June 2022
Nothing is permanent in nature. Even the surface of the planet is forever moving and changing with tectonic plate movements, usually too small to notice. A forest is a climax community and if humans allow it, satellite images of forest will show no apparent change over a human lifetime. However, most trees have an expected life span. Birches live for about 60 years, beech for about 300, oaks for about 600 and yews over 1,000.
When an old tree dies and falls over, it forms a clearing. Gradually, it will rot away and let the sunlight reach the floor. From that time, there is a period of succession as the ground becomes recolonised. The same happens within an abandoned field. Incidentally, the word field is derived from ‘a felled area of forest’. On bare ground, the first visible organisms are the herbs, usually grasses and other seedlings. Second come the larger plants such as nettles and brambles, following on from that come the woody saplings of shrubs and small trees such as heather, gorse, hawthorn and elder. All these have a low maximum height so that eventually birch, beech, oak, yew and others can push through to the light and out-shade everything below that has gone before.
If the canopy of the forest is not completely closed, parts of these layers can persist, and it is interesting to see how this succession happens every year concerning the leafing and flowering in some woodlands. In a balanced ancient woodland, first the wood anemone leaves appear followed by their white flowers as the bluebell leaves push through and then flower, taking over from the anemones. After that, the hawthorn leaves and May blossom break bud with the honeysuckle and eventually the leaves in the giant trees burst and grow to form a shadowing canopy resulting in a decayed forest floor. The insects follow this succession and pollinate the flowers in all these plants including the trees, which are sometimes also wind pollinated, and eventually form seeds through the summer and autumn. They drop their seeds, then (if deciduous) their leaves and the cycle starts again. Everything green in the plant world is a solar panel, converting carbon dioxide into oxygen and organic material. It is lovely to see the breeze gently coaxing the mature fresh green leaves during May as I write these notes.