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Sarah West

Why do some trees go yellow and some go red in autumn?

28 October 2010

I was pondering this question as I looked outside my office window...

Yellow and red trees

So, thanks to the wonders of the internet, I have now found answers to this question! The yellow and orange colours in leaves at this time of year are caused by pigments in the leaves that are there throughout the year. The rest of the year though, the colours are hidden by the green of the chlorophyll in the leaves - this is the stuff that trees need to make food for themselves by the process of photosynthesis.

The beautiful red colours that you see in some species of cherry and acers etc is caused by pigments called anthocyanins - these are only present in the leaf once the green colour (chlorophyll) has started to break down. Anthocyanins are thought to act as sunscreens, as they filter out the UV elements of sunlight, protecting the leaf from light energy that earlier in the year would have been absorbed by the chlorophyll.

However, like so often in science, this has ended up being a very complicated question, and there is still much research that needs to be done to answer it! The Leaf Color Bibliography website gives links to some detailed research if you have the time to read it...

Horse chestnut leaf miner

14 October 2010

Last weekend I visited the Yorkshire Sculpture Park, which is an odd mixture of sculpture and rather "human-made" nature, with lots of big trees in a parkland setting. There were a few horse chestnuts there, whose leaves seemed to be turning brown more quickly than some of the other species. I had a closer look and noticed that the leaves were covered in little yellow/brown blotches. This was evidence of the horse chestnut leaf miner, Cameraria ohridella, a moth whose caterpillar lives between the surfaces of the leaf. Here's a picture of what the mines look like earlier in the year:

Horse chestnut leaf miner

This photo is from Encyclopaedia of Life, as once again I forgot to take my camera! A bit of digging on the internet found a project called "Conker Tree Science" which is trying to track the progress of the leaf miner across the UK. It's a nice little site with lots of information about how you can get involved, and some interesting information, including that apparently infected trees produce smaller conkers.... That may explain why when I cracked open a conker shell, expecting to find a beautiful, gleaming conker, I instead found a tiny shriveled brown blob the size of a small pea.

One of the world's longest noses? Nope, not an elephant.....

5 October 2010

Last month we went to the fabulous Wild About Wood Festival at Castle Howard, North Yorkshire, and ran "minibeast hunting" sessions. Everyone seemed to enjoy themselves and we found all sorts of weird and wonderful creatures. We lent nets for sweeping through grassland to a couple of lads, who came back with one of these:

Weevil

How amazing is that?! It's called Curculio betulae, and it is a weevil. Weevils are herbivorous, and their long nose (called a rostrum) has biting jaws at the end of it. This particular species has such a long rostrum that it is about as long as its body.

Not only was this weevil amazing to look at, it is also quite rare. Roger Key was on hand to identify it, and he said that it was "Nationally Scarce B", which means that it is found in less than 100 10km squares in the UK. To give you some idea of what that means, there are 2644 10km squares in the UK (according to my GIS expert friend Anne Owen!).

So, a great find lads! These species live on birch trees, so keep an eye out for them when you do the Biodiversity survey!

OPAL Yorkshire and the Humber

I'm Sarah West, OPAL community scientist for the Yorkshire and Humber region. My blog will keep you up to date with all the fun stuff we’re doing across the region.