Swedish scientists from the University of Gothenburg have proposed a simple way to make trees in cities taller and allow them to develop more spreading crowns. This helps cool the air due to green areas on hot days. The study was published in the scientific journal magazine Landscape and Urban Planning (LUP).
Experts studied the effect of ground cover type around the trunks of oak, chestnut and linden trees in various areas in the cities of Gothenburg and Mölndal. The assessment was based on several parameters, including canopy density, tree height, and the amount of moisture evaporated by leaves (transpiration). All these determine the effect of the tree on the microclimate, as the crown provides shade and the transpiration process cools the air like a natural air conditioner.
The study showed that mature 20- to 30-year-old trees surrounded by grass were an average of 2.6 meters taller than the same trees growing among asphalt or pavers. In addition, the crowns of plants in green areas are approximately 1.3 meters wider and 61% denser than the same species without grass. In general, replacing hard surfaces with soil approximately doubles the cooling effect of a tree.
Scientists have also discovered how different types of trees perform depending on the surface around them. Chestnut turned out to be the most unpretentious in this regard. However, worse cooling was seen among grasses compared to oaks and lime trees.
Previous scientists discovered Millions of hectares of unaccounted forests across Europe.