High‐altitude tropical grasslands, known as “páramos,” are characterized by high solar radiation, high precipitation, and low temperature. They also exhibit some of the highest ecosystem carbon stocks per unit area on Earth. Recent observations have shown that páramos may be a net source of CO₂ to the atmosphere as a result of climate change; however, little is known about the source of this excess CO₂ in these mountainous environments or which landscape components contribute the most CO₂. We evaluated the spatial and temporal variability of surface CO₂ fluxes to the atmosphere from adjacent terrestrial and aquatic environments in a high‐altitude catchment of Ecuador, based on a suite of field measurements performed during the wet season. Our findings revealed the importance of hydrologic dynamics in regulating the magnitude and likely fate of dissolved carbon in the stream. While headwater catchments are known to contribute disproportionately larger amounts of carbon to the atmosphere than their downstream counterparts, our study highlights the spatial heterogeneity of CO₂ fluxes within and between aquatic and terrestrial landscape elements in headwater catchments of complex topography. Our findings revealed that CO₂ evasion from stream surfaces was up to an order of magnitude greater than soil CO₂ efflux from the adjacent terrestrial environment. Stream carbon flux to the atmosphere appeared to be transport limited (i.e., controlled by flow characteristics, turbulent flow, and water velocity) in the upper reaches of the stream, and source limited (i.e., controlled by CO₂ and carbon availability) in the lower reaches of the stream. A 4‐m waterfall along the channel accounted for up to 35% of the total evasion observed along a 250‐m stream reach. These findings represent a first step in understanding ecosystem carbon cycling at the interface of terrestrial and aquatic ecosystems in high‐altitude, tropical, headwater catchments.

中文翻译：

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高海拔热带流域陆地和水生环境中的二氧化碳排放量

高海拔的热带草原，被称为“帕拉莫斯”，具有高太阳辐射，高降水量和低温的特点。它们还表现出地球上每单位面积生态系统碳储量最高的一些地区。最近的观察表明，由于气候变化，帕拉莫斯可能是大气中CO ₂的净来源。但是，对于这些山区环境中过量的CO ₂的来源或景观成分贡献最大的CO ₂知之甚少。我们评估了表面CO _2的时空变化根据在雨季期间进行的一系列野外测量，从厄瓜多尔高海拔流域的邻近陆地和水生环境向大气通量。我们的发现揭示了水文动力学在调节河流中溶解碳的量和最终命运方面的重要性。尽管已知上游流域向大气中排放的碳比下游下游成比例地大得多，但我们的研究强调了复杂地形的上游流域中水生和陆地景观要素之间以及之间的CO ₂通量的空间异质性。我们的发现表明，从河流表面逃逸出的CO ₂最多比土壤CO ₂高一个数量级。从邻近陆地环境流出。流入大气的碳流似乎在其上游受到运输的限制（即，由流动特性，湍流和水速度控制），而在排放源中的碳源受到限制（即，由CO ₂和碳可利用性控制）。溪流的下游。沿河道的4 m瀑布占沿250 m河段观测到的总逃逸量的35％。这些发现代表了了解高海拔，热带，水源流域陆地和水生生态系统界面的生态系统碳循环的第一步。