Salt marshes have among the highest carbon (C) burial rates of any ecosystem and often rely on C accumulation to gain elevation and persist in locations with accelerating sea level rise. Net ecosystem carbon balance (NECB), the accumulation or loss of C resulting from vertical CO₂ and CH₄ gas fluxes, lateral C fluxes, and sediment C inputs, varies across salt marshes; thus, extrapolation of NECB to an entire marsh is challenging. Anthropogenic nitrogen (N) inputs to salt marshes impact NECB by influencing each component of NECB, but differences in the impacts of fertilization between edge and interior marsh must be considered when scaling up. NECB was estimated for the 0.5 km² Spartina alterniflora marsh area of Freeman Creek, NC, under control and fertilized conditions at both interior and edge berm sites. Annual CO₂ fluxes were nearly balanced at control sites, but fertilization significantly increased net CO₂ emissions at edge sites. Lateral C export, modeled using respiration rates, represented a significant C loss that increased with fertilization in both edge and interior marsh. Sediment C input was a significant C source in the interior, nearly doubling with fertilization, but represented a small source on the edge. When extrapolating C exchanges to the entire marsh, including edge which comprised 17% of the marsh area, the marsh displayed net loss of C despite a net C gain in the interior. Fertilization increased net C loss fivefold. Extrapolation of NECB to whole marshes requires inclusion of C fluxes for both edge and interior marsh.

中文翻译：

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美国北卡罗莱纳州盐沼的净生态系统碳平衡

盐沼是所有生态系统中最高的碳（C）埋葬率之一，通常依靠C积累来提高海拔，并在海平面上升加速的地方持续存在。盐沼中的生态系统净碳平衡（NECB），由于垂直CO ₂和CH ₄气体通量，横向C通量和沉积物C输入导致的C积累或损失；因此，将NECB外推到整个沼泽地具有挑战性。盐沼的人为氮输入会通过影响NECB的每个成分而影响NECB，但是在扩大规模时，必须考虑边缘和内部沼泽之间施肥的影响差异。NECB估计为0.5 km ² 互花米草在北内弗里曼河的边缘和边缘施肥条件下，在受控和施肥条件下进行沼泽化处理。对照地点的年度CO ₂通量几乎平衡，但施肥显着增加了净CO _2量边缘站点的排放。使用呼吸速率模拟的侧向碳出口代表了显着的碳损失，该损失随着边缘和内部沼泽的施肥而增加。沉积物碳输入是内部重要的碳源，受精后几乎增加了一倍，但在边缘处却代表很小的碳源。将C交换推算到整个沼泽（包括占沼泽面积17％的边缘）时，尽管内部C净增加，但沼泽仍显示C净损失。施肥使净碳损失增加了五倍。将NECB外推到整个沼泽地需要边缘和内部沼泽地C流量。