Monday, October 3, 2022

Harbingers of spring defined by temperature, growing degree days and phenology

Spring equinox: Our equal hours of day and night begin their upswing toward the light on the morrow, at least for us (opposite, of course, in the Southern Hemisphere). Yet there are a variety of different modes of parsing “springtime.”

The spring months for us of March, April, and May only partly track the March 20 (11:33 am) to June 21 (12:21 am) official spring this year. Spring months for Australia are Sept. 1 to Nov. 30; if you are Irish and follow the Gaelic calendar, the three spring months are February, March and April; In Sweden, at least according to Wikipedia, meteorologists “define the beginning of spring as the first occasion on which the average 24-hour temperature exceeds zero degrees (Celcius) for seven consecutive days, thus differing by latitude and elevation.” Very fluid, I must say.

Then there are the “harbingers of spring” as defined by temperature, growing degree days and phenology.

Pieris flowers in Wadsworth last year.

Phenology

Now is the time of year when “phenology” is most fun and functional. As Dan Herms, vice president of research and development at The Davey Tree Expert Co. and formerly chair of the Ohio State University Entomology Department, defines it: Phenology “is the world’s oldest science; the foundational science of human existence.”

So, what is it? In broad terms it is the “study of recurring biological events,” the way that early harvesters and gatherers and then farmers figured out when to plant: It matches biological phenomena with triggering environmental conditions, predicting bird migrations, seed germination, when plants will flower .

Nation World News Desk
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