How many conservation volunteers does it take to measure a tree?

2012/04/01

Our friend Colin McLean, retired convenor of Bawsinch, Addiewell and Roslin SWT reserves, set us a task for our day off at Scone. In 1970, while working at the Scone Palace pinetum he had measured one of the Wellingtonia (Sequoiadendron giganteum) trees. Planted in 1862 it was due to turn 150 in 2012: re-measurement seemed a fitting birthday present.

In 1970 it was 115 feet (thirty-five metres) tall and twenty-six feet and eight inches (eight metres and thirteen centimetres) in girth. Colin informed us that the convention was to measure at chest height, taken to be four feet three inches (one metre and three centimetres) from the ground.

First we had to find the tree - quite a challenge given the abundance of towering specimens in the pinetum - but made significantly easier by Scone's useful labelling system. Finally Greg located the one Sequoiadendron which rose above them all. Gazing skywards from its base was quite breathtaking, particularly with the bark glowing russet in the sunlight. We had found our quarry.

Measuring the girth was easy enough: thirty-three feet and nine inches (ten metres and twenty-nine centimetres) - a difference of seven feet and one inch (two metres and sixteen centimetres) in forty-two years...which, come to think of it, is the age of LCV.

But how were we to measure its height? A quick pre-resi Google revealed three methods:

1. Climb to the top of the tree, drop a rope to the ground and then measure the rope.

We decided against that, as we doubted the LCV ropes would be long enough. And the risk assessment would require a Sequoiadendron's-worth of paper.

Nicola ponders the giant

Nicola ponders the giant

Looking upwards

Looking upwards

2. Use of a clinometer

A quick search of the LCV tool store revealed our only specialised tree-measuring tool to be a tape-measure (or perhaps also the cross-cut saw to enable the counting of rings?) so that method was also rejected.

The stick and muddy puddle method, as recommended by the Woodland Trust.

"That's more like it!" we thought.

This method involved the following:

  1. Find a stick about two metres in length
  2. Find a helper to hold the stick for you
  3. Take twenty-seven steps away from the base of your tree and stand the helper and stick there
  4. Take three more steps and lie on the ground with your eye as close to ground level as possible (the muddy puddle bit)
  5. Locate the top of your tree and line it up with the stick
  6. Mark where the top of your tree crosses your stick
  7. Multiply this by ten and this is approximately your tree's height
Ken and Sarah try the 'hug' method

Ken and Sarah try the 'hug' method

Elite tree-measuring team at work

Elite tree-measuring team at work

So, off set Keith, Christine, Greg and I deep into the pinetum. Our first problem was noticing that a two-metre stick would only be useful for trees less than twenty metres tall: our tree was considerably higher than that. Keith, always reliable in a crisis, utilised his planet-sized brain to hastily recalculate that we would need to place the stick at ninety-eight paces and take a measurement from 100 paces.

Ninety-eight paces later, Keith bravely volunteered to hold the stick, having quite worn himself out with all that mental arithmetic. Christine fortified us with chocolate biscuits. I got to lie in the mud. And Greg was team photographer, documenting the occasion for posterity.

Keith:	   	Gosh this is hard work! My arm's getting awfully tired. 
Sarah:	   	Mutter.

Keith: Gosh this is hard work! My arm's getting awfully tired. Sarah: Mutter.

Christine: 	Are you sure you've got the right tree there, Sarah?
Sarah: 	   	Of course I have. Grumble. Whose idea was this anyway?

Christine: Are you sure you've got the right tree there, Sarah? Sarah: Of course I have. Grumble. Whose idea was this anyway?

I expect you're keen to know the tree's height? Well, I'm afraid to say that despite our careful preparations our plan was foiled at the last minute by human error - I measured the wrong tree!

In my defence, there wasn't a clear view of the top due to the wealth of neighbouring pines. And shortly after realising my mistake, we had to start packing up to leave Scone in light of a bad weather forecast.

So if that's not yet another reason to go back to Scone Palace for a residential, then I don't know what is. Sorry Colin.