The field of phenology investigates the timing of seasonal patterns of plants and animals and how seasonal activity relates to climate and weather. Phenology is considered a robust indicator of climate change and is a critical component for understanding how species and communities will respond to variability and shifts in temperature and precipitation.
In our recent Journal of Ecology paper, co-authors Natalie Rossington and Susan Mazer and I show how phenological patterns and their relationships with climate drivers vary across and within four oak species (Quercus agrifolia, Q. alba, Q. lobata, and Q. rubra).
We found that in water-limited systems in the Western US, species tend to display phenophases, or observable phases in the seasonal life cycle (such as breaking leaf buds and flowering), intermittently throughout the year. In contrast, species in temperate systems (including the Eastern US) are more likely to have one distinct seasonal period of activity. Western species are also more likely to show longer phenophase durations and to be more influenced by geographic location independent of climate, whereas the Eastern species are more consistently influenced by climate variables.
Oaks are well suited for comparative ecological and evolutionary studies of phenology, physiology, and adaptation due to the wide distribution of the genus Quercus across the globe. Species occupy a range of ecosystems, from tropical to Mediterranean, and exhibit a diversity of life history strategies, such as masting. Oaks play key roles in their ecosystems, providing food and habitat for a variety of animals.
However, obtaining a large dataset that contains information on many species and ecosystems across a large geographic area can be logistically challenging despite a growing interest in understanding phenological responses to climate change. Collecting precise, high-quality phenological data requires regular, intensive measurements across time and space, rendering it impossible for an individual scientist, or even a research team, to collect and curate a dataset sufficient to investigate short and long-term patterns and drivers beyond a handful of sites.
Recently, more scientists and land managers have begun to capitalize on the enormous data resources available through citizen science programs such as Nature’s Notebook, a phenological monitoring program of the USA National Phenology Network. Regional efforts that contribute to the National Phenology database, such as the California Phenology Project and the Appalachian Seasons project, can provide particularly rich datasets for ecologists; they involve multiple partner organizations that train participants to collect data on ecologically important focal taxa along elevation and latitudinal gradients. These datasets often represent a broad range of conditions experienced by species across their ranges, allowing the measurement of many species’ phenological sensitivity to spatial and temporal variation in climate. Additionally, the species and sites targeted for monitoring are often selected because they were determined to be critically important for natural resource decision-making; research that emerges from these datasets will have direct management applications.
Our study would not have been possible without the dedication of the many citizen and professional scientists who submit their observations to Nature’s Notebook. Since 2009, over 10 million observation records have been collected by over 9000 observers at over 9000 sites on over 40,000 plants and animals. These data undergo rigorous quality control measures and are are unique in that observers monitor marked individual plants through time using rigorous standardized protocols; the result is an increasingly deep temporal record over a broad geography that is ripe for exploration. The data are freely available to explore and download.
I encourage all ecologists, especially those with an interest in species ecological and evolutionary responses to climate change, to seize upon the wide range of opportunities to incorporate data provided by citizen science programs into your research.
Kathy Gerst, University of Arizona and the USA National Phenology Network