Herbarium-Derived Phenological Data in North America

Phenological data pertaining to flowering times in this dataset consist of 2,319,672 specimen records of plant species collected in flower, while strobilating, or while fertile (this last category primarily applied to graminoids). These data were derived from the digital archives of 440 herbaria (see Readme for full listing), and subsequently cleaned and modified using several criteria described below to facilitate their use in phenological assessment. To ensure the quality of the data used in this study, specimens were included in the dataset analyzed here only if, at the time of digitization, herbarium personnel had: verified that the specimens were collected when in flower, strobilating, or fertile; recorded GPS coordinates of the location from which the specimen was collected; and provided the precise date of collection (including month, date, and year). Only those specimens that were explicitly recorded reproductive status within either the DarwinCore “reproductivecondition” or “lifestage” fields of their source's database were included in this study. The taxonomic nomenclature used to describe each specimen was standardized using the Taxonomic Name Resolution Service iPlant Collaborative, Version 4.0 (Boyle et al., 2013, Accessed: 30 August 2021; https://tnrs.biendata.org/). Duplicate collections of a species at the same location, DOY, year, and location were also removed. The resulting dataset included 2,319,672 specimens distributed throughout North America. Climate data associated with the year and location of each specimen collection was then integrated into this data. All climate data was drawn from PRISM climate data (https://www.prism.oregonstate.edu/) and incorporated both long-term normal conditions at the location of each collection as well as the predicted conditions in the year and location of each collection.