Saturday, October 05, 2013

Early autumn leaves

click photo to enlarge
Autumn is upon us with the leaves of many species of tree starting to change colour. Leaf fall has begun too and our first collection from lawns and gravel can't be too distant. In my garden the flowering cherries are among the earliest to reflect the change that autumn brings, though the maples and silver birches aren't too far behind. The other day I was reflecting that even though, in recent years, the onset of autumn hasn't been marked with quite the dip in temperatures that I remember from, say, twenty or thirty years ago, nonetheless the change in the colour of trees is happening distinctly earlier. Moreover, this is down to a single species - the horse chestnut.

In a post of October 2010 I commented on the impact of the horse chestnut leaf miner moth (Cameraria ohridella) on trees in south-east England and parts of central England: how the burrowing larvae cause leaves to turn brown, become dry and crisp, then fall earlier than they would were the trees not infected. This activity begins in summer, but the way it appears to accelerate the onset of autumnal colour becomes very obvious in late August and September. My photograph of the River Welland and Deeping Gate bridge that I posted a couple of weeks ago features a horse chestnut on the left of the frame exhibiting quite deep browns and oranges due to the activity of this insect pest.  I don't have any data on which to base my opinion, but I have the distinct impression that I'm seeing increasing numbers of horse chestnuts that are affected. Certainly if the trend shown in these maps has continued during the past three years then the damage will be quite widespread across much of England and have made significant inroads in the west and north.

Today's landscape photograph doesn't show a horse chestnut but it does show a carpet of leaves from one that has been affected by the leaf miner (the tree is just out of shot). I took it when I recently spent a few days in the area where Cambridgeshire abuts Bedfordshire and Northamptonshire - in what was once the county of Huntingdonshire. More photographs from that trip coming next.

photograph and text © Tony Boughen

Camera: Sony RX100
Mode: Aperture Priority
Focal Length: 13.1mm (35mm - 35mm equiv.)
F No: f5.6
Shutter Speed: 1/40
ISO: 200
Exposure Compensation:  0 EV
Image Stabilisation: On