Plant & lichen species composition data for Saddle Nodal Plots, 1971 - ongoing.

To study long-term changes in alpine tundra plant communities, thirty permanently marked plots were surveyed in 1971. These same plots were surveyed at twenty, thirty, forty and fifty year intervals from the initial sampling date; in 1991, 2001, 2011, and 2021. Due to covid and other events, data for the 50-year time point was collected over three summers, from 2021-2023. Plots are one by ten meters, divided into ten subplot quadrats, and marked with rebar. The presence or absence of each vascular plant species was recorded per plot. The cover was recorded for each species that appeared in a one meter by ten centimeter strip at the base of each quadrat within each plot. The cover of non-vascular plants, soil, rocks, and lichens was also recorded within the strip in most sampling years. Lichen were also surveyed in 1971 and 2021.These data have been used to study the changes in vascular plant and lichen communities and cover across habitats following a moisture gradient on the saddle portion of Niwot Ridge; these habitats include dry fellfield, dry meadow, moist meadow, wet meadow, snow bank, and shrub tundra. While we have observed some changes in species richness and cover in the plots, overall the plant communities seem fairly stable over time. Lichen species richness has increased in some habitats, while some lichen species have been disappearing from others.

为探究高山冻原（alpine tundra）植物群落的长期动态变化，研究团队于1971年对30个永久标记样地开展了基线调查。此后分别在初始采样后的20年、30年、40年与50年节点，即1991年、2001年、2011年及2021年，对同一批样地进行了重复采样调查。受新冠疫情及其他事件影响，50年时间节点的调查数据耗时三个夏季（2021-2023年）完成采集。
每个样地规格为1米×10米，划分为10个小样方（subplot quadrats），并以钢筋（rebar）做永久标记。调查内容包括：记录每个样地内所有维管植物（vascular plant）物种的存在与否；在每个样地内各小样方底部的1米×10厘米样条带中，对出现的各物种的盖度进行定量记录。多数采样年度还会在该样条带内同步记录非维管植物（non-vascular plants）、土壤、岩石及地衣（lichen）的盖度；地衣群落还额外在1971年与2021年开展了专项调查。
本数据集已被用于研究尼沃特岭（Niwot Ridge）鞍部区域沿湿度梯度分布的各类生境中，维管植物与地衣群落组成及盖度的时空变化，涉及的生境类型包括干旱碎石坡（dry fellfield）、干旱草甸、湿润草甸、湿生草甸、雪斑生境（snow bank）及灌丛冻原（shrub tundra）。尽管研究团队在部分样地中观测到物种丰富度与盖度的局部变化，但整体而言植物群落在时间序列上保持相对稳定；部分生境的地衣物种丰富度有所提升，而另一些生境中则有地衣物种逐渐消失。