Plant phenology and performance in the International Tundra Experiment (ITEX) plots at Utqiaġvik and Atqasuk, Alaska

Arctic ecosystems are changing in response to arctic warming, which is proceeding more than twice as fast as the global average. The International Tundra Experiment (ITEX) was established in the early 1990s to understand the effects of warming and environmental variability on tundra vegetation properties and ecosystem function. The ITEX program has been extremely valuable for detection of changes in tundra plant and ecosystem responses to experimental warming and to background climate change across sites that span the major ecosystems of the Arctic. These files contain data representing the periodic plant measures of all species within each plot in a text comma delimited format. The data presented are phenological development (date of leaf bud burst, inflorescence emergence, flower bud, flower opening, flower withering, seed development, seed dispersal, and senescence), seasonal growth (length of leaf, and length of inflorescence), seasonal flowering (number of inflorescences in flower within a plot), occurrence of events (yes or no for leaf, inflorescence, bud, flower, and seed), and annual growth and reproductive effort (number of leaves, diameter of rosette, number of branches, maximum leaf length, number of inflorescences, maximum inflorescence length, number of buds, number of flowers, and number of seeds) collected weekly or yearly for all plant species during the summers of 1994-2019 for 48 plots (24 experiment open-top chamber plots and 24 control plots) at four sites (Atqasuk Wet Meadow, Atqasuk Dry Heath, Utqiaġvik Wet Meadow, and Utqiaġvik Dry Heath) and during the summer of 2021 at two sites (Utqiaġvik Wet Meadow and Utqiaġvik Dry Heath).

北极生态系统正随北极变暖发生改变，而北极变暖的速率是全球平均水平的两倍以上。国际冻原实验计划（International Tundra Experiment, ITEX）于20世纪90年代初启动，旨在探明增温与环境变异对冻原植被特征及生态系统功能的影响。该项目在覆盖北极主要生态系统的多个样地中，为检测冻原植物及生态系统对实验增温和背景气候变化的响应变化提供了极高的科研价值。
本数据集采用文本逗号分隔格式存储，包含各观测样地内所有植物物种的周期性观测测量数据。所收录的数据涵盖物候发育（叶芽萌发期、花序抽出期、花蕾期、花朵开放期、花朵萎蔫期、种子发育期、种子扩散期及植物衰老期）、季节生长指标（叶片长度与花序长度）、季节开花情况（样地内开花花序总数量）、事件发生记录（叶片、花序、花蕾、花朵及种子的存在与否，以是/否标记），以及年度生长与繁殖投入指标（叶片数量、莲座直径、分枝数、最大叶长、花序数量、最大花序长度、花蕾数量、花朵数量及种子数量）。上述数据于1994-2019年夏季，在4个站点（阿特瓦苏克湿草甸、阿特瓦苏克干石南灌丛、乌特恰维克湿草甸、乌特恰维克干石南灌丛）的48个样地（24个开顶箱（open-top chamber）增温实验样地与24个对照样地）中按周或年度频次采集；并于2021年夏季在乌特恰维克湿草甸、乌特恰维克干石南灌丛2个站点完成补充采集。