## Make a Quadrat

There are plenty more beach fieldwork options to come, but first you need to make yourself another piece of equipment – a quadrat.

To make one of these you need something to make the outside frame and then string to divide the central area into smaller squares.  You also need a tape measure to help you get everything in the right place.

For the frame I used garden canes, but lengths of wood would work too and would probably be more robust.  You need to cut 4 lengths of about 60 cm.  The inside edge of the frame will be 50 cm x 50 cm, but you need the extra length to fix them together.

Use string to lash the frame together at the 4 corners.  (Lengths of wood could be screwed together.)

Make sure the internal area of the square is exactly 50 cm by 50 cm.

You are going to divide the frame every 10 cm.  Mark the edge with permanent marker so that you know where to fix the strings, and so that you can see where they should be, if they slip out of position.  There should be marks at 10, 20, 30 and 40 cm on each side.

Now tie strings across.  Go first one way…

…and then the other way, twisting around each of the first set as you go.

Check the squares are still square (10 cm by 10 cm) and adjust if necessary.

And there you have it…

…a very useful piece of kit.

Here’s one way to use it.

As you can see my patio needs weeding!  We can use the quadrat to help us estimate the percentage of my patio that is covered in weeds.

Throw the quadrat down.  Yes, don’t place it, since that would be you choosing the results.

The quadrat has 25 small squares so each of them represents 4%.  Give each square a score:

• Square is all weeds = 4
• Square is ¾ weeds = 3
• Square is ½ weeds = 2
• Square is ¼ weeds = 1
• Square has no weeds = 0

Add them up and you can see that 45% of my patio is covered in weeds.

I’m off to do some gardening, but I’ll be back next week to tell you how to use your quadrat at the beach.

## Scilly’s Changing Habitats

As the sea level rose around Ennor, so the land was reducing in size.

With over 150 bronze age burial mounds in the islands, (dating from 2000BC), it seems there were quite a few people in residence, in what was a gradually reducing land area.

The natural vegetation for an unpopulated Scilly Isles, would be deciduous forest.  Samples of peat show that there was woodland – mainly oak, with some elm and ash.

However, by the time of the late iron age village of Halangy Down, (which was believed to be occupied into the 2nd century AD), the forest had been almost completely cleared, to make way for farming, as the population grew and the land size reduced.

There are few trees on the islands today, most being planted as windbreaks.

The loss of the woodland habitat led to the loss of the animals that would have lived in that habitat.  Many animals, that are common just 28 miles away in Cornwall, are not found on the Scilly Isles.

However, it hasn’t all been loss.  Some species have arrived on the islands.  Shipwrecks have caused this to happen by accident, but some introductions have been deliberate, such as the planting of Tresco’s sub-tropical gardens.  Seeds from there have dispersed across the islands, with the help of the wind and birds.

Introducing a new species often upsets the previous balance of nature.  Hedgehogs were brought in as pets and have since escaped and multiplied.  They are fairly safe on the islands, without foxes etc to hunt them down, and are disrupting the food chain by consuming too many slugs and snails.  They also eat bird’s eggs and nestlings.

But for the birds there is also a success story.  I’ll tell you about that next week.

## Overton’s Yew Trees

Pistyll Rhaeadr and Wrexham steeple,
Snowdon’s mountain without its people,
Overton yew trees, St Winifred’s Well,
Llangollen’s Bridge and Gresford’s bells.”

Today we are going to look at another of the 18th century tourist attractions that were the “Wonders of Wales“.

The Yew tree is found in western, central and southern Europe and Britain has many fine examples. The churchyard of St Mary the Virgin, Overton contains a notable collection of them.

The big daddy of them all is this fine specimen.

It is believed to be between 1500 and 2000 years old but age is difficult to determine since the boughs become hollow as the tree gets older. You can’t just count the rings because there is unlikely to be any wood that is as old as the whole tree.

Yews are known for their longevity. When the boughs get too heavy the tree can split without succumbing to disease in the fracture. Here the natural processes have been halted by supporting the tree with props.

Yew trees are often associated with churchyards, though the reason is far from clear. The oldest specimens often pre-date the church as is the case in Overton.

If you want to find your own example, the nearest churchyard might be a good place to start. This is what you are looking for. Please note that yews, particularly the needles, are poisonous.

If you fancy hunting down a giant, ancient specimen they are surprisingly common. Follow this link to an interactive map, where you can home in on your locality.

## Unpolluted Scilly

If you thought that some of the rocks in the photos for my geology post last week had a greenish tinge to them, then you would have been right.  It was actually quite hard to find a good picture of the crystals in the rock.  More commonly the surfaces were hidden like this.

Most of the rock surfaces are covered in greenish or grey lichen.  There were other colours too.

The lichen thrives because, unlike mainland Britain, the air is very clean and unpolluted.  There’s hardly any traffic…

…and plenty of fresh sea air to blow any fumes away.

Lichen love it.