Physiographic Controls and Wildfire Effects on Aquatic Biogeochemistry in Tundra of the Yukon‐Kuskokwim Delta, Alaska
Physiographic Controls and Wildfire Effects on Aquatic Biogeochemistry in Tundra of the Yukon‐Kuskokwim Delta, Alaska
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DOI：
10.1029/2022jg006891
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发表时间：
2022-07
期刊：
影响因子：
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通讯作者：
S. Zolkos;E. MacDonald;J. Hung;J. Schade;S. Ludwig;P. Mann;Rachael Treharne;S. Natali
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文献类型：
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作者：
S. Zolkos;E. MacDonald;J. Hung;J. Schade;S. Ludwig;P. Mann;Rachael Treharne;S. Natali
北部高纬度三角洲是生物地球化学处理、陆地与水生连通性以及阿拉斯加育空-库斯科奎姆三角洲 (YKD) 苔原野火的热点。然而，在北部三角洲地区，野火对水生生物地球化学的影响仍未得到充分研究，从而限制了对高纬度生物地球化学循环的更全面的了解。在这项研究中，我们使用来自五个水生环境（泥炭高原池塘、沼泽池塘、沼泽河道、湖泊和溪流）的多年（2015-2019）水化学测量数据集（n = 406）评估野火对 YKD 苔原夏季水生生物地球化学的影响。我们的目标是 (a) 表征水生环境中水化学的变化； (b) 确定野火对水化学的影响； (c) 评估湖泊（较低的陆地淡水连通性）和沼泽池塘（较高的连通性）火灾后水化学的多年模式。与野火相比，环境之间水化学的变化与流域特征（例如陆地-水生连通性）的相关性更强。然而，某些水化学成分表现出一致的野火效应。溶解有机碳 (DOC) 和 CO2 的减少，以及 pH 值、电导率、NH4+ 和 NO3− 的增加表明，通过燃烧土壤有机物，野火减少了可用于水文运输和微生物呼吸的有机物，并将氮动员到淡水中。湖泊和沼泽池塘中的电导率、DOC 和 CO2 的多年火灾后变化表明，流域特征是 YKD 生态系统对野火响应和恢复的基础。总之，这些结果表明，北部高纬度地区苔原野火发生的增加可能会推动多年来向更强的水生无机养分循环的转变，而地形特征的变化可能是野火对更广泛范围内的水生生态系统产生影响的基础。
Northern high‐latitude deltas are hotspots of biogeochemical processing, terrestrial‐aquatic connectivity, and, in Alaska's Yukon‐Kuskokwim Delta (YKD), tundra wildfire. Yet, wildfire effects on aquatic biogeochemistry remain understudied in northern delta regions, thus limiting a more comprehensive understanding of high latitude biogeochemical cycles. In this study, we assess wildfire impacts on summertime aquatic biogeochemistry in YKD tundra using a multi‐year (2015–2019) data set of water chemistry measurements (n = 406) from five aquatic environments: peat plateau ponds, fen ponds, fen channels, lakes, and streams. We aimed to (a) characterize variation in hydrochemistry among aquatic environments; (b) determine wildfire effects on hydrochemistry; and (c) assess post‐fire multi‐year patterns in hydrochemistry in lakes (lower terrestrial‐freshwater connectivity) and fen ponds (higher connectivity). Variation in hydrochemistry among environments was more strongly associated with watershed characteristics (e.g., terrestrial‐aquatic connectivity) than wildfire. However, certain hydrochemical constituents showed consistent wildfire effects. Decreases in dissolved organic carbon (DOC) and CO2, and increases in pH, specific conductance, NH4+, and NO3− indicate that, by combusting soil organic matter, wildfire reduces organics available for hydrologic transport and microbial respiration, and mobilizes nitrogen into freshwaters. Multi‐year post‐fire variation in specific conductance, DOC, and CO2 in lakes and fen ponds suggest that watershed characteristics underlie ecosystem response and recovery to wildfire in the YKD. Together, these results indicate that increasing tundra wildfire occurrence at northern high latitudes could drive multi‐year shifts toward stronger aquatic inorganic nutrient cycling, and that variation in terrain characteristics is likely to underlie wildfire effects on aquatic ecosystems across broader scales.