Ash dieback research hopes to save Denmark's trees – in pictures

Slot is in his final year of studies for his bachelor degree in forest and landscape engineering at the forestry school at Nødebo, a branch of the University of Copenhagen, which is based in Gribskov forest Photograph: Marte Franck/University Post

The trees become sick after a fungus has entered the stem of the trees. Slot shows how the fungus spreads into the tree, discoloring the wood Photograph: Marte Franck/University Post

Once hit by the disease, the ash trees dry out. Approximately 95% of all ash trees in Denmark now have this disease Photograph: Marte Franck/University Post

To estimate how long a tree has been infected, researchers look at the year rings. The disease slows the growth rate, meaning that the rings will be narrow and positioned close together Photograph: Marte Franck/University Post

In younger trees, the disease spreads faster. By looking at the stem, Slot finds black spots which indicate that this tree is in the process of dying. These young trees are of no use, as they are not large enough to be used for timber. Looking closer at the tree, the severity of the problem is clear Photograph: Marte Franck/University Post

Large areas are harvested at the same time. All of these logs were diseased ash trees. When harvested in an early phase, they are still valued as good timber Photograph: Marte Franck/University Post

Luckily, not all trees are sick. Keeping track of the healthy ones is an important part of the project. Slot hopes to develop a method to help save the ash trees from complete eradication Photograph: Marte Franck/University Post