While inundated, small ponds (< 1000 m² area) account for disproportionately large contributions of CO₂ efflux to the global carbon budget and also store carbon in anoxic sediments. However, pond hydrology is shifting toward increasingly dry conditions in alpine and temperate zones, which might lead to increased exposure of shallow pond sediments. We analyzed sediment CO₂ efflux rates in dried sediments of multiple ponds of varying hydrology and sediment characteristics at montane and subalpine elevations near the Rocky Mountain Biological Laboratory in Colorado. Average CO₂ efflux rates from exposed sediments, 331.5 ± 11.5 mmol m⁻² d⁻¹ at the montane sites and 142.8 ± 45.1 mmol m⁻² d⁻¹ at the subalpine sites, were 10 times higher than average CO₂ efflux rates from pond water. Principal components analysis to reduce dimensionality of sediment characteristics revealed that random inter‐pond differences rather than exposure timing or hydroperiod drove variation among sediments. In linear mixed effects models of CO₂ flux rates, significant predictors included sediment moisture and temperature, pH, total organic carbon, and organic matter content at all pond hydroperiod classifications and sites. However, the sediment characteristics explaining the most variance differed among sites and hydroperiods and included nitrate concentrations, pH, bulk density, and temperature. We conclude that pond sediments are heterogeneous both within and among ponds in close proximity, and drivers of relatively high CO₂ efflux rates differ among pond hydroperiods and elevations. This work emphasizes that local differences can impact predictions of CO₂ flux from lentic sediments which are becoming increasingly exposed.

中文翻译：

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生物地球化学特征和水文周期影响暴露的高海拔池塘沉积物的二氧化碳通量率

虽然被淹没，但小池塘（面积<1000 m ²）对CO ₂外排对全球碳预算的贡献不成比例，并且还会将碳存储在缺氧沉积物中。但是，池塘水文学正在向高寒和温带地区日益干燥的环境转变，这可能导致浅池沉积物的暴露增加。我们分析了科罗拉多州落基山生物实验室附近山地和亚高山海拔多处水文和沉积特征不同的多个池塘的干沉积物中的CO ₂外排速率。平均CO ₂从暴露沉积物流出率，331.5±11.5毫摩尔米^-2 d ^-1在山地站点和142.8±45.1毫摩尔米亚高山站点的^-2 d ^-1是池塘水中平均CO ₂外流速率的10倍。降低沉积物特征维数的主成分分析表明，随机的相互作用差异而不是暴露时间或水动力驱使了沉积物之间的变化。在CO _2的线性混合效应模型中流量，重要的预测因素包括所有池塘水期分类和地点的沉积物水分和温度，pH，总有机碳和有机物含量。但是，解释最大差异的沉积物特征在站点和水文时段之间有所不同，其中包括硝酸盐浓度，pH，堆积密度和温度。我们得出的结论是，在池塘内部和附近的池塘之间，池塘沉积物是非均质的，并且相对较高的CO ₂外排率的驱动因素在池塘水周期和高程之间是不同的。这项工作强调，局部差异会影响越来越多地暴露于透镜沉积物中的CO ₂通量的预测。