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When trees age

Many people certainly imagine biodiversity in nature differently. But it is worth taking a closer look here.
Photo: Kerstin Braun

It towers up in a scraggly way and at first glance seems like a disturbance in the otherwise idyllic flowering landscape: a cherry tree next to the WALA laboratory building, one which has not blossomed for quite a while. Shouldn’t it have been cut down long ago? No, says Dr Sonja Adamczyk, an agricultural biologist and member of WALA’s biodiversity working group. ‘Deadwood is very precious and promotes enormous biodiversity. Many species benefit from this wood: from microorganisms to birds and small mammals such as bats and squirrels,’ she explains.

Wood in transition

The term ‘deadwood’ is indeed somewhat contradictory: ‘Its many inhabitants make it very much alive. The “only” part of the tree that is dead is the part that doesn’t grow anymore. In the end, all that remains is the pure substrate in its smallest components.” However, this is a lengthy process. The different phases are particularly valuable, because each one brings forth a new biocoenosis: ‘First, the xylophages, the wood-eaters, come and help themselves to the wood. Many people think of the bark beetle with horror, but in a healthy ecosystem, this insect is part of the natural cycle,’ the scientist explains. Beetles and other insects eat their way through the wood, and their boreholes create habitats for other inhabitants. These include wild bees and wasps, for example, which find a nesting place here.

Upcycling: Mother Nature is the trendsetter

When the insects drill into the wood, it forms a waste product of a mixture of wood and animal excrement: duff. This is used as building material. For example, as a protective shell for a beetle larva, while it metamorphoses into an adult beetle inside. By the way, there are a total of around 1,400 beetle species that depend on deadwood. ‘Many people ask: what does that have to do with us humans? Well, it is a huge circle: the beetles and insects are also food for birds and other creatures. Only through this intact biodiversity can we have a healthy ecosystem,’ Adamczyk elaborates. Part of this important value chain is also the decomposition process of the wood. In the final phase, the ‘destructors’, i.e., decomposers such as fungi, bacteria and microorganisms, break down the wood into its basic building blocks.

The station ‘Wood in transformation’ is part of our biodiversity path.
Photo: Kerstin Braun
Sonja Adamczyk discovered an abandoned wasp nest. The wasps take the building material for their nest from deadwood and process it into a filigree sheath.
Photo: Kerstin Braun
The trees’ ‘age spots’ – lichens settle here over time and become increasingly visible.
Photo: Kerstin Braun

Spores of ageing

When trees age, you can tell by the lichens that gradually settle on the bark. We also affectionately call these the “age spots” of a tree,’ Adamczyk adds with a smile. As with the unloved bark beetle, there are often reservations. “The spores only settle on suitable substrate, depending on, for example, the moisture content or pH value of the tree bark.” Moreover, lichens are important bio-indicators: by closely studying which lichen species and how often they colonise, you can determine the air quality, for example.

The root of goodness

Just as fascinating as the complex decomposition processes above ground are the processes that take place behind the scenes. As a supplier of nutrients, the roots essential for survival. In a nutrient-rich soil, roots live in a symbiotic community with fungi, which experts call ‘mycorrhiza’. The fungi supply the root with minerals and water – in return, the tree releases glucose. However, this partnership can only function if a healthy soil provides the ‘ingredients’. An important cycle, in which deadwood comes back to life.

Regaining ground

The decomposition process of a tree takes decades, if not centuries. The last components are decomposed into tiny particles by soil organisms such as worms, springtails and soil bacteria. This creates a valuable humus containing numerous microorganisms, such as bacteria and fungi. ‘The higher the species diversity, the healthier the soil,’ explains the agricultural biologist. Soil health, in turn, is important for us humans to grow healthy food and create a sustainable habitat. This is in line with the One Health concept, which is based on the understanding that human, animal and environmental health are closely linked.