The resilience of salt marshes to sea level rise depends on vertical accretion through belowground biomass production and sediment deposition to maintain elevation above sea level. Increased nitrogen (N) availability from anthropogenic sources may stimulate aboveground biomass production and sediment deposition and, thus, accretion; however, increased N may also negatively impact marsh accretion by decreasing belowground biomass and increasing net CO₂ emissions. A study was conducted in Spartina alterniflora‐dominated salt marshes in North Carolina, USA, to determine how responses to fertilization vary across locations with different physical and chemical characteristics. Pore water residence time, inundation time, and proximity to tidal creeks drove spatial differences in pore water sulfide, ammonium, and dissolved carbon concentrations. Although annual respiration and gross primary production were greater at the creek edge than interior marsh sites, net ecosystem CO₂ exchange (NEE) was nearly balanced at all the sites. Fertilization decreased belowground biomass in the interior sites but not on the creek edge. Aboveground biomass, respiration, gross primary production, and net CO₂ emissions increased in response to fertilization, but responses were diminished in interior marsh locations with high pore water sulfide. Hourly NEE measured by chambers were similar to hourly NEE observed by a nearby eddy covariance tower, but correcting for inundation depth relative to plant height was critical for accurate extrapolation to annual fluxes. The impact of fertilization on biomass and NEE, and thus marsh resilience, varied across marsh locations depending upon location‐specific pore water sulfide concentrations.

中文翻译：

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施肥对北卡罗莱纳州盐沼生物量和代谢的影响：受位置特定因素的调节

盐沼对海平面上升的适应力取决于通过地下生物量生产和沉积物沉积来保持海平面以上海拔的垂直积聚。人为来源增加的氮（N）利用率可能会刺激地上生物量的产生和沉积物的沉积，从而增加吸积；但是，增加的氮也可能通过减少地下生物量和增加净CO ₂排放量而对沼泽的积聚产生负面影响。在互花米草中进行了一项研究在美国北卡罗来纳州以盐沼为主导的区域，以确定对具有不同物理和化学特征的位置对施肥的反应如何变化。孔隙水的停留时间，淹没时间以及与潮汐小溪的邻近关系，导致孔隙水硫化物，铵盐和溶解碳浓度的空间差异。尽管小溪边缘的年呼吸量和初级总产值高于内陆沼泽地，但所有地点的净生态系统CO ₂交换量（NEE）几乎平衡。施肥减少了内部地点的地下生物量，但没有减少小溪边缘的生物量。地上生物量，呼吸作用，初级总产值和净CO ₂排放量因施肥而增加，但是在高孔隙水硫化物的内部沼泽地，其响应却减弱了。隔室每小时的NEE值与附近的涡度协方差塔观察到的每小时NEE值相似，但是相对于植物高度校正淹没深度对于准确推断年通量至关重要。施肥对生物量和NEE的影响以及因此对沼泽的复原力的影响在不同的沼泽地之间有所不同，具体取决于特定位置的孔隙水硫化物浓度。