Riparian ecosystems provide critical habitat and functions while being some of the most productive areas in forests. Both conifers and hardwoods contribute to maintenance of habitat and function. To determine the impact of water stress on growth of red alder (Alnus rubra Bong.) and western hemlock (Tsuga heterophylla [Raf.] Sarg.), we installed Nelder type 1a combined with replacement series plots on three Oregon Coast Range sites. Densities ranged from 988 to 85,400 trees/hectare, with ratios (hemlock:alder) of 100:0, 75:25, 50:50, 25:75, and 0:100. In the first 4 years after planting, alder used water in the growing season at greater depths earlier than western hemlock. Higher densities resulted in greater water stress later in the growing season in weeded areas (maintained by herbicide applications), but stress was similar across densities in unweeded areas. Water stress at early ages was correlated with decreased size 14 or 24 years after planting for both species, but these correlations were confounded with other effects of density. Increasing water availability in areas with low summer precipitation could enhance growth of red alder and western hemlock, even in highly productive riparian areas.

中文翻译：

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红Al木/西铁杉沿海俄勒冈人工林可变密度的植物水分胁迫和土壤耗竭

河岸生态系统提供了关键的栖息地和功能，同时又是森林中生产力最高的地区。针叶树和硬木都有助于维持生境和功能。要确定水分胁迫对赤al（Alnus rubra Bong。）和西铁杉（Tsuga heterophylla）生长的影响[Raf。Sarg。），我们在三个俄勒冈海岸山脉地点安装了Nelder类型1a，并结合了替换系列样地。密度范围为988至85,400棵树/公顷，比率（铁杉：al木）为100：0、75：25、50：50、25：75和0：100。播种后的最初四年中，al木在生长期中比西部铁杉更早地使用了水。较高的密度在杂草区的生长季后期（通过施用除草剂维持）导致更大的水分胁迫，但在非杂草区的密度之间的胁迫相似。两种物种在种植后14或24年的幼龄期水分胁迫都与体型减小有关，但这些相关性与密度的其他影响相混淆。夏季降水少的地区增加水的供应量可以促进赤der和西铁杉的生长，