Autumn – Signs & Hues

Popped out to Dolgellau last week, late afternoon was dull cloudy & wet, yet within a little over an hour, a beautiful but fleeting sunset developed.

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Typical changeable autumn conditions for us. The picture above is of the old bridge over the Afon Mawddach, between Dolgellau & Llanelltyd. A  fly fisherman stands in front of the bridge enjoying the evening. These days the bridge is closed to motorised traffic and it is very peaceful despite being only just off the A470.

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At home in Aberllefenni, the autumn colours have been richening up. This image shows some of our horses enjoying the autumn grass. The paddock is bordered by deciduous woodland, mainly oak, ash and hazel. Beyond that, the mountain is planted with spruce, larch and pine. All the trees have their own distinctive autumn shades, with the spruce & pine remaining green.

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Even some of the horses are trying to blend in!

Have you ever wondered why the leaves change colour in autumn? It’s due to the range of pigments that are in the leaves. Chlorophyll is the main pigment that plants use to help them harness sunlight to produce carbohydrates. Chlorophyll appears green, it isn’t very stable though and plants have to continually synthesise it. It’s production falls when temperature & daylight levels drop.  This happens in autumn allowing other pigments to become the dominant leaf colouring agents.

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The beech trees are a particular show at the moment.

So what are these other pigments? Carotenoids are a group of yellowy coloured pigments and they are significantly more stable than chlorophyll. Thus some leaves turn yellow as the green fades. What about the reds, I hear you call. Well they are due to a family of pigments called anthocyanins. As the tree prepares for leaf senescence (dropping of its leaves) the amount of sugar in a leaf may build. Depending upon temperature & light levels, this can trigger flavonoids to be converted to anthocyanins. The exact resulting colour tone depends upon the pH (acidity) of the plant sap.

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But eventually they’ll all end up on the floor.

Finally a membrane between leaf stem & tree is completed, it now separates the leaves from the tree. As the membrane joint withers the leaves fall from the tree and carpet the floor.

Any how, it all produces a marvelous sight for us to enjoy.

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