The USA National Phenology Network has developed scientific protocols to systematize the tracking of phenology in the plants and animals it studies. It organizes their behavior into standardized phenophases: observable stages of growth defined by discernible start and end points. Plant phenophases include when leaf buds first burst open, when flowers form and when they open to release pollen and make nectar available, and when fruit forms, ripens, and disperses. For animals, phenophases may include emergence from hibernation or arrival of migrants, feeding behavior, and phases of reproduction, like vocalizing, mating, nest-building, and the bearing of young.
Data about these phases is collected by mostly volunteer observers who have taken an online training course and selected specific plants or animals to study at a specific site. For each phenophase, observers are asked to visit their target plants or animals at regular intervals and submit status reports by recording Yes if they observe the phase occurring and No if they do not. By tracking when No answers shift to Yes answers or vice versa, the NPN can establish when a phenophase began or ended. Is it not necessary for observers to capture the exact date when gray catbirds arrived, or when milkweed started to bloom, for instance. By comparing data for different individuals of the same species in the same area, the NPN can establish a reliable range of dates for that phenophase. Comparing date ranges for multiple years and mapping them against climate data can help reveal the effects of changing climate on the behavior of species.
Sample data sheet from https://www.usanpn.org/nn
It’s also important for observers to try to estimate the intensity or degree of some phenophases. Knowing what percentage of a tree canopy is full of green leaves helps scientists track the progress of spring. Knowing when most flowers reach their full bloom helps researchers predict when pollen levels will peak and when the most nectar will be available for pollinating insects. Knowing how many fruits are present allows biologists to estimate how many flowers were successfully pollinated.
Nature’s Notebook
The NPN has developed an online platform (also available in a convenient smartphone app) called Nature’s Notebook https://www.usanpn.org/nn to record, collate, and visualize observations. Nature’s Notebook makes it easy for volunteer observers to contribute to phenology monitoring. In 2023, over 3,400 volunteers submitted over 4.3 million individual observation records to the NPN. https://usanpn.org/files/reports/usa-npn_annualreport2023.pdf By gathering and analyzing information submitted by large numbers of observers, the NPN can provide vastly larger data sets than professional scientists and decision makers could collect on their own.
Arlington Regional Master Naturalists are doing their part to monitor plant phenology in our area. ARMN began a multi-year monitoring project in 2022 at several sites in Arlington County, including Marcey Park and the native plant gardens at Arlington Central Library and at Potomac Overlook Regional Park. Specimens were chosen from a list of species that Nature’s Notebook has identified as particularly important for research purposes. These include a selection of native oaks and maples. Tracking the timing of their green up and fall color change helps scientists build and validate models of how climate is affecting tree phenology (https://www.usanpn.org/nn/campaigns/Greenwave). In 2023 Master Naturalists started to contribute data on three eastern redbuds (Cercis canadensis) for Nature’s Notebook’s Redbud Phenology Project (https://www.usanpn.org/nn/campaigns/Redbud). ARMN’s phenology project also monitors plants important for providing nectar to native insects, including common buttonbush (Cephalanthus occidentalis), swamp milkweed (Asclepias incarnata), butterfly weed (Asclepias tuberosa), and cardinal flower (Lobelia cardinalis). For three years in a row, the ARMN team has placed in the top six nationally among groups submitting records to Nature’s Notebook’s “Nectar Connectors” campaign https://www.usanpn.org/nn/campaigns/NectarConnectors ).
The user-friendly interface on the Nature’s Notebook platform makes it easy for citizen science volunteers to learn how to observe phenology and track phenological change in their own back yards. Learn more about how you can participate here https://www.usanpn.org/nn
Learn About Phenology | Conducting Phenological Research | ARMN Phenology Project