Forest evolution under the magnifying glass


The research was ambitious: inventory the distribution of mushrooms on a European scale. Recently published in the journal Nature, it could not have been completed without the help of collaborators throughout Europe. As the leader of the ICP Forests programme – the European forest health monitoring network – for Wallonia, the Forest Sciences Research Group at the UCLouvain Earth and Life Institute contributed to the study.

‘Here’s the main part of the plot’, says agricultural engineer and UCLouvain researcher Hugues Titeux, stopping in a fenced area in the heart of the Lauzelle woods (Louvain-la-Neuve). ‘Here we measure the quality of the water that passes through the foliage. Around it, probes and sensors, buried or visible, record a series of parameters and collect all kinds of samples in order to monitor soil moisture content. In all, on our eight parcels in Wallonia, we collect 450 water samples and 15 leaf samples per year. This allows us to assess and measure nutrients in all the components, such as leaves and soil. We can then calculate the flows that pass from one to another, see if the amount of nutrients that arrives is equal to that which comes out. We want to know whether the system is in balance or in a state that’s cause for concern. One of the main parameters that we measure is defoliation, that is, leaf loss. When we notice a disturbance, we try to find the cause. It can be drought, disease...Follow-ups must be conducted over long periods, otherwise, statistically, we can’t draw any conclusions.’

The plot of 70 meters by 70 meters is used to observe and monitor the health of trees and vegetation. There are seven other plots, scattered all over Wallonia. All are managed by UCLouvain, with the help of local collaborators who regularly take samples, check that the systems are functioning, and intervene in case of problems.

A study conducted through the network

If the team in charge of this work is currently in the spotlight, it’s because it has taken part in ambitious research: an inventory of the distribution of ectomycorrhizae mushrooms on a European scale, which has recently been published in the journal Nature.

To do so, it was impossible to work behind closed doors. The work required the cooperation of dozens of stakeholders in the countries concerned. In Wallonia, Dr Titeux, a member of the Forest Sciences Research Group at the Earth and Life Institute, collaborated in the study as the coordinator for Wallonia of the European ICP Forests (International Co-programme on Assessment  and Monitoring of Air Pollution Effects on Forests) programme.

‘Practically speaking,’ he says, ‘to carry out the work researchers took 9,888 soil samples from 103 plots in Europe, from which they isolated 29,664 ectomycorrhizae in order to describe and identify them on the basis of DNA analysis. It’s a huge job! In general, when you’re working on plant diversity, visiting a site three or four times per year is enough to inventory all that’s there. But for mushrooms, fructification doesn’t form every year and as it’s ephemeral DNA analysis was necessary.’

While mycology isn’t the specialty of Prof. Ponette ’s team, UCLouvain researchers nevertheless contributed to soil sampling and provided all data concerning their plots. ‘All network managers have been associated with the publication’, he  says. All of the plot information collected over the years contributed to the interpretation of results pertaining to fungi identification. This made it possible to highlight the environmental variables that best explain the variability of mycorrhizal communities and identify the indicator species for the variables. This is an example of using the ICP Forests network for a different use than the one for which it was set up, and it’s a fine example of collaboration between researchers working on very specific topics and a network that pursues applied research objectives.’ 

Better management through monitoring

Because initially, while ICP Forests helped advance research, it was created for a very different reason. It’s a European forest health monitoring programme that was established in the 1980s to measure the impact of acid rain – which is linked to excessive nitrogen and sulphur oxide emissions – on ecosystems and better understand their evolution. ‘At the time, a forest dieback attributed to rain acidity in Central Europe signalled the need to act, especially in terms of pollution’, Dr Titeux says. ‘The authorities feared the dieback was spreading. The idea was to monitor forest evolution carefully and understand it.’

Since then, drastic measures have been taken, and abandoning the once widespread use of coal has reduced acid deposits. But there’s no question of stopping the surveillance given that forests are subjected to other ‘attacks’, such as droughts, excess water, insects or pollution, the repeated stress of which weakens trees. The network helps to identify new threats, understand their effects and better guide forest management to ease the consequences.

6,500 observation sites 

The project  brings together most European Union member states and a dozen European non-member states. It’s based on two levels. The first is comprised of 6,500 observation points in Europe, including 65 in Wallonia, where tree health and growth are monitored. Observations are made by agents of Wallonia’s Département de l'Etude du milieu naturel et agricole (Department for the Study of the Natural and Agricultural Environment, DEMNA), while UCLouvain is responsible for data analysis and interpretation.

The second level is comprised of 860 plots, including eight in Wallonia since 1996. The latter are funded by Wallonia and managed entirely by UCLouvain, which handles daily management, maintenance, observation, measurements, results and interpretation. They’re equipped to help researchers understand processes and identify factors responsible for forest health evolution. 

Each year, the UCLouvain team’s analytical results and findings are entered into a European database. The network organises trainings to ensure that all researchers work according to the same methods, and thus obtain comparable data.

A glance at Hugues Titeux's bio

Hugues Titeux is a specialist in soil chemistry and passionate about the study and protection of biodiversity. He earned his bachelor’s degree in agricultural engineering at UCLouvain in 1998. After completing his UCLouvain PhD on the functioning of forest soils, he carried out research at INRA-Nancy and the UCLouvain Soil Science Laboratory. He has participated in research projects dedicated to system fertility management of family-owned banana plantations in the African Great Lakes region (CIALCA), as well as in the characterization of historical pollution in Walloon soils (POLLUSOL2). At the same time, he has taught courses on the study and sustainable management of soil to UCLouvain bioengineering students. Since 2013, he has been a researcher at the Forest Science Research Group (ELI-e), where he ensures the coordination and scientific surveillance of projects related to forest health monitoring in Wallonia (ICP Forests).

Published on August 22, 2018