Assessing the potential to decrease the Gulf of Mexico hypoxic zone with Midwest US perennial cellulosic feedstock production
Assessing the potential to decrease the Gulf of Mexico hypoxic zone with Midwest US perennial cellulosic feedstock production
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评估美国中西部常年纤维素原料生产减少墨西哥湾缺氧区的潜力
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发表时间：
2017
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通讯作者：
C. Bernacchi
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作者：
A. VanLoocke;T. Twine;C. Kucharik;C. Bernacchi
本研究的目的是确定与密西西比-阿查法拉亚河流域 (MARB) 内一系列大规模专用常年纤维素生物能源生产情景相关的水流、溶解无机氮 (DIN) 浸出和出口到墨西哥湾的变化。为了实现这一目标，我们使用了 Agro-IBIS（一种能够模拟行间作物、芒草和柳枝稷生物地球化学的植被模型）以及 THMB（一种能够模拟水流和 DIN 输出的水文模型）。在不同的施肥量（0-200 kg N ha−1）和整个 MARB 中用芒草或柳枝稷部分替代当前中行作物（5-25%）的情况下进行了模拟。该分析还包括两种情况，其中芒草和柳枝稷（分别为 MRX 和 MRS）分别取代了 ca。目前 40% 的玉米产量用于生产乙醇。在所有情景中，整个 MARB 的径流和水流均略有减少，其中最大的差异（约 6%）发生在该地区较干燥部分的最高替换分数情景中的芒草。然而，即使在 MRX 情景下，流域出口处 MARB 总排放量的差异也小于 1.5%。按百分比计算，DIN 出口减少量远大于径流减少量，最高替代情景使长期平均 DIN 出口量减少约 10%。柳枝稷和芒草分别为 15% 和 20%。施肥情景表明，即使柳枝稷和芒草的施肥量分别为 100 kg N ha−1 和 150 kg N ha−1，也可以显着减少 DIN 浸出。这些结果表明，考虑到有针对性的管理策略，芒草和柳枝稷有潜力通过减少 DIN 的出口来提供关键的生态系统服务，同时避免水流减少的水文影响。
The goal of this research was to determine the changes in streamflow, dissolved inorganic nitrogen (DIN) leaching and export to the Gulf of Mexico associated with a range of large‐scale dedicated perennial cellulosic bioenergy production scenarios within in the Mississippi–Atchafalaya River Basin (MARB). To achieve this goal, we used Agro‐IBIS, a vegetation model capable of simulating the biogeochemistry of row crops, miscanthus and switchgrass, coupled with THMB, a hydrology model capable of simulating streamflow and DIN export. Simulations were conducted at varying fertilizer application rates (0–200 kg N ha−1) and fractional replacement (5–25%) of current row crops with miscanthus or switchgrass across the MARB. The analysis also includes two scenarios where miscanthus and switchgrass (MRX and MRS, respectively) each replace the ca. 40% of maize production currently devoted to ethanol. Across the scenarios, there were minor reductions in runoff and streamflow throughout the MARB, with the largest differences (ca. 6%) occurring for miscanthus at the highest fractional replacement scenarios in drier portions of the region. However, differences in total MARB discharge at the basin outlet were less than 1.5% even in the MRX scenario. Reductions in DIN export were much larger on a percentage basis than reductions in runoff, with the highest replacement scenarios decreasing long‐term mean DIN export by ca. 15% and 20% for switchgrass and miscanthus, respectively. Fertilization scenarios show that significant reductions in DIN leaching are possible even with application rates of 100 and 150 kg N ha−1 for switchgrass and miscanthus, respectively. These results indicate that, given targeted management strategies, there is potential for miscanthus and switchgrass to provide key ecosystem services by reducing the export of DIN, while avoiding hydrologic impacts of reduced streamflow.