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首页> 外文期刊>Aquatic Sciences >Comparing streambed light availability and canopy cover in streams with old-growth versus early-mature riparian forests in western Oregon
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Comparing streambed light availability and canopy cover in streams with old-growth versus early-mature riparian forests in western Oregon

机译：比较俄勒冈州西部老树区和早熟河岸林的溪流光能利用率和冠层覆盖度

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Light availability strongly influences stream primary production, water temperatures and resource availability at the base of stream food webs. In headwater streams, light is regulated primarily by the riparian forest, but few studies have evaluated the influence of riparian forest stand age and associated structural differences on light availability. In this study, we evaluated canopy cover and streambed light exposure in four second-order streams within paired reaches of primary old-growth versus second-growth mature riparian forests. Stand age class was used as a proxy here for canopy complexity. We estimated stream canopy cover using a spherical densiometer. Local streambed light exposure was quantified and compared within and between reaches using fluorescein dye photo-degradation. Reaches with complex old-growth riparian forests had frequent canopy gaps which lead to greater stream light availability compared to adjacent reaches with simpler second-growth riparian forests. We quantified light exposure at relatively high resolution (every 5 m) and also found greater variability in stream light along the reaches with old-growth riparian forests in three of the four streams. Canopy gaps were particularly important in creating variable light within and between reaches. This work demonstrates the importance of the age, developmental stage, and structure of riparian forests in controlling stream light. The highly variable nature of light on the stream benthos also highlights the value of multiple measurements of light or canopy structure when quantifying stream light.
机译：光的可利用性强烈影响着溪流食物网基础上的溪流初级生产，水温和资源可用性。在源头溪流中，光主要受河岸林调节，但很少有研究评估河岸林分龄和相关结构差异对光利用率的影响。在这项研究中，我们评估了主要的老树和第二树的成熟河岸森林成对成对范围内的四个二次流中的冠层覆盖和流光暴露。在这里，林分年龄等级被用来代替树冠。我们使用球形密度计估算了河流冠层的覆盖率。使用荧光素染料光降解，对局部流光曝光量进行定量，并在达到范围之内和之间进行比较。与较近的次生河岸森林相比，拥有复杂的老龄河岸森林的地区经常出现树冠间隙，从而导致溪流光利用率更高。我们以相对较高的分辨率（每5 m）对暴露的光线进行了量化，并且在四个溪流中的三个溪流中，沿河沿岸的古老林地森林流域的变化更大。冠层间隙对于在伸手可及的距离之间产生可变的光线特别重要。这项工作表明了年龄，发育阶段和河岸森林结构在控制溪流光中的重要性。溪流底栖生物上光的高度可变性也突出了在定量溪流光时对光或冠层结构进行多次测量的价值。

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