Timing the bloom season: a novel approach to evaluating reproductive phenology across distinct regional flora
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Just as the timing of the vegetative growing season affects a host of ecological processes, the seasonality of floral availability impacts ecological processes from nectar availability and allergen production to competition for pollinator attention. However, no existing methodology is capable of evaluating multi-species bloom phenology in a standardized fashion across multiple ecosystems or compositionally distinct local flora. Thus, the manner in which the onset of the bloom season (during which the majority of species flower) differs along climate gradients and among distinct local flora remains largely unknown.
This study evaluates differences in the timing of the bloom season throughout the western United States, and the relationship of the bloom season to the vegetative growing season and to local climate conditions.
This study estimated the season during which all but the earliest and latest 5 % of local species flower (the bloom season) using digital herbarium records. Bloom season timing was compared to land surface phenology, SI-x phenoclimate metrics, and PRISM climate normals.
Local differences in mean temperature of the coldest month explained 76 % of observed variation in bloom season onset. Variation in land surface phenology explained 50 % of observed variation, while SI-x Bloom estimates explained 64 % of observed variation in bloom season onset.
These results confirm that bloom season phenology is distinct from the vegetative growing season, and that local temperature is a good predictor of bloom season onset. This work represents a new modality for studying multi-taxa flowering phenology at landscape and regional scales.
KeywordsPhenology Climate Herbarium records Flowering Land surface phenology
I would like to acknowledge Mark D. Schwartz, Toby R. Ault, and Julio L. Betancourt for access to SI-x bloom data. The SI models were developed using phenological data that now reside and are available through the National Phenology Database at the USA National Phenology Network. Land surface phenology data used in this study were drawn from Conterminous U.S. 1 km AVHRR Remote Sensing Phenology Data developed by the USGS (http://phenology.cr.usgs.gov). I would also like to acknowledge Alison Donnelly and anonymous reviewers for advice that improved this manuscript. Herbarium data used in this study was provided by: University of Arizona Herbarium, the herbarium of Arizona State University, the Chicago Botanic Garden Herbarium, the Cococino National Forest Herbarium, the University of Colorado-Boulder Museum of Natural History, the Colorado State Herbarium, the Desert Botanical Herbarium, the Florissant Fossil Beds National Monument, Grand Canyon National Park, the Gila National Forest Herbarium, the Denver Botanic Gardens, the Walter A. Kelly Herbarium at Colorado Mesa University, the Museum of Northern Arizona, the Navajo Nation Herbarium, the Rocky Mountain Herbarium, the Rocky Mountain Biological Laboratory, the San Diego State University Herbarium, the Morton Arboretum Herbarium, the Southwestern Research Station, the Tarleton State University Herbarium, the US Forest Service Southwestern Region Herbarium, the University of California-Riverside Herbarium (Accessed through SEINet, seinet.asu.edu, 11 August 2014). Herbarium data throughout the Pacific northwest was provided by: the Harold M. Tucker Herbarium at the College of Idaho, the Evergreen College Herbarium, the Portland State Herbarium, the Stillinger Herbarium at the University of Idaho, the herbarium of Idaho State University, the Montana State University Herbarium, the University of Montana Herbarium, the Pacific Lutheran University Herbarium, Southern Oregon University, the Snake River Plains Herbarium at Boise State University, The Burke Museum at the University of Washington, the Western Washington University Herbarium (Accessed through the Consortium of Pacific Northwest Herbaria web site, www.pnwherbaria.org, 27 August 2014). Herbarium data throughout the northern Great Plains was provided by: the Black Hills State University Herbarium, the Theodore M. Sperry Herbarium, Minot State University (Accessed through Northern Great Plains Herbaria web site, (http://ngpherbaria.org/portal/collections/index.php, 21 August 2014). Additional herbarium data throughout the western United States was provided by: the S. L. Welsh Herbarium at Brigham Young University, the Eastern Nevada Landscape Coalition, the Snow College Herbarium, The University of Nevada Herbarium, the Utah State University Uintah Basin Herbarium, the Intermountain Herbarium (Accessed through the Intermountain Region Herbarium Network, http://www.intermountainbiota.org/portal/index.php, 11 August 2014), Additional herbarium data was also provided by the A. C. Moore Herbarium at the University of South Carolina, the Auburn University Museum of Natural History and the the Clemson University Herbarium (Accessed through Southeastern Biota Data Portal, http://sernecportal.org/portal/index.php, 17 August 2014) as well as the herbarium of Florida State University, the Western Illinois University herbarium and the University of Connecticut Herbarium.
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