The «HOUSE TREE» project

The STUDENT MENTOR FOUNDATION LUCERNE decided to plant a green belt with trees in order to bring the unpretentious, grey building of the Schweighof residential area into a harmonious interplay with the surrounding landscape. Diverse native trees of high ecological value were selected for this purpose. The tree garden provides the building with a green gown, which not only makes an important contribution to the CO₂ balance, but also creates a pleasant microclimate. The deciduous trees allow the low winter sun to enter the apartments and efficiently cool the surroundings in summer.

Similar to the residents inside the student apartments, also the groups of trees around them form communities, which communicate and exchange resources with each other. However, the interaction between humans and nature is of even higher importance. These interactions play a crucial role for our climate and shall thus be focussed on in the “house tree” project. Thus, each apartment has been assigned to an individual tree in the green belt as a reminder not to lose nature out of sight.

Nowadays, humans emit billions of tons of carbon dioxide (CO₂). To combat the climate crisis, we must dramatically reduce fossil fuel emissions and sequester excess CO₂, in order to restore the balance of greenhouse gases in our atmosphere.

Trees fulfil a variety of important tasks therein. They withdraw CO₂ from the atmosphere over years and bind it in their biomass as well as in the soil in the long-term.

Forests are among the most diverse ecosystems on land because they are home to the vast majority of the world's terrestrial species. Therefore, the conservation and restoration of forests are crucial to preserve global biodiversity.

Trees also influence rainfall and are an integral part of the water cycle. In a single day, a large tree can absorb up to several hundred litres of water from the ground and release it into the atmosphere as vapour. The leaves of trees also collect water in the form of raindrops. This water then evaporates and can form new clouds and precipitation elsewhere.

Already Charles Darwin himself compared plant roots, especially the sensitive root tips, to the brains of lower organisms and spoke of the powerful agility of plants. Latest research supports his observations.

Deep underground, roots gather information and transmit it to the leaves high above – for instance in case of drought. The tree will "shut down" at least part of its canopy to cope with the water shortage. Conversely, the leaves inform the root system about the weather conditions high above and, through the process of photosynthesis, supply the roots with nutrients in the form of sugars.

The Canadian forest ecologist Suzanne Simard from the University of British Columbia was the first to demonstrate that forest trees are interconnected through what she called a Wood Wide Web. Using radioactive carbon, Simard showed that trees exchange nutrients and information throughout the forest via their roots and the web of mycorrhizal fungi. If a tree lacks nutrients, others in the forest can supply them. Simard also demonstrated that even trees of different species support each other: birches provided nutrients to Douglas firs. The basis for such a behaviour is the symbiotic exchange of trees with fungi, the mycorrhiza. Each tree lives in close association with these fungi, which supply the tree with inaccessible nutrients from the soil through a fine network of roots. In return, the tree provides the fungi with sugars that they could not produce themselves. The two organisms communicate with each other through the roots, informing each other of their needs.