City of Seattle, Seattle Public Utilities, Riparian Permanent Sample Plots 2003-current, Cedar River Municipal Watershed, King County, WA

The City of Seattle’s Cedar River Municipal Watershed is managed to support and supply clean drinking water to the greater Seattle area. The watershed covers 91,000 acres, hosts a rich diversity of plants, animals, and habitats, and is owned by the City of Seattle. From 2003 to 2005, Seattle Public Utilities established 61 permanent sample plots (PSP) in riparian habitats of the Cedar River Municipal Watershed. 31 of these plots (plot #s 1-31) were established in 2003 upstream of Chester Morse Lake, the drinking water reservoir for the City of Seattle. 30 additional plots (plot #s 32-61) were established in 2005 downstream of Chester Morse Lake. In 2012, 6 of the 61 total plots (plot #s 4, 11, 12, 27, 28, 29) were resampled and the sampling methods were simplified. Each sampling year had different surveyors. The riparian permanent sample plots were limited to low gradient, moderately to unconfined reaches along the Cedar River and its tributaries because they typically show the most variability in riparian condition, stream-riparian interactions are greatest, and fish use is highest. Sites were randomly selected along these reaches, with two plots located at each site, one on each side of the stream. Sites were stratified into four stand types: deciduous dominated, mixed deciduous/conifer, conifer dominated in stem exclusion phase with little understory, and conifer dominated differentiated with well-developed understory, with at least five plots in each type. Each plot was measured for tree species and diameter, snag diameter and height, shrub species and cover, herb species and cover, sapling species and cover, percent canopy cover, and other species found in the plots but not previously recorded in the tree, shrub, and herb sampling. Selection of riparian plots for resampling in 2012 was designed to include plots in second and old growth forests and with medium and large stream sizes. Future resampling is expected to occur at an approximately ten-year interval. The third resampling effort is expected to begin in 2025. This data package will be updated after resampling efforts occur.

西雅图市雪松河城市集水区（Cedar River Municipal Watershed）的管理目标为保障大西雅图地区的清洁饮用水供应。该集水区占地91000英亩，孕育了丰富多样的动植物类群与栖息地类型，权属归西雅图市所有。
2003年至2005年间，西雅图公共事业局（Seattle Public Utilities）在雪松河城市集水区的河岸生境中设立了61个永久样地（permanent sample plots, PSP）。其中31个样地（编号1至31）于2003年设立于切斯特·莫尔斯湖（Chester Morse Lake，西雅图市饮用水水库）上游区域；剩余30个样地（编号32至61）则于2005年设立在该水库下游区域。
2012年，研究人员对全部61个样地中的6个（编号4、11、12、27、28、29）开展了重采样，并简化了采样流程。每个采样年度均由不同的调查人员完成。
本次河岸永久样地仅限定于雪松河及其支流的低坡度、中等至无约束河段——此类河段通常呈现出最为显著的河岸生境变异，溪流与河岸的交互作用最强，且鱼类栖息利用度最高。样点沿此类河段随机选取，每个样点设置2个样地，分别位于溪流两岸。
样点被划分为四种林分类型：以落叶林为主的林分、落叶-针叶混交林、处于立木排斥阶段（stem exclusion phase）且林下植被稀少的针叶纯林，以及林下植被发育良好的针叶纯林，每种林分类型至少设置5个样地。
每个样地均完成以下调查内容：树木种类与胸径、枯立木（snag）的直径与高度、灌木种类与盖度、草本植物种类与盖度、幼树种类与盖度、冠层覆盖率百分比，以及样地内此前未在树木、灌木和草本调查中记录的其他物种。
2012年的河岸样地重采样筛选标准涵盖了次生林与原始林以及中、大型溪流河段的样地。
预计后续重采样工作将以约10年为周期开展，第三次重采样工作预计于2025年启动。本次数据集包将在每次重采样工作完成后进行更新。