Nature 2014 February

Nature Notes – February 2014

Turning over a new leaf…

…as we are inclined to say from time to time, not least to describe the simple action that has taken place resulting in one arriving at this page and also a decisive action bringing about a major change of direction. Such a decisive change also takes place annually when Winter gives way to Spring and again as Summer gives way to a mellow Autumn.

I recently came across several poems by a local author and poet, and sometime boxer, Vernon Scannell who grew up and lived in Aylesbury before the Second World War. In his Autobiography he recalls his frequent walks “in the Chiltern Hills above Wendover”, which usually concluded with a jar or two in the hilltop pubs. The following short poem caught my eye.

The Day that Summer died

From all around the mourners came
The day that Summer died,
From hill and valley, field and wood
And lane and mountainside.

They did not come in funeral black
But every mourner chose
Gorgeous colours or soft shades
Of russet, yellow, rose.

Horse chestnut, oak and sycamore
Wore robes of gold and red;
The rowan sported scarlet beads;
No bitter tears were shed.

Although at dusk the mourners heard,
As a small wind softly sighed,
A touch of sadness in the air
The day that Summer died.

After last Summer ‘died’ and Autumn hastened on you may recall, somewhat unusually this year, that trees had retained almost their full complement of leaves which were then all shed in just a matter of a few windswept days. Leaf-fall is dictated by a combination of shortening day-length and falling temperatures and a relatively warm September and October served to delay this year’s ‘fall’. As a consequence, for a few days the ground beneath our woodland trees was swathed in an extra deep carpet of leaves, all bearing a fresh abscission scar, signifying their very recent departure from the canopy. However, within just a few days the soluble carbon molecules had leached out of the leaf-litter as water drained away.

This is the start to the process of conversion into a fine layer of dark brown compost. First on the scene in this underground world are the earthworms who churn up and transport leaf litter beneath the surface and also aerate it by creating tunnels between the surface and deep down layers. The scene is now set for the decomposers the large (or macro) fungi such as the stinkhorn which uses enzymes to dissolve the humus. The way is clear for the ‘detritivores’ which consume and digest the now finely tilled fragments of leaves and twigs. These are the ants, slugs , woodlice, insect larvae, mites, potworms et al. Chief amongst these though are the springtails. One of the most primitive arthropods but also one of the most numerous invertebrates in the soil, with over 100,000 per cubic metre. The final stage of conversion involves the invasion of the mycelia of microscopic fungi and the even more ancient and mysterious slime moulds, which can attack the most resistant fibrous material.

Alongside the leaves the autumn brings dead animals and birds as well as a not inconsiderable amount of animal waste deposited by our modest array of woodland inhabiting mammals. Left to rot away of its own accord it would hang around for a very long period eventually contaminating the ground. In fact so long would it take the waste materials to disappear unaided that it would only have to be a small number of seasons to pass before we would find ourselves wading waist-deep through a morass of unpleasant detritus. But as this is not the case its worth considering what happens in places where the numbers of larger animals are much greater than ours.

I recall a segment in an episode of one of Sir David Attenborough’s wildlife series when he was talking about the animals of the African Plains. Here it is not the build up of vegetable matter, but rather the even more unpleasant prospect of the carcases and waste products from hundreds and thousands of large mammals, including the massive pachyderms – elephants and rhinos – and a complete alphabet soup of grazing herd animals from antelopes to zebras. Sir David explained that these vast savannahs are kept clear of dead animal remains firstly through the efforts of scavengers such as vultures. More important though is the most prodigious of insects, the African Dung Beetle. Without it parts of Africa would be submerged beneath 12 foot of dung within a year. The beetles consume such large quantities of dung that they alone are responsible for continuously refereshing grazing land. Also known as ‘roller beetles’ because the male of also dedicate their lives to collecting, conveying and burying dung. In doing so they not only provide a reserve of food for their progeny but greatly hasten the breakdown of the manure. Although the dung beetle plays a crucial role, they are but part of an army of organisms, such as other coprophilous insects, fungi, nematodes, earthworms bacteria etc.

Though on an entirely different scale in The Chilterns, country cousins of the African Dung Beetle are at the forefront of a comparable army of animals, fungi and bacteria whose activities result in our local woodlands being rich and diverse habitats. Mind you, though the largest mammal we might encounter today is probably a Fallow Deer. In the not too dim and distant past some 3-5000 years ago much larger mammals roamed the Chilterns, such as bears. However, if we could go back in time until what is known as the interglacial period the Palaeolithic – between 125,000 and 70,000 years ago, not only would we experience a tropical climate, but dominant animals of the period would have included both ancestral rhinos, elephants, horses and elk. So it would be correct to presume there was also a healthy community of dung beetles removing dung and earthworms turning over a new leaf!

As we move from Winter to Spring give some thought that without the activities of nature’s recyclers we could not look forward once again to a fertile greening of the Chiltern woodlands.

 

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