Saltwater and nutrient legacies reduce net ecosystem carbon storage despite freshwater restoration: insights from experimental wetlands
Saltwater and nutrient legacies reduce net ecosystem carbon storage despite freshwater restoration: insights from experimental wetlands
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盐水和营养遗产减少净生态系统碳储存，尽管淡水恢复：来自实验湿地的见解
DOI：
10.1111/rec.13524
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发表时间：
2021-08
影响因子：
3.2
通讯作者：
D. Y. Lee;J. Kominoski;Michael S. Kline;Michelle Robinson;Suzy Roebling
中科院分区：
文献类型：
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作者：
D. Y. Lee;J. Kominoski;Michael S. Kline;Michelle Robinson;Suzy Roebling
生态系统净碳平衡是对生态系统功能的综合评价，可以检验生态系统恢复效果。沿海泥炭地是全球重要的碳汇，易受海水入侵造成的碳损失的影响。目前尚不清楚在淡水恢复过程中，湿地碳储量和通量在暴露于盐水和高营养物质后是如何变化的。我们从美国佛罗里达州Everglades的淡水沼泽中将淡水恢复为锯草（Cladium jamaicense）泥炭块，这些泥炭块先前暴露于湿地中生态系统中升高的盐度（约9 ppt）和磷(P)负荷（1 g P m−2年−1年）。我们量化了恢复过程中水土物理化学、植物和土壤碳和养分蓄积量以及生态系统净生产力的变化。加入淡水后，孔隙水的矿化度立即从bb0.8降至约2ppt，但孔隙水溶解有机碳的升高仍然存在。地表和地下生物量、叶片磷浓度、生态系统总生产力（GEP）和生态系统呼吸（ER）的瞬时速率仍然高于先前添加的磷，在有盐水和磷遗产的沼泽中，模拟的月GEP和ER较高，导致负净生态系统生产力比对照低12倍。添加了咸水和磷的湿地凋落叶分解率和凋落叶磷浓度比添加了咸水和磷的湿地高2倍，尽管有淡水恢复，但咸水和磷对碳损失的影响仍然存在，但仅暴露于咸水的淡水湿地恢复最大。我们的研究结果表明，在受盐水入侵和养分富集影响的营养有限的淡水湿地，恢复是一个缓慢的过程。
Net ecosystem carbon balance is a comprehensive assessment of ecosystem function that can test restoration effectiveness. Coastal peatlands are globally important carbon sinks that are vulnerable to carbon loss with saltwater intrusion. It is uncertain how wetland carbon stocks and fluxes change during freshwater restoration following exposure to saltwater and elevated nutrients. We restored freshwater to sawgrass (Cladium jamaicense) peat monoliths from freshwater marshes of the Everglades (Florida, U.S.A.) that had previously been exposed to elevated salinity (approximately9 ppt) and phosphorus (P) loading (1 g P m−2 year−1) in wetland mesocosms. We quantified changes in water and soil physicochemistry, plant and soil carbon and nutrient standing stocks, and net ecosystem productivity during restoration. Added freshwater immediately reduced porewater salinity from >8 to approximately 2 ppt, but elevated porewater dissolved organic carbon persisted. Above‐ and belowground biomass, leaf P concentrations, and instantaneous rates of gross ecosystem productivity (GEP) and ecosystem respiration (ER) remained elevated from prior added P. Modeled monthly GEP and ER were higher in marshes with saltwater and P legacies, resulting in negative net ecosystem productivities that were up to 12× lower than controls. Leaf litter breakdown rates and litter P concentrations were 2× higher in marshes with legacies of added saltwater and P. Legacies of saltwater and P on carbon loss persisted despite freshwater restoration, but recovery was greatest for freshwater marshes exposed to saltwater alone. Our results suggest that restoration in nutrient‐limited freshwater wetlands exposed to saltwater intrusion and nutrient enrichment is a slow process.