A Scots pine in National Park Bosland

Daily dynamics of a living tree

Where science and imagination listen together to a tree

In the heart of National Park Bosland stands a tree that speaks. Not in words, but through data, rhythms, and stories. This tree — a Scots pine, characteristic of the sandy soils of National Park Bosland — shares its daily life with anyone willing to listen. Sensors measure how water flows through its trunk, how its bark expands or contracts, and how it responds to sun, wind, and drought. In this way, we can follow in real time how a tree lives in a changing climate.

The scientific research behind this tree is part of TreeWatch, a project of Ghent University. Researchers aim to understand how trees function and how they cope with stress such as drought or heat. By measuring sap flow, stem diameter, and temperature, they gain a unique insight into the physiology of a living tree.

At the same time, artists from Anaïs Berck give the tree a voice. They translate its data into language, poetry, and images. These narrative interpretations of what the tree experiences invite visitors to look at science, nature, and interspecies communication in a different way. It is a remarkable dialogue between measuring and imagining — between numbers and meaning.

How does a tree work?

A tree is a living system that transforms water, air, and light into growth. Through its roots, it absorbs water and dissolved minerals from the soil. That water rises through fine tubes in the trunk — the tracheids in the xylem — up to the needles. There it evaporates, or transpires, through tiny openings called stomata, which at the same time take up CO₂ from the air. Using sunlight as an energy source, the tree produces sugars that it uses for growth and repair.

Every change in weather or soil conditions leaves traces in this system. On warm days, more water flows; during drought or heat waves, the needles close their pores; and at night the tree “breathes” more calmly. Even the trunk moves along: it expands at night when more water is taken up than is transpired through the needles, and it shrinks during the day when the tree uses internally stored water or dries out. In this way, a tree breathes — slowly but perceptibly — together with its environment.

Why a Scots pine in National Park Bosland?

The talking tree in National Park Bosland is a Scots pine (Pinus sylvestris), a species that naturally occurs on the dry sandy soils of the Kempen region. The park is one of the largest pine forest areas in Flanders, planted in the previous century and now in transition toward more mixed and resilient forests. The monitored tree is part of such a forest stand — surrounded by other pines and young broadleaved trees. Its measurements therefore reflect not only the rhythm of a single tree, but also that of the forest in which it lives.

Pines respond differently than broadleaved trees: they retain their needles year-round, have thicker bark, and react more slowly to sudden changes in temperature or precipitation. Measurements of this Scots pine in Nationaal Park Bosland reveal subtle differences in growth rhythm and recovery, depending on weather conditions and the tree’s position within the forest. Such variations help researchers better understand how forests cope with and adapt to a changing climate.

Shrinking, swelling, and growing — what the sensors measure

Attached to the trunk of the talking Scots pine is an extremely sensitive sensor that records changes in stem diameter at the micrometre scale. Over the course of a day, this diameter fluctuates continuously:

By tracking these subtle movements over longer periods, researchers can precisely identify when a tree is growing, resting, or experiencing stress. For the Scots pine in Nationaal Park Bosland, the measurements suggest that recovery after dry periods may be somewhat slower than in some broadleaved trees. This may be related to wood structure and the species’ adaptation to dry sandy soils, but also to its position within the forest. Such differences highlight how individual each tree rhythm is — and how valuable it is to be able to monitor these variations in living systems.

The search for the tree clock

The artists’ collective Anaïs Berck draws inspiration from an age-old idea: that trees follow their own clock. In the past, people determined the timing of planting, harvesting, watching, and resting based on what trees did — when they leafed out, flowered, or shed their leaves. The question that occupies them today is whether such a tree clock still exists, visible in the data collected by our sensors.

The talking Scots pine in National Park Bosland offers a unique opportunity to explore this. Its rhythm turns out to be surprisingly complex. Photosynthesis, for example, does not always start simultaneously with the lengthening of the days; sometimes it only begins later, depending on temperature, light intensity, and groundwater level. The tree’s location also matters: a solitary pine warms up faster and responds earlier than a tree embedded within the forest.

By studying — and imagining — these differences, Anaïs Berck searches for ways to read and feel the clock of the tree. Not to measure time as humans do, but to understand how a tree itself experiences the seasons.