly higher than those of other meadows（P〈0.01, the same below）. Moreover, the topsoil total N content of CK was the highest（4237.57 mg/kg） in November, which was significantly higher than those of other meadows（P〈0.05, the same below）. In the subsoil（20-40 cm）, the total N content of LD was the highest（4358.69mg/kg） in June, which was significantly higher than those of other meadows. And the subsoil total N content of CK was the highest（3011.86 mg/kg） in November, which had not significant difference with that of LD and was significantly higher than those of MD and HD. In addition, the decrement of total N in topsoil of CK, LD, MD and HD were 7.31%, 23.65%,20.87% and 2.45% from June to November, respectively, and the decrement of total N in subsoil of CK, LD, MD and HD were 16.94%, 32.57%, 28.30% and 5.27%, respectively. The total N content of topsoil was higher than that of subsoil in the sa