The Science of Autumn

After what feels like the soggiest summer I’ve ever experienced,  I’m absolutely loving the ‘proper autumn’ we’re having.I may be looking through rose tinted spectacles, but the changing tree colours seem even more intense than usual and the autumn walks I’ve been enjoying over the past week have been just spectacular, with beech trees in particular putting on a very impressive show.

I was thinking about the science behind the autumn colours and so thought I’d share it with you….

The leaf colour change demonstrates the process where broadleaf tree species such as oak, ash or beech, shut down their food production for the winter.The tree uses the green chlorophyll  in its leaves to make food (photosynthesis) and at the end of the growing season, the chlorophyll breaks down to reveal other colours in the leaf – yellow, orange or red – that are there all year but hidden from view by the dominant green.

Weather also has an effect on how vibrant the autumn colours are.Low temperatures break down the chlorophyll, making the leaves fade to yellow, but if temperatures stay above freezing, anthocyanin (red/purple pigment) is stimulated encouraging the leaves to take on a red colour.Similarly, if the weather is dry and/or sunny, sugars concentrate in the leaves making the leaves redder still.

So the best weather for autumn colour is dry and sunny days, with spells that are cold but not freezing – especially after a dry summer.

The Woodland Trust’s website has lots of information about how leaves change colour in the autumn, so have a look here to find out more.In the meantime, enjoy the autumn while it lasts!

http://www.woodlandtrust.org.uk/en/our-woods/activities/Documents/why-leaves-change-colour.pdf

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