As part of our Cycles of Gaia ecological calendar project, over the next year, we will share an insight each month on one of the member species of the calendar, or some other ecological element of the Northeast Coastal Zone (southern New England) drawn out by the calendar. This month, September 22nd marked the transition from summer to fall.
Sunday, September 22nd marked the day when summer turned to fall, also known as the autumnal equinox, which occurs annually in September in the northern hemisphere. The Earth is tilted on an axis, so usually the Sun hits more of the northern hemisphere or more of the southern hemisphere, depending on the time of year. However, there are two days each year when both hemispheres receive the same amount of sunlight: the equinoxes (one that marks the coming of spring, and one that marks the coming of fall). On these two days, with the Earth’s axis being perpendicular to the angle of sunlight, this also means Earth experiences equal amounts of daylight and nighttime. While the vernal equinox marks the shift from shorter days to longer days, the autumnal equinox is the inverse: summer’s predominance of daylight over darkness shifts to shorter days and longer nights, leading up to the winter.
In the northern hemisphere, and particularly in New England, the autumnal equinox implicates biological and ecological changes, like birds migrating to warmer climates and foliage turning color then falling off their branches. Looking at the Cycles of Gaia Ecological Calendar, one can see that no drastic changes appear from August in terms of precipitation and amount of fruiting and foliage. However, the overall decrease in sunlight brings about the gradual transition into autumn. With shorter days and the sun’s rays hitting the northern hemisphere at more oblique angles, temperatures drop. Cooler temperatures and shorter days trigger the reduction in production of a growth and development regulator hormone in trees called auxin, straining the abscission layer, weakening the bond between the branch and leaf. This joint continues to weaken until a mere gust of wind can blow the leaf away. (Why Do Trees Lose Their Leaves?)
As September comes to a close, you may notice the leaves starting to change color here in the Northeast Coastal Zone. Species like Flowering Dogwood and Eastern Redcedar (Juniper) also come to fruition, while Pagoda Dogwood fruits phase out. The Flowering Dogwood showcases its bright red berries, attracting birds and other wildlife as the air begins to chill—these berries make for a crucial food source for birds in migration! The Juniper also begins to produce its small, blueish-gray cones, which resemble berries, providing nourishment for many bird species as well. Meanwhile, the Pagoda Dogwood’s dark blue, almost black, fruits start to dwindle and fall, signaling the end of their fruiting season. Although these changes in flora are subtle, they are essential to the ecological cycle of the transition from summer to fall, supporting wildlife as they prepare for the winter months ahead.
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