Raining acorns

At this time of year our woodlands are spectacular; seemingly a palette containing every colour ranging from the oranges and russet browns of fallen oak leaves, the red of hawthorn berries, to psychedelic pinks in Spindle fruits. Observe closely and your senses can be entertained in other ways too. During a walk through a local woodland with my dog, I was enthralled by a percussion performance by a stand of oak trees .. it was raining acorns.

I recorded the acorn music – click on the play button above to listen.

Listen carefully and you will hear three gusts of wind; each appearing as a rising crescendo of rustling approaching through the woodland. With each gust the shower of acorns increases. I love the way that the falling acorns make three distinct sounds: crashing through the leaves of the canopy, tonking on the branches that sometime block their way, and thudding as they hit the ground.  Some fall very close to my recording equipment too!

It seems that 2011 is a mast year for oak, at least in parts of southern Britain. Oak trees produce acorns every year but every four to seven years they produce an extra heavy crop.  These are called mast years. There is still plenty of debate as to why trees behave in this way: it could be to do with water availability, temperature (in winter or spring), lack of frost during flowering or other reasons (see this scientific paper). We know that the extra effort put into producing so much seed can reduce the amount that a tree grows that year. Here is an interesting piece of work I came across, called dendromastecology, that provides evidence about the tradeoff between incremental tree growth and reproductive effort.

My walk left me wondering, along the lines of a popular saying, whether:

If an acorn falls in a forest,

And no-one is around to hear it,

Does it make a sound?

Gabriel Hemery