Autumn really is one of the best times to visit the Heart of England Forest, with nature launching its own magnificent variety show as the deciduous trees begin shut down for winter and their leaves offer up a palette of dazzling colours to delight visitors.
With the onset of winter, the weather cools and sun-filled days become few and far between. This limits the ability of the leaves to undergo photosynthesis and convert that sunlight into the sugars that their host trees need for growth and the formation of new branches, fruit and seeds. Meanwhile, evergreen trees keep their leaves or needles all winter because they are better able to retain water, often due to their shape. These trees continue to photosynthesise, albeit to a lesser degree, during the winter months, meaning that they remain literally ‘ever green’ – although they do shed their greenery every few years.
To conserve energy during the winter months, when freezing temperatures can make the transport of water to their outer branches much more difficult, deciduous trees become dormant and their leaves begin to die and fall. This process serves the additional purpose of decreasing the surface area of the tree, reducing resistance to strong winter winds and lessening the chance of incurring damage during winter storms.
Some unassuming allies, in the shape of the fungi family that flourish during the cooler months, also come into play during the winter to help nourish deciduous species. By breaking down the leaf litter from the forest floor, fungi re-distribute the nutrients through an underground network of interconnected threads, known as hyphae, to the trees and plants above. You can find out more about the fascinating world of Forest fungi at https://www.heartofenglandforest.com/news/forestfungi/.
Going through ‘the change’
If the summer months have been very dry, the leaves will change colour earlier, but if it has been warm and wet, they may take a little longer to change and fall. This year we have experienced a beautiful autumnal spectacle in the Heart of England Forest.
When the autumn shut down eventually begins, the first casualty is the chlorophyll that gives leaves their green colour. It is this green-pigmented chlorophyll that absorbs the energy from sunlight through the process of photosynthesis, allowing trees to make their food, but with those trees now storing the energy that they have built up over the spring and summer months, it gradually begins to fade from the leaves.
As chlorophyll levels decline, a variety of other colours associated with other chemicals and molecules come to the fore; carotene and xanthophyll give leaves their orange and yellow hues, while anthocyanins combine with the remaining sugars to give some leaves a vivid red colouration.
As chlorophyll fades, other chemicals such as carotene influence the colour of leaves, turning them bright yellow before they fall to the ground.
Bucking the trend!
However, nature typically throws in the odd anomaly to confuse us! Some deciduous trees, such as oak or beech, are able to keep their leaves during winter although they are usually brown and dry by mid-December. This ‘holding on’ of leaves through the winter months is known as ‘marcescence’ (from the Latin word ‘to fade’) and occurs when the shrivelled leaves remain, somewhat precariously, attached to the tree until they are dislodged by new growth during the spring. The reasons for this are not fully known, although it is more commonplace in mature trees.
Whenever or wherever trees begin their autumn transformation, the Heart of England Forest is the perfect place to see the wonderful spectrum of golds, yellows and reds that provide a feast for the eyes. Come and see for yourself, let us know your favourite autumn tree and share your autumnal Heart of England Forest photos with us via our Flickr group at www.flickr.com/groups/hoef/