【摘要】 溶解性有机氮（DON）是土壤中活跃的氮库，其生态环境行为与其化学组分密切相关。为了探究冀西北寒旱区春玉米地膜覆盖及增施氮肥对土壤DON组分的影响，采用田间试验，设置不覆膜+N 225 kg·hm^-2、覆膜+N 225 kg·hm^-2和覆膜+N 300 kg·hm^-2处理，利用三维荧光光谱和紫外光谱联合分析土壤DON组分特征。结果表明，土壤总氮（TN）含量在569.81～1179.39 mg·kg^-1,DON含量在11.26～126.95 mg·kg^-1，土壤DON组分以类胡敏酸氮为主，占比在49.8%～58.1%，其次为类蛋白，占比18.4%～29.2%。覆膜及增加施氮量均提高了0～8 cm土层土壤铵态氮和TN含量，铵态氮含量分别增加了27.8%、55.1%，总氮含量分别增加了37.2%、31.2%，但高施氮量会降低土壤硝态氮、总溶解性氮（TDN）及DON含量。覆膜和施氮量主要影响0～8 cm土层DON荧光组分占比，增加土壤DON类蛋白组分占比，降低微生物代谢产物占比。地膜覆盖提高土壤DON腐殖化程度，增强微生物源，降低土壤DON芳香性和分子量；增施氮肥土壤DON腐殖化程度变弱，降低微生物来源的DON占比，促使土壤DON的外源输入特征较强。施氮量增加有助于土壤DON分子结构复杂性的提升，降低DON芳香性和分子量。覆膜及增加施氮量增强0～4 cm土层DON生物源特征，降低腐殖化程度。地膜覆盖通过提水增温促进土壤DON转化，提高土壤有效氮养分供给能力。更多还原

【Abstract】 Dissolved organic nitrogen（DON）is an active nitrogen pool in soil,and its ecological behavior is closely related to its chemical composition.To investigate the effects of plastic film mulching and increased nitrogen application on the composition of soil DON in spring maize fields in the cold and arid region of northwestern Hebei,a field experiment was conducted with three treatments:no mulching +N 225 kg·hm^-2,mulching +225 N kg·hm^-2,and mulching +N 300 kg·hm^-2.The characteristics of soil DON components were analyzed using a combination of three-dimensional fluorescence spectroscopy and ultraviolet spectroscopy.The results showed that soil total nitrogen（TN）content ranged from 569.81 to 1179.39 mg·kg^-1,and DON content ranged from 11.26 to 126.95 mg·kg^-1.The dominant component of soil DON was humic acid-like nitrogen,accounting for 49.8%-58.1%,followed by protein-like substances（18.4%-29.2%）.Both mulching and increased nitrogen application enhanced the contents of ammonium nitrogen and TN in the 0-8 cm soil layer;Ammonium nitrogen was increased by 27.8% and 55.1%,while TN was increased by 37.2% and 31.2%,respectively.However,high nitrogen input reduced the contents of nitrate nitrogen,total dissolved nitrogen（TDN）,and DON.Mulching and nitrogen application mainly affected the proportion of DON fluorescence components in the 0-8 cm soil layer by increasing the proportion of protein-like components and reducing the proportion of microbial metabolites.Mulching improved the humification degree of soil DON,enhanced microbial sources,and decreased the aromaticity and molecular weight of DON. In contrast,increased nitrogen application weakened the humification degree,reduced the proportion of microbially derived DON,and enhanced the characteristics of exogenous input.Higher nitrogen application contributed to the structural complexity of DON molecules and decreased their aromaticity and molecular weight.In the 0-4 cm soil layer,both mulching and nitrogen application strengthened the biological origin characteristics of DON while reducing its humification degree.Overall,plastic film mulching promoted DON transformation by increasing soil temperature and moisture,thereby improving the supply of available nitrogen in the soil.更多还原