Keeping an eye on the forest

At the top of a 35-metre pylon, Daniel Berveiller of the ESE (Laboratoire Ecologie, Systématique et Évolution, Ecology, Systems and Evolution Laboratory) adjusts the array of sensors. At the interface between the treetops and the sky, this platform is used to study exchanges of matter between the atmosphere and the forest. The equipment at the Barbeau site can measure more than 150 different types of data.

Rising nearly six metres above the tallest trees, the pylon, dubbed the “Barbeau Tower”, allows the researchers to monitor the evolution of the ecosystem and the health of the forest.

Berveiller performing maintenance operations on the Barbeau Tower’s measuring systems. At regular internals, the sensors collect data on the exchanges of matter (CO2, H2O) and energy (radiation, heat flows) between the forest ecosystem and the atmosphere.

A variety of indicators are recorded every week, including, for example, tree growth and soil temperature. Here we see Berveiller measuring water runoff on a tree trunk (left) and taking a hygrometric reading to record the moisture level of the soil down to a depth of 1.60 metres (right).

In the laboratory, the researchers study samples from the forest floor and compare them with data from the Barbeau Tower to fine-tune their model. First they sort the samples gathered in the field according to type and species (left). Then they scan the leaves with a planimeter to calculate their surface area and check whether climate change is affecting the plants’ size (right).

Hemispherical photos like this are used to measure the vegetation cover at different times of year. Based on these photos, researchers can deduce the evolution of the forest’s leaf surface, i.e. the density and distribution of leaves and other plant forms.

Researchers hope that this installation will help them understand the long-term impact of climate change on the health of the forest. The Barbeau initiative is part of ICOS (Integrated Carbon Observation System), a European network created to monitor the evolution of greenhouse gas cycles in the atmosphere, landmasses and oceans.

One of the oaks monitored by the ESE team. The forest comprises many species, such as bald cypress and northern red oak trees, whose preservation is crucial.