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Last Updated: Friday, 4 May 2007, 00:58 GMT 01:58 UK
Oak and ash contest thing of past
The magnificent spectacle of oak and ash trees coming into leaf together may be a thing of the past because of climate change and record temperatures.

Oak tree
Drier weather is favouring the oak with some ash trees dying this year

BBC environment correspondent Sarah Mukherjee travels to Priestley Wood in Suffolk to find out more

It's almost as if the countryside had skipped a season.

It doesn't seem long ago that winter's leaden skies were pierced by leafless branches. And now, lush summer foliage surrounds us.

It's quite difficult to hear what Nick Collinson, from the Woodland Trust, is saying over the sound of birdsong.

But the verdant aspect, and the gentle susurration of the wind in the trees, take on a more alarming quality as he points out things that should be different as we wander the paths of this ancient woodland.

Traditional lines

"Look at the bluebells," Mr Collinson says.

A lot of this foliage is out much earlier than we would expect
Nick Collinson
Woodland Trust

"They should be about half way through their season and yet they've almost finished.

"And the hawthorn - it's out a couple of weeks earlier than it should be. In fact, a lot of this foliage is out much earlier than we would expect."

We follow the path to a clearing. The trust works hard at conserving this woodland along traditional lines, and there are piles of logs all around where the trees have been managed to promote native woodland species.

Among the emerald green leaves, one species of tree stands out as if it were trapped in its own little winter time bubble.

Skeletal branches claw their way heavenwards.

This is the ash and it bears no resemblance to the lush oak trees planted next to it.

18th century records

The following rhyme shows that, for many country people, the two trees were early weather forecasters.

"If the oak before the ash, then we'll only have a splash, if the ash before the oak, then we'll surely have a soak."

So, if the oak buds appeared first, the summer would be dry. If the ash appeared first, we were in for a damp summer.

Scientists at the Centre for Hydrology and Ecology, at Monks Wood in Cambridgeshire, have records stretching back to the 18th century.

Ash has shallow roots and so oak does much better in drier conditions
Tim Sparks
Centre for Hydrology and Ecology

Then, the race between oak and ash was a far more equal one, with milder, wetter weather allowing the ash to win 40% of the time.

But climate change, they say, has now made that a very unequal competition.

"Oak now wins 90% of the time," says the centre's Tim Sparks.

"Ash has shallow roots and so oak does much better in drier conditions.

"In addition, the ash will lose out as the oak leaves, which have matured earlier, can then get more sun and use up more of the available water."

Mr Sparks says ash trees could die this year, up and down the country, if the weather stays dry.

Woodlands will survive but they might look very different
Nick Collinson

This could be an indication of how some of our traditional native habitats could change as climate change takes hold, he said.

But back in Priestley Wood, Mr Collinson says we must remember that the countryside has always been dynamic and changing.

"Woodlands will survive but they might look very different," he said.

What we must do, he says, is try and help native species adapt and move, if necessary, to new habitats where they have a chance of survival.




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