Veteran tree management – a new kind of woodpecker

Veteran tree management is a vital part of the work of the National Trust for Scotland. From north to south and east to west, almost all of our key gardens and designed landscapes (as well as countryside properties with natural woodlands) have a degree of tree cover. Each year Trust staff undertake tree safety management and tree inspections to assess the health and wellbeing of our trees, so that our visitors are kept safe and we also protect the health of the trees themselves.

Part of our work in caring for the environment is to keep our trees standing as long as possible. Trees inherently become more interesting as they age – more fungi, insects and birds are attracted to live on, in and around them. However, it is a balancing act to keep them standing and safe at the same time. Although many staff are trained to carry out visual tree inspections, it is an inexact science due to the fact that trees are living organisms. They react differently in all locations due to the type of soil, the climate, the tree species itself, wind conditions and many other environmental factors.

We haven’t had the ability to look inside the trees themselves with x-ray vision ... until now! We’ve recently purchased new equipment and trained some people to help us ‘look’ inside trees using a technique called sonic tomography.

This new equipment is called PiCUS and takes its name from the Latin for a woodpecker (Picus picus), which also translates as ‘tap tap’. The equipment allows the technician to send sound waves through a tree using sensors and special hammers; from these readings, they can then build an image of the internal structure of the tree.

First of all, we collect some key data about the tree such as its species, height, spread and overall health. We then input this into the computer.

Next, the geometry of the tree is assessed, using more specialised callipers. Once the geometry has been calculated, the sensors are placed around the tree.