All the leaves are green, and that’s because of the chlorophyll molecule in them that trees use to capture sunlight and convert into sugars and energy. But, that’s not the whole story, because inside the leaf there are molecules that have different colours, these molecules are produced as a defence mechanism against pests or are the result of waste products building up in the leaf.
When autumn comes, and light levels drop, the chlorophyll can no longer produce enough energy to sustain the tree over winter, so the tree reabsorbs the chlorophyll and sugars into its roots and branches to save for the spring resurgence. Now that the green chlorophyll has gone, the other colours shine through, these are carotenoid molecules – Xanthophyll being yellow, as in eggs, Carotene is orange, as with carrots and Anthocyanins are purple red, blueberries. It is the different combination of these molecules that give us the hues we see on leaves in autumn.
Now the leaf is no longer of use by the tree it gets rid of it by a process called abscission, but, what happens to all those leaves once they fall? Gardeners get nice and warm raking them up off their lawns and borders but what about the rest? Enter the humble earthworm, they will steadily munch away on them, improving the condition of the soil and locking carbon back into it as well, clever little fellows! You may, as you rake the lawn, see the odd leaf half sticking out of the ground, this is the large lob worm getting ahead of the game, by pulling the leaf into its burrow. Don’t put your rake up though as even they can’t manage every leaf.
So, how many leaves fall each year? A rough guestimate has been made by taking the number of annual leaf dropping (deciduous) trees in the world and multiplying it with the average number of leaves on a tree, that figure comes out at 84 thousand billion billion (84,000,000 000,000,000), wow, but I’m not going to count them, are you?
Natures calendar: November
November is, statistically, warmer than March, but only December and January have less hours of sunshine, this month should also bring the first real frosts of winter.
Hedgehogs should now be well fed and tucked up in their over wintering quarters. Frogs, also, will have settled down for winter under stones or in water.
Sloe berries, the fruit of the Blackthorn, are more evident now the leaves have fallen and are good pickings for some of our larger birds like the Blackbird and the Mistle Thrush. Starlings will also eat the fruit by piercing it with their sharp beaks to get at the pulp inside, often with very messy results. Pick your sloes now if you want to make that traditional Christmas drink, sloe gin, before they are all gone. Rose hips are also prominent and are a good source of seeds, for both, birds and small mammals.
The last House Martins will leave our shores by the middle of the month and, sadly, the last adult Common Shrews will pass away as only this year new born will overwinter.
Sorry, but did I just mention the ‘C’ word! Well it is next month after all, uh oh!!