Exceptionally warm spring weather in 2010 and 2012 resulted in the earliest flowering times known in 161 years of recorded history at two sites in the eastern US, according to research published January 16 in the open access journal PLOS ONE by Elizabeth Ellwood of Boston University and colleagues.
Many plants need a long winter break to undergo physiological changes that make them bloom in the spring. According to several previous studies, this blooming is occurring earlier than before due to warmer springs caused by climate change. The consequences of such early flowering for plant productivity, pollinators like bees, and ecosystems in general are still unknown.
In this new study, researchers compared flowering times recorded near Walden Pond in Massachusetts by Thoreau beginning in 1852, Aldo Leopold's records of spring flowering in Wisconsin beginning in 1935, and contemporary flowering times including 2010 and 2012, two of the warmest springs recorded in recent times. According to their analysis, many plants flower up to 4.1 days earlier for every degree Celsius rise in mean spring temperatures, but this relationship is linear from Thoreau's time to the present day. In other words, long-term observations could be used to predict plant response to weather extremes outside of the historical range. The authors explain that though spring rising temperatures are causing record earlier flowering, temperatures have likely not yet reached a point where plants are not able to respond in terms of their flowering times.
Ellwood adds, "We were amazed that wildflowers in Concord flowered almost a month earlier in 2012 than they did in Thoreau's time or any other recent year, and it turns out the same phenomenon was happening in Wisconsin where Aldo Leopold was recording flowering times. Our data shows that plants keep shifting their flowering times ever earlier as the climate continues to warm."
Citation: Ellwood ER, Temple SA, Primack RB, Bradley NL, Davis CC (2013) Record-Breaking Early Flowering in the Eastern United States. PLoS ONE 8(1): e53788. doi:10.1371/journal.pone.0053788
Financial Disclosure: CCD: National Science Foundation Grant Assembling the Tree of Life (AToL) EF 04-31242; RBP: National Science Foundation Grant DEB-0842749. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interest Statement: The authors have declared that no competing interests exist.
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