The Early Bloom of Hedgerows: A Sign of Changing Seasons
In mid-February, hedgerows that were once traditionally blanketed in white snow were instead adorned with the delicate blossoms of blackthorn this year, signaling the arrival of spring. While this sight may be a pleasant welcome after a long and dreary winter, seasoned observers of the seasons might question if there are changes afoot. Could it be that the flowering patterns of plants like blackthorn are shifting?
Thankfully, the practice of phenology, which involves recording and interpreting seasonal events, has been a longstanding tradition in Britain. Dating back to the 18th century, naturalist Robert Marsham meticulously documented the emergence of flowers, birds, and insects in his Norfolk village starting in 1736. This legacy was carried on by Marsham’s descendants until 1958, and today, the Woodland Trust continues this tradition through its Nature’s Calendar program, which invites the public to participate in recording various seasonal occurrences.
Recent research conducted in 2022 analyzed nearly half a million plant records, revealing that the average flowering time of plants in the UK has advanced by approximately a month over the past four decades. While there are variations among different species, common plants like hawthorn now bloom 13 days earlier compared to the early 1980s, with horse chestnut trees showing a similar shift of flowering ten days sooner.
The rapid warming of the climate since the 1980s has prompted this earlier flowering behavior in plants. By sensing the shorter and milder winters, plants adjust their spring development processes, reminiscent of humans shedding layers of clothing when feeling the warmth of the sun on their skin. Although the specific mechanisms differ between plants and animals, both are adapting to the changing climate in their own ways.
Plants possess remarkable abilities to detect environmental cues without the use of eyes or skin. In autumn, they perceive the decreasing daylight hours through a pigment called phytochrome, which is highly sensitive to red light wavelengths. As the nights grow longer, the quality of this red light changes, triggering a response in the plants.
Similar to how our bodies experience fluctuations in hormones like serotonin during seasonal shifts, plants respond to winter approaching by increasing the production of a hormone called abscisic acid. This hormone induces various changes in deciduous trees, such as halting twig growth and developing hardy winter buds capable of withstanding freezing temperatures.
While both light length and temperature play roles in determining spring growth, temperature tends to have a more significant impact. If plants relied solely on light cues, they could risk starting their growth during frosty conditions or missing out on optimal growing conditions in mild early spring days. Thus, the earlier appearance of spring flowers serves as a tangible indicator of the effects of global warming on plant behavior and development.
Source: [Phys.org]