Two o’clock on a cold December afternoon, and the sun is already sinking towards the western horizon, sending long shadows through Flatts Wood. Ahead, a blackbird lands beside the footpath and begins flinging aside dead leaves, with the irascible air of a gardener discovering fly-tipped rubbish on their lawn. During short winter days these birds expend a lot of energy excavating layers of decaying autumn leaves, in search of buried food. Head cocked to one side, he seems to be listening, perhaps sensing something hidden here, and ignores us until we are a few paces away.
When he flies, we take a closer look: what lives under last summer’s discarded foliage? Beneath loose, wind-dried leaf litter lies several years of accumulated dead foliage; a leafy lasagne welded together by fine fungal threads advancing from a spreading delta of pure white mycelium, creeping out from under a fallen branch. For every toadstool that appears above the surface, there will be miles of these fine hyphae, digesting their way through dead plants, until they can store enough energy to organise themselves into another fungal fruiting body.
We find worms below the hollow that the blackbird has excavated, but not the kind that he was searching for. Peeling apart layers of disintegrating leaves, the oldest already picked-clean skeletons of their former selves, we find tiny white specks. They are nematodes – eelworms – which, suddenly exposed to daylight, uncoil and snake their way across the wet surface. There must be hundreds in every cold, clammy handful of leaf mould. The largest, fully stretched, is less than a centimetre long and not much thicker than a human hair.
Collectively, nematodes, hidden heroes of woodland nutrient recycling, are the most numerous animals on Earth. In the fading light, this winter woodland seems lifeless and dormant, but below the surface billions of them will be busy. Their slender, cylindrical bodies are translucent, so when we examine one under a hand lens we can see minute bundles of partially digested food progressing down its gut.
Working in tandem with fungi, these ubiquitous animals are turning the detritus of autumn into crumblyhumus, one microscopically small mouthful at a time.
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