Abstract Rapidly increasing population pressure and land conversion from forests to urban and agricultural uses have been important stressors on coastal wetlands. Headwater wetlands in the southeast U.S. are particularly vulnerable because of their small size- they are easily filled or impacted through ditching, piping or impoundments. Since headwater areas have a disproportionately high influence on watershed flow and nutrient flux, alterations to their functionality can have impacts to downstream and coastal waters. Although headwater wetlands are generally understood to support water quality, the magnitude and mechanisms for this function are often uncertain. We compared flow, NO2−-N + NO3−-N (NO2 + NO3) concentrations, and NO2 + NO3 loads at the inlet and outlet of four headwater slope wetlands across common land covers/uses (i.e., commercial-urban, residential-suburban, agriculture, and forested) in coastal Alabama, USA. Watershed sizes draining to wetlands ranged from 0.5–1.8 km2 and each wetland showed distinct and shared trends. Measured NO2 + NO3 concentrations were typically low (

中文翻译：

---

表征不同土地利用的源头坡湿地氮衰减

摘要 快速增加的人口压力和土地从森林向城市和农业用途的转变一直是沿海湿地的重要压力源。美国东南部的源头湿地由于面积小而特别脆弱——它们很容易被沟渠、管道或蓄水池填满或受到影响。由于源头区域对流域流量和养分通量的影响不成比例，因此其功能的改变会对下游和沿海水域产生影响。尽管人们普遍认为源头湿地支持水质，但这种功能的大小和机制通常是不确定的。我们比较了常见土地覆盖/用途的四个源头水坡湿地入口和出口处的流量、NO2−-N + NO3−-N (NO2 + NO3) 浓度和 NO2 + NO3 负荷（即，商业城市、住宅郊区、农业和森林）在美国阿拉巴马州沿海地区。流向湿地的流域大小范围为 0.5-1.8 平方公里，每个湿地都显示出独特和共同的趋势。测得的 NO2 + NO3 浓度通常很低（