Forest Research have now provided us with the results of their analysis of the OneOak tree’s leaf area.

After taking the spectacular images of the tree canopy with the hemispherical camera lens (see post of September 18th), they used special software to calculate how much of the sky was visible underneath the tree.

Leaf Area Index analysis software

Leaf Area Index or LAI is the ratio of total upper leaf surface of vegetation divided by the surface area of the land on which the vegetation grows read more. Forest Research calculated that the LAI for OneOak was 1.4.

LAI values can range from 0 (no cover) to 6 (dense forest cover). Apparently our result of 1.4 is quite low for a mature broadleaved woodland. Scientists will now use this value in future calculations of the tree’s biomass.

We have received some stunning images of the canopy of the OneOak tree. These were taken when Forest Research scientists visited the tree last week to measure it.

Hemispherical image of the OneOak tree canopy

Using a fisheye lens fitted to a digital camera, they took hemispherical images looking up into the tree canopy. This produced a complete circular image taking in 180 degrees field of view.

The picture here is one of many taken by the scientists. Back in their laboratory they joined these all together to form a complete picture of the canopy from all angles. They then used special software that calculated the proportions of light and leaves. This gives us the Leaf Area Index.

The Leaf Area Index is used to calculate the biomass of the tree. Read more here.

Forest Research scientists measure the OneOak tree

Matt and Ian from Forest Research visited the tree today. They work with the government research agency as scientists specialising in tree measuring or ‘mensuration’.

Matt brought along a hemispherical camera – basically a normal camera fitted with a fisheye lens. A fisheye produces a picture that takes in an amazing 180 degrees field of view. We will be posting some the images that were taken with the fisheye on the website soon. Images taken looking up at the canopy will be analysed with special software that will calculate the leaf area index – effectively a measure of how much sky is visible between the leaves. This will be used to calculate the biomass of the tree.

Ian used some other equipment to measure tree height, timber height, crown width and stem diameter. Below is a picture of Ian using a hypsometer – this uses pythagoras to calculate (from a known distance from the tree + the the angle to the top of the tree) the total height of the tree. Look carefully at the photograph and you can see the distance to the tree is 36.3m. The tree measurements below it are the three different angle readings to the top of the tree. These will average at about 22.6m. However, after more readings from all directions, the final height of the tree has been estimated to be 23.9m.

We had estimated that the tree was 17.5m. We now know that we were quite inaccurate (or it grew 5+ metres in one year!). We look forward to receiving the detailed results from our friends at Forest Research, and will post them here in the OneOak blog, and on the web pages when available. You can read more on our Tree Facts & Figures page.

A hypsometer being used to measure tree height

Our thanks to Ian and Matt and to Forest Research.