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首页> 外文期刊>Ecosystems >Landscape and Ecosystem-Level Controls on Net Carbon Dioxide Exchange along a Natural Moisture Gradient in Canadian Low Arctic Tundra
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Landscape and Ecosystem-Level Controls on Net Carbon Dioxide Exchange along a Natural Moisture Gradient in Canadian Low Arctic Tundra

机译：加拿大低北极苔原沿自然水分梯度的二氧化碳净交换的景观和生态系统级控制

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摘要

Our understanding of the controls and magnitudes of regional CO exchanges in the Arctic are limited by uncertainties due to spatial heterogeneity in vegetation across the landscape and temporal variation in environmental conditions through the seasons. We measured daytime net ecosystem CO exchange and each of its component fluxes in the three major tundra ecosystem-types that typically occur along natural moisture gradients in the Canadian Low Arctic biweekly during the full snow-free season of 2004. In addition, we used a plant-removal treatment to compare the contribution of bulk soil organic matter to total respiratory CO loss among these ecosystems. Net CO exchange rates varied strongly, but not consistently, among ecosystems in the spring and summer phases as a result of ecosystem-specific and differing responses of gross photosynthesis and respiration to temporal variation in environmental conditions. Overall, net carbon gain was largest in the wet sedge ecosystem and smallest in the dry heath. Our measures of CO flux variation within each ecosystem were frequently most closely correlated with air or soil temperatures during each seasonal phase. Nevertheless, a particularly large rainfall event in early August rapidly decreased respiration rates and stimulated gross photosynthetic rates, resulting in peak rates of net carbon gain in all ecosystems. Finally, the bulk soil carbon contribution to total respiration was relatively high in the birch hummock ecosystem. Together, these results demonstrate that the relative influences of moisture and temperature as primary controls on daytime net ecosystem CO exchange and its component fluxes differ in fundamental ways between the landscape and ecosystem scales. Furthermore, they strongly suggest that carbon cycling responses to environmental change are likely to be highly ecosystem-specific, and thus to vary substantially across the low arctic landscape.
机译：我们对北极区域CO交换的控制和强度的了解受到不确定性的限制，这是由于整个景观中植被的空间异质性以及整个季节的环境条件随时间变化所致。我们在2004年的整个无雪季节中，测量了加拿大低北极地区每两周通常沿着自然湿度梯度发生的三种主要苔原生态系统类型的白天净生态系统CO交换及其组成通量。去除植物的处理，以比较这些生态系统中大量土壤有机物对总呼吸CO损失的贡献。由于特定于生态系统且总光合作用和呼吸对环境条件随时间变化的响应不同，春季和夏季各生态系统之间的净CO汇率变化很大，但不一致。总体而言，湿莎草生态系统中的净碳增加最大，而干荒地则最小。在每个季节阶段，我们测量的每个生态系统中的CO通量变化通常与空气或土壤温度最密切相关。然而，8月初的一次特大降雨事件迅速降低了呼吸速率并刺激了总的光合作用速率，导致所有生态系统的净碳增加峰值速率。最后，在白桦山岗生态系统中，土壤碳对总呼吸的贡献较高。总之，这些结果表明，作为主要控制因素的湿度和温度对白天净生态系统CO交换及其组成通量的相对影响在景观和生态系统规模之间存在根本性的差异。此外，他们强烈建议，碳循环对环境变化的响应很可能是高度生态系统特定的，因此在北极低地景观中差异很大。

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