Here you can find a Robinia growing in the middle of playgrounds thanks to its adaptability to different soil types. And it can substantially increase soil nitrogen levels. It collaborates with the bacteria Rhizobium co-living in its roots, fixing atmospheric nitrogen into its own body.
Root nodules of Robinia, where the bacteria Rhizobium live Photo by Ninjatacoshell, 2012
And when its nitrogen-rich leaves and branches fall to the ground and decompose, they release nitrogen into the soil, which increasingly promotes nutrient-loving plants in the understorey.
Another characteristic of Robinia comes into play, especially on very dry soils: their leaves contain toxins that contaminate the soil as they rot on the ground. As a result, many plants can no longer germinate, and savanna-like vegetation develops, with Robinia as the only tree and few grasses, especially pearl grass (Melica ciliata).
Robinia in the dry grasslands of the Venosta Valley of South Tyrol.
Planted in the mid-20th century, it has completely changed the vegetation.
Photo by Thomas Wilhalm, Museum of Nature South Tyrol archive