YOU may think that after visiting the nature reserves of Wyre Forest district year in, year out, there would be very few mysteries to be solved, especially on a dull winter's day.

However, here lies the wonder of the natural world. Just when you think you have got a handle on things you make the mistake of looking closer and a whole new universe of mystery seems to unfold before you.

I was leading an event for children in Habberley Valley last spring when one of them asked me "why do trees have different shaped leaves?" I was flummoxed. According to the theory of evolution, over the many hundreds of millions of years that trees have been around, some would eventually hit upon the most efficient shape of leaf.

This would have given these trees a particular advantage and over time allowed this efficient design to prosper and replace all but the more specialised trees. In an English wood though this is far from the case and we find trees with leaves that vary in shape.

This problem has troubled me since, until very recently, I settled on the explanation that broadleaf tree species all have slightly different survival strategies. For example, if we look at the oak and the birch trees, birch seeds are easily blown by the wind for huge distances.

Here the tree will stand proud of the landscape and frequently be battered by strong winds. Its small, highly mobile leaves present much less resistance to the wind, reducing the likelihood of wind damage. While acorns are usually planted by jays and squirrel, the young oak trees rarely establish in very exposed locations.

This can be seen taking place in some of the district's younger natural woods where oak trees are slowly taking over from the birch. This is possibly due to the maturing oak having such a dense and efficient canopy of oak leaves that it does not allow enough light through for young birch to grow.

Also, the oak has a much longer life span than the birch and therefore the oak then replaces the birch in the wood.