Post 447 - Terrific Transformations in Awesome Autumn Colour changes

Autumn colour along the River Swale

Hey everyone, well post 447 today and I thought that with all of the wonderful autumn colours that I've been seeing that I would look at why and how trees move from the big green leafy structures they are in summer to the bare brown skeletons of winter.

My bonsai is looking good too

I don't know about where you are but here in Yorkshire the changes have been going on for quite a while and have been really slow and gentle so that every day the autumn colours have been getting better and better. We had a bit of snow earlier in the week but it didn't last long enough for me to get any photographs, but the autumn colours against the snow were awesome. I think it's about at its best now though as lots of leaves are falling and some trees are starting to look a bit bare.

Well I knew a bit about why leaves change colours but I thought I'd look at this again to see what I could find out. Here's what I found out:

Breaking down the chlorophyll

• The first thing to say is that it is all to do with chlorophyll. This is the chemical in leaves which absorbs the energy from sunlight and uses it to make food, simple sugars or carbohydrates, from water and carbon dioxide.

• As the days start to get shorter and the temperatures start to cool off, deciduous trees and plants start to prepare for winter.

• Rather than just shutting down and dropping all their leaves they start to recover the chemicals and nutrients that are stored in the leaves.

Sunlight through autumn leaves

• They stop producing chlorophyll and break down the chlorophyll in their leaves into colourless compounds which they remove from the leaves and store in the branches and trunk.

• As this happens you start to see other pigments that are in the leaves all the time but they get masked by the chlorophyll. Chlorophyll uses red and green light but reflects green light so leaves look green.

• Weather can affect the colour changing process. Early frosts can disrupt the process that makes the red colour in some leaves like in maple. They make a chemical called anthocyanin which make them red. Some scientists think this acts as a sort of antifreeze to give the tree more time to remove valuable chemicals in the leaves.

A few Greylags enjoying the autumn colour
of Larches at Cod Beck

• It is only deciduous trees that do this as coniferous trees have needles which are thicker and waterproof, protected by waxy coatings and natural compounds that prevent freezing so they can survive frost and winter temperatures. Needles do get replaced gradually though. 

• Needles are less efficient at photosynthesis so the trees need them all year too to produce food. 

• There is an interesting tree though around a lake where I walk a lot at Cod Beck, the Larch. This is a coniferous tree that is deciduous.

Larch needles changing colour.

• It seems they do this as they tend to live in places where there is lots of snow in winter. By not having needles snow and ice doesn't build up on their branches so much so they don't break under the weight.

• As they can regrow their needles every season it also gives them the ability to survive forest fires.

Well that's more than I knew to start with and I always enjoy finding out what happens in all the processes that plants and animals go through.

Hope you enjoyed too.

Z.