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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 CO2 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 CO2 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 CO2 loss among these ecosystems. Net CO2 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 CO2 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 CO2 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：由于整个地区植被的空间异质性以及整个季节的环境条件随时间变化，我们对北极区域CO2交换的控制和强度的了解受到不确定性的限制。我们在2004年的整个无雪季节中，每两周测量一次加拿大低北极地区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中的白天净生态系统CO2 交换及其组成通量。 ，我们采用了除草处理，比较了这些生态系统中大量土壤有机物对总呼吸CO2损失的贡献。春季和夏季各生态系统之间的二氧化碳净交换率变化很大，但并不一致，这是由于特定于生态系统且总的光合作用和呼吸对环境条件随时间变化的响应不同而造成的。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二氧化碳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，在白桦树岗生态系统中，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CO2 交换及其组成通量的相对影响在景观和生态系统尺度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，因此在整个北极低地景观中变化很大。

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