Drivers of Methane Flux Differ Between Lakes and Reservoirs, Complicating Global Upscaling Efforts
Drivers of Methane Flux Differ Between Lakes and Reservoirs, Complicating Global Upscaling Efforts
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DOI：
10.1029/2019jg005600
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发表时间：
2021-04-01
影响因子：
3.7
通讯作者：
Holgerson, M. A.
中科院分区：
文献类型：
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作者：
Deemer, B. R.;Holgerson, M. A.
甲烷是一种重要的温室气体，其大气浓度不断增加。淡水湖泊和水库对大气中甲烷浓度的贡献很大，但这种贡献的大小很少受到限制。不确定性部分源于当前采样地点是否代表全球人口，以及对哪些环境变量预测甲烷通量的了解不完整。因此，确定不同水体类型甲烷通量的主要驱动因素将为更准确的升级方法提供信息。在这里，我们使用来自 313 个湖泊和水库（表面积范围从 6 m(2) 到 5,400 km(2)）的总、扩散和沸腾面积甲烷排放的新数据库来确定甲烷排放的最佳预测因子。我们发现，甲烷排放的最佳预测因子因水体类型（湖泊与水库）而异，生态系统形态变量（例如表面积和最大深度）在湖泊中是更重要的预测因子，而本地生产指标（例如叶绿素 a）在水库中更重要。我们还发现，生产力强烈预测甲烷沸腾，而生态系统形态和水体类型是甲烷扩散通量更重要的预测因素。最后，我们确定了限制升级工作的几个知识差距。首先，我们需要对小型水库、大型湖泊以及天然和人工池塘进行更多甲烷排放测量。此外，更准确的升级工作需要改进有关水体表面积、水体类型（湖泊与水库）、冰物候以及与生产力相关的预测变量（例如总磷、DOC 和叶绿素 a）分布的全球信息。
Methane is an important greenhouse gas with growing atmospheric concentrations. Freshwater lakes and reservoirs contribute substantially to atmospheric methane concentrations, but the magnitude of this contribution is poorly constrained. Uncertainty stems partially from whether the sites currently sampled represent the global population as well as incomplete knowledge of which environmental variables predict methane flux. Thus, determining the main drivers of methane flux across diverse waterbody types will inform more accurate upscaling approaches. Here we use a new database of total, diffusive, and ebullitive areal methane emissions from 313 lakes and reservoirs (ranging in surface area from 6 m(2) to 5,400 km(2)) to identify the best predictors of methane emission. We found that the best predictors of methane emission differed by waterbody type (lakes vs. reservoirs), and that ecosystem morphometric variables (e.g., surface area and maximum depth) were more important predictors in lakes whereas metrics of autochthonous production (e.g., chlorophyll a) were more important in reservoirs. We also found that productivity strongly predicted methane ebullition, whereas ecosystem morphometry and waterbody type were more important predictors of diffusive methane flux. Finally, we identify several knowledge gaps that limit upscaling efforts. First, we need more methane emission measurements in small reservoirs, large lakes, and both natural and artificial ponds. Additionally, more accurate upscaling efforts require improved global information about waterbody surface area, waterbody type (lake vs. reservoir), ice phenology, and the distribution of productivity-related predictor variables such as total phosphorus, DOC, and chlorophyll a.