The trees here in southeast Scotland are beginning to show hints of changing colours. At this time of year, temperatures begin to dip, the first night time frosts appear and actual daylight begins to reduce. This lack of sunshine and the cold air are both the major triggers for the leaves to change colour.
Carotene is a yellow chemical pigment found in leaf cells. Unlike chlorophyll (the green pigment found in leaves), carotene is not affected by sunlight and temperature, so it remains in the leaves, when the chlorophyll has disappeared, making the leaf look yellow. The green chlorophyll does fade as temperatures fall
Anthocyanin is a red/purple pigment and production is enhanced by sunlight, drought and temperature. If temperatures stay above freezing, which they do for the start of this October, more red is produced, = more colourful leaves
The dry summer has had an effect on some trees, especially birch where yellow leaves were seen falling early as these trees tried to compensate for the struggle of the dry conditions this summer
The Woodland Trust says “for the greatest variety and intensity of autumn colours, sunny, dry autumn days with cold but not freezing nights are best, especially if preceded by a dry summer.”
So with this week’s weather for the start of October, eastern Britain could be in for some beautiful ‘leaf peeping’ as we follow the driest UK summer in 7 years.
Woodland trust are asking people to help keep records of various seasonal events, to help show any climatic variations.
http://www.naturescalendar.org.uk/survey/help/The Fall, leaf peeping
http://www.maine.gov/doc/foliage/
