Laser equipped drones that can see underlying terrain beneath a forest canopy are helping Forestry and Land Scotland (FLS) to plan how it manages woodlands.
The Light Detection and Ranging (LIDAR) drones have been assisting with the planning and felling of trees affected by Phytopthora ramorum, an algae-like organism. It causes extensive damage and death to more than 150 plant species, including some forest species
LIDAR is a system that gathers very precise measurements of both the canopy and forest floor by bouncing laser beams from the drone to the surface and back again.
“This is a really terrible disease that devastates larch trees and if it were to reach the larch on Drummond Hill, the scenic beauty and character of the place would be very seriously affected,” said Robin Almond, FLS planning forester.
“There is no cure for the disease and the only tool at our disposal for tackling it is to fell trees already affected and to create a buffer zone around healthy trees that might keep the disease at bay.
“This is something that we have to start planning for Drummond Hill but we want to minimise the felling if we can and also carry it out with as little impact as possible on the more sensitive habitat areas on the hill. LIDAR lets us map the forest and the ground it sits on to a high resolution, which lets us plan this down to some very specific detail.”
Different felling techniques require different kinds of machinery, so mapping potential access routes helps the team to assess what technique is most appropriate for any given part of the woodland.
LIDAR is more effective than a visual walkover inspection when it comes to covering the entire site. It is also better at identifying surface hazards like crags or large, loose boulders, possibly hidden from view that might need to be made safe in case they are dislodged during the felling works.
The team can also use the data to assess the impact of having fewer trees on the hill on peak water flows so that they can design a suitable drainage plan to lessen the risk of flooding of the public road below the woodland.
“From the measurements gathered we can build up an extremely precise model of the forest floor, pinpoint any issues and along with the geotechnical engineers, from Mott MacDonald, identify where additional safety measures – such as catch-fencing – might be required,” said Jamie Watt survey director at Innovair.
“This helps ensure that the team can plan the work in meticulous detail and carry it out safely and sensitively.”
Once the felling has been completed, FLS intends to plant a mixture of tree species that will retain the site’s important landscape character for many years to come.