“Last summer, we conducted measurements in sites located in Liperi, Heinävesi and Outokumpu here in eastern Finland. We already had pre-existing data from these sites, thanks to measurements conducted three years ago. In addition to trees that had already been measured, we also measured all new trees with a diameter at breast height of five centimetres or more,” forestry student, Research Assistant Janne Toivonen says.
Although new methods are becoming available, traditional field measurement methods nevertheless remain.
“We examined forest stand sites of 30 x 30 metres in size, and measured all trees for their diameter and height, and determined the different tree species. Height was measured using the Vertex hypsometer. On some sites, we also determined height to crown base.”
First, researchers navigated to the centre of the site and identified each tree that was to be measured utilising a preliminary map of trees based on airborne laser scanning data. These trees were tagged with a piece of paper. On each site, one of the researchers would get on their knees and aim their camera upward, taking photos of trees at a four-metre interval, resulting in 49 photos per each site.
“This measurement method is used to determine canopy cover. One researcher was responsible for photography, while two others measured the trees.”
“Taking measurements of trees is bread-and-butter field work, and this is how it has been ‘always’ done,” Toivonen says.